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802.11g 802.11g is a Wi-Fi standard developed by the IEEE for transmitting data over a wireless network. It operates on a 2.4 GHz bandwidth and supports data transfer rates up to 54 Mbps. 802.11g is backward compatible with 802.11b hardware, but if there are any 802.11b-based computers on the network, the entire network will have to run at 11 Mbps (the max speed that 802.11b supports). However, you can configure your 802.11g wireless router to only accept 802.11g devices, which will ensure your network runs at its top speed.
1-tier architecture A simple form of standalone application architecture where everything resides in a single program. Contrast this to 2-tier and 3-tier architectures.
1000BaseT (Gigabit Ethernet) An extension of 100BaseT that runs 10 times faster than 100BaseT. It’s theoretically capable of 1Gbps (1000Mbps) transmission speed, and requires Category 6 cables to run over copper wire. Gigabit Ethernet can run over fiber-optic cabling as well.
100BaseT An extension of 10BaseT that runs 10 times faster than 10BaseT over copper wire. It’s theoretically capable of 100Mbps transmission speed. The drawback for some installations is that it requires more expensive Category 5 cable to run at high speeds, where 10BaseT will run on Category 3, 4, or 5 cable.
10Base2 A type of Ethernet cable that has been largely phased out. It’s also known as “thinnet.” Cable speeds are typically up to 10Mbps. 10Base2 uses RG-58 coaxial cable in a bus topology configuration with a maximum cable length of 185 meters. 10Base2 was used for desktop machines, while 10Base5 was used mainly for backbones.
10Base5 The original Ethernet specification, which is now more uncommon than 10Base2. It’s also known as “thicknet.” Cable speeds are typically up to 10Mbps. 10Base5 uses RG-11 coaxial cable in a bus topology configuration and has a maximum cable length of 500 meters, thus the 10(Mbps)Base5(00) name.
10BaseT A type of Ethernet cable topology that uses RJ-45 connectors, twisted pair wiring, and a star topology. Transmission speed is 10Mbps.
127.0.0.1 The IP address 127.0.0.1 is a special purpose address reserved for use on each computer. 127.0.0.1 is conventionally a computer's loopback address. Network software and utilities can use 127.0.0.1 to access a local computer's TCP/IP network resources. Messages sent to loopback IP addresses like 127.0.0.1 do not reach outside to the local area network (LAN) but instead are automatically re-routed by the computer's own network adapter back to the receiving end of the TCP/IP stack. Typically all IP addresses in the range 127.0.0.1 - 127.255.255.255 are reserved for private use, but 127.0.0.1 is by convention the loopback address in almost all cases.
128-bit Operating Systems Operating systems may eventually be 128-bit. The ability to address 128 bits of memory space is something that may someday be necessary for huge databases, and will speed up operations. Of course, this will not happen until after there are some 128-bit chips to run them on. So far there are some chips with 128-bit registers and special operations, but they are not fully 128-bit.
128-bit Video The bits referred to here describe the bus between the GPU and the video memory. Typically, larger buses mean faster video, but it also depends on the transmission speed over that bus. The first 128-bit video cards had only 2 MB or 4 MB of video memory on them.
1394 IEEE standard (FireWire) A serial connection technology that promises to speed data at 200-800Mbps and up. Digital video camera manufacturers and Apple have embraced this connection standard. It is also available on PCs, but adoption is not as widespread.
16-bit Operating Systems DOS and Windows 3.x are 16-bit operating systems. They are limited in complexity and suffer instability and slow speed (compared to 32-bit OSes) when run on 32-bit processors like the 386DX-compatible chips and above. 16-bit chips were limited to 65,536 (2^16) Kbytes of memory, or 64 MB. This limitation caused momentum for the move to 32-bit chips and operating systems.
2-tier architecture Applications that have a code base (1-tier) separate from the database management system (1-tier), such as using Delphi to interact with Microsoft SQL Server (1+1 = 2 tier). The application code resides on the “fat client,” which is used to process data. The problem with 2- tier applications is that they become complex and hard to support as the user base increases in size. What is good for 50 people may not work for 300 people.
24/7 24 hours a day 7 days a week. 24/7 means that a service is available at any time of day on any day of the week. A convenience store which is open 24/7 is permanently open (although it might still conceivably close for public holidays). A server which runs 24/7 is permanently available.
3-tier architecture This architecture splits the user interface from the application logic. Servers handle the database management and application logic. This works out to less complexity at the client and a more scalable application. Additional user interfaces can be added easily because the user interface is the only thing that resides on the client. For example, you can easily let customers view data from the Web without changing the application that lets your salespeople work with their data. The three tiers are basically the application code that resides on the client, the database management and logic, and finally the database itself.
3-way handshake Machine A sends a packet with a SYN flag set to Machine B. B acknowledges A's SYN with a SYN/ACK. A acknowledges B's SYN/ACK with an ACK.
32-bit Chips (32-bit processor) This type of processor can run a 32-bit OS, such as Windows NT or some versions of UNIX. You can also run a 16-bit or lesser OS, but performance is not optimal. Intel’s 386DX, 486, Pentium, and Pentium II/III/4 are all 32-bit processors. So are AMD’s 386, 486, Athlon, and Duron. 32-bit processors can address up to 4 GB of memory. Although this may be plenty for a typical desktop machine, higher end servers, workstations, and desktops require more memory and use 64-bit processors.
32-bit color depth Anything that supports 32-bit color supports over four billion different colors (2^32, or 4,294,967,296 to be exact). Graphics cards are supporting up to and over 32-bit color, but the human eye cannot discern between colors at that level, and you need more memory on your graphics card to display 32-bit color at high resolutions. Color scanners, however, use 32-bit or higher color depth. This is a more accurate scan, even though the color difference between two pixels may not be perceptible.
32-bit Memory Module DRAM modules with 32 separate data lines. 72-pin SIMMs are 32-bit memory modules. Using 32-bit modules with 64-bit memory interfaces requires pairing (inserting two like modules at a time) the modules on the motherboard.
32-bit Operating Systems Windows NT, OS/2, and some flavors of UNIX are 32-bit operating systems. Windows 95 is a 32-bit operating system running on top of a 16-bit operating system (DOS).
32-bit processor (32-bit Chips) This type of processor can run a 32-bit OS, such as Windows NT or some versions of UNIX. You can also run a 16-bit or lesser OS, but performance is not optimal. Intel’s 386DX, 486, Pentium, and Pentium II/III/4 are all 32-bit processors. So are AMD’s 386, 486, Athlon, and Duron. 32-bit processors can address up to 4 GB of memory. Although this may be plenty for a typical desktop machine, higher end servers, workstations, and desktops require more memory and use 64-bit processors.
32-bit Video Cards These are generally older cards that were only capable of addressing 1 MB of RAM. The 32 bits refers to the amount of information that can be transferred between the GPU on the video card and its local video memory.
3D (3-dimensional) The representation of objects in a space by length, width, and height (three planes). On a computer display device, 3D objects are typically represented on the 2D surface of a flat screen, but are computed as if they were actually in a three-dimensional environment. Advances in 3D technology are making gaming and other 3D environments more realistic.
3DNow! A set of 3D/multimedia floating point instructions first introduced in AMD’s K6-2 processor. Newer processors from AMD support the instructions as well. 3DNow! consists of 21 new instructions, and 8 64-bit registers dedicated to the instructions. Some older Cyrix and IDT x86 processors also supported 3DNow!, but most chips are now using Intel-defined standards such as SSE and SSE2.
3ware 3ware was founded in February 1997 by Mitch Altman, J. Peter Herz and Jim MacDonald. In April 2006, Applied Micro Circuits Corporation (AMCC) acquired 3ware for $150 million in cash and became a AMCC product line brand (manufacturing RAID controllers for Serial Attached SCSI, Serial ATA, and Parallel ATA devices). 3ware (also referred to as "AMCC Storage") was a product brand name of AMCC storage offering, and the product line was managed by Russell Johnson. AMCC / 3ware's initial business proposition was to enable low-cost desktop disk drives to be used in applications that were traditionally based on SCSI disk drives. In 1997 the cost per byte of SCSI disk drives carried a 2x premium over ATA disk drives. Rather than converging, price premium for SCSI disk drives actually grew to over 5x by 2002. This was not because SCSI drives became more expensive, rather both SCSI and ATA per byte disk drive prices dropped, but ATA drives were riding a much steeper price and performance ramp. AMCC / 3ware's differentiation from competitive offerings was its own proprietary I/O processor, trademarked as StorSwitch. The technology 3ware applied to scale performance was well known in the networking world: packet switching. AMCC / 3ware developed a high performance switching architecture that allowed all disk drives connected to a 3ware RAID controller to deliver data with full bandwidth in parallel. The combination of high streaming performance with very low cost per byte data storage was compelling in many applications. Prior to the acquisition by AMCC, 3ware marketed its products under the brand name "Escalade." Following the acquisition, AMCC used the brand "3ware" for its 7006/7506 (Parallel ATA), 8006/9500S/9550SX(U)/9650SE (Serial ATA) and 9690SA (Serial Attached SCSI) families of RAID controllers. On April 6, 2009, LSI Corporation announced an agreement to acquire the 3ware RAID adapter business of Applied Micro Circuits Corporation.
404 Error When a Web browser requests a page and the webserver doesn’t have that page available, the server returns a 404 Error, which states that the file you are looking for was not found. Reasons for this could be that the name of the file was misspelled, or that the file/page simply does not exist.
48-bit color depth Some scanners support 48-bit color, which offers the ability to identify over 281 trillion (2^48) colors. Such color differences may be imperceptible to the human eye, but as scanner DPI levels increase it helps keep colors more accurate.
56Kflex This was one of the two competing 56Kbps modem standards. It was developed by Rockwell and Lucent, and had more marketshare than USR’s X2 technology due to the fact that it was licensed to over 700 modem manufacturers. Eventually, the V.90 modem standard made 56Kflex and X2 irrelevant.
64-bit Chips (64-bit processor) A processor that can run a 64-bit OS. The DEC Alpha is 64-bit, and so are Intel’s Itanium and AMD’s Opteron and Athlon 64 processors. The 386, 486, and Pentium and Pentium II/III/4 are all 32-bit processors, even though the Pentium and newer chips have 64-bit memory buses.
64-bit Memory Module DRAM modules with 64 separate data lines. SDRAM and DDR DIMMs are an example of 64- bit memory chips.
64-bit Operating Systems An operating system that is programmed to run on 64-bit processors. Some flavors of UNIX–and now Linux–are 64-bit operating systems designed to run on 64-bit chips. There are also preliminary versions of Microsoft Windows that are 64 bits so that they can run on 64-bit processors.
64-bit processor (64-bit Chips) A processor that can run a 64-bit OS. The DEC Alpha is 64-bit, and so are Intel’s Itanium and AMD’s Opteron and Athlon 64 processors. The 386, 486, and Pentium and Pentium II/III/4 are all 32-bit processors, even though the Pentium and newer chips have 64-bit memory buses.
64-bit Video Cards Most current video cards have at least a 64-bit bus between the GPU and the video memory. The first 64- bit cards must had at least 2 MB of memory, up from 1 MB of memory on 32-bit cards.
8 bits A measure of memory. 8 bits make up 1 byte, and offer 256 (2^8) different combinations.
8-bit Memory Modules These DRAM modules have 8 separate data lines. 30-pin SIMMs are 8-bit memory modules. If you want to use them with a 32-bit chip such as a 386 or a 486 you need to put four of them in at a time–using the same size SIMM (all 1 MB SIMMs, all 2 MB SIMMs, etc.). With current microprocessors, 30-pin SIMMs are no longer used.
802.11a 802.11a is a Wi-Fi standard developed by the IEEE for transmitting data over a wireless network. It uses a 5 GHz band and allows data to be transferred up tp 54 Mbps. Other standards within the 802.11 family include 802.11b, which transfers data up to 11 Mbps and uses a 2.4 GHz band, and 802.11g, which also uses a 2.4 GHz band, but can transfer data up to 54 Mbps.
802.11b 802.11b is a Wi-Fi standard developed by the IEEE for transmitting data over a wireless network. It operates on a 2.4 GHz band and allows for wireless data transfers up to 11 Mbps. A faster standard, called 802.11g, was introduced a few years after 802.11b and supports data transfer rates up to 54 Mbps. This can make a difference in the speed of data transfers within a local network, but since broadband Internet access is limited to around 5 Mbps, a 802.11b wireless connection will not be a bottleneck for Internet access. Most wireless networks are based on either 802.11b or 802.11g.
802.11n 802.11n is a wireless (Wi-Fi) standard that was introduced in 2007. It supports a longer range and higher wireless transfer rates than the previous standard, 802.11g. 802.11n devices support MIMO (multiple in, multiple out) data transfers, which can transmit multiple streams of data at once. This technology effectively doubles the range of a wireless device. Therefore, a wireless router that uses 802.11n may have twice the radius of coverage as an 802.11g router. This means a single 802.11n router may cover an entire household, whereas an 802.11g router might require additional routers to bridge the signal. The previous 802.11g standard supported transfer rates of up to 54 Mbps. Devices that use 802.11n can transfer data over 100 Mbps. With an optimized configuration, the 802.11n standard can theoretically support transfer rates of up to 500 Mbps. That is five times faster than a standard 100Base-T wired Ethernet network. So if your residence is not wired with an Ethernet network, it's not a big deal. Wireless technology can finally keep pace with the wired network. Of course, with the faster speeds and larger range that 802.11n provides, it is more important than ever to password protect your wireless network.
A Record A Record Short for Address Record. It links a name to an IP address (or sometimes to another name). It is used within DNS, where each entry in the DNS table (an A Record) maps a domain name or sub-domain to an IP Address.
A/V audio/video
AC AC 1. Alternating Current. An electrical current that alternates its direction of flow (cf DC). The frequency (or number of cycles per second) is measured in hertz. 2. Air Conditioning. Air Conditioning units (which cool and de-humidify the air) are often rated in BTUs. 3. Administrator Account. A user account with full administrative rights. Depending on the context and operating system an administrator account may have full administrative rights over the local pc or over all pcs in a domain. cf LUA.
Access Microsoft Access, often abbreviated "MS Access," is a popular database application for Windows. Access allows users to create custom databases that store information in an organized structure. The program also provides a visual interface for creating custom forms, tables, and SQL queries. Data can be entered into an Access database using either visual forms or a basic spreadsheet interface. The information stored within an Access database can be browsed, searched, and accessed from other programs, including Web services. While Access is a proprietary database management system (DBMS), it is compatible with other database programs since it supports Open Database Connectivity (ODBC). This allows data to be sent to and from other database programs, such as MS SQL, FoxPro, Filemaker Pro, and Oracle databases. This compatibility also enables Access to serve as the back end for a database-driven website. In fact, Microsoft FrontPage and Expression Web, as well as ASP.NET have built-in support for Access databases. For this reason, websites hosted on Microsoft Windows servers often use Access databases for generating dynamic content. File Extension: .MDB
Access Control Access Control ensures that resources are only granted to those users who are entitled to them.
Access Point An access point provides wireless access to a network. Devices connected to an access point can communicate with other devices on the network. They may also connect to the Internet if the access point is linked to an Internet connection, which is commonly the case. Access points that use Wi-Fi are also called base stations. Example: "The coffee shop provides an access point for customers with Wi-Fi devices."
Access Speed The average amount of time it takes for a floppy drive, hard drive, CD drive, or other drive to find any particular piece of data on a disk and send it to your PC. Access speed is typically listed in milliseconds (ms).
Account Harvesting Account Harvesting is the process of collecting all the legitimate account names on a system.
ACE Access Control Entry. A single entry in an access control list.
ACK Short for Acknowledgement. Typically refers to an Acknowledgement message.
ACK Piggybacking ACK piggybacking is the practice of sending an ACK inside another packet going to the same destination.
ACPI Advanced Configuration and Power Interface.
ACPI (Advanced Configuration and Power Interface) This power management interface takes the power management out of the BIOS and gives control to the operating system (OS). Typically, a system’s BIOS is only able to turn a device off after a certain period of inactivity. With ACPI, the user can instruct the OS to slow down the processor or enter sleep mode. This basically gives the OS, and thus the user, more control of power management.
Active Collection / Seed collections or seed URLs that are scheduled for crawling.
active content Refers to content on a Web site that is either interactive, such as Internet polls or opt-in features, or dynamic, such as animated GIFs, stock tickers, weather maps, JavaScript applications, embedded objects, streaming video and audio or ActiveX applications. Streaming video and audio rely on browser plug-ins, such as RealPlayer, to display active content.
Active Directory A Microsoft technology based on LDAP that provides a unified view and way to manage all objects on a network. Microsoft created Active Directory as a response to Novell’s NDS system that allows administrators to control large networks in a similar manner. Active Directory was first introduced with Windows 2000, and many organizations are moving from the domain model of Windows NT to the Active Directory model of Windows 2000 because
Active Matrix LCD panels that are active matrix have a sharper, brighter image than those with passive matrix screens. They can also continue to be seen at much greater angles off of central viewing. In the early days of the LCD active matrix panels cost more to produce. The “active” part of the word describes the use of a transistor or diode that actively controls each pixel.
ActiveX This Microsoft-based technology was built to link desktop applications to the World Wide Web. Using ActiveX development tools, software developers can create interactive Web content for their applications. For example, Word and Excel documents can be viewed directly in Web browsers that supports ActiveX. While ActiveX is a useful technology, the downside is that you need to have a up-to-date version ActiveX installed on your machine in order to use ActiveX-enabled content.
Activity Monitor Activity Monitor is a utility for performing different tasks to a computer process in the Mac OS X operating system. Some of its functions include: Quitting or "killing" a computer process Viewing the computer's CPU load Checking the amount of random access memory in use or swapped out Checking the amount of hard disk read-ins and write-outs Checking the capacity of storage devices Monitoring the computer's network usage Inspecting running computer processes Viewing a process identifier number Viewing information about a particular process
Activity Monitors Activity monitors aim to prevent virus infection by monitoring for malicious activity on a system, and blocking that activity when possible.
Actuator The part of a hard drive that the read/write arms attach to. It is controlled by an electrical signal sent to it that extends or retracts the arms so that they can move across the tracks on the drive platters. Nowadays the movement of these lightweight arms is very fast, appearing like a flicker if you were to view it.
AD 1. Active Directory. 2. Administrative Domain. Refers to groups of computers and the network infrastructure operated and managed by a single organisation. 3. Abbreviation for the Latin phrase "Anno Domini", which means "in the year of our Lord". It denotes that a year is after the believed year of birth of Christ. "Anno Domini" is actually an abbreviation of "Anno Domini Nostri Jesu Christi" which means "in the year of our Lord Jesus Christ." 4. Abbreviation for "Advertisement". This can refer to any form of advertisement, including banner ads, pop-up (or pop-behind) advertisements, tv or radio advertisements etc. 5. Analogue to Digital conversion or Analogue to Digital converter. The process of converting an analogue input to a digital output.
Ad Hoc Network "Ad Hoc" is actually a Latin phrase that means "for this purpose." It is often used to describe solutions that are developed on-the-fly for a specific purpose. In computer networking, an ad hoc network refers to a network connection established for a single session and does not require a router or a wireless base station. For example, if you need to transfer a file to your friend's laptop, you might create an ad hoc network between your computer and his laptop to transfer the file. This may be done using an Ethernet crossover cable, or the computers' wireless cards to communicate with each other. If you need to share files with more than one computer, you could set up a mutli-hop ad hoc network, which can transfer data over multiple nodes. Basically, an ad hoc network is a temporary network connection created for a specific purpose (such as transferring data from one computer to another). If the network is set up for a longer period of time, it is just a plain old local area network (LAN).
ADC (Analog-to-Digital Converter) Stands for "Analog-to-Digital Converter." Since computers only process digital information, they require digital input. Therefore, if an analog input is sent to a computer, an analog-to-digital converter (ADC) is required. This device can take an analog signal, such as an electrical current, and digitize it into a binary format that the computer can understand. A common use for an ADC is to convert analog video to a digital format. For example, video recorded on 8mm film or a VHS tape is stored in an analog format. In order to transfer the video to a computer, the video must be converted to a digital format. This can be done using an ADC video conversion box, which typically has composite video inputs and a Firewire output. Some digital camcorders that have analog inputs can also be used to convert video from analog to digital. ADCs may also be used to convert analog audio streams. For example, if you want to record sounds from a microphone, the audio must be converted from the microphone's analog signal into a digital signal that the computer can understand. This is why all sound cards that have an analog audio input also require an ADC that converts the incoming audio signal to a digital format. The accuracy of the audio conversion depends on the sampling rate used in the conversion process. Higher sampling rates provide a better estimation of the analog signal, and therefore produce a higher-quality sound. While ADCs convert analog inputs into a digital format that computers can recognize, sometimes a computer must output an analog signal. For this type of conversion, a digital-to-analog converter (DAC) is used. NOTE: ADC can also stand for "Apple Display Connector," which was a proprietary video connector developed by Apple. It combined DVI, USB, and AC power into a single cable. Apple stopped producing computers with ADC ports in 2004 in favor of the standard DVI connection.
Address Munging Address Munging is the process of modifying an e-mail address to make it invalid, in such a way that a legitimate reader can put it back together again. This technique is used to hide (valid) e-mail addresses from e-mail harvesters (and thus reduce the likelihood of receiving spam).
ADO ADO: Microsoft® ActiveX® Data Objects. Encompasses the functionality of both RDO and DAO.
ADS 1. Active Directory Service. 2. Active Directory Structure. 3. Automated Deployment Services.
ADSL (Asymmetric Digital Subscriber Line) A DSL line where the upload speed is different from the download speed. Usually the download speed is much greater.
Advanced Host Controller Interface (AHCI) The Advanced Host Controller Interface (AHCI) is an application programming interface defined by Intel which defines the operation of Serial ATA host bus adapters in a non-implementation-specific manner. The specification describes a system memory structure for computer hardware vendors to exchange data between host system memory and attached storage devices. As of June 2008, the current version of the specification is v. 1.3.[1] AHCI gives software developers and hardware designers a standard method for detecting, configuring, and programming SATA/AHCI adapters. AHCI is separate from the SATA 3Gb/s standard, although it exposes SATA's advanced capabilities (such as hot-plugging and native command queuing) such that host systems can utilize them. Many SATA controllers offer selectable modes of operation: legacy Parallel ATA emulation, standard AHCI mode, or vendor-specific RAID. Intel recommends choosing RAID mode on their motherboards (which also enables AHCI) rather than the plain AHCI/SATA mode for maximum flexibility, due to the issues caused when the mode is switched once an operating system has already been installed.[2] Legacy mode is a software backward-compatibility mechanism intended to allow the SATA controller to run in legacy operating systems which are not SATA-aware or where a driver does not exist to make the operating systems SATA-aware. AHCI is fully supported out of the box for Windows Vista and Linux operating systems from kernel 2.6.19, as well as later operating systems such as Windows 7. NetBSD also supports drivers in AHCI mode out of the box in certain versions. OpenBSD has had an AHCI driver starting with OpenBSD 4.1. DragonFlyBSD based its AHCI implementation on OpenBSD's and added extended features such as port multiplier support. FreeBSD supports AHCI as well. Solaris 10 introduced AHCI support in the 8/07 release [3]. Older operating systems require hardware-specific drivers to support AHCI.
Advanced Micro Devices (AMD) Advanced Micro Devices, Inc. (AMD) (NYSE: AMD) is an American multinational semiconductor company based in Sunnyvale, California, that develops computer processors and related technologies for commercial and consumer markets. Its main products include microprocessors, motherboard chipsets, embedded processors and graphics processors for servers, workstations and personal computers, and processor technologies for handheld devices, digital television, automobiles, game consoles, and other embedded systems applications.
Advanced SCSI Programming Interface (ASPI) This was developed by Adaptec so that different devices could be controlled by different SCSI cards, and therefore the SCSI card version would not matter. Basically, if the correct ASPI driver is being used, you can send the same command to any Adaptec SCSI card to make something happen to a device. Most commonly, ASPI is associated with CD-ROM and CD-RW drives.
Adware Adware A collective name for software which displays advertising banners or pop-ups while the user is using the application. Typically the software may be free at the point of use and is supported by the revenue generated from displaying advertisements. Sometimes the advertisements are independent of the application the user originally installed. Adware can be distracting and sometimes annoying, but other than taking up bandwidth (because the application will typically download new adverts) it is not in itself harmful.
AES Advanced Encryption Standard. An encryption standard widely seen as more secure and a natural successor to 3DES and DES.
AFAIK Online speak for “As Far As I Know”
Affiliate Website affiliates are what drive Internet marketing. Companies run affiliate programs to generate leads and sales from other Websites. They pay the sites who host their ads a commission for products sold through the links on their sites. For example, if a site owner signs up for Amazon.com's affiliate program, he will receive ad banners or links from Amazon.com that he can place anywhere on his site. Then, if a visitor clicks on the Amazon.com banner or a link on his site and buys something, he will receive a commission. Unfortunately for Website owners, affiliate commisions are seldom above 5%, since most Web sales are made with small profit margins. The introduction of Website affiliate programs in the late 1990s brought Internet marketing to a new level. The first companies that offered these programs saw sales increase dramatically. After all, these companies basically get free advertising and only pay their affiliates a percentage of the sales they generate. It is a win-win situation for the company that runs the affiliate program. The only drawback is that the programs take a lot of work (and sometimes a lot of money) to set up and maintain. Thus, smaller companies may not find it very beneficial to offer an affiliate program.
AFK Online speak for “Away From Keyboard”
AGP Advanced Graphics Port. Graphics card interface for high performance graphics (faster than PCI). Specification Denoted Notes AGP 1.0 AGP AGP x1 AGP x2 Supports 1x and 2x adapter cards. Uses a signal level of 3.3 volts. AGP 1.0 adapter cards have a different slot arrangement from AGP 2.0 (and later) and therefore an AGP 1.0 adapter card will not fit into an AGP 2.0 slot. AGP 2.0 AGP x4 Supports 4x adapter cards, i.e. 4 times faster than the original AGP specification. Uses a signal level of 1.5 volts. AGP 3.0 AGP x8 Supports 8x adapter cards. Uses a signal level of 0.8 volts. The slot for AGP 3.0 is identical to that for AGP 2.0. AGP 2.0 and AGP 3.0 cards and motherboards should be compatible with each other - but an AGP 8x card fitted to a motherboard that only supports AGP 4x will be forced to work at the slower 4x rate.
AGP (Accelerated Graphics Port) A dedicated expansion port that began to show up on motherboards in the second half of 1997. It bypasses the PCI bus and allows higher throughput from the graphics card to the processor and memory for speedier 3D graphics. Original AGP cards were “1x” versions that ran at 66MHz, offering 266MB/second throughput; but now AGP supports up to 8X data transfer speeds, which means the card still runs at 66MHz, but transfers 8x as much data per clock tick, upping the throughput to 2.1GB/second. Although the throughput is much greater, most graphics cards have a large amount of local memory and thus do not get much of a bonus from faster AGP speeds.
AGP 1x The original parallel AGP standard that operates on a 32-bit bus at 66MHz speed for a maximum data transfer rate of 256MB/second.
AGP 2x This AGP standard features a parallel 32-bit bus running at 133MHz effectively (66MHz*2 literally) for a maximum data transfer rate of 512MB/second. AGP 2x slots will accept AGP 1x cards as well as 2x cards.
AGP 4x This AGP standard features a parallel 32-bit bus running at 266MHz effectively (66MHz*4 literally) for a maximum data transfer rate of 1GB/second. AGP 4x slots are compatible with 1x, 2x, and 4x graphics cards.
AGP 8x This AGP standard features a parallel 32-bit bus running at 533MHz effectively (66MHz*8 literally) for a maximum data transfer rate of 2GB/second. This is the last parallel form of AGP, and is compatible with all previous AGP cards.
AGP Aperture The amount of system memory that the AGP board can address and use as graphics memory. Often, the default setting is 64 MB. Increasing this value (assuming you have enough system memory) may increase performance in 3D games that use more memory than is available on the video card. Once an AGP video card is installed, this setting can usually be changed in the computer’s BIOS.
AGP Pro This AGP standard allows the graphics card to draw more than four times the electrical power of the regular AGP 4x standard, i.e., 110 watts up from 25 watts. AGP Pro transfers data at the same speed as AGP 4x and requires a special AGP Pro slot that is larger than the standard AGP slot.
AHCI Advanced Host Controller Interface (specification).
AI Artificial Intelligence. The emulation of intelligent behaviour by software (and or machines).
AIFF Stands for "Audio Interchange File Format." AIFF is an audio format originally developed by Apple Computer for storing high-quality sampled audio data. AIFF files are similar to Windows WAVE files in both size and quality. Both AIFF and WAVE files can hold CD quality audio and therefore can be burned onto an audio CD. Though the AIFF format was created by Apple, audio programs on both the Mac and PC can typically read the files. File extensions: .AIF, .AIFF
Air Cooling Cooling that involves a heatsink and/or fan. Even though a metal heatsink may make contact with the microprocessor package (or whatever is being cooled), the heatsink ultimately exchanges the heat with air, whether a fan is used or not. Contrast this with water cooling. Air cooling is less efficient than water cooling.
Air gap A type of network security in which a network is secured, at least in part, by keeping it physically separate from other local networks and the Internet. This can be an effective type of security, but it is also limiting in that clients may not be able to get to all resources they need from a single computer.
AJAX AJAX Asynchronous JavaScript and XML. A development technique for web pages that uses JavaScript and XML to create dynamic web page content, which has the capability to be updated as the user interacts with it. AJAX is described as asynchronous because it allows data to be exchanged with the server and parts of the page updated dynamically without delay to the user experience or the need to reload the entire page. The philosophy behind AJAX is to load the static parts of a webpage once, updating the dynamic parts (i.e. those bits which can change) as necessary without needing to reload anything unnecessary (such as the static parts of the page). This makes small updates much faster, because the majority of the page is unchanged and does not need to be reloaded. As well as a quicker user experience, AJAX also reduces the amount of data that needs to be downloaded from the server to the client, reducing bandwidth and potentially also processing requirements. AJAX makes use of and builds upon JavaScript, XML, HTML and CSS. There is some dispute over whether or not the name should be capitalised, i.e. AJAX or Ajax. The argument in favor of not capitalizing the name is that Ajax stands for an approach rather than an acronym.
Aka Also Known As. Used to refer to other names for something. Aka may be used to indicate more or less common names. For example "sol aka the sun". Aka is also expressed as A.K.A. i.e. with a period between each letter. It is pronounced A-K-A, emphasising each letter in turn.
Alert Box An alert box, sometimes called a message box, is a small window that pops up on your screen to warn you that your computer is about to perform an operation with potentially damaging consequences. For example, when you choose to empty the Trash or Recycle Bin on your computer, an alert box may pop up, saying "Are you sure you want to permanently remove these items?" You are then given the choice to select "OK," to delete the items, or "Cancel," to prevent the items from being removed. Alert boxes act as a safeguard for users, preventing us from doing things we wish we hadn't. Perhaps the most common alert box is the one that pops up when you try to close a document without saving it. You'll mostly likely see an alert box with the message, "Save changes to this document before closing?" You can select "Don't Save," to discard the changes, "Save," to save the changes before closing the document, or "Cancel," to cancel closing the document and continue working on it. Most alert boxes include the standard alert icon -- a triangle with an exclamation point in the middle -- to get your attention. However, not all alert boxes have multiple options, such as "Cancel" and "OK." For example, an alert box may show up on your screen saying a program performed an illegal operation and has unexpectedly quit. When that happens, your only option is to select "OK" and then kick your computer for quitting the program before you had a chance to save your work.
Algorithm Algorithm An organised method for solving a problem (and producing a result). Algorithms are expressed as a finite sequence of clearly defined steps for accomplishing a task or solving a problem. cf heuristic.
Alpha Test (Alpha) A term given to a very early version of a hardware or software product which is not yet stable and may lack features. After some testing and some revision, the product will assume beta status.
ALS Active Line State. A signal or LED indicating that a communication line, connection or cable is in use.
Alt (Alternate) 1. There is an Alt key found on a computer keyboard. The Alt key functions much like a third Ctrl/Shift key in that it alters the value of other characters pressed on the keyboard. 2. The term Alt has also been used to refer to using the Esc key (ASCII 27) to alter the next input. 3. Finally, Alt is used as a prefix for usenet newsgroups that can be created without going through the standard voting procedures, such as alt.pictures.angry.pandas.
AMT Active Management Technology. A specification from Intel for a set of hardware components designed to provide remote management of PCs
Analog As humans, we perceive the world in analog. Everything we see and hear is a continuous transmission of information to our senses. This continuous stream is what defines analog data. Digital information, on the other hand, estimates analog data using only ones and zeros. For example, a turntable (or record player) is an analog device, while a CD player is digital. This is because a turntable reads bumps and grooves from a record as a continuous signal, while a CD player only reads a series of ones and zeros. Likewise, a VCR is an analog device, while a DVD player is digital. A VCR reads audio and video from a tape as a continuous stream of information, while a DVD player just reads ones and zeros from a disc. Since digital devices read only ones and zeros, they can only approximate an audio or video signal. This means analog data is actually more accurate than digital data. However, digital data can can be manipulated easier and preserved better than analog data. More importantly, computers can only handle digital data, which is why most information today is stored digitally. But if you want to transfer video from old analog video tapes into your computer so you can edit them, you're not out of luck. You can use a digital to analog converter (DAC) to convert the analog information into a digital signal that can be recognized by your computer.
Analog Control An analog control changes value in non-discrete steps. You can tune an analog control to non-distinct values (selecting 107.41234723947392… as the radio station you are tuned to instead of 107.40000000000000…). In some cases, like for volume, analog controls are better. Have you ever used a digital volume control on a new TV, and one setting is too loud while the other is too soft? You just can’t get it in between. However, for channel tuning, where values change by fixed steps, a digital control is much better–you just don’t need to get in between channel 4 and 5. Also see Digital Control
Analogue Modem analogue modem A modem for use with analogue equipment, such as a phone line. Typical analogue modem speeds are: Common name Maximum download speed Maximum upload speed kbps bytes/sec kbps bytes/sec 4.8 4.8 600 4.8 600 9.6 9.6 1200 9.6 1200 14.4 14.4 1800 14.4 1800 28.8 28.8 3600 28.8 3600 33.6k 33.6 4200 33.6 4200 56k v90 53 6600 33.6 4200 Modems can operate at speeds much slower than their rated maximum. Where a cable modem has LEDs on the front, these are typically one or more of: LED Short for Description PWR Power Power-on/ready indicator. MR Modem Ready AA Auto Answer Modem is ready to answer incoming calls. CD Carrier Detect Indicates that the modem has detected a valid carrier signal from the remote modem. (When modems communicate they establish a carrier signal for handshaking purposes.) HS High Speed Indicates if the connection is considered by the modem to be "High Speed" this is at the modem's top speed or above 4800bps (depending on the modem). RD Receive Data Flashes when the modem is receiving data (from the modem at the other end of the link.) SD Send Data Flashes when the modem is sending data (to the modem at the other end of the link). TR Terminal Ready On indicates that the computer (that the modem is locally connected to) is ready to receive data. DTR CS Clear to Send On indicates that the modem is ready to receive data from the computer it is connected to. CTS ARQ/FAX Error correction fax OH Off Hook Indicates that the phone line is active and the modem has control of the line.
Anonymous FTP FTP services requiring no specific authentication, using a login name of “anonymous” and your e- mail address as a password.
ANSI American National Standards Institute. A long standing not-for-profit American standards organisation.
Antivirus Antivirus (or anti-virus) software is used to prevent, detect, and remove malware, including computer viruses, worms, and trojan horses. Such programs may also prevent and remove adware, spyware, and other forms of malware. A variety of strategies are typically employed. Signature-based detection involves searching for known malicious patterns in executable code. However, it is possible for a user to be infected with new malware in which no signature exists yet. To counter such so-called zero-day threats, heuristics can be used. One type of heuristic approach, generic signatures, can identify new viruses or variants of existing viruses by looking for known malicious code (or slight variations of such code) in files. Some antivirus software can also predict what a file will do if opened/run by emulating it in a sandbox and analyzing what it does to see if it performs any malicious actions. If it does, this could mean the file is malicious. However, no matter how useful antivirus software is, it can sometimes have drawbacks. Antivirus software can degrade computer performance if it is not designed efficiently. Inexperienced users may have trouble understanding the prompts and decisions that antivirus software presents them with. An incorrect decision may lead to a security breach. If the antivirus software employs heuristic detection (of any kind), success depends on achieving the right balance between false positives and false negatives. False positives can be as destructive as false negatives. In one case, a faulty virus signature issued by Symantec mistakenly removed essential operating system files, leaving thousands of PCs unable to boot.[1] Finally, antivirus software generally runs at the highly trusted kernel level of the operating system, creating a potential avenue of attack.[2] In addition to the drawbacks mentioned above, the effectiveness of antivirus software has also been researched and debated. One study found that the detection success of major antivirus software dropped over a one-year period. Identification methods ClamWin 0.95.1 running on Windows XP There are several methods which antivirus software can use to identify malware. Signature based detection is the most common method. To identify viruses and other malware, antivirus software compares the contents of a file to a dictionary of virus signatures. Because viruses can embed themselves in existing files, the entire file is searched, not just as a whole, but also in pieces.[9] Heuristic-based detection, like malicious activity detection, can be used to identify unknown viruses. File emulation is another heuristic approach. File emulation involves executing a program in a virtual environment and logging what actions the program performs. Depending on the actions logged, the antivirus software can determine if the program is malicious or not and then carry out the appropriate disinfection actions.[10] [edit]Signature based detection A command-line virus scanner, Clam AV 0.95.2, running a virus signature definition update, scanning a file and identifying a Trojan Traditionally, antivirus software heavily relied upon signatures to identify malware. This can be very effective, but cannot defend against malware unless samples have already been obtained and signatures created. Because of this, signature-based approaches are not effective against new, unknown viruses. Because new viruses are being created each day, the signature-based detection approach requires frequent updates of the virus signature dictionary. To assist the antivirus software companies, the software may allow the user to upload new viruses or variants to the company, allowing the virus to be analyzed and the signature added to the dictionary.[9] Although the signature-based approach can effectively contain virus outbreaks, virus authors have tried to stay a step ahead of such software by writing "oligomorphic", "polymorphic" and, more recently, "metamorphic" viruses, which encrypt parts of themselves or otherwise modify themselves as a method of disguise, so as to not match virus signatures in the dictionary.[11] [edit]Heuristics Some more sophisticated antivirus software uses heuristic analysis to identify new malware or variants of known malware. Many viruses start as a single infection and through either mutation or refinements by other attackers, can grow into dozens of slightly different strains, called variants. Generic detection refers to the detection and removal of multiple threats using a single virus definition. [12] For example, the Vundo trojan has several family members, depending on the antivirus vendor's classification. Symantec classifies members of the Vundo family into two distinct members, Trojan.Vundo and Trojan.Vundo.B.[13][14] While it may be advantageous to identify a specific virus, it can be quicker to detect a virus family through a generic signature or through an inexact match to an existing signature. Virus researchers find common areas that all viruses in a family share uniquely and can thus create a single generic signature. These signatures often contain non-contiguous code, using wildcard characters where differences lie. These wildcards allow the scanner to detect viruses even if they are padded with extra, meaningless code. [15] Padded code is used to confuse the scanner so it can't recognize the threat. A detection that uses this method is said to be "heuristic detection."
Anycast A method available in IPv6 of sending information over a network. It allows a device to send data to the nearest (fastest) of a group of receivers.
Apache The most common web server (or HTTP server) software on the Internet. Apache is an open-source application originally created from a series of changes ("patches") made to a web server written at the National Center for Supercomputing Applications, the same place the Mosaic web browser was created. In early 1995, a group of webmasters decided to get together and expand on the original NCSA HTTP daemon (webserver software), and Apache was born. Today, Apache is the most used webserver on the Internet. Apache is Open Source freeware, and is available for Linux, Windows, and many versions of UNIX. Apache is designed as a set of modules, enabling administrators to choose which features they wish to use and making it easy to add features to meet specific needs inlcuding handling protocols other than the web-standard HTTP.
API 1. Application Programming Interface. The definition of procedures (and protocols) that a software application can make use of. 2. Advance Passenger Information (system). A system for an airlines to send passenger information to a destination airport for customs and immigration purposes before the flight leaves.
Apple The reason this term is in the glossary is because way too many people confuse "Apple" with "Macintosh." Apple is the company that makes Macintosh computers -- not the other way around. Apple's product line includes Power Macs, PowerBooks, iMacs, iBooks, and the popular hard drive-based MP3 player, the iPod. Apple also develops a large number of software programs, such as iTunes, iPhoto, iMovie, and iDVD. Notice a pattern here? Though most of Apple's product names now start with the letter "i", the company has a history of creative innovation. Though Apple has less than ten percent of the marketshare in the computer business, the company still manages to lead the industry in new directions.
Applet A small Java program that can be embedded in an HTML page. Applets differ from full-fledged Java applications in that they are not allowed to access certain resources on the local computer, such as files and serial devices (modems, printers, etc.), and are prohibited from communicating with most other computers across a network. The common rule is that an applet can only make an Internet connection to the computer from which the applet was sent.
AppleTalk Macintosh computers networking protocol.
Application An application, or application program, is a software program that runs on your computer. Web browsers, e-mail programs, word processors, games, and utilities are all applications. The word "application" is used because each program has a specific application for the user. For example, a word processor can help a student create a research paper, while a video game can prevent the student from getting the paper done. In contrast, system software consists of programs that run in the background, enabling applications to run. These programs include assemblers, compilers, file management tools, and the operating system itself. Applications are said to run on top of the system software, since the system software is made of of "low-level" programs. While system software is automatically installed with the operating system, you can choose which applications you want to install and run on your computer. Macintosh programs are typically called applications, while Windows programs are often referred to as executable files. This is why Mac programs use the .APP file extension, while Windows programs use the .EXE extension. Though they have different file extensions, Macintosh and Windows programs serve the same purpose and can both be called applications.
Application Failover The capability of an application to recover from the failure of a database (that the application is connected to and using) by automatically switching over to using a surviving database instance. Application Failover should provide no loss of data or continuity. It tends to be used with high end database systems, such as Oracle Parallel Server (OPS). Also known as ‘run-time failover’. Application Failover is often used in connection with Connection Failover.
Application Programming Interface (API) APIs allow you to program to a pre-constructed interface (the API) instead of programming a device or piece of software directly. This allows for faster development, since programming to a device’s API is designed to be easier than programming to a device directly. APIs allow you to program without having intimate knowledge of the device or software to which you are sending commands. For example, the OpenGL API allows you to create 3D effects without actually knowing the innards of your video card.
Application Server Server software that manages one or more other pieces of software in a way that makes the managed software available over a network, usually to a Web server. By having a piece of software manage other software packages it is possible to use resources like memory and database access more efficiently than if each of the managed packages responded directly to requests.
Apt-get Part of “apt,” a package retrieval tool that automatically connects to known Linux package repositories and checks for new packages. It also works out dependencies between packages. Apt-get is used with the Debian Linux distribution.
Archive As a noun, this refers generally to any type of backed-up data. It can refer to tapes, disks, or just simply a group of data that is an old copy of current data. That copy could be one minute old or several years old. As a verb, archive is the act of backing up data or creating an archive.
ARP Address Resolution Protocol. A network protocol used for mapping an IP address to a physical hardware address (MAC Address).
Array 1. This can be an abbreviation for a group of hard drives functioning as a RAID (Redundant Array of Inexpensive Drives). 2. This also describes a common data structure that holds values in a consecutively numbered group, such as A[1]…[7], where A is an array of 7 different values. There are also multi-dimensional arrays such as A[1,1,1]…A[8,8,8], which can hold many values and still be fairly simply referenced.
ASCII American Standard Code for Information Interchange. In ASCII the letters of the alphabet, digits and various punctuation symbols are assigned a unique 7 bit number (0-127). cf Unicode. On most systems there is also an additional set of 128 "extended ASCII codes" that are used to represent a variety of other symbols. These extended codes are not part of the ASCII standard.
ASCII file A file that can be opened and read by standard text editor programs (for example, Notepad or Simple Text) on almost any type of computer. Also referred to as "plain text files". Examples: documents saved in ASCII format within word processors like Microsoft Word or WordPerfect; e-mail messages created by a program like Outlook; or HTML files.
ASDL 1. Asynchronous Digital Subscriber Line. Provides a permanent link to the internet. 2. Asymmetric Digital Subscriber Line. Technology allowing high data rates over existing copper telephone lines. ASDL supports from 1.5mbps to 9mbps download and from 15kbps to 640kbps upload.
ASFN Alliance for Spam Free Networks. An alliance developed with the mission of creating a spam free internet, targeted membership includes ISPs and large companies.
ASIO Audio Stream Input/Output.
ASP 1. Active Server Pages. A specification for a dynamically created web page. Allows a script or ASP application to be executed on a web server to generate a web page sent to a viewer. Requires IIS. cf JSP. Pages generated using ASP generally have the file extension of .asp.
ASP.NET ASP.NET Microsoft's server based framework for running .NET code on web servers. Similar model to ASP, but for running ASP.NET applications. Requires a web server running IIS. ASP.NET applications can be written using a text editor, but are normally developed using an IDE such as Microsoft's Visual Studio .Net or Borland's Delphi.
Aspect Ratio The ratio of the width by the height on a monitor or television screen. Most TVs and monitors have a 4×3 aspect ratio–the screens are 4 units wide and 3 units high. A movie screen has an aspect ratio of 16×9 (a bit wider than 5×3), and that’s why we have letterboxed movies (when you show a movie in true form on a TV you get black boxes on the top and bottom of the screen). HDTV screens today and some monitors support 16×9 aspect ratios, but most televisions and monitors still retain the 4×3 aspect ratio.
ASPI (Advanced SCSI Programming Interface) This was developed by Adaptec so that different devices could be controlled by different SCSI cards, and therefore the SCSI card version would not matter. Basically, if the correct ASPI driver is being used, you can send the same command to any Adaptec SCSI card to make something happen to a device. Most commonly, ASPI is associated with CD-ROM and CD-RW drives.
ASR 1. Automatic Speech Recognition. Any system for translating speech into commands or for translating speech into an electronic document. 2. Access Service Request.
Assembly Language A programming language specific to a microprocessor. It is a very low-level language, where you actually give the processor instructions like “MOV A,B”, which moves a value from one register to another. As you might imagine, programming directly in assembly language is quite tedious. Thus, higher level languages, such as C++, Visual Basic, or Java, are normally used and then compiled into assembly language specific to the microprocessor on which the program will be run. The compiler tries to optimize the code during this process (e.g., “MOV A,B” followed by “MOV B,C” might be replaced by “MOV A,C”). Depending on how elegant the optimization is, the code may run faster than if no optimization is used. Today, very small and fast programs can be created by using assembly language (defeating code bloat), but assembly language programming is becoming a dying art.
ASTA Anti-Spam Technical Alliance. ASTA was formed in April 2003 to recommend actions and policies for ISPs and e-mail service providers, governments, private corporations and online marketing organisations. It consists of several large companies, including Yahoo, Microsoft, AOL and Earthlink Inc.
Asynchronous This word is used in the telecommunications and distance learning fields. It has a similar meaning in both fields. In telecommunications, it refers to an exchange of data at intermittent, or non-synchronized intervals between two devices. In the distance learning field, it refers to learning systems in which the instructor and students do not have to synchronize their presence. The use of Web-based discussion boards is an asynchronous distance learning activity, because the students and instructor can post their thoughts to the board at any time. The SVETN electronic classrooms and the Holton Governor's School LearnLinc system are synchronous distance leaning activities, because they require the facilitator and students to synchronize their presence.
AT Form Factor A PC form factor that describes the way a motherboard fits into a case and works with a power supply. Thus, you match an AT power supply with an AT case and an AT motherboard. Some of the things common to AT motherboards are a large 5-pin DIN socket for plugging a keyboard in, and serial and parallel port interfaces available via riser cards that are not part of the motherboard itself. The AT form factor was succeeded by the ATX form factor.
ATA AT Attachment. A popular 16-bit interface standard that extends the ISA bus of the IBM PC-AT to attach peripherals;. It has been developed through a number of generations. The original ATA specification defined what was commonly known as Integrated Drive Electronics (IDE). Later versions defined EIDE and then higher speed interfaces. ATA Version Also known as Bus width Maximum dData rate Notes ATA-1 IDE 8 or 16 bit 8.3MB/sec 40 pin ribbon cable. Maximum of two devices. ATA-2 EIDE Fast ATA Fast IDE 8 or 16 bit 16.6MB/sec Maximum number of devices increased to four. ATA-3 16 bit 16MB/sec CRC added. ATA-4 Ulta-ATA/33 16 bit 33MB/sec ATA-5 Ulta-ATA/66 16 bit 66MB/sec 80 pin ribbon cable, 40 pin connector (extra cables for noise reduction). These cables typically have three connectors. The blue connector should be plugged into the mother board, the grey (middle) connector to any slave device and the grey (end) connector to the master device. ATA-6 Ultra-ATA/100 16 bit 100MB/sec ATA-7 Ultra-ATA/133 16 bit 130MB/sec ATA is but is now generally referred to as PATA to distinguish it from SATA. SATA uses a totally different interface from PATA and is seen as its natural successor.
ATA (AT Attachment) A storage (hard drive, CD-ROM, etc.) interface more commonly known as IDE. The “AT” refers to the IBM-AT computer where this interface was first used.
ATA/100 (Ultra ATA/100) Another extension to the ATA interface that adds a 50% increase in top speed over ATA/66, getting to 100MB/second, up from 66MB/second. This standard also adds some additional error-checking not found in earlier ATA standards. Like Ultra ATA/66, ATA/100 requires an 80-conductor cable to work at full speed.
ATA/133 (Ultra ATA/133) This refers to what is most probably the final extension to the parallel ATA connection standard. The proposal was created by Maxtor, and allows a top data transfer rate of 133 megabytes per second. Intel didn’t support this standard in its chipsets, instead opting to wait for Serial ATA. See Serial ATA for further details.
ATA/33 (Ultra ATA/33) An extension to the ATA interface (IDE) that effectively doubles the top data transfer speed of IDE from 16.6MBytes/second up to 33 MBytes/second. Also known as Ultra-IDE.
ATA/66 (Ultra ATA/66) An extension to the ATA interface (IDE) proposed by Quantum that effectively doubles the data transfer speed of the Ultra ATA/33 interface to 66MBps. To achieve the increase in speed you must use a special 80-conductor cable with 40 data lines and 40 ground lines to keep the signal stable.
ATM (Asynchronous Transfer Mode) A networking protocol initially designed to move multimedia data around with high reliability and speed. It uses small, fixed-size cells of data that can be more easily controlled and kept at specific service levels than TCP/IP. Some ISPs use ATM as the protocol for their backbones.
Attachment A file embedded in an e-mail message. It is possible to have one or more attachments embedded in an e-mail message. If you are sending or receiving attachments, you must have an e-mail client that supports MIME encoding, or the attachments will show up in encoded form, which basically looks like a large block of numbers and letters.
ATX Form Factor The ATX form factor specification takes the original Baby AT-sized motherboard, rotates it 90 degrees, and calls for a power supply with a side-mounted fan that cools not only the power supply, but also the processor and add-in boards. This new approach was designed to lower costs and provide better motherboard placement in an ATX case. In addition, the ATX form factor introduced a large set of I/O ports that are wired directly to the motherboard, and standard support for PS/2 keyboard and mouse connections.
ATX12V A superset of the ATX form factor that is used for systems with the Pentium 4 processor. It features a power supply with an extra four-pin connector for 12 volt power to the motherboard so that the processor has enough power. There is also a 6-pin auxiliary connector for additional 3.3 or 5 volt power.
Auditing Auditing is the information gathering and analysis of assets to ensure such things as policy compliance and security from vulnerabilities.
AUI A synonym for the 10Base5 Thicknet Ethernet standard.
Authorization Authorization is the approval, permission, or empowerment for someone or something to do something.
Autonomic Computing Autonomic Computing is an initiative started by IBM in 2001. Its ultimate aim is to develop computer systems capable of self-management, to overcome the rapidly growing complexity of computing systems management, and to reduce the barrier that complexity poses to further growth. In other words, autonomic computing refers to the self-managing characteristics of distributed computing resources, adapting to unpredictable changes whilst hiding intrinsic complexity to operators and users. An autonomic system makes decisions on its own, using high-level policies; it will constantly check and optimize its status and automatically adapt itself to changing conditions. As widely reported in literature, an autonomic computing framework might be seen composed by Autonomic Components (AC) interacting with each other [1]. An AC can be modeled in terms of two main control loops (local and global) with sensors (for self-monitoring), effectors (for self-adjustment), knowledge and planer/adapter for exploiting policies based on self- and environment awareness. Driven by such vision, a variety of architectural frameworks based on “self-regulating” autonomic components has been recently proposed. A very similar trend has recently characterized significant research work in the area of multi-agent systems. However, most of these approaches are typically conceived with centralized or cluster-based server architectures in mind and mostly address the need of reducing management costs rather than the need of enabling complex software systems or providing innovative services. Autonomy-oriented computation is a paradigm proposed by Jiming Liu, in 2001 that uses artificial systems imitating social animals' collective behaviours to solve hard computational problems. For example, ant colony optimization could be studied in this paradigm.[1]
Autonomous System One network or series of networks that are all under one administrative control. An autonomous system is also sometimes referred to as a routing domain. An autonomous system is assigned a globally unique number, sometimes called an Autonomous System Number (ASN).
Availability A measure of how much time a network or a connection is running. Generally the equation is: Time Running / Time Measured (time running divided by time measured). Thus, if you measured something for 20 minutes and it was only up for 19 of them, you’d have 95% availability.
Avast! avast! Antivirus is an antivirus program developed by ALWIL Software a.s., a company based in Prague, Czech Republic. It was first released in 1988. Avast! is based on a central scanning engine that is certified by ICSA Labs[1] and West Coast Lab's Checkmark process[2] and incorporates anti-spyware technology, also certified by West Coast Lab's Checkmark process,[3] as well as anti-rootkit and self-protection capabilities. It is a multiple recipient of the Virus Bulletin VB100 Award, for detection of 100% of "in-the-wild" viruses,[4] and is a past winner of the Secure Computing Readers' Trust Award.[5] Avast! Free Antivirus is the freeware version of Avast! antivirus software available to Microsoft Windows and Linux users, while Avast! Pro Antivirus is offered to businesses and users that want additional features. Priority updates are delivered automatically using PUSH update technology in Avast! Pro Antivirus. Avast! Pro Antivirus also has a command line scanner and a script blocker.
Avatar An avatar is an online character that represents a person. For example, games like World of Warcraft and the Sims Online allow players to create custom characters, known as avatars. Players can control their avatars and interact with other players in an online world. An avatar may also refer to the icon and username that a user chooses when registering for a website or online discussion forum. The avatar name and image typically shows up next to any contributions the user makes on the website.
Avocent Avocent Corporation (NASDAQ: AVCT) is an information technology products manufacturer headquartered in Huntsville, Alabama. Avocent was formed in 2000 from the merger of the world’s two largest KVM (keyboard, video and mouse) switch manufacturers: Apex and Cybex Computer Products Corporation. Product Ranges Avocent focuses on out of band infrastructure management solutions within 8 major fields: Server Management Power Management Service Processor Management Console Server and KVM Management Desktop Management ITIL market IT Service Management Service Desk
BACK / FORWARD Buttons in most browsers' Tool Button Bar, upper left. BACK returns you to the document previously viewed. FORWARD goes to the next document, after you go BACK.
Back-end A type of program or process that is not directly accessed by a user. Often it will carry out its tasks independently of the front-end or user interface. For example, a user could request data from a database, not knowing that the data is refreshed on the back-end on a daily basis.
Backbone A high-speed line or series of connections that forms a major pathway within a network. The term is relative as a backbone in a small network will likely be much smaller than many non-backbone lines in a large network.
Backdoor A backdoor is a tool installed after a compromise to give an attacker easier access to the compromised system around any security mechanisms that are in place.
Backplane As opposed to standard cabling schemes where flexible wires are used, a backplane refers to a rigid circuit board that will support higher connection speeds and more logic. For example, many SCSI systems today ship with small SCSI backplanes because the transfer rate of SCSI is getting high enough that standard cables are causing problems when connecting devices. Another example of a backplane is in network connection devices, such as large enterprise scale switches, routers, or PBXs. Some of these devices have a high- speed backplane, and you can plug a group of slower network connection devices into the high-speed backplane.
Backup Backup 1. A recovery system or means to recover in the event of a disaster. 2. To take a copy of files (directories or data) so that these can be restored later if needed. Backups should always be taken regularly to protect against accidental deletion of files or hardware failure. Many applications generate a backup file as they work. For example most work processors can be configured to generate a backup file of the document they are working on, allowing the previous version to be recovered if necessary. However this type of backup will not protect against hardware failure, if the disk fails then you loose your original and the backup. A good backup scheme will ensure that files are copied to a separate medium (such as cd or tape) and physically moved to a different area, ideally to a different site. Moving a backup (or a copy of a backup) to an offsite location is referred to as an "offsite backup", and the advantage of maintaining an "offsite backup" is that it allows files to be recovered in the event of a disaster such as a fire that may destroy the entire building. 3. The copy of a file (or set of files or data) that has been taken. A backup may therefore be the copy of a file or it may refer to a disk, cd or tape that contains files (or data) that have been backed up.
Backup Mail Server A secondary email server to which emails are delivered should the primary email server be offline. A backup email server will then forward emails to the primary email server once the primary email server comes back on-line. When an email server is down most sending email servers will retain the email and try sending again later. Generally most servers will give up and issue a non-delivery notification (NDR) to the sender after about two days (the actual time varies between servers). So even without a backup mail server emails will normally be delivered if the mail server is down for a short period of time. A backup mail server provides resilience where: The sending server has a very short timeout before giving up and issuing an NDR. The server will be down for a long period - as a guide anything over a day or so. In these scenarios a backup mail server will receive emails and ensure that they are delivered once the primary mail server comes back on-line. cf SMTP, MX Record.
Balance The control for the level of sound coming out of the left or right speakers. If you turn the balance control all the way in either direction, you can isolate the sound to the left or right channel, which helps in troubleshooting whether both speakers are connected properly. Other than that, the balance control can fine-tune volume levels to compensate for sound conditions in the room.
Bandwidth The amount of data that can be transmitted in a fixed amount of time. cf bps.
Banner Ad Whether you like it or not, much of the Web is run by advertising. Just like television or radio, websites can offer free content by generating revenue from advertising. While you may get tired of Web ads from time to time, most people would agree that seeing a few advertisements here and there is better than paying a usage fee for each website. Perhaps the most prolific form of Web advertising is the banner ad. It is a long, rectangular image that can be placed just about anywhere on a Web page. Most banner ads are 468 pixels wide by 60 pixels high (468x60). They may contain text, images, or sometimes those annoying animations that make it hard to focus on the page's content. Regardless of the type of banner ad, when a user clicks the advertisement, he or she is redirected to the advertiser's website.
Bare metal environment A virtual environment where the virtualization product is directly installed on physical hardware, acting like a host OS. The opposite of hosted environment.
Baseband A baseband signal is an original transmission signal that has not be modulated, or has been demodulated to its original frequency. Most telecommunications protocols require baseband signals to be converted, or modulated, to a higher frequency so they can be transmitted over long distances. Therefore, the original baseband, or lowpass, signals are converted during the transmission process. When the signal arrives at the destination, it is demodulated so that the recipient receives the original baseband signal. Ethernet is an example of a protocol that does not require signal modulation, since it transmits data in baseband. Example: "Baseband signals must be modulated to higher frequencies for radio transmission."
BASIC Beginners All-purpose Symbolic Instruction Code. A high level programming language which has been widely used, particularly since the advent of personal computers. Originally an unstructured programming language, the language has been adapted over the years to encompass new programming paradigms.
Basic Authentication Basic Authentication is the simplest web-based authentication scheme that works by sending the username and password with each request.
Batch File A batch file is a type of script that contains a list of commands. These commands are executed in sequence and can be used to automate processes. For example, some programs may include a batch file that executes a number of commands as the program starts up. A user can also create a custom batch file to automate tedious processes such as copying multiple directories or renaming several files at once. Batch files are run by the COMMAND.COM program, which is part of DOS and Windows. Therefore, batch files can only be run within the Windows operating system. Macintosh and Unix have other scripting tools, such as AppleScript and Unix shell commands, that can be used for similar tasks. Because batch files contain executable commands, it is important not to open unknown batch files on your hard disk or in e-mail attachments. File Extensions: .BAT, .CMD
Baud In common usage the "baud" of a modem is how many bits it can send or receive per second. Technically, baud is the number of times per second that the carrier signal shifts value - for example a 1200 bit-per-second modem actually runs at 300 baud, but it moves 4 bits per baud (4 x 300= 1200 bits per second).
BBL Online speak for “Be Back Later”
BBS 1. Bulletin Board System. A system for storing information and messages that can be accessed by other computers. Typically accessed by dial-up, Bulletin Boards pre-date the internet. Bulletin Board Systems were a forerunner to Forums. 2. Chat abbreviation for: Be Back Soon.
Bcc (Blind Carbon Copy) Stands for "Blind Carbon Copy." When you send an e-mail to only one person, you type the recipient's address in the "To:" field. When you send a message to more than one person, you have the option to enter addresses in the "Cc:" and "Bcc:" fields. "Cc" stands for "Carbon Copy," while "Bcc" stands for "Blind Carbon Copy." A carbon copy, or "Cc'd" message is an e-mail that is copied to one or more recipients. Both the main recipient (whose address is in the "To:" field) and the Cc'd recipients can see all the addresses the message was sent to. When a message is blind carbon copied, neither the main recipient nor the Bcc'd recipients can see the addresses in the "Bcc:" field. Blind carbon copying is a useful way to let others see an e-mail you sent without the main recipient knowing. It is faster than sending the original message and then forwarding the sent message to the other recipients. It is also good netiquette to use Bcc when copying a message to many people. This prevents the e-mail addresses from being captured by someone in the list who might use them for spamming purposes. However, if it is important that each recipient knows who your message was sent to, use carbon copy (Cc) instead.
BCP 1. Best Current Practice. 2. Bridging Control Protocol. 3. Bulk Copy Process (or Bulk Copy Program). A utility provided with SQL Server databases for bulk copying of data, such as between a database and a file. 4. Business Continuity Plan. A contingency plan covering how a business should recover from potential disasters disaster and continue functioning. More commonly known as a disaster recovery plan (DRP).
BDC (backup domain controller) One or more computers running Windows NT that act as a backup to the primary domain controller (PDC). These machines can authenticate security requests just like the primary domain controller, and will take over for the PDC if it is not available. However, a BDC will remain a BDC until it is manually promoted to a PDC by a domain administrator. With Active Directory Windows no longer requires the sometimes confusing primary and backup domain controllers, just domain controllers instead.
Beep 1. Blocks Extensible Exchange Protocol. A set of building blocks for creating customised protocols.
Beep Code When you turn on your PC–and all is well–you typically hear a single beep from your computer speaker, signaling that all is OK. If things are wrong–and the computer BIOS senses that things are wrong–a series of beeps will be emitted. This is the beep code. Based on the number of beeps, you can look up the meaning in your motherboard documentation and often diagnose the problem. Obvious things to check are whether your video card, processor, and/or memory are plugged in and seated properly.
Benchmarking The process of measuring the performance of hardware or software in a specifically defined and strictly controlled environment. The benchmarking result is usually represented by a time or number rating that corresponds to how quickly certain tasks can be completed. The benchmark must be reproducible, of course, to have any meaning.
Beta A term given to a product that isn’t ready for public consumption, but is good enough for a wider testing scope. Many companies publicly release their beta software to a fraction of their users to let them get experience with the new software while the company gets feedback on bugs and features. Also see Alpha
BGP Border Gateway Protocol
Binary Information consisting entirely of ones and zeros. Also, commonly used to refer to files that are not simply text files, e.g. images.
Binary code Binary consists of a string of bits, with bits represented by 1s and 0s, e.g., 01010111000000001. The “bi” refers to base 2 mathematical representation (1s and 0s).
Binary Translation (BT) Technique used by virtualization softwares to translate instruction set guest OSes send to virtual hardware in instruction set understandable by physical hardware. It's an alternative approach to paravirtualization.
BIND Berkley Internet Name Domain.
Binhex A method for converting non-text files (non-ASCII) into ASCII. This is needed because Internet e-mail can only handle ASCII.
Biometrics Biometrics use physical characteristics of the users to determine access.
BIOS Basic Input/Output System. The BIOS provides an interface between a computer's operating system and the computer's hardware. Unlike the operating system the BIOS is built into the computer and thus is always available. Many computers hold the BIOS in Flash and allow it to be upgraded. The BIOS will normally perform various diagnostic tests straight after power-up (see POST). At this point it is usual for a BIOS to allow you to enter a "BIOS Screen" to configure aspects of the BIOS (not every BIOS supports this). Whilst each BIOS may have a different way of invoking its "BIOS Screen" and the correct method should be stated in the manual, the following key combinations (at start-up) are common: DEL F2 F1
Bit Binary digIT. The fundamental unit of binary notation and storage. 0 (off) or 1 (on). There are 8 bits to a byte.
Bit rate An alternate name for bits per second (bps).
BitTorrent BitTorrent is a peer-to-peer (P2P) file sharing protocol designed to reduce the bandwidth required to transfer files. It does this by distributing file transfers across multiple systems, thereby lessening the average bandwidth used by each computer. For example, if a user begins downloading a movie file, the BitTorrent system will locate multiple computers with the same file and begin downloading the file from several computers at once. Since most ISPs offer much faster download speeds than upload speeds, downloading from multiple computers can significantly increase the file transfer rate. In order to use the BitTorrent protocol, you need a BitTorrent client, which is a software program that accesses the BitTorrent network. The client program allows you to search for files and begin downloading torrents, which are in-progress downloads. Most BitTorrent clients allow you to resume torrents that have been paused or stopped. This can be especially helpful when downloading large files.
BL 1. Black List. See Blacklist for details. 2. Boundary Layer. In a GIS context a boundary layer is a feature layer on a map which contains boundaries (for example district or regional boundaries). In other contexts a boundary layer is the surface on which two boundaries meet. For example the surface of the sea is the boundary layer between sea-water and air. 3. Back Link. A link to a web page from another. Back links represent those pages (or specifically the links on those pages) that link to a given page. Back Links are also known as inbound links. 4. Block List. A list of IP addresses from which email addresses should be blocked. See DNSBL for details.
Black hat A malicious hacker. If a hacker finds a security hole and exploits it or lets others know about it before letting the people affected by the hole know about it, that hacker is described as a black hat hacker. This term comes from cowboy movies, where the bad guy would wear a black hat.
Blacklist Blacklist A list of disapproved people, companies or items. Companies may refuse to deal with individuals or other companies that have been blacklisted. SPAM filters will often maintain a blacklist, which holds e-mail addresses from which any e-mail is to be considered SPAM. Also sometimes referred to as a "Stop List". Sometimes abbreviated to simply BL.
Blade A hot-pluggable motherboard, equipped with processors, memory and disks for use in a Blade Server.
Blade Server An emerging modularized server configuration made by a standard rack featuring an embedded networking subsystem and several bays, where blades can be plugged while the system is turned on.
Block Cipher A block cipher encrypts one block of data at a time.
Block Mode A setting in the computer BIOS relating to IDE hard drives. The setting determines the type of Logical Block Addressing that will be used to translate large hard drives properly to the computer BIOS. On most machines with up-to-date BIOSes, you can set this to “Auto” and have hard drives recognized with no further specification on your part. If that doesn’t work, you may need to tinker with other settings or use the software provided by the hard drive manufacturer for software translation.
BLOG or WEB LOG A blog (short for "web log") is a type of web page that offers a series of posted items (short articles, photos, diary entries, etc.). Blogs usually include a searchable archive of old postings. Blogs have become a common medium for communication in professional, political, news, trendy, and other specialized web communities. Many blogs provide RSS feeds, to which one can subscribe and receive alerts to new postings in selected blogs.
Blu-ray Blu-ray is an optical disc format such as CD and DVD. It was developed for recording and playing back high-definition (HD) video and for storing large amounts of data. While a CD can hold 700 MB of data and a basic DVD can hold 4.7 GB of data, a single Blu-ray disc can hold up to 25 GB of data. Even a double sided, dual layer DVD (which are not common) can only hold 17 GB of data. Dual-layer Blu-ray discs will be able to store 50 GB of data. That is equivalent to 4 hours of HDTV. Blu-ray discs can hold more information than other optical media because of the blue lasers the drives use. The laser is actually blue-violet, but "Blu-ray" rolls off the tounge a little easier than "Blu-violet-ray." The blue-violet laser has a shorter wavelength than the red lasers used for CDs and DVDs (405nm compared to 650nm). This allows the laser to focus on a smaller area, which makes it possible to cram significantly more data on a disc the same size as a CD or DVD. Proponents of the Blu-ray format say they expect Blu-ray devices to replace VCRs (thank goodness) and DVD recorders as more people make the transition to HDTV.
Bluetooth This wireless technology enables communication between Bluetooth-compatible devices. It is used for short-range connections between desktop and laptop computers, PDAs (like the Palm Pilot or Handspring Visor), digital cameras, scanners, cellular phones, and printers. Infrared once served the same purpose as Bluetooth, but it had a number of drawbacks. For example, if there was an object placed between the two communicating devices, the transmission would be interrupted. (You may have noticed this limitation when using a television remote control). Also, the Infrared-based communication was slow and devices were often incompatible with each other. Bluetooth takes care of all these limitations. Because the technology is based on radio waves, there can be objects or even walls placed between the communicating devices and the connection won't be disrupted. Also, Bluetooth uses a standard 2.4 GHz frequency so that all Bluetooth-enabled devices will be compatible with each other. The only drawback of Bluetooth is that, because of its high frequency, its range is limited to 30 feet. While this is easily enough for transferring data within the same room, if you are walking in your back yard and want to transfer the address book from your cell phone to your computer in your basement, you might be out of luck. However, the short range can be seen as a positive aspect as well, since it adds to the security of Bluetooth communication.
BMP Bitmap file; a common image format on Windows computers. Files of this type usually have the suffix ".bmp" as part of their name.
Bookmark Similar to a real-life bookmark, an Internet bookmark acts as a marker for a Web site. (In Internet Explorer, they're called "Favorites".) When using a Web browser, you can simply select a bookmark from the browser's Bookmarks menu to go to a certain site. This way, you don't have to go through the redundant process of typing in the Internet address each time you visit one of your favorite sites. Also, who remembers those 200-character addresses anyway? In most browsers, to create a bookmark, you simply choose "Add Bookmark" from the Bookmarks menu when you're at a page that you'd like to bookmark. Woah, four "bookmarks" in one sentence. That's what happens with words that serve as both nouns and verb. So, now that you know how to create a bookmark, be sure to bookmark this website! =)
Boolean This is the logic that computers use to determine if a statement is true or false. There are 4 main boolean operators: AND, NOT, OR, and XOR. Below are some examples of how the 4 operators work: x AND y retuns True if both x and y are true, otherwise the expression returns False. NOT x returns True if x is false (or null) and False if x is true. x OR y returns True if either x or y or both are true; only if they are both false will it return False. x XOR y returns True if either x or y are true, but not both. If x and y are both true or false, the statement will return False. While boolean expressions are what drive the CPUs in computers, they can also be used by computer users. For example, when searching for information on the Web, many search engines accept boolean operators in the search phrases (i.e. "Yamaha AND piano NOT motorcycle"). Programmers often use boolean expressions in software development to control loops and variables as well.
Boot When you boot a football, you kick it really far. When you boot a computer, you simply turn it on. Kicking your computer really far is not recommended, though you may be tempted to do so at times. The term "boot" comes from the word "bootstraps," which people at one time used to get their boots on. Likewise, "booting" a computer gets it up and running. In simple terms, to boot a computer is to turn it on. Once the computer's power is turned on, the "boot process" takes place. This process involves loading the startup instructions from the computer's ROM, followed by loading the operating system from the current boot disk. The boot disk is usually an internal hard drive, but can also be an external drive, a CD or DVD-ROM, or even a floppy disk. Once the operating system software is loaded, the boot process is complete and the computer is ready to be used.
Boot Disk A boot disk is actually not a computer disk in the shape of a boot. If it was, most disk drives would have a difficult time reading it. Instead, a boot disk is a disk that a computer can start up or "boot" from. The most common type of boot disk is an internal hard drive, which most computers use to start up from. The operating system installed on the hard drive is loaded during the boot process. However, most computers allow you to boot from other disks, including external Firewire hard drives, CD-ROMs, DVD-ROMs, and floppy disks. In order to function as boot disks, these disks need to have an operating system installed that is understandable by the computer. This can either be a full-blown operating system like Windows or Mac OS X, or a small utility operating system, such as Norton Utilities or DiskWarrior. CD and DVD boot disks are often used to start up a computer when the operating system on the internal hard drive won't load. This can happen when bad data blocks or other errors occur on the disk. By running a disk repair utility from the CD or DVD, you can often fix the hard drive and restart from it, using the full operating system.
Boot Record (Master Boot Record) The first sector on a hard disk or other disk media. When a computer boots up it searches for a master boot record wherever the BIOS tells it to (usually the master hard drive on the first IDE channel, but this can also be checked for in CD/DVD drives and floppy drives) and, based on what the master boot record says, loads up an operating system. Thus, if the master boot record becomes corrupt or is tampered with by a virus, it can cause your computer to be unable to boot.
Boot Record Infector A boot record infector is a piece of malware that inserts malicious code into the boot sector of a disk.
Boot Sector boot sector is the first section of a hard drive or other data storage media. It contains the master boot record (MBR) which is accessed by the computer during the boot sequence. The boot sector may also include a partition map, which defines each disk partition.
Boot Sequence Each time a computer boots up, it goes through an initial series of processes. This sequence of events is aptly named a "boot sequence." During the boot sequence, the computer activates the necessary hardware components and loads the appropriate software so that a user can interact with the machine. The boot sequence starts by accessing the the computer's BIOS on Windows PCs or the system ROM on a Macintosh. The BIOS and ROM contain basic instructions that tell the computer how to boot up. These instructions are then passed to the computer's CPU, which begins loading information into the system RAM. Once a valid boot disk or startup disk is found, the computer begins loading the operating system into the system memory. After the operating system finishes loading, the computer is ready to be used. The boot sequence can take anywhere from a few seconds to several minutes, depending on the computer's configuration. If the system is booting from a CD or DVD, the boot time may be significantly longer than if the computer is booted from a hard drive. Also, if your computer was turned off unexpectedly, the boot time might increase since the system may perform some additional checks to make sure everything is OK.
BootP (Bootstrap Protocol) This protocol is the basis for DHCP. It allows a client computer to receive an IP address from a BootP server without having a static IP address defined beforehand on the client machine.
Bootstrap This either refers to a small piece of intermediate code that will boot up an operating system, or the act of building something without help. See also Bootstrapping
Bootstrap Protocol (BootP) his protocol is the basis for DHCP. It allows a client computer to receive an IP address from a BootP server without having a static IP address defined beforehand on the client machine.
Bootstrapping (v. to bootstrap) The process of developing something without reliance on outside help such as investor money. It’s referred to often today, and often in the Dot-Com heyday, to describe website designers and entrepreneurs who effectively start their own companies on the Web with only their own investment.
Border Gateway Protocol (BGP) The protocol used by the core routers on the Internet to route TCP/IP packets. BGP replaces the older Exterior Gateway Protocol. Core routers use BGP exchange routing information to determine optimal routing paths and also exchange TCP/IP data packets.
Bot hort for web-robot, search-bot, robot or info-bot. A program that searches (trawls) the internet for information. Search engines use bots (search-bot) to gather information that the search engine uses to respond to search queries. A harvester-bot is used spammers to harvest e-mail addresses from web pages.
Bottleneck Part of a system that limits the performance of the system. This term was derived from the neck of a bottle, which limits the flow of liquid due to the smaller circumference of the neck as compared to the wider body of the bottle. Often you will hear of people attempting to find and eliminate the bottlenecks in their computer systems or networks. This is certainly a helpful practice if the bottleneck is slowing things down inordinately, but as soon as you remove one bottleneck from a system remember that something else immediately becomes the bottleneck. For example, if you get a faster processor to speed up your 3D video, the 3D video card may be the bottleneck afterwards.
Bounce The term "bounce" has several different IT related meanings, yet none of them include bouncy balls. The most common definition of bounce used in the computer world refers to e-mail messages. 1. Returning E-mail When you send an e-mail message to another person, the mail server processes the message and delivers it to the appropriate user's mailbox. For example, if you send a message to "mrman@mail.com," the mail.com server looks for a user named "mrman" to deliver the message to. If the user does not exist, the mail server may bounce the message back to the sender, saying "Sorry, that user does not exist." These messages often come from "Mail Delivery Subsystem" and have a subject line that reads "Returned mail: see transcript for details." If you receive a bounced message, you may want to check the e-mail address you sent the message to and make sure it was typed correctly. If the address is correct, it may help to read the body of the bounced message for more details. The transcript may say something like "User quota over limit," which means the recipient has reached his or her e-mail quota and must delete some messages and/or attachments in order to receive new mail. If this is the case, you may want to call the person or use an alternative e-mail address to let the person know he or she has some Inbox maintenance to do. 2. Restarting a Computer The term "bounce" can also describe the process of rebooting or restarting a computer. For example, a workstation may need to be bounced after installing new software. Similarly, a Web server may be bounced if websites hosted on the server are not responding correctly. 3. Exporting Audio "Bounce" can also describe the process of exporting several tracks in an audio mix to one mono track or two stereo tracks. This helps consolidate audio tracks after they have been mixed. Bouncing audio tracks limits the need for processing power since the computer only has to process one track instead of all the tracks individually. Digital Performer is the primary audio software program that uses bouncing to export audio. 4. Hiding a Network Connection Finally, "bouncing" can also be used in networking to describe a method of hiding the source of a user's network connection. This type of bouncing is often abbreviated "BNC." Someone who bounces his network connection is called a "bouncer," though this is not the same person who checks your ID at the bar.
Boxed Processor A microprocessor that is sold singly in a retail box, like something you would buy at a store. This compares to just buying a processor that some OEM takes out of a bulk box of 1,000 processors and throws in a static bag for you to take home. Boxed processors typically come with multi-year warranties directly from the manufacturer.
BPS Bits Per Second. Also known as bit rate. Used when specifying connection speeds across networks. When calculating the maximum throughput across a network remember that network communications itself has some overhead, so as a rule of thumb therefore divide by 10 to get the number of bytes that this equates to. For typical connection speeds this equates to: Speed Maximum achievable throughput 28.8Kbps 2.8 K-bytes per second 56Kbps 5.6 K-bytes per second 10Mbps 976 K-bytes per second (almost 1MB a second) 100Mbps 9.5 M-bytes per second (almost 10MB a second) Actual throughput rates may be less than this because of other factors such as other network traffic.
BRB Online speak for “Be Right Back”
Brick and Mortar A store or business that either doesn’t have a Web presence or has mainly physical locations as opposed to websites. Bricks and mortar are common building materials.
Bridge When a road needs to extend across a river or valley, a bridge is built to connect the two land masses. Since the average car cannot swim or fly, the bridge makes it possible for automobiles to continue driving from one land mass to another. In computer networking, a bridge serves the same purpose. It connects two or more local area networks (LANs) together. The cars, or the data in this case, use the bridge to travel to and from different areas of the network. The device is similar to a router, but it does not analyze the data being forwarded. Because of this, bridges are typically fast at transferring data, but not as versatile as a router. For example, a bridge cannot be used as a firewall like most routers can. A bridge can transfer data between different protocols (i.e. a Token Ring and Ethernet network) and operates at the "data link layer" or level 2 of the OSI (Open Systems Interconnection) networking reference model.
Bridged networking A type of network connection between a virtual machine and the rest of the world. Under bridged networking, a virtual machine appears as an additional computer on the same physical Ethernet network as the host. See also Host-only Networking.
Broadband Generally refers to connections to the Internet with much greater bandwidth than you can get with a modem. There is no specific definition of the speed of a "broadband" connection but in general any Internet connection using DSL or a via Cable-TV may be considered a broadband connection.
Broadcast To simultaneously send the same message to multiple recipients. One host to all hosts on network.
Broadcast Address An address used to broadcast a datagram to all hosts on a given network using UDP or ICMP protocol.
Browser Short for Web browser, a software application used to locate and display Web pages. The two most popular browsers are Microsoft Internet Explorer and Firefox. Both of these are graphical browsers, which means that they can display graphics as well as text. In addition, most modern browsers can present multimedia information, including sound and video, though they require plug-ins for some formats.
browser sniffing Browser sniffing describes the process by which a Web site detects which versions of various browsers users are running, in order to determine whether or not they can access certain Web site features. Browser sniffing--usually accomplished with JavaScript--can also be used to detect whether or not a user has a specific plug-in required to access the site (such as Macromedia's Flash or RealNetworks' RealPlayer).
Brute Force A cryptanalysis technique or other kind of attack method involving an exhaustive procedure that tries all possibilities, one-by-one.
BSOD Blue Screen of Death Terminal error screen displayed by Microsoft Windows, not normally recoverable except by a reboot. Also known as BSOD or a Stop Screen. A blue screen will display a STOP error code, which may give some indication as to the cause. Relevant links:
BSOD (Blue/Black Screen of Death) A Windows error message that is shown on a screen with a blue background. In Windows NT/2000/XP, this type of message causes the computer to stop completely, and is usually caused by improperly written hardware drivers or faulty hardware. Other BSODs can occur in different versions of Windows (95/98/Me) as well, but are not always as disastrous. Less frequently, black screens of death (also BSOD) are referred to as well during a complete system crash which may or may not have anything to do with the Windows OS.
BSSID Basic Service Set Identification. The BSSID is the identifying name of an ad-hoc wireless network. BSSID is one type of SSID (the other being ESSID).
BST British Summer Time. In the UK, the period between the last Sunday in March through to the last Sunday in October when the clocks are moved forward by one hour (at 1am in the morning). cf GMT and DST. BST = GMT + 1, so 16:00 GMT = 17:00 BST.
BTU British Thermal Unit. One BTU is defined as the energy required to increase the temperature of one pound of water by one degree Fahrenheit. BTUs are typically used to rate air conditioners (and some heaters). To convert from BTUs to KWs: use 1 watt = 3.4129BTUs. This means that for typical air-conditioners: BTUs approx watt equivalent 6000 1.8KW 8000 2.3KW For air conditioners (AC) the typical power consumption will be less than half their cooling rating. As a guide: 1 person approximates to 500 BTU and likewise one PC approximates to 500 BTU.
BTW Abbreviation: By The Way.
Buffer buffer contains data that is stored for a short amount of time, typically in the computer's memory (RAM). The purpose of a buffer is to hold data right before it is used. For example, when you download an audio or video file from the Internet, it may load the first 20% of it into a buffer and then begin to play. While the clip plays back, the computer continually downloads the rest of the clip and stores it in the buffer. Because the clip is being played from the buffer, not directly from the Internet, there is less of a chance that the audio or video will stall or skip when there is network congestion. Buffering is used to improve several other areas of computer performance as well. Most hard disks use a buffer to enable more efficient access to the data on the disk. Video cards send images to a buffer before they are displayed on the screen (known as a screen buffer). Computer programs use buffers to store data while they are running. If it were not for buffers, computers would run a lot less efficiently and we would be waiting around a lot more.
Buffer Overflow A buffer overflow occurs when a program or process tries to store more data in a buffer (temporary data storage area) than it was intended to hold. Since buffers are created to contain a finite amount of data, the extra information - which has to go somewhere - can overflow into adjacent buffers, corrupting or overwriting the valid data held in them.
Buffer underrun An error that can occur data is recorded onto CDs, when the data stream falls behind the laser that's burning the CD. Usually buffer underrun results from poor CD recording software, a slow computer, or a recordable-CD drive with insufficient buffer memory.
Buffer Zone An area around a feature (i.e. the area around a point, a line, a poly-line or an area).
Buffered memory Memory modules that have extra chips on them to support Error Checking and Correcting (ECC) functionality.
Burn When you "burn a disc," you write data on it. If you were taking an SAT test, the analogy would look something like this: Hard Disk : Write :: CD/DVD : Burn The reason the term "burn" is used is because the CD-writer, or burner, literally burns the data onto a writable CD. The laser in a CD-writer can be cranked up to a more powerful level than an ordinary CD-ROM laser. This enables it to engrave thousands of 1's and 0's onto a CD. So that is why people talk about "burning" songs or files to CDs. They could just say they are "writing" the data to a CD, and it would make sense, but people seem to think "burning" sounds cooler.
Bus The computer's primary bus is called the frontside bus and connects the CPU to the rest of the components on the motherboard. Expansion buses, such as PCI and AGP, allow data to move to and from expansion cards, including video cards and other I/O devices. While there are several buses inside a computer, the speed of the frontside bus is the most important, as it determines how fast data can move in and out of the processor.
Bus Topology This network topology has computers connected to a strand of network cabling that is connected to network repeaters at one end and terminated at the other. If you break part of the cable or remove the terminator, all machines on that segment lose communication with the network. 10Base2 was a widely used bus topology network in its day.
Business to Consumer (B2C) A form of doing business that deals with selling goods and services to the consumer marketplace. Examples of this would be selling consumer electronics, toys, or pet supplies. This contrasts with the business to business model.
Byte In computing a byte is the basic unit of storage. A byte is a logical collection of 8 binary bits. A byte can therefore store a single integer value from 0 to 255. Collections of bytes can store larger number ranges or be used to represent other forms of data. Half a byte is a nibble, other common names given to collections of bytes are: Name Number of bytes nibble 2-1 0.5 byte 20 1 word 21 or 22 2 or 4 dword 22 4 kilobyte 210 1024 megabyte 220 1,048,576 gigabyte 230 1,073,741,824 terabyte 240 1,099,511,627,776 petabyte 250 1,125,899,906,842,624 exabyte 260 1,152,921,504,606,846,976 zettabyte 270 1,180,591,620,717,411,303,424 yottabyte 280 1,208,925,819,614,629,174,706,176
C/C++ C is a high-level programming language that was developed in the mid-1970s. It was originally used for writing Unix programs, but is now used to write applications for nearly every available platform. Compared to most previous languages, C is easier to read, more flexible (can be used for a wide variety of purposes), and more efficient at using memory. C++, pronounced "C plus plus," is a programming language that was built off the C language. The syntax of C++ is nearly identical to C, but it has object-oriented features, which allow the programmer to create objects within the code. This makes programming easier, more efficient, and some would even say, more fun. Because of the power and flexibility of the language, most software programs today are written in C++.
CA Certificate Authority.
Cab file (cabinet file) A compressed file with the extension .cab. Cabinet files are used to store installation files for Microsoft applications, most commonly Windows 9x operating systems and Internet Explorer. Cab files were initially designed to fit large installations onto a group of 1.44 MB floppy disks.
Cabinet file (cab file) A compressed file with the extension .cab. Cabinet files are used to store installation files for Microsoft applications, most commonly Windows 9x operating systems and Internet Explorer. Cab files were initially designed to fit large installations onto a group of 1.44 MB floppy disks.
Cable Modem A modem for use with cable systems. Offers much higher data rates than conventional analogue modems. Where a cable modem has LEDs on the front, these are typically one or more of: LED Short for Description PWR Power Power on indicator. USB USB Indicates activity on USB connection. ENET Ethernet Indicates activity on Ethernet connection. U/S Up Stream D/S Down Stream SYNC RDY Ready Indicates that the modem is ready for normal use. Off indicates that it is performing its self test or that there is a fault.
Cable Select (CSEL) This is basically Plug-and-Play ATA. You plug in your ATA/IDE hard drives, set them to CSEL (Cable Select), and they determine whether they are master or slave automatically, saving you from manual configuration.
Cache A memory store used to hold a copy of data, to improve the apparent speed of computer components including processors, disk drives, graphics cards etc. Where data is available in the cache it is retrieved from the cache instead of the device. For example most processors contains a memory cache with faster access than main memory, data that is available in the cache is therefore available to the processor much faster than it would be if it had to go to main memory to retrieve the data. Information available in a disk cache can be returned almost instantly whilst data that is not available in the cache would need to be read from the physical disk and this would be magnitudes slower. cf buffer. It is common for a cache to use a LRU algorithm to determine which item to remove from the cache when new data needs to be loaded into the cache. However there are other algorithms that some caches use, for example discarding the oldest item or an algorithm based on the frequency of use.
Cache Cramming Cache Cramming is the technique of tricking a browser to run cached Java code from the local disk, instead of the internet zone, so it runs with less restrictive permissions.
Cache memory Generally a small chunk of fast memory that sits between either 1) a smaller, faster chunk of memory and a bigger, slower chunk of memory, or 2) a microprocessor and a bigger, slower chunk of memory. The purpose of cache memory is to provide a bridge from something that’s comparatively very fast to something that’s comparatively slow. Most microprocessors have built-in cache memory that holds some of the information from main memory. When the processor needs the information it takes it from the speedy cache instead of the slower main memory. Cache memory GREATLY increases the speed of a computer by storing data that is most often accessed.
Cache Poisoning Malicious or misleading data from a remote name server is saved [cached] by another name server. Typically used with DNS cache poisoning attacks.
CACHED LINK In search results from Google, Yahoo! Search, and some other search engines, there is usually a Cached link which allows you to view the version of a page that the search engine has stored in its database. The live page on the web might differ from this cached copy, because the cached copy dates from whenever the search engine's spider last visited the page and detected modified content. Use the cached link to see when a page was last crawled and, in Google, where your terms are and why you got a page when all of your search terms are not in it.
Caching To make us of a cache, for improved performance (i.e. typically to increase apparent speed).
CAD Stands for "Computer-Aided Design." Also known by engineers and architects as the best invention of all time. Today, CAD software is used for nearly all three-dimensional designing. Designers can turn an object into an electronic representation more quickly and accurately than by diagraming it with a pencil and paper. Better yet, objects created with CAD software can be moved, resized, and rotated instantly. With a pencil and paper, you can only erase so much before it starts to smudge.
CAL 1. Client Access License. 2. Computer Aided Learning or Computer Assisted Learning.
Camera RAW Most digital cameras process and compress the pictures you take immediately after capturing the image. This can be helpful, as it keeps the file sizes low (using JPEG compression) and takes care of color correction, including white-balance, tint, and exposure, so you don't have to. However, some people, such as professional photographers, prefer to have more control over how each image is processed. Therefore, many high-end cameras have the ability to shoot in RAW mode. This mode does not compress the images at all and leaves them completely unprocessed. Because Camera RAW files are uncompressed, they take up more space than typical JPEG images. In fact, RAW files often require 2 to 3 times more space for each image captured. So, you'll want to have an extra-large memory card in your camera if you plan on shooting in RAW mode. But since RAW photos are not compressed, you maintain the full quality of each image. This can make a noticeable difference when printing images, especially for large prints. Camera RAW files are also unprocessed, meaning all the photo processing is done on the computer. It is like taking a film negative to a dark room to be developed. The RAW file is the negative and the computer serves as the dark room. With a RAW file, you have complete control over the temperature adjustments (for white-balance), tint, hue, and exposure. However, since Camera RAW files are not typical images, most image-viewing programs will not open them. Therefore, most camera companies include Camera RAW editing software with their high-end cameras. These programs allow you to open RAW files, do the necessary processing, and save them in common image formats such as bitmap, TIFF, and JPEG. While shooting in Camera RAW mode offers a lot of control over your photos, it takes additional software and extra time to open and edit each picture you take. For most casual photography, using the camera's built-in processing is the most suitable option.
Capacitor An electronic component that stores up an electrical charge to a certain level and then releases it. A capacitor stores energy between two conducting plates separated by an insulator, or dialectric. Capacitance, or the amount of current that is stored, is measured in farads. You may notice large looking electronic cylinders on your motherboard. These are capacitors, and they are used to provide clean power to your processor. You’ll also find larger capacitors in your power supply. CRT televisions and monitors contain many capacitors, that’s why you are warned against opening up a CRT device or power supply even when it is off, as there may still be electrical energy in the capacitors.
Capacity Planning The operation of calculating how many resources a physical server will need for hosting a certain amount of virtual machines. It's a critical task to be achieved at very beginning of any virtualization project.
caps Upper-case letters. When you press the Caps Lock key on your keyboard, it makes everything you type upper-case. In the early days of computing, many computers had no way of representing lower-case and upper-case letters, but all computers today have that capability. You should avoid typing a message in all caps, because it makes the text harder to read.
Captcha A captcha is a challenge-response test that determines whether a user is human or an automated bot. A typical captcha includes an image of distorted text and a form field for the user to enter the text. Captchas are commonly found at the end of website forms, and must be filled out in order for the form to be submitted. By requiring users to decipher and enter the captcha text, webmasters can prevent automated programs from sending spam or other unwanted data through online forms.
Capture The process of copying digital information from the web to a repository for collection or archive purposes.
Cardbus The 32-bit PCMCIA card slot and cards that can work in this slot. Standard PCMCIA, or PC Card, slots were originally 16-bit slots. This caused problems when 100Mbit network cards and fast SCSI cards were used and throughput would not go high enough because the 16-bit slots were too slow.
CAS Code Access Security. The security mechanism used in the Microsoft CLR. CAS works by assigning trust levels (i.e. permissions) to software code (rather than the traditional model of assigning permissions by user).
CAT5 Category 5 Ethernet network cabling. The CAT5 standard allows for transmission speeds of up to 100mbps over distances of up to 100m. cf CAT5E, CAT6.
CAT5E Category 5 Ethernet network cabling. (CAT 5 Enhanced.) The CAT5E standard allows for transmission speeds of up to 1000mbps (giga-bit Ethernet). There is little real difference in the cabling standards between CAT5 and CAT5E, the standards for CAT5E being only a little more stringent over CAT5. CAT6 gives a more stringent standard for 1000mbps Ethernet network cabling.
CAT6 Category 6 Ethernet network cabling. The CAT6 standard allows for transmission speeds of up to 1000mbps (giga-bit Ethernet). CAT6 is similar to CAT5E, but to a higher standard. cf CAT5E.
CC 1. Carbon Copy. An e-mail or memo that is CC'd to someone is copied to that person, with all the recipients of the e-mail or memo seeing the person named on the distribution list. cf BCC. 2. Continuity Check. 3. C Compiler. cc is the name of a C language compiler available on most Unix systems. 4. Credit Card. Any credit card. 5. Conditional Compilation. A software language construct which allows blocks of code to be included or excluded at compile time. Software which is conditionally compiled out, will not then exist in the resultant library or executable. 6. Conditional Comments. Comments embedded in HTML that allow sections of the HTML to be included or excluded depending on a specified condition. Supported by Internet Explorer (IE), but not commonly supported by other browsers. 7. Cubit Centimeter. Also written as cm3. The SI-unit of volume, corresponds to the volume of a cube measuring 1cm on each side (i.e. the volume enclosed by the cube measuring 1cm x 1cm x 1cm). 1cc of water is also defined as equal to 1 gram of water. 8. Cubic Capacity. Term used when describing the volume of a cylinder in an engine (for example in a car engine). It is the available volume of the cylinder when the piston is pushed fully out. Also known as engine displacement. It should be appreciated that cubic capacity is a term and does not imply units. Cubic capacity is typically (but not always) expressed in cubic inches or cubic centimeters. 9. Closed Caption (or Closed Captioning). A system for encoding a text version of the dialog contained on a TV, film or computer presentation allowing the captions to be displayed for those who are hard of hearing. Closed Caption is encoded with the video. Video or DVD players which support closed caption allow the closed captions to be displayed as subtitles. In most contexts "Closed Caption" means the same as "Subtitles".
Cc (Carbon Copy) Stands for "Carbon Copy." The term comes from carbon copying, in which a piece of carbon paper copies writing from one paper to another (often used when filling out forms). However, the term is now commonly used in reference to e-mail. When you send an e-mail message, you typically type the recipient's address in the "To:" field. If you want to send the message to one or more other recipients, you can use the "Cc:" field to add additional addresses. This will send the e-mail to the address in the "To:" field and to each address listed in the "Cc:" field as well. The "Cc:" option is often used in business communications when a message is intended for one person, but is relevant to other people as well. For example, a retail employee may e-mail another employee saying he can work for her on a certain day. He might include his manager's and assistant manager's e-mail addresses in the "Cc:" field to let them know he is taking the work shift. Similarly, a team member working on a product design may e-mail his boss with the latest design revisions and may "Cc:" the other members of his team to let them know the e-mail has been sent. "CCing" (yes, it can also be used as a verb) is a quick way to let other people in on your e-mail communications. It is efficient because you don't have to send separate messages to each individual address. However, remember that When you Cc an e-mail, all the recipients can see the other addresses the message was sent to. If you want to hide the additional addresses, use Blind Carbon Copy (Bcc) instead.
CCD Charge Coupled Device. The image recording device inside a digital camera.
CCTV Closed Circuit Television. A television system where the camera and video monitor (or TV) are connected directly via cables and the camera signal is not broadcast for others to pick-up. CCTV is typically used for video monitoring and surveillance and used as part of a security system.
CD-R CD-Recordable. A recordable (normally write once) compact disc (CD), cf CD-RW.
CD-RW CD-Readable-Writable. A compact disc (CD) which can be recorded to and overwritten many times. cf CD-R.
CDP Server CDP Server 2.0 is a near continuous backup application for Windows and Linux computers, produced by R1Soft. CDP Server 2.0 provides user scheduled near continuous disk-based online backups for one or more Windows or Linux servers. Each time a user scheduled backup is performed, Delta encoding deltas are transmitted to a backup repository effectively creating a virtual Disk image. CDP Server can restore previously captured disk images to another disk effectively replicating the structure and contents to a new disk. Individual files inside of a disk image can be restored to their original location or an alternate computer. As of November 2008 the application is reported to be used on over 90,000 Linux servers.[4] Operation The first time the CDP Server application is used on a new backup target computer it creates a replica of all data and structure on disk to a disk-based backup repository. After this initial replica the CDP Server application uses a volume filter device driver to track block level deltas between scheduled synchronizations. The next scheduled backup operation involves creating a point in time snapshot and reading the deltas as tracked by the volume filter device driver. Synchronizations can be scheduled as frequently as every 15 minutes for an entire server.[4] CDP Server is known for its simple web based interface.[5] Microsoft Volume Shadow Copy Service is used on Windows to take a point in time snapshot. On Linux a proprietary Linux kernel module is used. [edit]Supported File Systems File systems supported by software:[6] NTFS ext2 ext3 ReiserFS Linux Swap Limitations CDP Server 2.0 can only backup disks or volumes less than or equal to 8TB in size.[7] Each disk is required to contain a valid partition table.[8] Bare-metal system restore can only be performed to the same hardware.
cell The box in a spreadsheet that occurs at each intersection of a row and column. You can use a cell to store text, number, formulas, or dates.
CentOS CentOS is a community-supported, free and open source operating system based on Red Hat Enterprise Linux. It exists to provide a free enterprise class computing platform and strives to maintain 100% binary compatibility with its upstream distribution.[1] CentOS stands for Community ENTerprise Operating System. Structure Red Hat Enterprise Linux is available only through a paid subscription service that provides access to software updates and varying levels of technical support. The product is largely composed of software packages distributed under open source licenses, and the source code for those packages is made public by Red Hat. CentOS developers use Red Hat's source code to create a final product very similar to Red Hat Enterprise Linux. Red Hat's branding and logos are changed because Red Hat does not allow them to be redistributed.[2] CentOS is available free of charge. Technical support is primarily provided by the community via official mailing lists, web forums, and chat rooms. The project is not affiliated with Red Hat and thus receives no financial or logistical support from the company; instead, the CentOS Project relies on donations from users and organizational sponsors.
Certificate An SSL certificate, or secure certificate, is a file installed on a secure Web server that identifies a website. This digital certificate establishes the identity and authenticity of the company or merchant so that online shoppers can trust that the website is secure and reliable. In order to verify that these sites are legitimate (they are who they say they are), the companies and their websites are verified by a third party, such as Verisign or Thawte. Once the verification company establishes the legitimacy of an organization and the associated website, they will issue an SSL certificate (for the small fee of a few hundred dollars). This digital certificate is installed on the Web server and will be viewable when a user enters a secure area of the website. You can tell you are visiting a secure page when the URL starts with "https." To view the certificate, click the lock icon near one of the edges of your browser window. Because digital certificates verify a company's current status, they do not last forever. SSL certificates typically expire every one to three years. If the certificate is not renewed in time, you may see an alert box pop up that says "This website's certificate has expired." This error has nothing to do with you or your computer, but is displayed because the Web server you connected to has not renewed its SSL certificate. While this does not necessarily mean the site is fraudulent, it does show that the site is less than professional.
Certificate-Based Authentication Certificate-Based Authentication is the use of SSL and certificates to authenticate and encrypt HTTP traffic.
cf is an abbreviation for the Latin word confer, meaning "compare" or "consult", and is hence used to refer to other material or ideas which may provide different information or arguments. It is mainly used in scholarly or educated contexts, such as in academic (mainly humanities) or legal texts.
CGI Common Gateway Interface. Interface standard allowing programs to interface to web servers. CGI programs can be written in any compilable language. CGI programs are executed on the server, normally in response to some input from a web page. See also: ASP.
cgi-bin The most common name of a directory on a web server in which CGIprograms are stored.
Challenge-Handshake Authentication Protocol (CHAP) The Challenge-Handshake Authentication Protocol uses a challenge/response authentication mechanism where the response varies every challenge to prevent replay attacks.
Channel The group of resellers that supply most companies with software, hardware, and support. The channel is a force to be reckoned with, and it competes directly against, and works with, companies like Dell and IBM. A channel can also be a content container, like a television channel.
CHAP 1. Challenge Handshake Authentication Protocol. An authentication protocol. The server sends the client a (one time) key to be used to encrypt a username and password combination. Subsequently the server may reconfirm the connection by repeating the process - this is to protect against an attacker substituting a different client once the connection has been made. 2. In general speech: A man or boy.
Character A character is any letter, number, space, punctuation mark, or symbol that can be typed on a computer. The word "computer," for example, consists of eight characters. The phrase "Hi there." takes up nine characters. Each character requires one byte of space, so "computer" takes up 8 bytes. The list of characters that can be typed is defined by the ASCII and extended ASCII set. Some of the symbols available are pretty strange and may even make you say, "That's quite a character!"
Chassis Pronounced “chassy,” this is the frame or case which holds your computer components.
Checkpoint At a database checkpoint the database flushes out data not yet written to disk.
Checksum A checksum is a calculated sum used to check the integrity of a file. It can be generated from one of many algorithms, such as cyclic redundancy check (CRC) or a cryptographic hash function. When the checksums of two sets of data match, it indicates that the data sets are identical. Therefore, checksums are a quick and easy way to verify disk images, burned discs, and other types of files.
Chip Technically speaking, a computer chip is a piece of silicon with an electonic circuit embedded in it. However, the word "chip" is often used as a slang term that refers to various components inside a computer. It typically describes an integrated circuit, or IC, such as a central processor or a graphics chip, but may also refer to other components such as a memory module. While "chip" is a somewhat ambiguous term, it should not be confused with the term "card." For example, a laptop might have a graphics chip embedded in the motherboard, while a desktop computer may contain a graphics card connected to a PCI or AGP slot. A graphics card may contain a chip, but the chip cannot contain a card. Similarly, a CPU may contain a chip (the processor), but it may also contain several other components. Therefore, the term "chip" can be used to refer to specific components, but should not be used describe multiple components that are grouped together.
Chipset chipset describes the architecture of an integrated circuit. This includes the layout of the circuitry, the components used within the circuit, and the functionality of the circuit board. For example, the chipset of a modem card is much much different than the chipset of a computer's CPU. Processors themselves also have different chipsets. For example, A PowerPC processor, which uses RISC architecture, will have a much different chipset than an Intel processor that uses CISC technology. Even a Pentium II and Pentium III have slightly different chipsets, though they are both made by Intel. Regardless of what chipset a circuit uses, the important thing is that it works with other components inside the computer. Therefore, whenever you upgrade your computer's hardware, make sure you buy components that are compatible with the chipsets in your machine.
chkdsk (check disk) A Microsoft program that checks your hard drive for logical errors as opposed to physical defects. This program is supported in DOS and all versions of Windows. Windows NT/2000/XP uses it as its main disk checking program. DOS and Windows replaced this program with the friendlier scandisk.exe, but chkdsk.exe is still available and is still the main disk checking program for NTFS partitions.
Chmod Abbreviation for "Change Mode". Chmod is a command line utility available on both Unix systems which allows the file permissions of files to be changed. (The closest equivalent to Chmod on Windows is the command line utility chmod, but the permissions settings are very different.) For full details on how to use chmod consult the Unix man pages. The following is intended as a summary: The syntax for using chmod is as follows: chmod switches mode file Where switches can be any of: -R --recursive Recursive. Change the mode of the directories as well as the files. -P --physical --nofollow Do not follow symbolic links. -f --quiet --silent Do not display any messages. -h --symlink For symbolic links, change the mode of the link -v --verbose Show all files and changes. The mode indicates file permissions for the owner, group and all users. These can either be expressed using a number or symbolically. As a number, it appears as a three digit octal number. The first digit specifying the owner permissions, the second group permissions and the final digit all user (i.e. world) permissions. Where each digit is made up of any combination of the following binary flags: Flag Meaning 4 Allow read 2 Allow write 1 Allow execute (for scripts and programs) Thus the 8 possible values for each digit are: Digit Meaning 0 Deny all 1 Execute only (no read or write permissions) 2 Write only. 3 Write or execute (but not read) 4 Read only. 5 Read and execute. 6 Read and write. 7 Allow all. So to grant the owner full access, members of the group read and execute and all other users execute only, would be: chmod 751 file
CIDR Classless Inter-Domain Routing. An addressing scheme for IP addresses, providing greater flexibility in defining the domain than was possible with simple class A, B and C addressing.
CIFS Common Internet File System. File sharing protocol based originally on SMB (Server Message Block).
Cipher A cryptographic algorithm for encryption and decryption.
Ciphertext Ciphertext is the encrypted form of the message being sent.
Circuit breaker A device that interrupts the flow of electricity if an excessive level of current is detected. It’s a better design than the fuse, as it can just be reset (instead of replaced) to turn the electrical flow back on.
Circuit Switched Network A circuit switched network is where a single continuous physical circuit connected two endpoints where the route was immutable once set up.
CISCO Cisco Systems is a leading network solutions provider. The term CISCO is normally used to refer to network equipment produced by Cisco or one of their certification schemes (see also CCNA and CCNP).
Class A IP A group of IP addresses where the first number remains the same, and the last three can vary. It could be represented by w.x.y.z, where the x, y, and z can be any number from 0-255, and the w represents the first static part of the IP address (e.g., 10.x.y.z). Thus, the number of possible combinations within the Class A address are 256*256*256 = 16,777,216. Of course, some of the addresses, like those ending in .0 and .255, are not used, so the actual number of usable addresses in a Class A is somewhat less than that. The subnet mask of a class A IP address is 255.0.0.0. Thus, only the last three digits of the IP address are used to determine where traffic gets routed within the Class A. There are 254 class A groups in existence.
Class B IP A group of IP addresses where the first two numbers remain the same and the last two can vary. It could be represented by w.x.y.z, where the y and z can be any number from 0-255, and the w and x represent the first static part of the IP address (e.g., 10.251.y.z). Thus, the number of possible combinations within the Class B address are 256*256 = 65,536. Of course, some of the addresses, like those ending in .0 and .255, are not used, so the actual number of usable addresses in a Class B is somewhat less than that. The subnet mask of a class B IP address is 255.255.0.0. Thus, only the last two digits of the IP address are used to determine where traffic gets routed within the Class B. There are about 65,000 class B groups in existence.
Class C IP A group of IP addresses where the first three numbers remain the same and the last one can vary. It could be represented by w.x.y.z, where the z can be any number from 0-255, and the w, x, and y represent the first static part of the IP address (e.g., 10.251.37.z). Thus, the number of possible combinations is 256. Of course, some of the addresses, like those ending in .0 and .255, are not used, so the actual number of usable addresses in a Class C is 254. The subnet mask of a class C IP address is 255.255.255.0. Thus, only the last digit of the IP address is used to determine where traffic gets routed within the Class C. There are about 16.7 million class C groups in existence.
CLEC (Competitive Local Exchange Carrier) The Telecommunications Act of 1996 sought to create this type of service company that would offer local calling, long distance, international calling, and Internet access. The CLECs would compete with the incumbent local exchange carrier (then Bell Atlantic) by leasing their local loops and creating their own on which to sell services.
CLI 1. Call Level Interface. An interface with a computer requiring solely textual input and providing only textual output. 2. Command Line Interface. cf GUI. 3. Caller Line Identification. Allows the recipient of a telephone call to see the caller's phone number before answering the call.
Click Fraud Click Fraud The repetitive clicking on ads on a website in order to generate revenue for the website. More accurately known as pay-per-click fraud, for more details see Pay-Per-Click Fraud.
Client A software program that is used to contact and obtain data from a Server software program on another computer, often across a great distance. EachClient program is designed to work with one or more specific kinds of Server programs, and each Server requires a specific kind of Client. A Web Browser is a specific kind of Client.
Client/Server Client server technology came about when computers began to cost less. Mainframes are very expensive, and didn’t give users much personal freedom. The client/server model promised to change that scenario, and it’s much more popular today. Basically, a client computer with its own memory and hard drive communicates with a server whenever it needs data from the server. The client can run by itself without the server and communicate with different servers as it needs to.
Clipboard The clipboard is a section of RAM where your computer stores copied data. This can be a selection of text, an image, a file, or other type of data. It is placed in the clipboard whenever you use the "Copy" command, which is located in the Edit menu of most programs. Data from the clipboard can be pasted into a document or program using the "Paste" command, which is also located in most programs' Edit menu. For example, an image copied to the clipboard from your photo album may be pasted into an image editing program such as Photoshop. A Web address can be copied to the clipboard from an e-mail and pasted into your Web browser's address field. Some programs allow you to see what data is stored in the clipboard. For example, the Finder in Mac OS X allows you to choose "Show Clipboard" from the Edit menu. When you copy data to the clipboard, whatever data was already stored in the clipboard is typically replaced by the new data. Because the clipboard data is stored in RAM, it is also deleted when your computer is shut down or restarted.
Clock Cycle Think of a clock cycle as one tick of the second hand (but generally at a much higher speed). Computer clocks run voltage through a tiny crystal that oscillates at a predictable speed to give a meaningful timing method to the computer. One clock cycle doesn’t necessarily mean that the processor does one operation. Today’s high-end processors often complete more than one operation per clock cycle, and other times, in the worst cases, it will take several clock cycles to complete one operation.
Clock Speed Clock speed is the rate at which a processor can complete a processing cycle. It is typically measured in megahertz or gigahertz. One megahertz is equal to one million cycles per second, while one gigahertz equals one billion cycles per second. This means a 1.8 GHz processor has twice the clock speed of a 900 MHz processor. However, it is important to note that a 1.8 GHz CPU is not necessarily twice as fast as a 900 MHz CPU. This is because different processors often use different architectures. For example, one processor may require more clock cycles to complete a multiplication instruction than another processor. If the 1.8 GHz CPU can complete a multiplication instruction in 4 cycles, while the 900 MHz CPU takes 7 cycles, the 1.8 GHz processor will be more than twice as fast as the 900 MHz processor. Conversely, if the 1.8 GHz processor takes more cycles to perform the instruction, it will be less than 2x as fast as the 900 MHz processor. Other factors, such as a computer's bus speed, cache size, speed of the RAM, and hard drive speed also contribute to the overall performance of the machine. Therefore, while the processor's clock speed is a significant indicator of how fast a computer is, it is not the only factor that matters.
Clone What do sheep, droids, and computers all have in common? They can all be cloned! Of the three, computer clones are by far the most common. The term "clone" arose in the mid-1980s to describe DOS or Windows-based computers made by companies other than IBM. The machines were often referred to as "IBM clones," or "IBM compatible" computers. They were called clones because the computers functioned exactly the same way as the ones made by IBM. They used similar hardware and ran the same software. PC clones are still around today. In fact there are dozens more manufacturers of Windows-based computers now than there were in the 1980s. Companies like Dell, Gateway, HP, Compaq, and Sony all make Windows-based computers, as well as many other manufacturers. Today, the term "PC," which technically stands for "Personal Computer," is often used to refer to IBM clones. Macintosh clones were made for a few years in the late 1990s, but Apple forced the end of their production by making the Macintosh operating system only run on the Apple-branded machines. "Clone" can also be used to refer to software that serves the same purpose as another more mainstream software program. It can also refer to electronic devices other than computers that are similar to other electronics.
Cloud computing Cloud computing is Internet- ("cloud-") based development and use of computer technology ("computing").[1] In concept, it is a paradigm shift whereby details are abstracted from the users who no longer have need of, expertise in, or control over the technology infrastructure "in the cloud" that supports them.[2] Cloud computing describes a new supplement, consumption and delivery model for IT services based on the Internet, and it typically involves the provision of dynamically scalable and often virtualized resources as a service over the Internet.[3][4] The term cloud is used as a metaphor for the Internet, based on the cloud drawing used to depict the Internet in computer network diagrams as an abstraction of the underlying infrastructure it represents.[5] Typical cloud computing providers deliver common business applications online which are accessed from a web browser, while the software and data are stored on servers. These applications are broadly divided into the following categories that emphasize the notion of "Everything-as-a-Service"[6]: Software as a Service (SaaS), Utility Computing, Web Services, Platform as a Service (PaaS), Managed Service Providers (MSP), Service Commerce, and Internet Integration.
CLR Common Language Runtime. The CLR executes .NET code and is similar in concept to the Java Virtual Machine.
Cluster Cluster 1. In general usage a cluster is a number of similar things which are grouped together. For example a cluster of stars or a set of events grouped by date and/or geographic location. 2. A number of linked computers, which work together and can appear and be treated in some respects as though they were a single computer. Also known as clustering. 3. The smallest amount of space that is allocated on a disk for a file or folder. The cluster size is fixed when a disk is formatted, and may vary between systems as a function of disk size, operating system, file system type (e.g. FAT or NTFS). cf cluster size.
Cluster Size The smallest amount of space that a file can occupy on a disk. Storage on a hard or floppy disk is made up of disk sectors, a cluster is a set of one or more adjacent disk sectors. The operating system allocates disk storage by allocating one or more whole clusters, so the space occupied by a file is always an integral multiple of the cluster size.
Clustering Connecting many computers together so that they appear (for many purposes) as a single machine. Clustering computers together in this way is normally done to provide greater reliability and performance. It is also known as a (computer) cluster.
CMOS Stands for "Complementary Metal Oxide Semiconductor." This technology is typically used in making transistors. The "complementary" part of the term unfortunately does not mean these semiconductors are free. Instead, it refers to how they produce either a positive or negative charge. Because CMOS-based transistors only use one charge at a time, they run efficiently, using up very little power. This is because the charges can stay in one state for a long period of time, allowing the transistor to use little or no power except when needed. Because of their wonderful efficiency, processors that use CMOS-based transistors can run at extremely high speeds without getting too hot and going up in flames. You may also find CMOS memory in your computer, which holds the date and time and other basic system settings. The low power consumption of CMOS allows the memory to be powered by a simple Lithium battery for many years.
CMS 1. Content Management System. An application designed to help manage the content of a website. Typically a CMS allows multiple people to work on the content of a website without them needing to know HTML. A CMS system will provide the ability to edit and update pages as well as adding new pages and adding pictures. A CMS system may also provide the ability to update the navigation and menu structure of a site.
CMYK (Cyan-Magenta-Yellow-Black) An alternate color scheme to the RGB color scheme. Combinations of cyan, magenta, yellow, and black are used to represent colors. The CMYK scheme is used mainly in print, such as magazines. Combining cyan, magenta, and yellow produces black, but that black is not always pure enough, thus, the addition of the K, for pure black. Color inkjet printers use CMYK to represent images. The best printers have separate black instead of wasting all the colors to print a faux brownish black.
CNAME Canonical Name. A domain name alias. It allows a domain name to act as an alias for an existing domain. A CNAME record should point to either an "A record" (recommended) or another CNAME.
Co-Location Most often used to refer to having a server that belongs to one person or group physically located on an Internet-connected network that belongs to another person or group. Usually this is done because the server owner wants their machine to be on a high-speed Internet connection and/or they do not want the security risks of having the server on thier own network.
COA . Certificate Of Authentication (or Certificate of Authenticity). A paper document which certifies that an item is genuine. A COA is typically used where the certificate is easier to verify than the item. The COA is intended as an mechanism to help prevent piracy or imitation. For example Microsoft Windows comes with a COA which is normally stuck to the side of the PC on which Windows has been installed. Similarly some works or art (or even children's toys) come with a certificate of authenticity to help distinguish them from imitations or fakes. 2. Course (or Courses) of Action.
Coaxial cable he type of cable used by the 10Base2 Ethernet standard, and also in most home cable television. It consists of a single, insulated copper wire, surrounded by a copper braid or foil that acts as a ground. The entire wire is then coated with plastic.
COD Cash on delivery. Indicates that a purchase will be paid for at the point (or time) or delivery.
Code A series of instructions that make up a program.
Code generator A code generator is part of a compiler. It takes intermediate code and translates it into the final workable code in the target language.
Codec No, this is not just a cheap rip-off of Kodak. The name "codec" is short for "coder-decoder," which is pretty much what a codec does. Most audio and video formats use some sort of compression so that they don't take up a ridiculous amount of disk space. Audio and video files are compressed with a certain codec when they are saved and then decompressed by the codec when they are played back. Common codecs include MPEG and AVI for video files and WAV and AIFF for audio files. Codecs can also be used to compress streaming media (live audio and video) which makes it possible to broadcast a live audio or video clip over a broadband Internet connection.
Collision What happens on a piece of networking equipment, usually a shared hub, that is being asked to transfer more data than it can handle. Collisions occur when a client on the network tries to transfer data and has to retry because the device is busy and the data figuratively “collides” with other data on the network.
COM 1. Component Object Model. Defined by Microsoft.
COM Port An abbreviation for communications port, this generally refers to a serial port.
command key A key on Mac keyboards only that is used to access commands through the keyboard rather than the menus. commands are commonly shortcuts.
Command Prompt Any blinking cursor waiting, or prompting, for user input. In DOS the C: prompt greets you on most systems–this is a type of command prompt. As well, if you use any version of Windows you can get to a DOS-looking window that allows you to type in commands. UNIX can also greet you with a command prompt. For novice users a command prompt can be confusing, as it’s unclear what to do next; but for experts a command prompt is a necessity at times.
Commercial Software Computer software comes in three different flavors: freeware, shareware, and commercial software. Freeware is free to use and does not require any payment from the user. Shareware is also free to use, but typically limits the program's features or the amount of time the software can be used unless the user purchases the software. Commercial software requires payment before it can be used, but includes all the program's features, with no restrictions or time limits. Commercial software programs typically come in a physical box, which is what you see displayed in retail stores. While it's true that the software boxes are not as big as they used to be, they still contain the software CD or DVD and usually a "getting started" manual along with a registration key used for registering the product. Most commercial software programs ask that the user register the program so the company can keep track of its authorized users. Some commercial software programs, such as newer versions of Microsoft and Adobe programs, require the user to register the programs in order to continue using them after 30 days. While most commercial software programs are sold in the physical box, many software titles are now available as downloads. These downloads are typically made available from the company's website. The user pays for the program directly on the website and instead of receiving the software in the mail, the user downloads it to his computer. Another popular way of purchasing commercial software online is simply paying for a registration key, which unlocks the features of a shareware program. This upgrades the shareware program to the commercial version, which removes any feature limitations from the shareware version.
Compact Flash Often abbreviated as simply "CF," Compact Flash is a type of flash memory. Compact flash cards are most commonly used for storing pictures in digital cameras, but are also used in devices such as PDAs and portable music players. There are two types of Compact Flash cards, creatively named "Type I" and "Type II." Type I cards are 3.3 mm thick, while Type II are 5 mm thick. IBM makes a "MicroDrive" card that has the same dimensions as a Type II CF card, but uses an actual hard drive construction rather than flash memory. Compact Flash cards originally could only store a few megabyes of data, but now can store several gigabytes. The new CF+ standard can store a possible 137 GB of data. I don't know about you, but I'd think about backing up that information before throwing the card in my pocket.
Competitive Intelligence Competitive Intelligence is espionage using legal, or at least not obviously illegal, means.
Compile When programmers create software programs, they first write the program in source code, which is written in a specific programming language, such as C or Java. These source code files are saved in a text-based, human-readable format, which can be opened and edited by programmers. However, the source code cannot be run directly by the computer. In order for the code to be recognized by the computer's CPU, it must be converted from source code (a high-level language) into machine code (a low-level language). This process is referred to as "compiling" the code. Most software development programs include a compiler, which translates source code files into machine code or object code. Since this code can be executed directly by the computer's processor, the resulting application is often referred to as an executable file. Windows executable files have a .EXE file extension, while Mac OS X programs have an .APP extension, which is often hidden.
Compiler compiler is a software program that compiles program source code files into an executable program. It is included as part of the integrated development environment IDE with most programming software packages. The compiler takes source code files that are written in a high-level language, such as C, BASIC, or Java, and compiles the code into a low-level language, such as machine code or assembly code. This code is created for a specific processor type, such as and Intel Pentium or PowerPC. The program can then be recognized by the processor and run from the operating system. After a compiler compiles source code files into a program, the program cannot be modified. Therefore, any changes must be made in the source code and the program must be recompiled. Fortunately, most modern compilers can detect what changes were made and only need to recompile the modified files, which saves programmers a lot of time. This can help reduce programmers' 100 hour work weeks before project deadlines to around 90 or so.
Component Computers are made up of many different parts, such as a motherboard, CPU, RAM, and hard drive. Each of these parts are made up of smaller parts, called components. For example, a motherboard includes electrical connectors, a printed circuit board (PCB), capacitors, resistors, and transformers. All these components work together to make the motherboard function with the other parts of the computer. The CPU includes components such as integrated circuits, switches, and extremely small transistors. These components process information and perform calculations. Generally speaking, a component is a element of a larger group. Therefore, the larger parts of a computer, such as the CPU and hard drive, can also be referred to as computer components. Technically, however, the components are the smaller parts that make up these devices. Component may also refer to component video, which is a type of high-quality video connection. A component connection sends the video signal through three separate cables — one for red, green, and blue. This provides better color accuracy than composite video (typically a yellow connector), which combines all the color signals into a single cable.
Compression To reduce in size. The amount of storage space required to store data can be reduced if the data is compressed. Compression can be achieved either without loss of information (called lossless) or may result in some loss of information (called lossy). Lossy compression algorithms typically allow a choice between low compression and low data loss or high compression with correspondingly higher data loss. Lossless compression is used for compressing where no data loss can be tolerated, for example when compressing applications or application data. Lossy compression is used where some data loss can be tolerated and is typically used for images, for example jpeg and mpeg are lossy image compression techniques
Computer Technically, a computer is a programmable machine. This means it can execute a programmed list of instructions and respond to new instructions that it is given. Today, however, the term is most often used to refer to the desktop and laptop computers that most people use. When referring to a desktop model, the term "computer" technically only refers to the computer itself -- not the monitor, keyboard, and mouse. Still, it is acceptable to refer to everything together as the computer. If you want to be really technical, the box that holds the computer is called the "system unit." Some of the major parts of a personal computer (or PC) include the motherboard, CPU, memory (or RAM), hard drive, and video card. While personal computers are by far the most common type of computers today, there are several other types of computers. For example, a "minicomputer" is a powerful computer that can support many users at once. A "mainframe" is a large, high-powered computer that can perform billions of calculations from multiple sources at one time. Finally, a "supercomputer" is a machine that can process billions of instructions a second and is used to calculate extremely complex calculations.
Computer Emergency Response Team (CERT) An organization that studies computer and network INFOSEC in order to provide incident response services to victims of attacks, publish alerts concerning vulnerabilities and threats, and offer other information to help improve computer and network security.
Computer Ethics Ethics is a set of moral principles that govern the behavior of a group or individual. Therefore, computer ethics is set of moral principles that regulate the use of computers. Some common issues of computer ethics include intellectual property rights (such as copyrighted electronic content), privacy concerns, and how computers affect society. For example, while it is easy to duplicate copyrighted electronic (or digital) content, computer ethics would suggest that it is wrong to do so without the author's approval. And while it may be possible to access someone's personal information on a computer system, computer ethics would advise that such an action is unethical. As technology advances, computers continue to have a greater impact on society. Therefore, computer ethics promotes the discussion of how much influence computers should have in areas such as artificial intelligence and human communication. As the world of computers evolves, computer ethics continues to create ethical standards that address new issues raised by new technologies.
Computer model A computer model is a recreation of a static scene, be it a house or a complex CAD design.
Computer Network A collection of host computers together with the sub-network or inter-network through which they can exchange data.
Computer simulation A prediction of the outcome of events by using actual data and attempting to mimic the environment on a computer. Computer simulations are used often in predicting the weather.
Confidentiality Confidentiality is the need to ensure that information is disclosed only to those who are authorized to view it.
Configuration This is a general-purpose computer term that can refer to the way you have your computer set up. It is also used to describe the total combination of hardware components that make up a computer system and the software settings that allow various hardware components of a computer system to communicate with one another.
Configuration Management Configuration Management is a discipline to ensure that the configuration of an item (and its components) is known and documented and that changes are controlled and tracked. Sometimes abbreviated as CM.
Configure The act of changing software or hardware actions by changing the settings.
Connect A term that commonly refers to accessing a remote computer; also a message that appears at the point when two modems recognize each other.
Connection Failover Connection Failover Where if the server that an application wants to connect to is unavailable then a connection is made instead to a second server. Connection Failover is different to Application Failover, although the two are often implemented together to provide a fault tolerant solution.
Connection Oriented Protocol A protocol where a connection must be established before hosts can exchange data. TCP is an example of a connection oriented protocol. cf Connectionless protocol.
Connectionless Protocol A protocol where there is no handshaking between the sender and receiver. In a connectionless protocol neither the delivery of messages nor the correct sequencing of messages is guaranteed. UDP is an example of a connectionless protocol.
Connectivity A general term indicating the ability to connect two or more items. Generally used when referring to one of: Network connectivity - connecting and communicating between two or more computers. Database connectivity - connecting to and communicating with a database.
Console This term can be used generally to describe a computer, a terminal, or, more recently, a dedicated gaming system.
Contextual Menu A contextual menu is a pop-up menu that appears when you right-click on a certain area of the screen. It is "contextual" because the menu options are relevant to what you click on. While not all programs support contextual menus, most modern operating systems and applications include them as part of the interface design. Contextual menus provide a choice of options that depend on where the cursor is when you click the right mouse button. For example, if you right-click on your computer's desktop, the menu that appears will have desktop-specific commands. These may include options to change the desktop background, create a new folder, clean up the icons, or view the desktop properties. If you right-click within a desktop window, you might see options to create a new folder, change the view options, or view the folder properties. Right-clicking within an application typically provides menu options that are specific to the current program. For example, if you right-click in a Web browser window, the menu that appears may include options such as "Back," "Reload," and "Print." Right-clicking a misspelled word in a word processing program often presents a list of similar correctly spelled words. If you right-click a picture in an image-editing program, you may see a choice of editing options. These are just a few examples of the many contextual menus included in different programs. It may be helpful to think of a contextual menu of as a streamlined menu bar. This is because they typically contain many of the same options as the program's main menu, but only include the choices relevant to the location you clicked. Therefore, contextual menus can be a quick and efficient way of selecting the option you need. So next time you use your favorite program, try right-clicking in different areas of the screen. You might find some pretty useful options you didn't even know existed!
Control Panel The Control Panel is a feature of the Windows operating system that allows the user to modify system settings and controls. It includes several small applications, or control panels, that can be used to view and change hardware or software settings. Some examples of hardware control panels are Display, Keyboard, and Mouse settings. Software control panels include Date and Time, Power Options, Fonts, and Administrative Tools. Many control panels are included as part of the Windows operating system, but others can be installed by third-party applications or utilities. For example, if you add a new mouse to your computer, it may come with a CD for installing a control panel specific for that mouse. Some graphics cards may also install an additional control panel that gives the user greater control over the computer's visual settings. Regardless of when control panels are installed, they can always be found within the Control Panel folder. The Windows Control Panel can be accessed by clicking the Start menu and selecting Control Panel. It is also available in the "Other Places" section of the window's sidebar when you open My Computer. In Windows XP and Windows Vista the Control Panel can be viewed in either Category View or Classic View. Category View arranges the control panels into sections, while Classic View shows them all at once. While the Category View is designed to make locating different settings easier, people familiar with most of the control panels often find the Classic View more efficient. Control Panels were also used for many years by the Mac OS, through Mac OS 9. However, with the introduction of Mac OS X, control panels were consolidated into a single interface called System Preferences. The control panels themselves are now called "Preference Panes" in Mac OS X. They can be accessed by selecting "System Preferences" from the Apple menu or by clicking the System Preferences icon in the Dock.
Controller A device that manages the flow of data between a computer and a peripheral. Specific devices have their own kinds of controllers. PCs come with controllers for standard built-in devices such as hard drives, keyboards, and monitors. But other add-on peripherals may require expansion cards with new controllers.
Controller Card The controller card, or simply "controller," is a piece of hardware that acts as the interface between the motherboard and the other components of the computer. For example, hard drives, optical drives, printers, keyboards, and mice all require controllers to work. Most computers have all the necessary controllers built in the motherboard as chips, not full-sized cards. However, if you add additional components such as a SCSI hard drive, you may need to add a controller card as well. Controller cards are typically installed in one of the computer's PCI slots.
Convergence The ability of the three electron beams (red, green, and blue) in a CRT monitor to meet at a single point and produce one dot. If a monitor is mis-converging, you will notice shadows of blue or red around any white images. Often, this will occur in only some parts of the screen. Some CRT monitors have convergence controls, but most do not, making it impossible to correct this condition without opening it up, which isn’t a good idea due to how CRT monitors hold electrical energy.
Cookie Data stored locally by a browser when it visits a website, used to stored information to customise the browsing experience - for example name and language selections.
Cooperative Multitasking Cooperative Multitasking Multitasking operating system strategy in which each process has complete control of the system until it voluntarily relinquishes control. Cooperative multitasking systems are much simpler to design than pre-emptive multitasking systems, but suffers if one process hogs the processor. cf preemptive multitasking.
Copy Many software programs allow you to copy data, such as text in Microsoft Word or an image in Adobe Photoshop. To copy a piece of data, you need to first select it (or highlight it) and choose "Copy" from the Edit menu within the program. Most programs allow you to use the keyboard shortcut "Control-C" for Windows or "Command-C" for the Mac OS. When you copy a piece of data, it is moved to a buffer in the system's memory called the "Clipboard." This is a temporary storage area in your computer's RAM that holds the most recent item that has been copied. Of course, copying isn't very helpful if you can't use the data somewhere else. To insert the copied data into a document, choose "Paste" from the Edit menu and the data will be pasted into the document.
Core In UNIX systems this term is commonly used in reference to memory, and the crash dump “core” files you will find if you do something naughty in UNIX. The term goes back to when memory chips were actually magnetic coils, or core memory. Yeah, I want my enterprise systems running on that! Just kidding, real core memory hasn’t been built into systems in many, many years.
Core Dump In UNIX systems, when a program crashes it “dumps” out an image of the memory and registers so that you may go through and see what caused the problem. This is almost as useful as the Netware and Windows NT memory dumps (which is not very, if you can’t taste my sarcasm). The problem is that if you really have to know what’s going on at a low level, you won’t understand the dump–not many people can do that. However, if the problem is important enough and persistent enough, the dump gives knowledgeable developers/admins something to look at in order to try to fix the bugs in the system.
Corruption A threat action that undesirably alters system operation by adversely modifying system functions or data.
Cost Benefit Analysis A cost benefit analysis compares the cost of implementing countermeasures with the value of the reduced risk.
Countermeasure eactive methods used to prevent an exploit from successfully occurring once a threat has been detected. Intrusion Prevention Systems (IPS) commonly employ countermeasures to prevent intruders form gaining further access to a computer network. Other counter measures are patches, access control lists and malware filters.
courseware Software designed specifically for use in a classroom or other educational setting.
CPM Stands for "Cost Per 1,000 Impressions," and is used in online advertising. CPM defines the cost an advertiser pays for 1,000 impressions of an advertisement, such as a banner ad or other promotion. An impression is counted each time an advertisement is shown. While some advertisers pay publishers an amount based strictly on impressions, most advertisers pay for individual clicks or leads generated from their advertisements. Therefore, in Web advertising, it may be more effective to measure pay per click (PPC) or pay per lead (PPL) rates. Either way, the advertiser's goal is to generate as many leads as possible by keeping the rates as low as possible. Web publishers also use the CPM to measure the revenue per 1,000 impressions. While technically this should be "revenue per 1,000 impressions," or RPM, the terms CPM and RPM are often used interchangeably from the publisher's perspective.
CPU Central Processing Unit. The CPU is the part of a computer that executes machine code instructions and coordinates and directs the interaction of the different components of the computer. A typical computer has a single CPU, but some have dual (i.e. two) CPUs or even quad (i.e. four) CPUs.
Cracker This is the common term used to describe a malicious hacker, though it also can refer to code breakers. Crackers get into all kinds of mischief, including breaking or “cracking” copy protection on software programs, breaking into systems and causing harm, changing data, or stealing. Hackers largely regard crackers as a less educated group of individuals who cannot truly create their own work, and simply steal other people’s work to cause mischief or for personal gain, not to promote understanding.
crash A hardware or software problem that causes information to be lost or the computer to malfunction. Sometimes a crash can cause permanent damage to a computer.
CRAWLER or WEBCRAWLER Same as Spider.
CRM (Customer Relationship Management) A class of enterprise software that enables a large company to manage all contact (or “touches”) that it has with its customers. It would track, for example, calls to tech support, faxes, e-mails, direct mail, telephone contacts, and any other contact that a company would have with a customer and vice-versa. This information can be used for analysis of customer relationships, and gives salespeople an understanding of what to say when calling up a customer.
Cron A UNIX/Linux daemon that allows tasks to be scheduled on a regular basis. The crontab command is used to schedule and view jobs.
Crontab A UNIX/Linux command that allows you to view (crontab -l) or make changes (crontab -e) to the list of jobs scheduled to be run by the cron daemon.
Crop When you crop an image or photo, you remove part of the image. This may involve cutting some of the image from the left, right, top, bottom, or any combination thereof. It may also mean just cutting out a small rectangular of the image. For example, your friend takes a picture of your family and leaves a good five feet of headroom above the tallest person. If you are going to use the photo as your Christmas card picture, you probably don't want half the picture to be filled with sky. Therefore, you can use an image-editing program to crop the top part of the image, leaving only a small area above the tallest person's head. If the camera was zoomed out too far, you may want to crop some of the sides as well. Most image editing programs include a crop function. Typically, you select a rectangular area using the mouse and click "Crop" to remove the area outside the selection. Once the image is cropped, the cropped section is discarded, leaving only the remainder. Therefore, if you are working with an original photo, you may want to create a duplicate file before cropping and saving it. Note that cropping is different than simply reducing a image's size, which involves lowering the image resolution.
Cross-Browser When a software program is developed for multiple computer platforms, it is called a crossplatform program. Similarly, when a website is developed for multiple browsers, it is called a cross-browser website. The job of a Web developer would be much easier if all browsers were the same. While most browsers are similar in both design and function, they often have several small differences in the way they recognize and display websites. For example, Apple's Safari uses a different HTML rendering engines than Internet Explorer. This means the browsers may display the same Web page with slightly different page and text formatting. Since not all browsers support the same HTML tags, some formatting may not be recognized at all in an incompatible Web browser. Furthermore, browsers interpret JavaScript code differently, which means a script may work fine in one browser, but not in another. Because of the differences in the way Web browsers interpret HTML and JavaScript, Web developers must test and adapt their sites to work with multiple browsers. For example, if a certain page looks fine in Firefox, but does not show up correctly in Internet Explorer, the developer may change the formatting so that it works with Internet Explorer. Of course, the page may then appear differently in Firefox. The easiest fix for browser incompatibility problems is to use a more basic coding technique that works in both browsers. However, if this solution is not possible, the developer may need to add code that detects the type of browser, then outputs custom HTML or JavaScript for that browser. Making a cross-browser site is usually pretty simple for basic websites. However, complex sites with a lot of HTML formatting and JavaScript may require significant extra coding in order to be compatible with multiple browsers. Some developers may even generate completely different pages for each browser. While CSS formatting has helped standardize the appearance of Web pages across multiple browsers, there are still several inconsistencies between Web browsers. Therefore, cross-browser design continues to be a necessary aspect of Web development.
Crossover Cable An Ethernet cable using RJ-45 connectors, where one end of the cable has the order of the second two pairs of the 8 wires (green and orange) swapped. Instead of wires 1, 2, 3, and 6 going straight through, you have 1 going to 3, 2 going to 6, 3 going to 1, and 6 going to 2. (Thanks to DN for pointing that out.) You can use a crossover cable to directly connect two 10BaseT or 100BaseT network cards, basically making a network of two computers for easy file transfer or configuration of network printers or other devices. As well, crossover cables are often used to connect 10BaseT and 100BaseT hubs together.
Crossplatform Software that can run on multiple types of computer systems. For example, the graphics program Adobe Photoshop and the word processor Microsoft Word are both available for the Windows and Macintosh operating systems. Therefore, Photoshop and Word are considered to be crossplatform applications. While "crossplatorm" is typically used to describe computer software, it can refer to hardware as well. For example, peripherals such as keyboards, mice, printers, scanners, and digital cameras that work on both Mac and PC are crossplatorm. Software and hardware that work on more than one platform are also called multiplatform.
CRT Cathode Ray Tube. Most monitors and televisions (other than 'thin' LCD ones) use and are referred to as CRT monitors. Unlike LCD monitors, CRT monitors are characterised by being bulky and heavy (and can be prone to flicker because the image is repeatedly being redrawn each second).
Cryptanalysis The mathematical science that deals with analysis of a cryptographic system in order to gain knowledge needed to break or circumvent the protection that the system is designed to provide. In other words, convert the cipher text to plaintext without knowing the key.
Crypto (Cryptography) The study of decryption and encryption technologies
Cryptographic Algorithm or Hash An algorithm that employs the science of cryptography, including encryption algorithms, cryptographic hash algorithms, digital signature algorithms, and key agreement algorithms.
Cryptography (crypto) The study of decryption and encryption technologies.
CSS Cascading Style Sheet(s). Extension to HTML allowing paragraph formatting to be defined once and then applied to multiple paragraphs in an HTML document.
CSV Comma Separated Value. An ASCII text file containing values with comma delimiters (i.e. commas separating distinct fields). Occasionally, but by no means a standard, the first line may contain the names of the fields. CSV files are normally denoted with a .csv file extension. Most spreadsheet packages will import csv files directly and can also save a csv file. Some databases provide tools to import and/or export csv files. Some systems, when generating csv files, will place double quotes around strings others will not - there is no defining standard.
CSV (Comma Separated Values) A file extension used for a flat text data file consisting of items of data separated by commas. Each line of data is separated by a carriage return.
CTR Click Through Rate. Abbreviation used by affiliate networks. Is the percentage of the number of advertisement displays that resulted in a click.
CUPS Common UNIX Printing System. CUPS provides a portable printing layer for UNIX based operating systems.
Cursor The cursor on your screen can indicate two things: 1) where your mouse pointer is, or 2) where the next character typed will be entered in a line of text. The mouse cursor is most often an arrow that you can use to point to different objects on your screen. When the cursor is over an object, you can click or double-click the mouse button to perform an action on that object (such as opening a program). The mouse cursor can change into other images, such as a small hand (when you roll over a link in a Web page), or an hourglass (when Windows is "thinking" so hard, it won't let you click on anything). The text cursor is typically a straight vertical line or I-shaped object that flashes in a line of text. Typically, when you are typing a paper, the cursor will be at the end of the line, because you are adding new text to the uncharted white area of the page. However, if you want to insert a word or phrase somewhere else in a line of text, you can use the mouse cursor to click the position where you would like to insert the text. In most word processing programs, once you start typing, the text cursor continues to flash, but the mouse pointer disappears until you move the mouse again. This is to avoid "cursor confusion," since most people can't type and click on things at the same time.
CUSTOM SEARCH ENGINE (CSE) A Google service in which individuals can create a Google account (free) and create a search engine directed to search within a group of websites or pages they select. More information at CSEs: Make Your Own Search Engine and Finding CSEs.
Cut The Cut command removes a selected object and copies it to the clipboard. It performs both a Delete and Copy operation at the same time. After data has been cut from a document, it can be pasted into another similar document. Objects like text, images, audio, and video selections can be cut. However, only editable items can be cut since the command removes the selection from the document.
cut and paste A type of editing in which data is copied or moved from one location to another. Example: rearranging paragraphs within a document.
Cut-Through ut-Through is a method of switching where only the header of a packet is read before it is forwarded to its destination.
Cybercrime Cybercrime is criminal activity done using computers and the Internet. This includes anything from downloading illegal music files to stealing millions of dollars from online bank accounts. Cybercrime also includes non-monetary offenses, such as creating and distributing viruses on other computers or posting confidential business information on the Internet. Perhaps the most prominent form of cybercrime is identity theft, in which criminals use the Internet to steal personal information from other users. Two of the most common ways this is done is through phishing and pharming. Both of these methods lure users to fake websites (that appear to be legitimate), where they are asked to enter personal information. This includes login information, such as usernames and passwords, phone numbers, addresses, credit card numbers, bank account numbers, and other information criminals can use to "steal" another person's identity. For this reason, it is smart to always check the URL or Web address of a site to make sure it is legitimate before entering your personal information. Because cybercrime covers such a broad scope of criminal activity, the examples above are only a few of the thousands of crimes that are considered cybercrimes. While computers and the Internet have made our lives easier in many ways, it is unfortunate that people also use these technologies to take advantage of others. Therefore, it is smart to protect yourself by using antivirus and spyware blocking software and being careful where you enter your personal information.
Cyberspace Term originated by author William Gibson in his novel Neuromancer the word Cyberspace is currently used to describe the whole range of information resources available through computer networks.
Cyclic Redundancy Check (CRC) A test to see whether data has been transferred properly over a modem or to and from disk media. The sender of the data adds a check number to the end of the data being sent, and the receiver applies the same check to the data and compares the number it gets with the check number. If they don’t match, the data can be requested again.
Cylinder This term is somewhat synonymous with the tracks on a hard disk drive. However, instead of a single track, a cylinder refers to the location of all the drive read and write heads, typically accessing multiple platters. Thus, when these tracks are mentally pictured, they are stacked up like a cylinder. Since all the heads are locked together, a specific cylinder number is equivalent to a track number on a specific platter, but refers to all platters at once.
D-Link D-Link Corporation was founded in 1986 in Taipei as Datex Systems Inc. It began as a network adapter vendor and has gone on to become a designer, developer, and manufacturer of networking solutions for both the consumer and business markets. Product Range D-Link’s products are geared towards the networking and communications market. Its business products include switches, security devices, and business wireless, whilst consumer products cover consumer wireless devices, broadband devices and the Digital Home devices (which includes media players, storage and surveillance). It was the first wired and wireless networking company to launch “green” technology, D-Link Green. D-Link first applied the power saving technology to their unmanaged switches and later on, its wireless routers.
Daemon The word "daemon" actually comes from the Greek language, meaning an "inner or attendant spirit" (Oxford American Dictionary). This is a fitting name, as a computer daemon is a constantly running program that triggers actions when it receives certain input. For example, a printer daemon spools information to a printer when a user decides to print a document. A daemon running on a mail server routes incoming mail to the appropriate mailboxes. Web servers use an "HTTPD" daemon that sends data to users when they access Web pages. While daemons were first used by the Unix operating system, they have also been incorporated into Mac OS X, which is Unix-based.
Daisy Chain In computer terminology, this refers to connecting one device (historically SCSI, but now USB or FireWire as well) to another device, instead of directly to a computer. In fact, you can daisy chain several SCSI devices to one another, and only one of them needs to be connected to a computer with a SCSI interface for them all to be controlled by it.
Dark Fiber Fiber optic wiring that has been installed but has not been turned on yet. Often, companies that lay fiber optic cabling will lay extra cable, since the laying of miles of cable is a very costly and time consuming procedure. This dark fiber will lay dormant until the company needs extra capacity, or until it leases it to another company that needs the capacity. Then the company “lights it up” by sending optical data over the fiber.
DAS Direct Attached Storage, i.e. disk storage directly connected to a computer, as opposed to NAS or SAN.
Dashboard Dashboard is a user-interface feature Apple introduced with the release of Mac OS X 10.4 Tiger. It allows access to all kinds of "widgets" that show the time, weather, stock prices, phone numbers, and other useful data. With the Tiger operating system, Apple included widgets that do all these things, plus a calculator, language translator, dictionary, address book, calendar, unit converter, and iTunes controller. Besides the bundled widgets, there are also hundreds of other widgets available from third parties that allow users to play games, check traffic conditions, and view sports scores, just to name a few. The dashboard of widgets is accessed by clicking the Dashboard application icon, or by simply pressing a keyboard shortcut (F12 by default). Clicking a plus "+" icon in the lower-left hand corner of the screen provides the user with a list of all installed widgets. Clicking the widgets or dragging them onto the desktop makes them active. They can be individually closed by clicking the close box, just like other open windows. Pressing the keyboard shortcut (F12) makes them instantly disappear, removing them from view until the user needs them again.
Data Computer data is information processed or stored by a computer. This information may be in the form of text documents, images, audio clips, software programs, or other types of data. Computer data may be processed by the computer's CPU and is stored in files and folders on the computer's hard disk. At its most rudimentary level, computer data is a bunch of ones and zeros, known as binary data. Because all computer data is in binary format, it can be created, processed, saved, and stored digitally. This allows data to be transferred from one computer to another using a network connection or various media devices. It also does not deteriorate over time or lose quality after being used multiple times.
Data Aggregation Data Aggregation is the ability to get a more complete picture of the information by analyzing several different types of records at once.
Data Center Any computing environment where there is a service agreement between the people managing the computing resources and the users. A company computer network is a data center, but so is a network at an ISP. Additionally, data center has come to mean a website or network with its resources dedicated to providing information on a particular subject.
Data Compression (Compression) Takes something large and makes it smaller. Compression generally comes in two forms: lossy and lossless. Lossy compression is best used on graphics files and sound files, where loss of quality is acceptable in many situations. Lossy compression crunches down the data at a much higher ratio, at the expense of having an image or a sound that isn’t quite the same as before it was compressed. In the best scenario the data takes up less space, but the person viewing the graphic or listening to the sound file will not be able to notice. Lossless compression squeezes data down so that at some later date it can be uncompressed and returned to its exact structure. Lossless compression is best used on data files and programs.
Data Custodian A Data Custodian is the entity currently using or manipulating the data, and therefore, temporarily taking responsibility for the data.
Data Encryption Standard (DES) An encryption method developed by IBM in 1977. It uses a private 56-bit key that is applied to each 64- bit block of data. The sender and receiver must each know the private key. Anything encrypted by DES encryption has 72,000,000,000,000,000 (or 72 quadrillion) possible keys. DES encryption has been broken, but it took over 14,000 computers operating in succession to crank through codes until the proper key was found. See also Triple DES encryption.
Data Entry A job function where the employee is expected to enter data into a computer. Typically, the only technical skill you need for such jobs is typing. Some people use data entry positions to springboard into low-end technical support and head on towards more technical jobs.
Data Integrity The reliability and correctness of data. Typically the reliability and correctness of data in a database, but can apply to the reliability and correctness of data in any context. Data Integrity checks are checks or tests to confirm the integrity of data. Such tests normally verify the relationships between data as well as ensuring that data elements are within expected limits.
Data Management Data management refers to the way individuals, companies, and organizations manage computer data. It includes micro applications, such as data architecture and design, as well as macro applications, including data storage, access, and security. While computer data may be intangible, it can also be valuable. Therefore, it is important for all users to consider how they manage their data. This may involve taking steps such as backing up important files and encrypting personal information.
Data Mining Generic term for identifying possible relationships and trends between data items. Typically data mining is the statistical analysis of data to identify commonalities and patterns.
Data Owner A Data Owner is the entity having responsibility and authority for the data.
Data Transfer Rate The data transfer rate is commonly used to measure how fast data is transferred from one location to another. For example, a hard drive may have a maximum data transfer rate of 480 Mbps, while your ISP may offer an Internet connection with a maximum data transfer rate of only 1.5 Mbps. Data transfer rates are typically measured in bits per second (bps) as opposed to bytes per second, which can be understandably confusing. Because there are eight bits in a byte, a sustained data transfer rate of 80 Mbps is only transferring 10MB per second. While this is confusing for consumers, Internet service providers must enjoy measuring data transfer rates in bps since it makes their Internet access speeds sound 8x faster than they really are.
Data Type A data type is a type of data. Of course, that is rather circular definition, and also not very helpful. Therefore, a better definition of a data type is a data storage format that can contain a specific type or range of values. When computer programs store data in variables, each variable must be assigned a specific data type. Some common data types include integers, floating point numbers, characters, strings, and arrays. They may also be more specific types, such as dates, timestamps, boolean values, and varchar (variable character) formats. Some programming languages require the programmer to define the data type of a variable before assigning it a value. Other languages can automatically assign a variable's data type when the initial data is entered into the variable. For example, if the variable "var1" is created with the value "1.25," the variable would be created as a floating point data type. If the variable is set to "Hello world!," the variable would be assigned a string data type. Most programming languages allow each variable to store a single data type. Therefore, if the variable's data type has already been set to an integer, assigning string data to the variable may cause the data to be converted to an integer format. Data types are also used by database applications. The fields within a database often require a specific type of data to be input. For example, a company's record for an employee may use a string data type for the employee's first and last name. The employee's date of hire would be stored in a date format, while his or her salary may be stored as an integer. By keeping the data types uniform across multiple records, database applications can easily search, sort, and compare fields in different records.
Data Warehouse A large database where information is gathered from various online transaction systems. Usually, this information is put together and “mined,” as in datamining, to learn more about customers or customer purchasing habits. Data warehouses are used to gather information that may not be obvious when viewed in one context, but when grouped together in the data warehouse and properly queried, you can find out useful information. For example, a supermarket may find out that 47% of its customers buy light bulbs at the same time that they purchase shoelaces. Some of this data may be useful in a business sense, and some of it not so useful.
Data Warehousing The act of putting data together in a Data Warehouse.
Database A collection of related records. In computing a database is normally taken as a structured collection of records, that is managed and queried using a database management system (DBMS).
Database Connectivity Connecting and communicating between an application and a database system.
Database Schema The description of the tables and views in a database together with the relationships between them.
Datagram Request for Comment 1594 says, "a self-contained, independent entity of data carrying sufficient information to be routed from the source to the destination computer without reliance on earlier exchanges between this source and destination computer and the transporting network." The term has been generally replaced by the term packet. Datagrams or packets are the message units that the Internet Protocol deals with and that the Internet transports. A datagram or packet needs to be self-contained without reliance on earlier exchanges because there is no connection of fixed duration between the two communicating points as there is, for example, in most voice telephone conversations. (This kind of protocol is referred to as connectionless.)
Daughter Board (Daughterboard) A circuit board that plugs into a larger circuit board, or motherboard. Often processors are contained on daughterboards, along with cache memory. For example, Intel’s Pentium II (and pre-FC-PGA Pentium III) processors shipped on a daughter board that plugs into the Slot 1 on the motherboard.
Daughter Card (Daughter Board) A circuit board that plugs into a larger circuit board, or motherboard. Often processors are contained on daughterboards, along with cache memory. For example, Intel’s Pentium II (and pre-FC-PGA Pentium III) processors shipped on a daughter board that plugs into the Slot 1 on the motherboard.
Day Zero The "Day Zero" or "Zero Day" is the day a new vulnerability is made known. In some cases, a "zero day" exploit is referred to an exploit for which no patch is available yet. ("day one"-> day at which the patch is made available).
DB 1. Database (DB). Common abbreviation for database. The abbreviation may be applied to any form of database, and does not imply any specific type of database. 2. Decibel (dB). A standard logarithmic scale for measuring the loudness of sound.
DBA 1. Database Administrator. The DBA is responsible for the day to day efficient management of a database system. 2. Decibels Adjusted. This is written as dB(A).
DBMS Database Management System. The system (i.e. software) for managing a database.
DC 1. Direct Current. Electrical current that flows in a single direction only, cf AC. 2. Domain Controller.
DDI 1. Direct Dialling In (or Inwards). If a phone number is quoted as "DDI" then it indicates a direct dial and not via switchboard (i.e. phone and ask for an extension). Most phone numbers are DDI. 2. Device Driver Interface.
DDNS Dynamic DNS. Provides a central (public) database where DNS information can be stored and retrieved. See Dynamic DNS for details.
DDOS Distributed Denial-of-Service (attack). A Denial of Service attack which is launched from multiple systems. A DDOS attack works by trying to overwhelm a server by the sheer number of requests generated by each of the systems participating in the attack.
DDR Double Data Rate. A type of SDRAM that provides twice the data rate of conventional SDR SDRAM, by allowing data to be read on both the rising and falling edge of each clock cycle. DDR is sometimes referred to as DDR1 to distinguish it from DDR2, which can run at higher bus speeds.
DDR2 Double Data Rate x2, or double data rate DDR. Like DDR, DDR2 is a type of SDRAM that allows data to be read on both the rising and falling of each clock cycle. DDR2 allows the bus to run twice as fast as DDR, and so can achieve double the throughput.
DDR3 SDRAM In electronic engineering, DDR3 SDRAM or double-data-rate three synchronous dynamic random access memory is a random access memory interface technology used for high bandwidth storage of the working data of a computer or other digital electronic devices. DDR3 is part of the SDRAM family of technologies and is one of the many DRAM (dynamic random access memory) implementations. DDR3 SDRAM is an improvement over its predecessor, DDR2 SDRAM, and the two are not compatible. The primary benefit of DDR3 is the ability to transfer at twice the data rate of DDR2 (I/O at 8× the data rate of the memory cells it contains), thus enabling higher bus rates and higher peak rates than earlier memory technologies. In addition, the DDR3 standard allows for chip capacities of 512 megabits to 8 gigabits, effectively enabling a maximum memory module size of 16 gigabytes. With data being transferred 64 bits at a time per memory module, DDR3 SDRAM gives a transfer rate of (memory clock rate) × 4 (for bus clock multiplier) × 2 (for data rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus with a memory clock frequency of 100 MHz, DDR3 SDRAM gives a maximum transfer rate of 6400 MB/s. DDR3 is a DRAM interface specification; the actual DRAM arrays that store the data are the same as in any other type of DRAM, and have similar performance.
Debian Debian (pronounced /ˈdɛbiən/) is a computer operating system composed of software packages released as free and open source software especially under the GNU General Public License and other free software licenses.[3] The primary form, Debian GNU/Linux, which uses the Linux kernel and GNU OS tools,[4] is a popular and influential GNU/Linux distribution.[5] It is distributed with access to repositories containing thousands of software packages ready for installation and use. Debian is known for strict adherence to the Unix and free software philosophies as well as using collaborative software development and testing processes.[6] Debian can be used as a desktop as well as server operating system.
Debug Computer programmers, like everybody else, are not perfect. This means the programs they write sometimes have small errors, called "bugs," in them. These bugs can be minor, such as not recognizing user input, or more serious, such as a memory leak that crashes the program. Before releasing their software to the public, programmers "debug" their programs, eliminating as many errors as possible. This debugging process often takes a long time, as fixing some errors may introduce others. Debugging your windshield at a gas station is much easier than debugging a computer program.
Debugger Even the most experienced software programmers usually don't get it right on their first try. Certain errors, often called bugs, can occur in programs, causing them to not function as the programmer expected. Sometimes these errors are easy to fix, while some bugs are very difficult to trace. This is especially true for large programs that consist of several thousand lines of code. Fortunately, there are programs called debuggers that help software developers find and eliminate bugs while they are writing programs. A debugger tells the programmer what types of errors it finds and often marks the exact lines of code where the bugs are found. Debuggers also allow programmers to run a program step by step so that they can determine exactly when and why a program crashes. Advanced debuggers provide detailed information about threads and memory being used by the program during each step of execution. You could say a powerful debugger program is like OFF! with 100% deet.
Decapsulation Decapsulation is the process of stripping off one layer's headers and passing the rest of the packet up to the next higher layer on the protocol stack.
DECnet Digital Equipment Corporation network protocol.
Decrypt (v. to decrypt) The act of decoding data that has been encrypted.
Decryption The act of decoding encrypted data so that it can be understood.
Dedicated Line Often used to mean a telephone line used solely for your computer modem or fax machine, and not used for voice calls–although it technically could be.
Defacement Defacement is the method of modifying the content of a website in such a way that it becomes "vandalized" or embarrassing to the website owner.
Default 1. A defined behaviour (or value) to be taken when no other behaviuor (or value) has been specified. For example: in software procedures often take parameters and here a default value would indicate the value to use for a parameter when the caller does not explicitly provide a value to use. 2. In finance a default indicates an inability to pay a debt when it becomes due.
Defaults 1. A collection of default values. For example a function may take several parameters each of which might have a default value, together these represent the defaults for that function. 2. The act of using a default value.
Defense In-Depth Defense In-Depth is the approach of using multiple layers of security to guard against failure of a single security component.
Defrag 1. Common abbreviation for degrament, the process of rearranging how files are stored on a disk to make them contiguous rather than scattered all over the disk. See defragment for details. 2. The name of the disk defragmentation utility included in MS-DOS and newer versions of Windows.
Defragment Defragmenting your hard disk is a great way to boost the performance of your computer. Though the term "defragment" sounds a little abrasive, it is actually a simple and helpful process. After all, a defragmented hard disk is a happy hard disk. Adding and deleting files from your hard disk is a common task. Unfortunately, this process is not always done very efficiently. For example, when you delete a bunch of little files and add a new large file, the file may get broken up into mulitple sections on the hard disk. The computer will still read the newly added file as a single valid file, but the drive will have to scan multiple parts of the disk to read it. Because hard disk seek time is one of the most significant bottlenecks in a computer's performance, this can drag down your computer's speed quite a bit. If you have a ton of "fragmented" files on your hard disk, you might hear extra grinding, sputtering, and other weird noises coming from your computer. You computer does not like having fragmented files any more than you do. This is why defragmenting your hard disk is such a good idea. When you start to hear extra grinding sounds, or your computer doesn't open files as quickly as it did before, it's time to defragment. With Windows, you can use the pre-installed Intel defragment program to defragment your hard disk. You can also use a commercial software program like Norton Utilities to defragment your hard disk more efficiently and with more options. For Mac users, a disk utility such as DiskWarrior or Tech Tool Pro is the only way to do it. If you use your computer daily, defragmenting your hard drive once a month should keep the fragment-fiends away.
Degauss Ever wonder what that "degauss" button on your monitor does besides make a buzzing noise and cause the screen to go crazy for a second? Though that's its main purpose, the degauss button has another useful feature. To understand it, you'll first need to know that the earth has natural magnetic fields. The magnetic charges from these fields can build up inside your monitor, causing a loss of color accuracy. Degaussing scares the bad magnetism out of the monitor and fills it with good karma. If your monitor doesn't have a degauss button, fear not -- many new monitors automatically degauss themselves. If you have a flat-panel display, there is no degauss button because magnetism doesn't build up in flat screen displays.
Delegate Pointer to a function in .NET.
Delete Delete is computer terminology for remove or erase. You can delete text from a document of delete entire files or folders from your hard drive. When typing a document, you can remove characters behind the cursor by pressing the delete key. If you want to remove characters in front of the cursor, you can press the smaller delete key near the home and end buttons on the keyboard. You can also remove entire sections of text by selecting the text you wish to delete and pressing either delete button on the keyboard. Files and folders can be removed from your hard drive by dragging them to the Recycle Bin (Windows) or the Trash (Macintosh) and then emptying the trash. When you delete a file, it is actually not erased, but instead the reference to the file is removed. This means deleted files are still intact until they are written over. Special utilities such as Norton Unerase can recover accidentally deleted files.
Dell Dell Inc. is a multinational information technology corporation that develops, manufactures, sells, and supports personal computers and other computer-related products. Based in Round Rock, Texas
Denial of Service Denial of Service is an attack on a system (typically a server or a network) that aims to crash, block or overload the system and thereby deny its services to others. A denial of service attack is illegal in most countries.
DEP Data Execution Protection. DEP prevents code from executing from areas of memory that should only contain data (and not code), such as the stack and various memory pools. The rational for this is to prevent an attacker from inserting rogue code into a PC's memory and then persuading Windows to run it. To operate, DEP needs to be supported by both the Operating System and the Processor. Also known as Execution Protection, NX or No Execute.
Deprecated Notice that a particular software API or interface standard is being retrained only for backwards compatibility with earlier versions and that it may be removed from future versions of the software or interface. In general an item is marked as deprecated because it has been replaced with a newer method. In any event "deprecated" should be regarded as a warning not to use the item because it may be withdrawn in future releases, and as a hint that there may be a better (or newer) way to achieve the desired effect.
DES Data Encryption Standard. Algorithm for secret-key cryptography (where both sender and receiver must know the same secret key). DES uses a 56bit key to encrypt data to be transmitted, the receiver uses the same key to decrypt the data. Encrypted data cannot be decrypted without the key or brute force attack methods, which may not be viable because of the time required.
Desktop Your computer's desktop is much like a physical desktop. You probably keep a number of commonly used items on your desk such as pens, papers, folders, and other items. Your computer's desktop serves the same purpose -- to give you easy access to items on your hard drive. It is common to store frequently used files, folders, and programs on your desktop. This allows you to access the items quickly instead of digging through the directories on your hard drive each time you want to open them. Both the Macintosh and Windows interfaces use the desktop as a central part of the interface. Both operating systems allow you to move items on and off the desktop as you wish and offer organization tools to arrange and clean up the items on the desktop. Yes, it would be nice if there was an option like that for a real-life desktop. You can also customize your computer's desktop with the pattern or background image of your choice.
Developer A person who creates computer programs, and may specialize in one or more methods of creating computer programs, Web pages, or programming languages, such as Java, C++, or Fortran, for example. Microsoft CEO Steve Ballmar is very fond of this term, as noted when he continually stated, “Developers, developers, developers, developers …” in a now infamous speech to Microsoft personnel.
Device Driver This is basically synonymous with the term “driver.” It’s a piece of software that tells an operating system specifically how to communicate with a device. For high speed devices such as 3D graphics cards, using an up-to-date device driver is important to guarantee performance and stability.
DFS Distributed File System. Simplifies the process of creating a single directory hierarchy that includes multiple file servers and shared folders in a group, division or enterprise. This allows files and folders to be located on different computers but appear to users as though they are in the same directory tree.
DHCP Dynamic Host Configuration Protocol. DHCP is a communications protocol where a range of IP addresses are managed centrally and assigned automatically to computers on demand. The alternative is to use static IP address where each computer is permanently allocated a fixed IP address. An advantage of DHCP (over static IP address allocation) is that it removes the burden of configuring each computer to use a unique IP address and removes the need to manually keep records on which IP address has been allocated to which computer. The disadvantage is that the IP address of a computer cannot be known in advance and its IP address may change over time.
DHCP (Dynamic Host Configuration Protocol) A method of automatically assigning a TCP/IP address to a client. A DHCP server is used to dole out a TCP/IP address from a pool of TCP/IP addresses to a client that supports DHCP. When you connect to your ISP over a modem or broadband you are typically assigned a dynamic (non-static) TCP/IP address via DHCP. The big advantage to DHCP is that you don’t need to manually assign a TCP/IP address to a client–the DHCP server takes care of that. After an amount of time passes where the client does not contact the server, the server puts the TCP/IP address of the client back into the pool to be assigned to that client or any other client hat requests a TCP/IP address. The disadvantage of DHCP for the DHCP client is that the client is not guaranteed to have a particular TCP/IP address at any given time. For that you want a static IP address.
Diagnostics A procedure or program that is run internally to test a piece of software or hardware and ensure that it is operating properly. For example, if R2-D2 of Star Wars decided to start running into walls, C3PO would probably make him run diagnostics on himself to try to figure out what his problem was.
Dial-up A dial-up connection uses a modem to connect to an ISP or another computer. It uses standard analog phone lines to transfer data up to 56 Kbps. Before the year 2000, dial-up was the standard way to connect to Internet. However, most users now connect to the Internet is via a DSL or cable modem connection. Both cable and DSL services provide a constant connection and support data transfer speeds over 100 times faster than dial-up modems.
Dialog Box As the name implies, a dialog box serves to initiate a dialog with the user. It is a window that pops up on the screen with options that the user can select. After the selections have been made, the user can typically click "OK" to enter the changes or "Cancel" to discard the selections. It is customary for menu options that include an ellipsis at the end, such as "Preferences..." or "Save As...", to open a dialog box when selected. For example, if a user selects "Internet Options..." from the Options menu in Internet Explorer, a dialog box will pop up allowing the user to choose the default home page, change the security settings, empty the browser cache, and modify several other settings. Once the selections have been made, the user can click "OK" to use the new settings, or "Cancel" to discard the changes. Some Windows programs also have an "Apply" option that activates the selections without closing the dialog box. When a user selects "Open..." from the File menu, an "Open dialog box" appears, allowing the user to browse the hard drive and other disks for files to open. When "Save As..." is chosen from the File menu, a "Close dialog box" pops up, allowing the user to type the name of the file and choose where to save it. While dialog boxes may not seem too exciting, they provide an intuitive way to communicate with the computer and are an essential part of today's computer interfaces.
DIB (Dual Independent Bus) The bus architecture between Intel’s Pentium II processor, memory, and L2 cache. One bus connects the processor to L2 cache and a second connects the processor to main memory. Having two buses instead of one increases performance over single-bus architectures. In addition, the speed of the external L2 cache can scale up independently from the speed of the system bus.This allows for faster cache access. The final feature of the DIB architecture is a pipeline on the cache to the processor bus that allows multiple simultaneous cache requests.
Dictionary Attack An attack that tries all of the phrases or words in a dictionary, trying to crack a password or key. A dictionary attack uses a predefined list of words compared to a brute force attack that tries all possible combinations.
Die size Simply put, this is the two dimensional (length by width) measurement of a microprocessor. The thickness of the processor is not considered. Typical die sizes range between 20-500 square millimeters with most consumer processors from Intel and AMD around the 80-200 square mm mark. Smaller die size allows more chips to be created with a given amount of raw materials.
Differential SCSI This type of SCSI is used to connect devices that are far apart or that may suffer from interference. Standard SCSI cabling is limited to 6 meters; differential SCSI supports distances of up to 25 meters away from the SCSI host adapter.
Digest Authentication Digest Authentication allows a web client to compute MD5 hashes of the password to prove it has the password.
Digital Digital information is stored using a series of ones and zeros. Computers are digital machines because they can only read information as on or off -- 1 or 0. This method of computation, also known as the binary system, may seem rather simplistic, but can be used to represent incredible amounts of data. CDs and DVDs can be used to store and play back high-quality sound and video even though they consist entirely of ones and zeros. Unlike computers, humans perceive information in analog. We capture auditory and visual signals as a continuous stream. Digital devices, on the other hand, estimate this information using ones and zeros. The rate of this estimation, called the "sampling rate," combined with how much information is included in each sample (the bit depth), determines how accurate the digital estimation is. For example, a typical CD audio track is sampled at 44.1 KHz (44,100 samples per second) with a bit depth of 16 bits. This provides a high-quality estimation of an analog audio signal that sounds realistic the human ear. However, a higher-quality audio format, such as a DVD-Audio disc, may be sampled at 96 KHz and have a bit depth of 24 bits. The same song played on both discs will sound more smooth and dynamic on the DVD-Audio disc. Since digital information only estimates analog data, an analog signal is actually more accurate than a digital signal. However, computers only work with digital information, so storing data digitally makes more sense. Unlike analog data, digital information can also be copied, edited, and moved without losing any quality. Because of the benefits digital information offers, it has become the most common way of storing and reading data.
Digital Archive A digital collection for which an institution has agreed to accept long-term responsibility for preserving the resources in the collection and for providing continual access to those resources in keeping with an archive's user access policies.
Digital Certificate A digital certificate is an electronic "credit card" that establishes your credentials when doing business or other transactions on the Web. It is issued by a certification authority. It contains your name, a serial number, expiration dates, a copy of the certificate holder's public key (used for encrypting messages and digital signatures), and the digital signature of the certificate-issuing authority so that a recipient can verify that the certificate is real.
Digital Collection A collection consisting entirely of born-digital or digitized materials.
Digital Control A control that doesn’t directly cause a physical change in something, but rather sends a signal that a processor interprets. The processor then makes the change. An example of a digital control would be a television set with buttons instead of knobs. See also Analog Control.
Digital Data Storage (DDS) A storage standard used with medium cost tape media and tape drives, used mainly for small businesses and departmental backups. DDS tapes are the same size and form factor as DAT tapes used to store music digitally on tape media, but DDS media is more robust and more expensive. There are four different DDS standards: DDS-1 through DDS-4. The four standards allow for backup of 2 GB, 4 GB, 12 GB, and 20 GB worth of uncompressed (native) storage respectively. Storage sizes are typically listed as double for compressed data. DDS media is good for up to 10 years, but should not be used for more than 100 backups or it may become unreliable. DDS tapes are falling to the wayside as DLT, AIT, and other standards offer higher reliability. Sony and HP have both announced that they will not be supporting DDS-5, which pushes DDS data storage up to 40 GB of native storage per tape.
Digital Envelope A digital envelope is an encrypted message with the encrypted session key.
Digital Linear Tape (DLT) A technology designed by DEC and sold to Quantum used for backing up huge amounts of data (up to 35 GB per tape without compression, 70 GB with compression). The drives are very expensive and so is the media, but they are bulletproof.
Digital signature A form of electronic signature that works with a public and private key encryption system and a certificate authority. To sign an electronic document with a digital signature, you use digital signature software to select the document and enter an authorization code that is unique to your digital signature. The signature consists of a string of characters and the signer’s name, title, company, certificate serial number, and the name of the certificate authority.
Digital Signature Algorithm (DSA) An asymmetric cryptographic algorithm that produces a digital signature in the form of a pair of large numbers. The signature is computed using rules and parameters such that the identity of the signer and the integrity of the signed data can be verified.
Digital Signature Standard (DSS) The US Government standard that specifies the Digital Signature Algorithm (DSA), which involves asymmetric cryptography.
Diode An electronic device with two electrodes/terminals, one called the cathode and the other the anode, and a single PN junction (which uses part P-type and part N-type semiconductor material). The diode will conduct current in only one direction, and only when the cathode voltage is positive relative to the anode voltage by a specified amount. The specific voltage depends on which semiconductor materials the PN junction is manufactured from. Diodes are often used as a rectifier to convert AC power to DC, but they have many uses.
Dip Switch One or more switches that are housed in a rectangular box on a circuit board. The switches are binary in nature, either on or off for each switch. Dip switches were more common on old ISA cards, and are often used in place of groups of jumpers. Nowadays Plug-and-Play and the abundance of Flash memory for saving settings have all but eliminated these nasty things in consumer PCs.
Direct Connection A permanent connection between your computer system to a computer network.
Directory A directory is another name for a folder. Files on your hard disk are organized into various folders, or directories, so that it is easier to keep track of them. For example, you may keep your pictures in one folder and your music files in another folder. Folders can also contain other folders, allowing for more specific organization. Since you can have folders within a folder, files on your hard drive are organized much like branches on a tree. The main directory on your hard drive is appropriately called the "root directory." Folders that exist within the root directory most likely contain other folders, which may branch out to even more folders. When you are browsing one directory and want to open the folder that contains the current directory, it is called "moving up a directory." As you move up directories, you will eventually move up to the root directory. In Windows, this may be your C:\ directory, while on the Mac it will be the name of your hard drive, such as "Macintosh HD."
DirectX DirectX is a set of standard commands and functions that software developers can use when creating their programs. While any Windows-based software program can include DirectX commands, they are usually used in video games. For example, developers may use DirectX for controlling video playback, sound effects, and peripheral input (such as a keyboard, mouse, or joystick). By incorporating DirectX functions into a computer game, programmers can use predefined commands to manage the video and sound of their game, as well as user input. This makes it easier for programmers to develop video games and also helps the games look more uniform, since DirectX games use many of the same commands. Technically, DirectX is known as an application programming interface (API), which consists of predefined functions and commands. In order to create programs that use DirectX, software developers must use the DirectX software development kit, available from Microsoft. However, most users need only the DirectX "End-User Runtime" installed on their computer in order to run DirectX-enabled software. The DirectX API is available for Windows software and Xbox video games.
Disassembly The process of taking a binary program and deriving the source code from it.
Disaster Recovery Plan (DRP) A Disaster Recovery Plan is the process of recovery of IT systems in the event of a disruption or disaster.
Disc at Once (DAO) This is a single-session method of writing data to a CD-R/RW disc that creates a disc in a format suitable for commercial duplication. Basically, the entire disc is written at once in contrast to Track at Once.
Discretionary Access Control (DAC) Discretionary Access Control consists of something the user can manage, such as a document password.
Disk Drive Often, this is a synonym for hard drive, but it can also refer to a floppy drive or any type of removable drive that uses magnetic media.
Disk Duplexing (RAID 1) There are two forms of RAID 1: disk duplexing and disk mirroring. Disk mirroring involves two hard drives that are on the same drive controller. The same data is written to both drives, so write operations are slower because you must write data to two drives. Read operations are the same speed, as if you only had one drive. Disk duplexing is much like disk mirroring, but each drive is on a separate controller. This speeds up the normally slow write operations and also adds an additional level of redundancy, in case one of your controller cards dies. With RAID 1 you get half the space you paid for because you’re writing twice as much data.
Disk Image A disk image is a software copy of a physical disk. It saves the entire data from the disk, including the file structure and all files and folders from the disk, in a single file. Because disk images are exact copies, or "clones," of original disks, they can be used to duplicate disks or serve as full backups in case a system restore must be done. Disk images can be created from both hard disks and optical media, such as CDs and DVDs. However, optical media images are technically called "disc images" instead of "disk images." Several programs, such as Nero, IsoBuster, and Norton Ghost can be used to make disk images for Windows. Programs like Apple Disk Utility and Roxio Toast can create disk images for Mac OS X. Most disk image files store data in a raw, binary format. This means they do not have a file system, which tells the computer how to access the files and folders in the disk image. Therefore, in order for the data in a disk image to be readable by the computer, the image must first be mounted by either the operating system or a disk utility program. File extensions: .ISO, .BIN, .DMG
Disk Mirroring (RAID 1) There are two forms of RAID 1: disk duplexing and disk mirroring. Disk mirroring involves two hard drives that are on the same drive controller. The same data is written to both drives, so write operations are slower because you must write data to two drives. Read operations are the same speed, as if you only had one drive. Disk duplexing is much like disk mirroring, but each drive is on a separate controller. This speeds up the normally slow write operations and also adds an additional level of redundancy, in case one of your controller cards dies. With RAID 1 you get half the space you paid for because you’re writing twice as much data.
Disk mode Disk mode A property of a virtual disk that defines its external behavior but is completely invisible to the guest operating system. There are three modes: persistent (changes to the disk are always preserved across sessions), nonpersistent (changes are never preserved), and undoable (changes are preserved at the user's discretion). Disk modes may be changed from the Configuration Editor's IDE Drives or SCSI Drives panels. For a detailed explanation of disk modes refer to this tech note if your host operating system is Linux or this tech note if you have a Windows NT or Windows 2000 host.
Disk Operating System (DOS) This OS is what got it all started for PCs. It was produced by Microsoft and was a 16-bit command line (non-GUI) operating system, designed to run on 16-bit chips. It was still used for years on 32-bit chips. Today you can find a similar command line interface in all Windows products for quick and easy mouse-less file manipulation by running the “cmd” command.
Disk Striping (RAID 0) Also known as disk striping, this form of RAID combines two or more hard drives into a single logical drive. Any data is written in blocks first to one drive, then the next, and so on. A RAID 0 configuration sacrifices redundancy for raw speed. The more drives you use the faster your logical drive will be. The space available on the logical drive is the sum of space on all of the drives used, assuming that all drives are the same size. If drives are of disparate sizes, RAID 0 generally only uses a piece of the drive equal to the smallest drive. Of course, if one drive dies, you lose all of the information on the entire RAID. Use RAID 0 with care.
Disk Striping with Parity (RAID 5) A RAID 5 configuration utilizes three or more hard drives and stripes the data across them, much like RAID 0. The difference is that parity information is striped across the drives as well, so if you lose any one drive the information can be reconstructed from the parity information. For example, with three drives the first stripe is data (on drive 1), data (on drive 2), parity (on drive 3); then data, parity, data; then parity, data, data. This pattern continues. If one drive fails, you get a mix of parity and data on the remaining two drives, and you can reconstruct all of the data. Of course, before the data is reconstructed the RAID operates in “degraded mode” and is slow. To reconstruct the data you must remove the failed drive and replace it with another, or use a “hot spare.” During reconstruction the array continues to be slow. Once the RAID is reconstructed performance returns to normal levels. RAID 5 performance is similar to RAID 0 performance, but a bit slower due to the parity information. Performance increases, like RAID 0, when more drives are added. With RAID 5 you get most of the space that you’ve paid for, minus one drive’s worth. A common option with RAID 5 is the hot spare, where a drive sits idle until needed. If you lose a drive, the hot spare takes over and the RAID is rebuilt automatically. Of course you still get the performance penalty during the rebuilding stage, but it can be set to happen automatically.
Disk Thrashing On a system with Virtual Memory, pages of memory are read from and written to the swap file as necessary. Disk Thrashing is when there is excessive paging, specifically when the I/O system is busy paging memory but the CPU is not fully utilized - generally if the system is unresponsive (i.e. slow) and there is lots of disk activity then the system is likely to be thrashing. If disk thrashing is a problem then a short term solution may be to reduce the number of running applications. A longer term solution is to add more memory. Also known as Thrashing.
diskette Also referred to as a "floppy disk;" a portable magnetic disk most often used for secondary file storage. Current floppy disks are usually 3 1/2 inches in size with a storage capacity of up to 1.44 MB.
Disruption A circumstance or event that interrupts or prevents the correct operation of system services and functions.
Distance Vector Distance vectors measure the cost of routes to determine the best route to all known networks.
Distributed File System (DFS) A Microsoft technology introduced in Windows 2000 that allows multiple servers and shared directories on a network to appear as a single network drive, thus helping to ease the annoying problem of running out of drive letters in complex environments. With DFS, you can have your users’ H: drive, for example, be a collection of network resources instead of just a single share.
Distributed Scans Distributed Scans are scans that use multiple source addresses to gather information.
DLL Dynamic Link Library. A shared library that can be loaded once by the operating system but used simultaneously by different processes and applications. Typically these have the file extension .dll.
DMA Stands for "Direct Memory Access." DMA is a method of transferring data from the computer's RAM to another part of the computer without processing it using the CPU. While most data that is input or output from your computer is processed by the CPU, some data does not require processing, or can be processed by another device. In these situations, DMA can save processing time and is a more efficient way to move data from the computer's memory to other devices. For example, a sound card may need to access data stored in the computer's RAM, but since it can process the data itself, it may use DMA to bypass the CPU. Video cards that support DMA can also access the system memory and process graphics without needing the CPU. Ultra DMA hard drives use DMA to transfer data faster than previous hard drives that required the data to first be run through the CPU. In order for devices to use direct memory access, they must be assigned to a DMA channel. Each type of port on a computer has a set of DMA channels that can be assigned to each connected device. For example, a PCI controller and a hard drive controller each have their own set of DMA channels.
DMI Desktop Management Interface. This is a method for managing computers in an organisation. The main component, the Management Information Format Database (MIFD), is a database that contains all the information about the local computer and its components.
DMI Pool The set of data about a computer and its components, including partition data for your hard drive. When a PC boots it will display the message, “Verifying DMI Pool,” and if it will not boot past this it typically means your motherboard is not able to access your hard drive properly. This can be caused by a wrong BIOS setting for your hard drive (try “Auto”) or a non-bootable floppy disk if your floppy drive is set to boot first.
DMZ Demilitarised Zone. A computer within a DMZ is unprotected by a firewall and typically any port accesses are routed through to that computer. A router will forward all traffic to the computer in the DMZ if it does not otherwise have a rule for how to forward traffic on a given port. (The computer within the DMZ may still be protected by its own separate firewall.)
DMZ (DeMilitarized Zone) A part of a network that is protected by a firewall, but may be accessed by external Internet clients. The DMZ generally contains servers such as SMTP servers, remote access machines. or webservers. Client machines and internal servers that do not need to be accessed by Internet clients are kept in a more protected segment of the network than the DMZ. Alternately, DMZ can be used to refer to the media layer where route peering is done among multiple administrative regions with their own traffic policies.
DNS Domain Name Service or Domain Name System. Provides hostname to IP address translations. See also A Records, CNAME.
DNS (Domain Name Service) This service maps TCP/IP numbers, such as 123.12.4.245, to a more easily remembered name, such as www.geek.com. Thus, when you type www.geek.com into your browser, it goes out to the DNS server specified by your ISP and asks for a matching TCP/IP address.If the browser finds a DNS entry for the name you typed in, you see the appropriate website. If not, it lets you know. Every domain name that is actually being used for a website has a corresponding TCP/IP address. When you set up a site you have your ISP add a DNS entry to its DNS servers (or manage it yourself). This entry gets replicated across the Internet in a matter of hours, and, once fully replicated, you can reach your website from any Internet connection.
DNS Entry The DNS routing tables are filled with DNS entries that map TCP/IP addresses to more easily recognized names. If your browser says it can’t find a particular DNS entry, here are some possible reasons: you may not be able to communicate with your DNS server, the site may not be responding, or your connection is broken. If a DNS server really doesn’t have the entry, there may be nothing mapped to that particular domain name address. If the domain name was just set up, the entry may not have fully replicated to your DNS server. Remember, people can own a domain name and not have an entry for it on any DNS server if they are not paying an ISP to host it.
DNS Record DNS records are stored in zone files and are used for translating domain names to IP addresses. They also contain other data, including the domain name's name server and mail server information. If there are domain name aliases, such as the commonly used "www" preceding the domain name, these will also be listed in the DNS record. A typical DNS record may look something like this: ; Nameservers ; IN NS ns1.4servers.com. ; 123.456.789.01 IN NS ns2.4servers.com. ; 123.456.789.02 ; ; Domain Mail Handlers ; yourdomain.com. IN MX 0 mail yourdomain.com. IN MX 10 mail ; ; ; hosts in order ; yourdomain. IN A Your.IP.XXX www IN A Your.IP.XXX smtp IN CNAME www pop IN CNAME www ftp IN CNAME www mail IN A Your.IP.XXX ; ; end Since DNS records are made up entirely of text, they are easy to modify when needed. However, one small typo could redirect a domain name to the wrong Web server or prevent it from showing up at all. This is why it is important to enter DNS information accurately and double-check your changes entry before saving the zone file.
DNS Server DNS Server A server providing DNS name translations. A DNS Server translates from names to IP Addresses. A DNS Server on a LAN will provide translations from local computer names to their IP addresses, and forward requests for unrecognised names to external DNS servers for name resolution. Also known as a nameserver.
DNSBL DNS Block List. A DNSBL is a list of DNS entries from which incoming emails should be blocked. Also known as a DNS Black-hole List. DNSBLs typically list open relays and servers which can be used for RNDR attacks. These are typically used as a means to reduce spam by blocking emails from known (or likely) spammers. However, it should be appreciated that DNSBL works on listing IP addresses and does not provide any intelligent filtering based on the content of an email. DNSBL can be created and customised within a company, but there are also third party DNSBL services available on the internet. DNSBL are sometimes also referred to as RBL or simply BL.
Dock The Dock is a feature of the Mac OS X Finder that provides quick access to programs, files, and folders. By default, the Dock sits at the bottom of the screen, though it can be moved to the left or right and can be hidden if preferred. It contains application icons on the left side and files and folders on the right. You can open programs and files directly from the Dock and can add or remove items by dragging the corresponding icons to or from the Dock.
Document A document, or web document, is a resource on the World Wide Web that has a distinct web address. It could be an embedded image, whole web page, pdf or any other component of a web page. A document can be any kind of MIME type.
Domain While the term "domain" is often used synonymously with "domain name," it also has a definition specific to local networks. A domain contains a group of computers that can be accessed and administered with a common set of rules. For example, a company may require all local computers to be networked within the same domain so that each computer can be seen from other computers within the domain or located from a central server. Setting up a domain may also block outside traffic from accessing computers within the network, which adds an extra level of security. While domains can be setup using a variety of networking software, including applications from Novell and Oracle, Windows users are most likely familiar with Windows Network Domains. This networking option is built into Windows and allows users to create or join a domain. The domain may or may not be password-protected. Once connected to the domain, a user may view other computers within the domain and can browse the shared files and folders available on the connected systems. Windows XP users can browse Windows Network Domains by selecting the "My Network Places" option on the left side of an open window. You can create a new domain by using the Network Setup Wixard. Mac users using Mac OS X 10.2 or later can also connect to a Windows Network by clicking the "Network" icon on the left side of an open window. This will allow you to browse local Macintosh and Windows networks using the SMB protocol.
Domain Hijacking Domain hijacking is an attack by which an attacker takes over a domain by first blocking access to the domain's DNS server and then putting his own server up in its place.
Domain Name The unique name that identifies an Internet site. Domain Names always have 2 or more parts, separated by dots. The part on the left is the most specific, and the part on the right is the most general. A given machine may have more than one Domain Name but a given Domain Name points to only one machine.
Domain Suffix A domain suffix is the last part of a domain name and is often referred to as a "top-level domain" or TLD. Popular domain suffixes include ".com," ".net," and ".org," but there are dozens of domain suffixes approved by ICANN. Each domain suffix is intended to define the type of website represented by the domain name. For example, .com domains are meant for commercial websites, whereas .org domains are to be used by organizations. However, since any entity can register domain names with these suffixes, the domain suffix does not always represent the type of website that uses the domain name. For example, many individuals and organizations register .com domain names for non-commercial purposes, since the .com domain is the most sought after. Each country also has a unique domain suffix used for websites within the country. For example, Brazilian websites may use the .br domain suffix, Chinese websites may use the .cn suffix, and Swedish websites may use the .se suffix. These country-based TLDs, sometimes referred to as "country codes," are also used by international websites for defining the language of website. For example, the German home page for Google is "www.google.de" instead of "www.google.com."
Dongle This funny-sounding computer term has two widely different definitions that are completely unrelated: 1. A security key. This is a little hardware device that plugs into the serial or USB port of a computer. Its purpose is to ensure that only authorized users can use certain software applications. If you have never seen a dongle, don't be surprised. They are only used with expensive, high-end software programs that most people have never heard of, much less use. When a program that comes with a dongle runs, it checks the dongle for verification as it is loading. If it doesn't find the dongle, the computer explodes. Well, not really -- usually the program just quits. If more than one application requires a dongle, multiple dongles using the same port can be daisy-chained together. Basically, if you ever find yourself daisy-chaining multiple dongles together, you must be doing pretty well in life. 2. A laptop Ethernet card adapter. This is a little connector that attaches to a PC card in a laptop on one end, and to an Ethernet cable on the other end. Since most PC (or PCMCIA) network interface cards are too small to connect directly to a standard RJ-45 Ethernet cable, they need this little adapter that connects the card to the cable. (3Com cards that use an "X-Jack" connector do not need a dongle.) As far as why the name dongle is used, I have no idea.
DOS 1. Disk Operating System. The original command line based operating system used on IBM personal computers and compatibles. Technically PC-DOS refers to the version of DOS used on IBM computers and MS-DOS the version of DOS used on compatible clones from other manufacturers. Both PC-DOS and MS-DOS were written by Microsoft and were essentially identical. DOS predates Windows. Earlier versions of Windows (notably Windows 9x) provided the option to restart in "DOS mode". Current Windows versions still support a "Command Prompt", which provides a DOS like interface.
double buffering This programming technique uses two buffers to speed up any computer task when the hardware can process and push information around at the same time. In graphics cards, double buffering is often used to store the next frame in a video clip in an offscreen frame buffer while displaying the current frame. This way, when the present frame is finished, the next frame is ready to write to the displayable portion of the buffer. See also: frame buffer
Double Click Double clicking involves clicking your mouse button quickly two times. To perform a double click, and not just two clicks, the mouse button must be pressed twice within a very short time, typically about half a second. Most operating systems allow you to lengthen or shorten the maximum time allowed for a double click, using the Mouse Control Panel or System Preference. A double click is recognized by your computer as a specific command, just like pressing a key on your keyboard. Double clicking is used to to perform a variety of actions, such as opening a program, opening a folder, or selecting a word of text. In order to double click an object, just move the cursor over the item and press the left mouse button quickly two times.
Down In computing "Down" is usually used to mean "Off", "not working" or "not available". For example "the database is down" is a statement that the database is not available for use and the statement "to power down" means to shutdown and power off. cf Up.
Download To receive (or copy) data from a remote computer to a local computer via a network, modem, serial or parallel cable. For example to copy a file from a server on the internet to the local computer you are said to be downloading the file. cf Upload.
Downstream The downloading (receiving) of data from the Internet to a client machine. Downstream speeds are typically much greater than upstream speeds in high speed consumer Internet connections such as cable modems and ADSL.
DPI Dots Per Inch. A measure of the resolution of scanners, printers and display devices.
Dr. Watson This is diagnostic software that runs automatically in Windows NT/2000/XP and can be turned on in Windows98/Me. Dr. Watson takes over when a program crashes and writes a snapshot of information about the crash to disk.
Drag You can use your mouse to drag icons and other objects on your computer screen. Dragging icons from your desktop or an open window to another folder will move the objects to the new folder. You can also drag icons to the Trash (Mac) or the Recycle Bin (Windows) if you want to delete tehm. Some word processing programs allow you to select text and drag the selected text to another place in the document. To select the text, you may have to "drag" the mouse over the text you want to select. Dragging is an important technique for using today's graphical user interfaces (GUIs). In fact, there are many other things you can drag besides icons. For example, you can drag the top of windows to reposition them, you can drag the scroll bar in open documents or Web pages to scroll through them, and you can drag messages to different folders in your mail program. Other programs, such as video games and image-editing programs use dragging to reposition items on the screen. To drag an item, first move the cursor over the item you want to drag. Then click and hold down the left mouse button to "grab" the item. Move the mouse to position the item where you want it. Let go of the mouse button once you have moved the item to "release" it. This technique is known as a "drag and drop."
drag and drop The act of clicking on one icon and moving it on top of another icon to initiate a specific action. Example: Dragging a file on top of a folder to copy it to a new location.
DRAM Dynamic Random Access Memory (Dynamic-RAM).
Drive Bay This is usually a 5.25″ wide 1″ tall hole in a computer case suitable for the installation of some sort of drive. Some are exposed so that a removable drive (e.g., floppy, CD-ROM) can fit. Some are not exposed and are meant for hard drives that users don’t need access to.
Driver A driver is software that works to communicate between an operating system and a peripheral. Think of it as a translator. If you use a crappy driver, your OS won’t understand your video card and may become unstable and crash. Hardware manufacturers constantly update drivers to make them faster and more stable. Operating systems typically come with a set of drivers, but peripherals newer than your operating system typically require new drivers which must be installed via CD-ROM, floppy, or downloaded from the Web.
Driver Software Software used to make computer peripherals function. Driver software is written specifically for the device to allow it to work with a particular operating system of the computer. If you upgrade your computer operating system, such as moving from Windows 98 to Windows XP then you will normally require new driver software for each of your peripherals. However, depending on the peripheral, more modern versions of Windows may already come supplied with the necessary drivers.
DRM Stands for "Digital Rights Management." DRM refers to a collection of systems used to protect the copyrights of electronic media. These include digital music and movies, as well as other data that is stored and transferred digitally. For example, the Apple iTunes Music Store uses a DRM system to limit the number of computers that songs can be played on. Each audio file downloaded from the iTunes music store includes information about the owner of the file and how many times the file has been transferred. The protected files will not play on computers that have not been authorized to play the music. Digital Rights Management is important to publishers of electronic media since it helps ensure they will receive the appropriate revenue for their products. By controlling the trading, protection, monitoring, and tracking of digital media, DRM helps publishers limit the illegal propagation of copyrighted works. This can be accomplished by using digital watermarks or proprietary file encryption on the media they distribute. Whatever method publishers choose to employ, DRM helps them make sure that their digital content is only used by those who have paid for it.
Dropdown Menu A type of menu that appears as a text box with an arrow pointing down in part of the box. It allows a user to click on it, and a list of choices appear below the menu. After the information drops down, one of the items can be selected. It’s possible that the information appears above the menu if there is not space below it.
DRP Disaster Recovery Plan. A contingency plan covering how a business should recover from potential disasters disaster and continue functioning. Occasionally referred to as a Business Continuity Plan (BCP).
Drum The part of a laser printer onto which the laser produces an electrostatic image. The drum is then rolled in toner and that toner is transferred to paper with pressure and heat. Most drums are coated with selenium for its electrical properties. Selenium is a nonmetallic element in the sulfur family, and it allows the drum to hold a charge and attract toner.
DS-0 (Digital Signal level 0) The signal used to carry a standard analog or digital phone line connection. 24 DS-0 connections can be carried on a T1 line. The speed of the line is either 64Kbps, or 56Kbps if the eighth bit is used for signaling information
DS-1 (Digital Signal level 1) Synonym for T1.
DS-2 (Digital Signal level 2) Synonym for T2.
DS-3 (Digital Signal level 3) Synonym for T3.
DS-4 (Digital Signal level 4) Synonym for T4
DS-5 (Digital Signal level 5) Synonym for T5.
DSL (Digital Subscriber Line) A method for moving data over regular phone lines. A DSL circuit is much faster than a regular phone connection, and the wires coming into the subscriber's premises are the same (copper) wires used for regular phone service. A DSL circuit must be configured to connect two specific locations, similar to a leased line (howeverr a DSL circuit is not a leased line. A common configuration of DSL allows downloads at speeds of up to 1.544 megabits (not megabytes) per second, and uploads at speeds of 128 kilobits per second. This arrangement is called ADSL: Asymmetric Digital Subscriber Line. Another common configuration is symmetrical: 384 Kilobits per second in both directions. In theory ADSL allows download speeds of up to 9 megabits per second and upload speeds of up to 640 kilobits per second. DSL is now a popular alternative to Leased Lines and ISDN, being faster than ISDN and less costly than traditional Leased Lines.
DSP Digital Signal Processing.
DST Daylight Saving Time. A system where the local clocks are advanced by an hour during the summer to make better use of the sunlight hours. Also known by different names in different countries, although "Summer Time" is common (e.g. BST = British Summer Time). In Europe (according to the European directive 2000/C 337 E/18) the official change time is 01:00 hours GMT. It is 02:00 hours in America.
DTD 1. Data Type Definition. 2. Document Type Definition. A document that formally specifies for an an XML schema the XML elements, their attributes and their syntax. Given a DTD an XML parser should then be able to parse the XML document for which the DTD relates.
DTD (Document Type Definition) Stands for "Document Type Definition." A DTD defines the tags and attributes used in an XML or HTML document. Any elements defined in a DTD can be used in these documents, along with the predefined tags and attributes that are part of each markup language. The following is an example of a DTD used for defining an automobile: ]> The above DTD first defines the header of the item as "Car Details." Then it provides elements to define the make and model of the automobile. The "#PCDATA" data type means it can be any text value). The "ATTLIST" tag on the next line provides options for a specific element. In this case, it states that the model can have either two or four doors. The DTD then provides elements for the year and engine type of the car, followed by a choice of either a manual or automatic transmission for the engine. The above example is a basic DTD that only uses a few data types. Document type definitions used for large XML databases can be thousands of lines long and can include many other data types. Fortunately, DTDs can be easily modified in a text editor whenever changes need to be made.
Dual boot A system that can boot to two different operating systems. Some OSes, such as Windows NT/2000/XP and versions of Linux, allow for dual booting when installed. Of course, you can also use other methods, such as commercial programs that install a special boot partition that is capable of launching operating systems from other partitions. You can also boot to many more than two operating systems on the same machine.
Dual-Core A dual-core processor is a CPU with two processors or "execution cores" in the same integrated circuit. Each processor has its own cache and controller, which enables it to function as efficiently as a single processor. However, because the two processors are linked together, they can perform operations up to twice as fast as a single processor can. The Intel Core Duo, the AMD X2, and the dual-core PowerPC G5 are all examples of CPUs that use dual-core technologies. These CPUs each combine two processor cores on a single silicon chip. This is different than a "dual processor" configuration, in which two physically separate CPUs work together. However, some high-end machines, such as the PowerPC G5 Quad, use two separate dual-core processors together, providing up to four times the performance of a single processor. While a dual-core system has twice the processing power of a single-processor machine, it does not always perform twice as fast. This is because the software running on the machine may not be able to take full advantage or both processors. Some operating systems and programs are optimized for multiprocessing, while others are not. Though programs that have been optimized for multiple processors will run especially fast on dual-core systems, most programs will see at least some benefit from multiple processors as well.
Dualscan A passive matrix LCD screen that uses a better method of displaying graphics, producing a sharper, more vivid image than standard passive matrix screens.
Due Care Due care ensures that a minimal level of protection is in place in accordance with the best practice in the industry.
Due Diligence Due diligence is the requirement that organizations must develop and deploy a protection plan to prevent fraud, abuse, and additional deploy a means to detect them if they occur.
Dumb Terminal These are hooked up to mainframes, and are little more than a monitor attached to a keyboard. All they are good for is running programs using the mainframe’s hard drive and memory, thus the “dumb” in the name.
DumpSec DumpSec is a security tool that dumps a variety of information about a system's users, file system, registry, permissions, password policy, and services.
Dumpster Diving Dumpster Diving is obtaining passwords and corporate directories by searching through discarded media.
Duplex A telecommunications term that describes part of the communications between a local modem and a remote computer. In full duplex mode, the remote computer is set up to return the characters that are sent to it so that they can be displayed on your screen. In half duplex mode, the remote computer does not return the characters sent to it. Also see full duplex and half duplex for descriptions of the those terms in other contexts.
DVD Digital Video Disk, or Digital Versatile Disk. DVDs have varying capacities from 4.7GB to 17GB. A conventional single layer recordable DVD will hold up to 4.7GB of data per disk. A recordable dual-layer DVD will hold up to 8.5GB of data. Dual-layering allows two layers to be stored on the same side of the DVD. When playing a DVD there is normally a slight pause when the DVD player switches layers (as the laser repositions to read the second layer).
DVI 1. Digital Visual Interface. An interface between a PC graphics card and a monitor (or other display device) that is completely digital. Being completely digital there is no digital to analogue conversion involved, there is no signal loss that such a conversion would otherwise introduce. DVI is commonly used as a connection standard for HDTVs.
DWORD Double-Word, meaning two words or typically four bytes.
Dynamic DNS Dynamic DNS Dynamic Domain Name Service (or Dynamic Domain Name System). DNS. Dynamic DNS provides a central (public) database where DNS information can be stored and retrieved. It allows those using a dynamic IP address (i.e. one where it changes each time the computer connects to the internet) to be registered centrally so others can connect to it by name (using standard DNS). Commonly abbreviated to DDNS.
Dynamic Website A dynamic website contains Web pages that are generated dynamically. Each time a user accesses a page within a dynamic site, the HTML is generated in real-time and is sent to the user's Web browser. The content is typically accessed from a database, which is why dynamic websites are often called "database-driven" sites. Most large sites contain dynamic content, while smaller sites may be designed as static websites.
e-book The concept behind an e-book is that it should provide all the functionality of an ordinary book but in a manner that is (overall) less expensive and more environmentally friendly. The actual term e-book is somewhat confusingly used to refer to a variety of things: custom software to play e-book titles, dedicated hardware to play e-book titles, and the e-book titles themselves. Individual e-book titles can be free or commercial (but will always be less expensive than their printed counterparts) and have to be loaded into a player to be read. Players vary wildly in capability level. Basic ones allow simple reading and bookmarking; better ones include various features like hypertext, illustrations, audio, and even limited video. Other optional features allow the user to mark-up sections of text, leave notes, circle or diagram things, highlight passages, program or customize settings, and even use interactive fiction.
E-mail This stands for electronic mail. It is a service provided over the Internet that allows you to send information to another person or list of people.
e-mail alias or e-mail forwarding Not every e-mail address has its own POP3 or Web-based mailbox. Some merely redirect e-mail traffic to another e-mail address. These P.O. Box-style addresses are called aliases or e-mail forwarding addresses. Domain hosts or registrars offer them as a service to people who register domains but don't want to reconfigure their e-mail software to pick up from another e-mail box--or pay for space on an e-mail server.
Easter egg Brightly colored protochickens? Not always. Easter eggs are also "hidden features" placed by programmers in software applications, operating systems, and even some hardware. Discover the hidden command sequence, and an Easter-egged product will perform an action, such as displaying a secret message or playing a sound or small animation.
Eavesdropping Eavesdropping is simply listening to a private conversation which may reveal information which can provide access to a facility or network.
ECC Error Correcting Code. An error correction code is additional data sent with a message which allows the recipient to identify whether the data has become corrupted in transit and to correct the error. The number of errors (typically the number of bit errors) which can be corrected will depend on the amount of error correction applied.
Echo Reply An echo reply is the response a machine that has received an echo request sends over ICMP.
Echo Request An echo request is an ICMP message sent to a machine to determine if it is online and how long traffic takes to get to it.
EDI Electronic Data Interchange. The transfer of data electronically between computers. The term is typically used to denote the transfer of data electronically across a network between two separate organisations. There are a wide range of standards for electronic data interchange, the two most common are ANSI X12 end EDIFACT.
EDIFACT EDI for Administration, Commerce and Transport. This refers to the United Nations rules for EDI for Administration, Commerce and Transport. ISO standard 9735.
EFS Encrypting File System. Strengthens security by encrypting files on the hard disk so that no one can access them without using the correct password. Encrypted files are visible only to the individual who encrypted them. This is handled seamlessly by EFS, so the owning user can still browse and open files as normal - at the same time preventing others from doing so. Encrypted files can also be recovered using the recovery agent - which uses certificates and public keys to decrypt files.
EFT Electronic Funds Transfer. A system where money is transferred electronically from one bank account to another, without the need for any paper work such as the traditional cheque.
EGA (Enhanced Graphics Adapter) The standard that came after CGA and before VGA. It allowed resolutions up to 640×350 pixels and 16 colors from a palette of 64. It was soon replaced by VGA. EGA images look squished because the aspect ratio of 640×350 is not flattering compared to the more standard 640×480 resolution of VGA that corresponded exactly to the 4:3 aspect ratio of most computer monitors.
Egress Filtering Filtering outbound traffic.
EIDE Enhanced IDE. See ATA.
eLearning lectronic learning; applies to a wide scope of processes including Web-based learning, computer-based instruction, virtual classrooms, and digital collaboration. Content may be delivered in a variety of ways including via the Internet, satellite broadcast, interactive TV, and DVD- or CD-ROMs.
Electromagnetic Field (EMF) A form of radiation given off by all electrical devices. Most notably for computer users, CRT computer monitors used to give off potentially dangerous amounts of EMF radiation, especially from the sides and rear. This radiation was blamed for causing miscarriages and even cancer. Newer monitors are heavily shielded and give off much lower levels of radiation, especially through the front, where users typically sit.
Email 1. Electronic Mail. Virtually instantaneous electronic messaging. cf SMTP, snail mail, spam, email address. Email can be written as either "email" or "e-mail". 2. Email Address. For details see email address.
Email Address Electronic mail address. For the recipient of an email, the email address is the address to which the email is sent. For a sender each (outgoing) email should identify the sender's email address (to allow for replies). An email address consists of two parts, a username and a domain (or host) name with an at symbol ('@') separating them. The domain specifies which server the email should be delivered to and the username tells the server at that domain which mailbox to deposit the email into.
Emanations Analysis Gaining direct knowledge of communicated data by monitoring and resolving a signal that is emitted by a system and that contains the data but is not intended to communicate the data.
Embedded Memory This is memory that is built directly onto a processor. For example, a graphics chip may have embedded memory instead of using separate memory chips. Use of embedded memory in PCs and PC components nowadays is fairly rare, as attaching a large amount of memory to a chip reduces yields and increases costs.
Embedded Processor A microprocessor used in an embedded system. Typically these processors are smaller, consume less power, and utilize a surface mount form factor, as opposed to more standard consumer processors. Embedded processors are only sold to consumers pre-built into embedded systems, not separately.
Embedded System A system that is located entirely on a processor. All logic is contained in a single chip and has a single purpose. New cars have many embedded systems working to keep emissions low and performance high.
EMEA Europe, Middle East and Africa. Refers to a large geographic region encompassing Europe, the Middle East and Africa.
EMF A form of radiation given off by all electrical devices. Most notably for computer users, CRT computer monitors used to give off potentially dangerous amounts of EMF radiation, especially from the sides and rear. This radiation was blamed for causing miscarriages and even cancer. Newer monitors are heavily shielded and give off much lower levels of radiation, especially through the front, where users typically sit.
emoticon A combination of keyboard characters meant to represent a facial expression. Frequently used in electronic communications to convey a particular meaning, much like tone of voice is used in spoken communications. Examples: the characters :-) for a smiley face or ;-) for a wink.
Emulation The term "emulation" comes from the verb "emulate," which means to imitate or reproduce. Therefore, computer emulation is when one system imitates or reproduces another system. This can be done using hardware, software, or a combination of the two. However, since hardware is expensive to reproduce, most emulation is done via software. One of the most common types of software emulation involves running different operating systems in a virtual environment. For example, programs like Parallels Desktop, VMware, and Apple's Boot Camp allow Windows and other operating systems to run on an Intel-based Macintosh computer. Sun Microsystems' xVM VirtualBox allows multiple operating systems to be run on Windows, Mac, and Unix platforms. These applications are collectively referred to as software emulators, since they emulate different computer systems. Another popular type of software emulation allows console video games, such as Nintendo, Sega, and PlayStation games, to be run on a PC. The program ZSNES, for example, allows Super Nintendo (SNES) games to be played on a Windows or Unix machine. The Virtual Boy Advance emulator allows users to play Game Boy Advance games on Windows or Macintosh computers. Games for these emulators are saved as ROM files, which are exact copies of a game cartridge or disk. Therefore, instead loading a physical cartridge, video game emulators simply load ROM files from the computer's hard drive. A third type of emulation uses a type of file called a disk image. While ROM files are used to emulate game cartridges, disk images can be used to emulate optical media and physical hard disk. For example, an .ISO file (Windows) or .DMG file (Mac) can be mounted on the desktop, which makes the operating system view the file as a physical disk. This provides an easy way to make exact copies of CDs, DVDs, and hard disks. Disk images are also commonly used to create virtual installer disks that can't be modified by the user. A software technology allowing an operating system or an application to run on hardware other than the one for which it was developed.
Emulator This is usually a program that performs the same operation of another program or a piece of hardware. For example, there are programs that allow a PC to act like a Commodore 64, a Nintendo Entertainment System, or even a Macintosh. These emulators are often developed by talented programmers just to prove that something can be done.
Encapsulation The inclusion of one data structure within another structure so that the first data structure is hidden for the time being.
Encryption A method of protecting data by transforming it in such as way that a reader cannot understand the data unless they know the decryption mechanism. Encryption algorithms come in two general types: Symmetric algorithms and Asymmetric algorithms. Symmetric algorithms uses the same key to encrypt and decrypt. Asymmetric algorithms use a different key to encrypt and decrypt. See also: DES, RAS
Enterprise The entirety of an organization that uses computers. Typically it refers to very large corporations, or software or hardware solutions designed for large organizations. Enterprise companies usually have numerous locations and hundreds, if not thousands, of users to support–a scenario which requires an entirely different type of IT system and management than a small to mid-sized company.
Environment Normally this is your surroundings. Inside your computer, the environment is the settings of a group of variables. Think of it as the surroundings or boundaries set for a process or program running inside your computer. Instead of having a wall and a door, a program in your PC may have x=4 and name=”Tara” as its environment.
EPC Earnings Per Click. Terms used by various affiliate schemes (where webmasters utilise some of the space on web pages for advertisements) to indicate the average earnings per click. EPC is only a guide, because most clicks will generate any revenue.
Ephemeral Port Also called a transient port or a temporary port. Usually is on the client side. It is set up when a client application wants to connect to a server and is destroyed when the client application terminates. It has a number chosen at random that is greater than 1023.
EPROM erasable programmable ROM Unlike dynamic and static RAM, EPROM chips do not require power to retain their data. Consequently, EPROM chips are commonly used to store BIOS information and basic software for modems, video cards, and other peripherals. EPROMs can be erased by exposure to ultraviolet light and then reprogrammed using a device called a PROM burner. See also: BIOS, DRAM, EEPROM, RAM, ROM, SRAM
Error This occurs in a program when it encounters a situation that it was not programmed to deal with. If errors are trapped properly, they can be dealt with by the program itself. If not, they will be dealt with by the operating system on which the program is running.
Error Checking and Correcting (ECC) This generally refers to memory chips or motherboards that support the checking for, and possibly correcting of, memory errors in full-parity memory chips. ECC memory uses some extra memory on the memory chips for parity information, and checks to see whether a memory error has occurred. If a minor (one-bit) memory error occurs, the ECC logic will handle it. With full-parity memory (one step below ECC), you will be alerted of a memory error and your system will stop. With non-parity memory you will experience random results, usually crashing, and possible data corruption. If a two-bit or larger error occurs in ECC memory, your system will be halted–similar to what happens with parity memory when any error is encountered. Many caches built into computer microprocessors now have ECC features.
Escrow Passwords Escrow Passwords are passwords that are written down and stored in a secure location (like a safe) that are used by emergency personnel when privileged personnel are unavailable.
ESSID Extended Service Set ID. The ESSID is the identifying name of a wireless network - strictly it is the identifying name of a wireless access point. It allows one wireless network to be clearly distinguishable from another. ESSID is one type of SSID (the other being BSSID).
EST 1. Eastern Standard Time. The time zone used on the East coast of America and Canada. 2. Abbreviation for Established. When used in this way it is normally followed by a year, for example "Est. 2001", meaning established in 2001. 3. Abbreviation for Estimated. For example, "est. population" would mean "estimated population".
ESX VMware ESX is an enterprise-level virtualization product offered by VMware, Inc. ESX is a component of VMware's larger offering, VMware Infrastructure, which adds management and reliability services to the core server product. The basic server requires some form of persistent storage—typically, an array of hard disk drives—for storing the virtualization kernel and support files. A variant of this design, VMware ESXi, does away with the first requirement by moving the server kernels into a dedicated hardware device. Both variants support the services offered by VMware Infrastructure.[2]
ESXi VMware ESX is an enterprise-level virtualization product offered by VMware, Inc. ESX is a component of VMware's larger offering, VMware Infrastructure, which adds management and reliability services to the core server product. The basic server requires some form of persistent storage—typically, an array of hard disk drives—for storing the virtualization kernel and support files. A variant of this design, VMware ESXi, does away with the first requirement by moving the server kernels into a dedicated hardware device. Both variants support the services offered by VMware Infrastructure.[2]
Ethernet A very common method of networking computers in a LAN. There is more than one type of Ethernet. By 2001 the standard type was "100-BaseT" which can handle up to about 100,000,000 bits-per-second and can be used with almost any kind of computer.
EULA End User License Agreement.
EULA (End User License Agreement) The contract found in most software packages that describes the rights to which the user of the software is entitled. Typically, it will explain how many people can use the software, whether it can be used on multiple machines, and whether it is transferable.
Event An event is an observable occurrence in a system or network.
event handler An event is an action that occurs on a Web page, such as clicking a link or changing the value of a text area. An event may be performed by the user or forced by a script. In JavaScript, an event handler is a mechanism for causing a script to react to an event. For example, if you set the onClick event handler equal to a function call or a JavaScript statement, and include the event handler as an attribute in a link, the code will be executed when the user clicks the link.
Evergreening policy for keeping software and hardware resources up to date. For example a simple evergreening policy might be to replace all computers older than four years with new models. cf "technology replacement", "technology refresh". An evergreening policy should state whether the purpose is to replace technology to maintain an acceptable level of reliability (mean time between failure), to acquire improved speed and capacity at an acceptable price or a combination of the two (i.e. to acquire the lowest or lower cost technology replacement with speed and capacity at least as good as its predecessor). cf "Technology Refresh" and "Technology Replacement".
Exabyte Unit of storage. Often abbreviated to EB. 1 exabyte (EB) = 2 to the sixtieth power (260) bytes = 1,152,921,504,606,846,976 bytes = 1024 petabytes = one billion gigabytes. See also zettabyte.
Excel Microsoft Excel is a spreadsheet program for Windows and Macintosh computers. It is part of the Microsoft Office suite, which includes other productivity programs, such as Word and PowerPoint. Though Excel is developed by Microsoft, the first version of the program was released for the Macintosh in 1985. It wasn't until 1987, when Microsoft introduced Windows 3.0, that Excel was made available for Windows. Since then, Microsoft has supported the program on both platforms, releasing updates about every two years. Some other popular spreadsheet programs include IBM Lotus 1-2-3 (for Windows) and the AppleWorks spreadsheet program (for the Mac). However, Microsoft Excel has led the spreadsheet market for many years and continues to be the most popular spreadsheet program for both businesses and consumers.
EXE File An executable file or application. Normally denoted by a file with a ".exe" file extension. Take care when deleting because executable files. On Windows systems it is preferable to use the Install/Uninstall applet in the Windows Control Panel to remove programs. If you receive an email attachment that is an executable file then only execute it if it is from a known and trusted source because many viruses spread by sending exe files as e-mail attachments.
Execution Unit The part of a microprocessor pipeline that actually follows and runs the instructions that are sent to the CPU after the instructions are decoded.
Expansion Card An expansion card is a printed circuit board that can be installed in computer to add functionality to it. For example, a user may add a new graphics card to his computer to give it more 3D graphics processing power. An audio engineer may add a professional sound card to his machine to increase the computer's audio input and output connections. Users that need more Firewire or USB ports can add Firewire or USB expansion cards, which provide additional connections. Most expansion cards are installed in PCI slots. This includes variations of PCI, such as PCI-X and PCI Express. Graphics cards may also be installed in an AGP slot, which is designed specifically for video cards. Since expansion cards require open slots, they can only be installed in computers that have available expansion slots. Therefore, computers like the Apple iMac and other all-in-one machines cannot accept expansion cards. Computer towers, however, often have two or three open expansion slots, and can accept multiple cards. Laptops don't use traditional expansion cards because of their small form factor. However, some models can accept removable PCMCIA cards that add extra ports or other functionality to the computer.
Expansion Slot Any type of slot in a computer into which you can plug an expansion card. Examples include ISA, EISA, PCI,PCI-X, and PCMCIA, but there are other types and there will be more in the future.
Exploit (n. exploit) A means of gaining access to a computer system, typically through a known bug in a program or operating system. Many webservers on the Internet that are not up to date with security patches are vulnerable to exploits, and the effects of these exploits are seen when malicious worms run rampant and spread to unpatched systems.
Exponential Backoff Algorithm An exponential backoff algorithm is used to adjust TCP timeout values on the fly so that network devices don't continue to timeout sending data over saturated links.
Export en you export data you are taking that data from a program, database, or file and saving it in another format that is generally easier to manipulate or pull into a different program. An example would be pulling data from a SQL database and saving it as text so that you can use it in a mailmerge. Thus, the exporting frees the mailmerge program from having to understand the complex SQL format–it just needs to understand the exported text file.
Exposure A threat action whereby sensitive data is directly released to an unauthorized entity.
Extended ACLs (Cisco) Extended ACLs are a more powerful form of Standard ACLs on Cisco routers. They can make filtering decisions based on IP addresses (source or destination), Ports (source or destination), protocols, and whether a session is established.
Extended partition A type of partition that is an extension of a primary partition. It’s possible to have many extended partitions on a hard drive.
Extensible Authentication Protocol (EAP) A framework that supports multiple, optional authentication mechanisms for PPP, including clear-text passwords, challenge-response, and arbitrary dialog sequences.
Extension (File Extension) DOS, Windows, and, to a lesser extent, UNIX and Linux use the last three characters of a filename, after a period, to signify what type of file a file is, such as text, movie, sound, etc. The MacOS has a file system that contains an identifier for file types that is invisible when looking at the filename, and allows you to call files whatever you want without a messy extension on the end. Some common examples are: .exe (executable file), .bat (batch file), .wav (wave sound file), and .txt (text file).
Exterior Gateway Protocol (EGP) A protocol which distributes routing information to the routers which connect autonomous systems.
External Hard Drive Nearly all personal computers come with an internal hard drive. This drive stores the computer's operating system, programs, and other files. For most users, the internal hard drive provides enough disk space to store all the programs and files. However, if the internal hard drive becomes full or if the user wants to back up the data on the internal hard drive, and external hard drive may be useful. External hard drives typically have one of two interfaces ? USB or Firewire. USB hard drives commonly use the USB 2.0 interface because it supports data transfer rates of up to 480 Mbps. USB 1.1 only supports transfers of up to 12 Mbps, which would make the hard drive seem slow to even the most patient people. Firewire drives may use either Firewire 400 or Firewire 800, which support data transfer rates of up to 400 and 800 Mbps respectively. The most likely users to need external hard drives are those who do audio and video editing. This is because high-quality media files can fill up even the largest hard drives. Fortunately, external hard drives can be daisy chained, which means they can be connected one after the other and be used at the same time. This allows for virtually unlimited amounts storage. Users who do not require extra storage may still find external hard drives useful for backing up their main hard drive. External hard drives are a great backup solution because they can store an exact copy of another hard drive and can be stored in a safe location. Using the drive to restore data or perform another backup is as simple as connecting it to the computer and dragging the necessary files from one drive to another. While most external hard drives come in heavy, protective cases, some hard drives are designed primarily for portability. These drives usually don't hold as much data as their larger desktop counterparts, but they have a sleek form factor and can easily be transported with a laptop computer. Some portable drives also include security features such as fingerprint recognition that prevent other people from accessing data on the drive in case it is lost.
Extranet An intranet that is accesible to computers that are not physically part of a companys' own private network, but that is not accessible to the general public, for example to allow vendors and business partners to access a company web site. Often an intranet will make use of a Virtual Private Network. (VPN.)
False Rejects False Rejects are when an authentication system fails to recognize a valid user.
Fan A device designed to move air by sucking air into one side and pushing it out the other. Fans are a necessary part of most computing devices because microprocessors heat up when run at high frequencies. Fans move the hot air away and allow the microprocessors to be cooled off. Fans are also used in power supplies to keep them cool.
FAQ Frequently Asked Questions. Normally used to refer to a published list of frequently (or commonly) asked questions with answers. In practice FAQs are sometimes lists of questions that the author anticipated that people would want answered, and these do not always necessarily reflect real questions. Nevertheless an FAQ is normally a good source of information about a product or service.
fast Ethernet Fast Ethernet is an upgraded standard for connecting computers into a local area network (LAN). It works just like regular Ethernet except that it can transfer data at a peak rate of 100 mbps. Also referred to as 100BaseT, fast Ethernet is more expensive and less common than its slower 10BaseT sibling. See also: Ethernet (10BaseT)
Fast File System The first major revision to the Unix file system, providing faster read access and faster (delayed, asynchronous) write access through a disk cache and better file system layout on disk. It uses inodes (pointers) and data blocks.
Fast SCSI 2 This version of SCSI transfers data at 10 megabytes per second. The connections all contain 50 pins. See also Fast-Wide SCSI 2.
Fast-SCSI lain vanilla fast-SCSI never really existed, but was sometimes used as slang for Fast SCSI 2. This version of SCSI transfers data at 10 megabytes per second. The connections all contain 50 pins. See also Fast-Wide SCSI 2.
Fast-Wide SCSI 2 This version of SCSI upped the pin count to 68, effectively doubling the signal speed of Fast-SCSI 2 to 20 megabytes per second.
FAT File Allocation Table. More commonly referred to as FAT16 following the advent of FAT32. Uses 16-bit addressing. DOS and Windows 3.x machines commonly use FAT16. Although FAT is still in use, it is generally seen as having been superseded by NTFS.
FAT (File Allocation Table) This is one way to index the contents of storage media, such as your hard drive. The operating system looks here to know where on the drive files are located. There are different flavors of FAT: the standard DOS flavor is called FAT-16; Windows 95 OSR2 and newer versions additionally supported FAT-32, which allows for larger hard drive partitions.
fat binary fat binary When you see a download or another program labeled "fat binary," it means that the program is a little larger than a regular app. The reason? A fat binary program can take full advantage of two hardware platforms: the Macintosh and the Power Mac.
Fat Client A client/server application that performs most of the processing itself rather than at a server. cf Thin Client.
FAT-16 The original DOS File Allocation system. It uses a table to tell the OS where on a hard drive or other storage media each file is located. Due to the 16-bit nature of FAT-16, it is limited to hard drive partitions that are 2 GB in size.
FAT16 File Allocation Table (FAT) based on 16-bit integer addressing, developed by Microsoft. FAT16 was the file system used by MS-DOS and Windows 3.1. FAT16 supports files of up to 2GB, and directories containing up to 65517 entries (files or folders). FAT16 has been superseded by FAT32.
FAT32 File Allocation Table (FAT) based on 32-bit integer addressing. FAT32 was the file system natively used by Windows 95, 98, 98SE and Windows ME. FAT32 supports files of up to 4GB. FAT32 has been superseded by NTFS.
Fault Line Attacks Fault Line Attacks use weaknesses between interfaces of systems to exploit gaps in coverage.
Fault Tolerance The ability for a computer to tolerate (hardware) faults developing in one or more of its components, and to continue operating despite those faults. For example a RAID (if appropriately configured) is fault tolerant because it can withstand a disk failing without loss of data..
Favorite A method of storing and organizing selected URLs in Internet Explorer. See also Bookmark.
FBDIMM Fully Buffered Dual In-line Memory Module.
FDD 1. Floppy Disk Drive.
FDDI Fibre Distributed Data Interface. One type of LAN technology.
FDisk The program Microsoft operating systems MS-DOS and non-NT versions of Windows use to create partitions on hard drives. Technically, the program is called fdisk.exe. It uses a text-based interface. Windows 95b first added support for FAT-32 partitions into fdisk. Before that it only supported partitions up to 2 GB using FAT-16. This is also a slang term for wiping a drive out completely, as in “I’m going to F-Disk this drive if Windows crashes one more time!” There are several non-Microsoft equivalents to fdisk, but all serve similar purposes–to allow partitioning of hard disk drives.
Feature A feature is something that a piece of hardware or software is designed to do. Many things that appear to be bugs are actually features. Often, a hardware or software developer will have to make a trade-off in functionality that causes some undesirable effects. If the developer is aware of this and accepts it, it is not a bug but a feature.
Fedora (operating system) Fedora (pronounced /fəˈdɔrə/) is an RPM-based, general purpose operating system built on top of the Linux kernel, developed by the community-supported Fedora Project and sponsored by Red Hat. The Fedora Project's mission is to lead the advancement of free and open source software and content as a collaborative community.[2] One of Fedora's main objectives is not only to contain software distributed under a free and open source license, but also to be on the leading edge of such technologies.[3][4] Fedora developers prefer to make upstream changes instead of applying fixes specifically for Fedora—this ensures that their updates are available to all Linux distributions.[5] Fedora has a comparatively short life cycle: version X is maintained until one month after version X+2 is released. With 6 months between releases, the maintenance period is about 13 months for each version.[6] Linus Torvalds, author of the Linux kernel, says he uses Fedora because it had fairly good support for PowerPC when he used that processor architecture. He became accustomed to the operating system and continues to use it (as of 2008).[7] According to Distrowatch, Fedora is the second most popular Linux-based operating system as of early 2010, behind Ubuntu.[8]
female connector A cable connector that has holes and plugs into a port or interface to connect one device to another.
Femtosecond (FS) One quadrillionth of a second (1/1,000,000,000,000,000 seconds). See also picosecond.
Fiber Optic A method of physical data transmission that is a newer alternative to sending electrical signals over copper wires. The way it works is by pulsing light down a strand of glass. These pulses represent binary code–so far that’s no better than copper. The advantage is that a single strand of fiber optic can carry thousands and thousands of different frequencies at once without data loss.
Fiber-Optic Cable This is a cable made up of super-thin filaments of glass or other transparent materials that can carry beams of light. Because a fiber-optic cable is light-based, data can be sent through it at the speed of light. Using a laser transmitter that encodes frequency signals into pulses of light, ones and zeros are sent through the cable. The receiving end of the transmission translates the light signals back into data which can be read by a computer. Because fiber-optics are based entirely on beams of light, they are less susceptible to noise and interference than than other data-transfer mediums such as copper wires or telephone lines. However, the cables are fragile and are usually placed underground, which makes them difficult and expensive to install. Some fiber-optic cables are installed above ground, but if they break, they often need to be completely replaced, which is not cheap. While copper wires can be spliced and mended as many times as needed, it is much harder to fix glass fiber-optic cables.
Fibre Channel The British spelling of “fiber”, i.e., “fibre” is used to describe this standard. Fibre Channel uses fiber-optic cable to connect computers or peripherals. It is much more expensive than standard copper cabling, and thus has been a niche product with lots of potential. Today it is used sparingly to connect RAID systems to computers, or to connect drives together within high-end RAID systems.
field Definition: In a database, a field holds exactly one type of information about an item or subject. It is like one line written on an index card in an index card file.
FIELD SEARCHING Ability to limit a search by requiring word or phrase to appear in a specific field of documents (e.g., title, url, link). See LIMITING TO FIELD.
File A file is a collection of data stored in one unit, identified by a filename. It can be a document, picture, audio or video stream, data library, application, or other collection of data. The following is a brief description of each file type. Documents include text files, such as a Word documents, RTF (Rich Text Format) documents, PDFs, Web pages, and others. Pictures include JPEGs, GIFs, BMPs, and layered image files, such as Photoshop documents (PSDs). Audio files include MP3s, AACs, WAVs, AIFs, and several others. Video files can be encoded in MPEG, MOV, WMV, or DV formats, just to name a few. A library file is a unit of data that is referenced by a specific program or the operating system itself. These include plug-ins, components, scripts, and many others. An application is a program, or executable file. Programs such as Microsoft Internet Explorer and Apple iTunes are both applications, but are also files. Files can be opened, saved, deleted, and moved to different folders. They can also be transferred across network connections or downloaded from the Internet. A file's type can be determined by viewing the file's icon or by reading the file extension. If the file type is associated with a specific application, double-clicking the file will typically open the file within the program.
File System Most people have several thousand files on their computer's hard disk, so imagine how hard it would be to find anything if the files were not organized. Fortunately, all hard disks use a file system, which organizes all the files on the disk. The file system is created when you initialize or format your hard disk. It sets up the root directory and subsequent directories beneath it. The file system allows you to create new files and folders, which are added to different parts of the "file tree" on your hard disk. For example, your hard disk probably has separate folders for programs, documents, pictures, music, and movie files. Within these folders, there are likely other folders that futher organize your files. All these folders (or directories) are organized by your computer's file system. There are also several folders your computer's operating system uses to store system files, such as startup data and system preferences. Some of these folders are invisible to the user, but are recognized by the computer's file system. Older Windows machines used a file system called FAT32, while newer Windows computers use NTFS. Macintosh computers used the HFS file system for a long time, but now use an updated version of HFS, called HFS+. Though you typically don't need to know all the details of your computer's file system, it is nice to know that it is always working to keep your files organized.
File Transfer Protocol (FTP) A TCP/IP protocol specifying the transfer of text or binary files across the network.
Filename A filename is a text string that identifies a file. Every file stored on a computer's hard disk has a filename that helps identify the file within a given folder. Therefore, each file within a specific folder must have a different filename, while files in different folders can have the same name. Filenames may contain letters, numbers, and other characters. Depending on the operating system, certain characters cannot be used since they conflict with operators or other syntax used by the operating system. Different operating systems also have different limits for the number of characters a filename can have. While older operating systems limited filenames to only 8 or 16 characters, newer OS's allow filenames to be as long as 256 characters. Of course, for most practical purposes, 16 characters is usually enough. Filenames also usually include a file extension, which identifies the type of file. The file extension is also called the "filename suffix" since it is appended to the filename, following a dot or period. For example, a Microsoft Word document may be named "document1.doc." While technically the filename in the preceding example is "document1" and "doc" is the extension, it is also acceptable to refer to "document1.doc" as the filename. In some cases, the filename may even refer to the file's directory location, i.e. ("\My Documents\School Papers\document1.doc"). You can name a file by clicking on the file's icon or filename, waiting for a second, then clicking on the filename again. As long as the file is not locked, the filename will become highlighted, and you can type a new name for the file. You can also name a file the first time you save it from a program or by selecting "Save As..." from the program's File menu.
filter Refers to: 1) a program that has the function of translating data into a different format (e.g., a program used to import or export data or a particular file); 2) a pattern that prevents non-matching data from passing through (e.g., email filters); and 3) in paint programs and image editors, a special effect that can be applied to a bit map.
Filtering Router An inter-network router that selectively prevents the passage of data packets according to a security policy. A filtering router may be used as a firewall or part of a firewall. A router usually receives a packet from a network and decides where to forward it on a second network. A filtering router does the same, but first decides whether the packet should be forwarded at all, according to some security policy. The policy is implemented by rules (packet filters) loaded into the router.
FIND Tool in most browsers to search for word(s) keyed in document in screen only. Useful to locate a term in a long document. Can be invoked by the keyboard command, CTRL-F (CMD-F on a Macintosh).
Finder The Finder serves as the primary graphical user interface (GUI) for Macintosh computers. It includes the desktop, icons, a menu bar, and the Dock. The Finder allows users to open windows and manage files and folders. While the Finder is technically a Mac OS X application, it automatically loads at startup and is always running.
Finger An Internet software tool for locating people on other Internet sites. Finger is also sometimes used to give access to non-personal information, but the most common use is to see if a person has an account at a particular Internet site. Many sites do not allow incoming Finger requests, but many do.
Fingerprinting Sending strange packets to a system in order to gauge how it responds to determine the operating system.
FiOS Stands for "Fiber Optic Service." FiOS is a data communications service provided by Verizon that uses fiber optic cables to transfer data. FiOS is called a "Fiber to the Premises," or FTTP service, since it brings fiber optic data transmission to residential homes as well as businesses. Since fiber optic technology sends data via pulses of light, it is the fastest method of transferring data. While FiOS is currently used primarily for Internet access, it can also be used for digital cable and voice over IP (VoIP) services. For this reason, FiOS is considered to be a potential competitor to both cable and Internet Service Providers.
Firefox A free internet browser. Firefox is a graphical web browser developed by the Mozilla Foundation and is based on the Mozilla browser. It is cross platform (so runs on a wide range of software platforms), and is widely regarded as the most popular alternative to Internet Explorer.
Firewall A program (or set of programs and/or hardware) that prevents unauthorised access to a network or to an individual computer. See also: SPI.
Firewire Firewire is a cross platform standard for the transmission of serial data between peripherals. Developed by Apple and defined by the IEEE 1394 standard, Firewire is available for all computers. The IEEE 1394 standard allows for transfer speeds of up to 400 mbps, the IEEE 1394b standard allows for transfer speeds of up to 800 mbps.
Firmware Firmware is a software program or set of instructions programmed on a hardware device. It provides the necessary instructions for how the device communicates with the other computer hardware. But how can software be programmed onto hardware? Good question. Firmware is typically stored in the flash ROM of a hardware device. While ROM is "read-only memory," flash ROM can be erased and rewritten because it is actually a type of flash memory. Firmware can be thought of as "semi-permanent" since it remains the same unless it is updated by a firmware updater. You may need to update the firmware of certain devices, such as hard drives and video cards in order for them to work with a new operating system. CD and DVD drive manufacturers often make firmware updates available that allow the drives to read faster media. Sometimes manufacturers release firmware updates that simply make their devices work more efficiently. You can usually find firmware updates by going to the "Support" or "Downloads" area of a manufacturer's website. Keeping your firmware up-to-date is often not necessary, but it is still a good idea. Just make sure that once you start a firmware updater, you let the update finish, because most devices will not function if their firmware is not recognized.
flame An insulting message exchanged via e-mail or within network newsgroups; a series of messages like this are called "flame wars".
Flash 1. Non-volatile memory. Flash devices allow data to be stored without power being applied (unlike conventional RAM). However, Flash is slower to access than RAM and can wear out. 2. Macromedia Flash. Depending on the content, this can refer to the Macromedia Flash player, Composer or Flash File (see .swf). Flash has become a popular and widely supported means for delivering graphics and animation over the internet. Flash was originally developed by the company Macromedia, hence the name "Macromedia Flash". Macromedia was subsequently bought by Adobe, so Flash is now more commonly referred to as "Adobe Flash".
Flash Drive Flash drives have many names — jump drives, thumb drives, pen drives, and USB keychain drives. Regardless of what you call them, they all refer to the same thing, which is a small data storage device that uses flash memory and has a built-in USB connection. Flash drives are typically no more than two to three inches in length and less than an inch in width. Their size and shape may resemble a thumb or a small pen (which is where the names "thumb drive" and "pen drive" come from). Flash drives are also very thin, often having a depth of less than a centimeter. Because of their small form factor, they are highly portable and can easily fit in a pocket or on a keychain (hence the name "keychain drive"). Early flash drives could store only a few megabytes of data, but modern flash drives can store several gigabytes of information. Since they are small in size but have large storage capacities, flash drives have replaced most previous portable data storage mediums such as floppy disks and removable hard disks like Zip disks. Because they have a built-in USB connection, flash drives also don't require a special disk drive to be used. Instead, they can be used on any computer with a USB port, which nearly all modern computers have.
Flash Memory Flash memory is a type of electrically erasable programmable read-only memory (EEPROM). Whew, that's a mouthful. The name comes from how the memory is designed -- a section of memory cells can be erased in a single action or in a "flash." A common use of flash memory is to store the BIOS settings in a computer's ROM. When the BIOS needs to be changed, the flash memory can be written in blocks, rather than bytes, making it easy to update. Most modems use flash memory for the same reason. Though flash memory was orginally used inside computers, it has invaded many other areas outside the box. Flash memory cards used for digital cameras, cellular phones, networking hardware, and PC cards. Though the memory's read/write speed is not lightning fast, it is nice to be able to tote around a little card rather than a cumbersome hard drive.
flash ROM This jargon refers to ROM chips that can be reprogrammed with new BIOS instructions after the chips have left the factory. Such ROM chips are technically called EEPROMs.
Flat File A flat file database is a database that stores data in a plain text file. Each line of the text file holds one record, with fields separated by delimiters, such as commas or tabs. While it uses a simple structure, a flat file database cannot contain multiple tables like a relational database can. Fortunately, most database programs such as Microsoft Access and FileMaker Pro can import flat file databases and use them in a larger relational database. Flat file is also a type of computer file system that stores all data in a single directory. There are no folders or paths used organize the data. While this is a simple way to store files, a flat file system becomes increasingly inefficient as more data is added. The original Macintosh computer used this kind of file system, creatively called the Macintosh File System (MFS). However, it was soon replaced by the more efficient Hierarchical File System (HFS) that was based on a directory structure.
Flat Screen This typically refers to a CRT monitor that is made more flat than a standard tube by using more than one electron gun. It is most useful to professionals who rely on the precision of their monitors. It is also better for the standard user because a straight light across the monitor looks straight and not curved. This can also refer to flat panels and projection screens, which are also flat.
Floating Point As the name implies, floating point numbers are numbers that contain floating decimal points. For example, the numbers 5.5, 0.001, and -2,345.6789 are floating point numbers. Numbers that do not have decimal places are called integers. Computers recognize real numbers that contain fractions as floating point numbers. When a calculation includes a floating point number, it is called a "floating point calculation." Older computers used to have a separate floating point unit (FPU) that handled these calculations, but now the FPU is typically built into the computer's CPU.
Flooding An attack that attempts to cause a failure in (especially, in the security of) a computer system or other data processing entity by providing more input than the entity can process properly.
FLOPS FLOPS is an acronym that means "Floating Point Operations Per Second." FLOPS is a measurement unit that defines the number of floating point operations a processor can perform each second. It is a means of measuring the raw processor's floating point unit, or FPU.
Flowchart A flowchart is a diagram showing the individual steps and sequence of those steps in a procedure or system. It provides a graphic pictorial representation of the sequence of steps.
Folder Just like real world folders, folders on your hard drive store files. These files can be documents, programs, scripts, libraries, and any other kind of computer file you can think of. Folders can also store other folders, which may store more files or other folders, and so on. Folders allow people to organize their files in a way that makes sense to them. For example, a college student might store all her photos in a folder named "Pictures," all her papers in a folder named "School Work," and all her financial information (including the tens of thousands of dollars in student loans) in a folder named "Finances." All these folders might reside within a folder called "My Documents." The computer's operating system also uses folders to store data such as system files, library files, and user preferences. Often, the folders that the system uses are locked, meaning users cannot alter their contents. While folders can store several gigabytes of data, folders themselves hardly take up any space on the hard drive. This is because the folders are really just pointers to files and other folders, telling the computer where they are located. The compilation of folders on your hard drive make up the "directory structure," or overall organization of your hard drive. For this reason, folders are also referred to as "directories." Thank goodness for folders, because without them our hard drives would be pretty cluttered!
Font A font is a specific typeface of a certain size and style. For example, one font may be Arial 12 pt bold, while another font may be Times New Roman 14 pt italic. Most word processing programs have a Font menu that allows you to choose the typeface, size, and style of the text. In order to use a font, you must have it installed on your computer. Windows provides access to fonts using the Fonts control panel. The Mac OS stores fonts in a Fonts folder and includes a separate "Font Book" application for managing fonts.
Footprint This refers to the general size of something, whether physical or virtual. The footprints of small Internet appliances are compared against those of larger PCs, as are smaller LCD screens vs. CRT screens. Different operating systems and programs have their own footprints in the amount of bytes they typically take up on a hard drive, or the amount of physical memory they consume while running.
Forest A forest is a set of Active Directory domains that replicate their databases with each other.
Fork Bomb A Fork Bomb works by using the fork() call to create a new process which is a copy of the original. By doing this repeatedly, all available processes on the machine can be taken up.
Form Factor Typically this refers to the compatibility among PC motherboards, cases, and power supplies. A motherboard, case, and power supply with the same form factor can be used together. Some examples of form factors are AT, ATX, Baby AT, or NLX. Some cases, power supplies, and even motherboards will work in multiple form factors. This is commonly seen in older computer cases that will work with AT or ATX motherboards.
Form-Based Authentication Form-Based Authentication uses forms on a webpage to ask a user to input username and password information.
Format The term "format" has several meanings, related to 1) disk formatting, 2) page formatting, and 3) file formats. 1) Disk formatting In order for storage media, such as a hard drive or flash drive to be recognized by your computer, it first needs to be initialized, or "formatted." Formatting a disk involves testing the disk and writing a new file system onto the disk. This enables the computer to read the disk's directory structure, which defines the way files and folders are organized on the disk. You can use a disk utility program to format or reformat a disk. This will create a blank, empty disk for storing your files. Therefore, only format disks that don't contain important data or make sure you have backed up your data before reformatting a disk! When you reformat a disk, it will appear to be empty. This is because the directory structure has been rewritten, making the entire disk space available for writing new data. However, the old files are still on the disk. They just don't show up since they are no longer included in the directory structure. So if you accidentally format a disk (which is pretty hard to do), you may be able to retrieve your files using a disk utility such as Norton Disk Doctor or DiskWarrior. 2) Page formatting The term "format" can also be used to describe the page layout or style of text in a word processing document. When you format the layout of a page, you can modify the page size, page margins, and line spacing. When you format the text, you can choose the font and font size, as well as text styles, such as bold, underlined, and italics. 3) File formats A file format refers to the way data is saved within a file. For example, some files are saved in a plain text format, while others are saved as binary files. Software developers often create proprietary file formats for their programs, which prevents the files from being used by other applications.
Forward Lookup Forward lookup uses an Internet domain name to find an IP address
Forward Proxy Forward Proxies are designed to be the server through which all requests are made.
FPU Stands for "Floating Point Unit." The first computer processors were far better at dealing with integers than with real numbers (a.k.a. floating point numbers). So a separate FPU processor was developed to handle the floating point calculations. That way, when the CPU encountered a floating-point expresion (ie. 1.62 * 0.87359), it would send the calculation to the FPU. Since the FPU is specifically designed to handle floating-point math, it computes expressions involving real numbers more efficiently. While the first floating point units used to be manufactured as individual chips, they are now typically integrated into the CPU.
FQDN Fully Qualified Domain Name. The full name assigned to an individual computer on a network. Consists of the hostname (i.e. the computer name) prefixed to the domain name.
Fragment Offset The fragment offset field tells the sender where a particular fragment falls in relation to other fragments in the original larger packet.
Fragment Overlap Attack A TCP/IP Fragmentation Attack that is possible because IP allows packets to be broken down into fragments for more efficient transport across various media. The TCP packet (and its header) are carried in the IP packet. In this attack the second fragment contains incorrect offset. When packet is reconstructed, the port number will be overwritten.
Fragmentation This occurs when a hard drive writes a file in multiple segments instead of in a physically contiguous area. A higher level of fragmentation means that most files are fragmented, and many files contain lots of fragments. A low level of fragmentation implies that more files are in one piece, and that if files are fragmented they are only in a few fragments. For example, say you have two files, file A and file B and you write them both to a hard drive. A low level of fragmentation may be represented by: AAAABBBB. A high level of fragmentation may be represented by: AABBABABA. Fragmentation is caused by deletion of small files, and then trying to fit larger files into the leftover spaces. Over time it is a common occurrence that is unavoidable in most file systems.
Frame In the computer world, a frame can be many different things. The different definitions of "frame" are listed below: Some Web sites use HTML frames, where the pages are broken up into various areas. Each area consists of an independent Web page. Frames allow the multiple Web pages to all show up in the same page. Graphics and desktop publishing programs also use frames. In these programs, frames are rectangular areas meant for inserting graphics and text. They allow users to place objects wherever they want to on the page. In video and animation, frames are individual pictures in a sequence of images. For example, a Flash movie you see on the Web may play 12 frames per second, creating the appearance of motion. Most video is shot at 24 or 30 frames per second, or FPS. FPS is often measured in 3D games as a way of checking how fast the graphics processor of a computer is.
frame buffer frame buffer The memory on a graphics card that stores information not being displayed onscreen is called a frame buffer. This memory buffer stores rendered frames offscreen; they are then converted by the RAMDAC and displayed. See also: double buffering, RAMDAC
Frame Relay A packet-based communications method for connecting networks. Nowadays it is commonly used to interconnect remote offices over the Internet or private LANs. Frame relay has no error checking, and assumes that devices on either side will be able to check for errors themselves. A frame relay connection can use an ISDN line for slow speeds, or can be over a T1 line or better if faster speeds are needed. To get a frame relay line installed you contact your phone company or Internet Service Provider.
Free Software Foundation Organisation aiming to promote the development of free software. See also GNU.
FreeBSD (Free Berkeley Software/Standard Distribution) A UNIX-like operating system that runs on the Intel x86 platform and is based on an OS developed at University of California at Berkeley. It is now a no-cost operating system, and the source can be downloaded and modified.
Freeware Like shareware, freeware is software you can download, pass around, and distribute without any initial payment. However, the great part about freeware is that you never have to pay for it. No 30 day limit, no demo versions, no disabled features -- it's totally free. Things like minor program updates and small games are commonly distributed as freeware. Though freeware does not cost anything, it is still copyrighted, so other people can't market the software as their own.
FRESHNESS How up-to-date a search engine database is, based primarily on how often its spiders recirculate around the Web and update their copies of the web pages they hold, and discover new ones. Also determined by how quickly they integrate new sites that web authors send to them. Two weeks is about as good as most search engines do, but some update certain selected web sites more frequently, even daily.
Front-end The part of a program or process that the user interfaces with and controls. See also back-end.
Frozen While "frozen" describes the state of Minnesota from November to March, it also refers to an unresponsive computer. When a computer does not respond to any user input, it is said to be frozen. When a computer system freezes, or "locks up," the screen stays the same and does not change no matter what buttons you press on your mouse or keyboard. You can tell if you computer has frozen if the cursor will not move when you move the mouse. A computer typically freezes due to a software malfunction that causes the operating system to "hang." This may happen because of many possible reasons, including a memory leak, an infinite calculation, or another reason. A computer can also freeze because of a hardware malfunction, such as a bad RAM chip or a processor error. Since computers are not supposed to freeze, a software crash is often due to a software programming error or unrecognizable input. Fortunately, modern operating systems, such as Mac OS X are designed so that if one program crashes, it will not affect other programs and the computer will not freeze. If your computer does freeze, you will need to restart the computer to make it function again. You can typically force your computer to shut down by holding the power button for several seconds. And remember - since most computer freezes happen unexpectedly, it is a good idea to save your work frequently!
FSB Front Side Bus.
fsck The system utility fsck (for "file system check") is a tool for checking the consistency of a file system in Unix and Unix-like operating systems such as Linux. Generally, fsck is run automatically at boot time when the operating system detects that a file system is in an inconsistent state, indicating a non-graceful shutdown, such as a crash or power loss. As the command must be tailored specifically to the design of the file system, the exact behavior of various fsck implementations will vary. Typically, fsck utilities provide options for either interactively repairing damaged file systems (the user must decide how to fix specific problems), automatically deciding how to fix specific problems (so the user doesn't have to answer any questions), or reviewing the problems that need to be resolved on a file system without actually fixing them. A system administrator can also run fsck manually if there is believed to be a problem with the file system. Because running fsck to repair a file system which is mounted for read/write operations can potentially cause severe data corruption/loss, the file system is normally checked while unmounted, mounted read-only, or with the system in a special maintenance mode that limits the risk of such damage. A journaling file system is designed such that tools such as fsck do not need to be run after unclean shutdown (i.e. crash). The UFS2 Filesystem in FreeBSD has background fsck, so it is usually not necessary to wait for fsck to finish before accessing the disk. The Microsoft equivalent programs are CHKDSK and SCANDISK.
FSF Free Software Foundation. See also GNU.
FTP FTP File Transfer Protocol. A popular protocol used for transferring files across networks. cf SFTP, PASV. FTP can be used to transfer files from an FTP client (i.e. the software that runs locally on a computer) and an FTP server. An FTP server accepts connections from FTP clients. FTP servers require clients to authenticate using a simple username and password. However many FTP servers allow what is known as anonymous access, whereby users do not need to identify themselves (and enter "anonymous" as their username). Almost all operating systems come with at least a simple FTP client. For example Windows provides a command line FTP client, which can be used to transfer files to and from an FTP server. With a traditional FTP client individual commands are issued to list files, upload or download individual files (see FTP command list in the relevant links below). There are also many GUI applications which provide a more intuitive interface and allow files to be copied without knowledge of the individual FTP commands.
Full Duplex Data can be sent and received simultaneously and at the same speed. cf Half Duplex.
Full parity This is synonymous with full duplex, but most often used when describing dial-up modem communications standards.
Function key (F1, F2, etc.) One of the set of 12 keys at the top of a standard computer keyboard. These keys are labelled F1 through F12. The keys are basically general purpose extra keys so that programmers can assign the keys to special functions in their programs. One handy and common use of F3 in applications is to “Find again,” or find the value again for which you most recently searched.
Fuse A device used to protect devices from excessive electrical current. It contains a conductor that melts and breaks the current flow when too much electricity flows through it. Once a fuse is blown it must be replaced with another one to close the circuit and allow electricity to flow again.
Fuzzing The use of special regression testing tools to generate out-of-spec input for an application in order to find security vulnerabilities. Also see "regression testing".
FW 1. Abbreviation for Firewall. 2. Forward (or Forwarded). Often used as a prefix to an e-mail subject ("FW:") to indicate that the email has been forwarded.
FWIW Abbreviation: For What Its Worth.
FX 1. Foreign Exchange. FX refers to the foreign exchange market, where currencies are bought and sold. 2. Short for "Effects", .sometimes used as an abbreviation for "Special Effects".
FYI Abbreviation: For Your Information. An abbreviation often used on emails or forwarded material to indicate that what is being forwarded is for information and does not necessarily require action.
Gamma In computer graphics and digital video, this refers to a numerical parameter that describes the nonlinearity of intensity reproduction. Basically, as colors get lighter the human eye has more trouble discerning them, and a gamma setting is used to compensate for this so that shades of color on an object, such as those caused by shadows, can be discerned properly. Incorrect gamma settings can cause colors to look too dark or too light, losing detail to the viewer.
Gamma Correction The process of altering the gamma of computer graphics, pictures, or video in order to make the picture show up properly and enable the proper recognition of shades of color. Some graphics accelerators have gamma correction features, as early 3D games often had issues with colors appearing too dark.
Gateway The technical meaning is a hardware or software set-up that translates between two dissimilar protocols, for example America Online has a gateway that translates between its internal, proprietary e-mail format and Internet e-mail format. Another, sloppier meaning of gateway is to describe any mechanism for providing access to another system, e.g. AOL might be called a gateway to the Internet.
GB 1. Giga-Byte. Unit of storage. Abbreviated as GB (not to be confused with Gb, which is giga-bit). For details see gigabyte. 2. Giga-bit. Unit of storage. Abbreviated as Gb, note the small "b" as this distinguishes it from GB. A Giga-bit is a (230) bits. Since there are 8 bits to a byte, 8 Gb = 1 GB.
GDI Graphics Device Interface. In Windows the GDI provides a common set of drawing routines (including both text and graphics). The GDI can be used to draw to most devices, such as screens, printers, plotters or bitmap images. Central to the GDI is the concept of a Device Context (DC) which is a handle to the specific device to be written to.
Gethostbyaddr The gethostbyaddr DNS query is when the address of a machine is known and the name is needed.
Gethostbyname The gethostbyname DNS quest is when the name of a machine is known and the address is needed.
GIF (Graphic Interchange Format) A common format for image files, especially suitable for images containing large areas of the same color. GIF format files of simple images are often smaller than the same file would be if stored in JPEG format, but GIF format does not store photographic images as well as JPEG.
GIG 1. Abbreviation for Gigabyte. GIG implies a single gigabyte, cf GIGS. 2. Abbreviation for Gigahertz.
Gigabyte Unit of storage, usually abbreviated to GB. 1 gigabyte = 2 to the thirtieth power (230) bytes = 1,073,741,824 bytes = 1024 megabytes. See also terabyte. Note: Storage devices sold by manufacturers normally assume 1GB = 1,000 MB = 1,000,000,000 bytes.
Gigahertz A unit of frequency, one gigahertz is one thousand million hertz or one thousand million oscillations (or cycles) per second. 1 gigahertz = 1 GHz = 1,000,000,000 Hz.
GIGS 1. Abbreviation for gigabytes (plural). Normally used in the context of expressing that space or transfer is large and many gigabytes worth. 2. Abbreviation for gigahertz. Normally used in the context of multiple gigahertz, such as when expressing the clock speed of a cpu.
GIS Geographic Information System(s). Geographic Information Systems are designed to work with data that is referenced by spatial or geographic coordinates. GIS includes tools and systems for managing, modelling and analysing data that can be referenced by spatial or geographic coordinates.
Glitch This often refers to a bug in a program that is somewhat different than a freeze or a crash, usually causing erroneous or garbage results to be displayed. The term glitch sounds like a mess, and that’s what programs with glitches create.
GMT Greenwich Meridian Time. The time zone from which all other time zones are measured. Now commonly referred to as UTC. See also UTC, time zone, BST.
GNU Recursive acronym standing for "GNU's not Unix". An ongoing project by the Free Software Foundation to create a free, freely distributable, set of UNIX like utilities.
Google Google is the world's most popular search engine. It began as a search project in 1996 by Larry Page and Sergey Brin, who were two Ph.D. students at Stanford University. They developed a search engine algorithm that ranked Web pages not just by content and keywords, but by how many other Web pages linked to each page. This strategy produced more useful results than other search engines, and led to a rapid increase in Google's Web search marketshare. The Google ranking algorithm was later named "PageRank" and was patented in September of 2001. In only a short time, Google became the number one search engine in the world.
GP 1. Group Policy.
GPF General Protection Fault. This is an error trapped by the OS when an application tries to access memory that it has not been allocated.
GPL General Public License. Normally taken to the mean the GNU GPL. A license statement from GNU, used on most of their software and on many free software packages from other sources.
Graphics omputer graphics are images displayed on a computer screen. They can be either two or three-dimensional. Two-dimensional graphics come in raster or vector formats. Raster graphics are the most common type of computer graphic and are used for icons, photos, and other basic images. Vector graphics are used for drawings, logos, and other scalable objects. 3D graphics are made up of polygons and can be created with CAD and 3D modeling programs. They are most commonly seen in video games and 3D animations.
Grep A UNIX program, now also available on other OSes, that allows you to search through one or more text files for a specific text string. As well, Grep allows the replacement of the found string.
Grid computing Grid computing (or the use of computational grids) is the combination of computer resources from multiple administrative domains applied to a common task, usually to a scientific, technical or business problem that requires a great number of computer processing cycles or the need to process large amounts of data. One of the main strategies of grid computing is using software to divide and apportion pieces of a program among several computers, sometimes up to many thousands. Grid computing is distributed, large-scale cluster computing, as well as a form of network-distributed parallel processing [1]. The size of grid computing may vary from being small — confined to a network of computer workstations within a corporation, for example — to being large, public collaboration across many companies and networks. "The notion of a confined grid may also be known as an intra-nodes cooperation whilst the notion of a larger, wider grid may thus refer to an inter-nodes cooperation".[2] This inter-/intra-nodes cooperation "across cyber-based collaborative organizations are also known as Virtual Organizations".[3] It is a form of distributed computing whereby a “super and virtual computer” is composed of a cluster of networked loosely coupled computers acting in concert to perform very large tasks. This technology has been applied to computationally intensive scientific, mathematical, and academic problems through volunteer computing, and it is used in commercial enterprises for such diverse applications as drug discovery, economic forecasting, seismic analysis, and back-office data processing in support of e-commerce and Web services. What distinguishes grid computing from conventional cluster computing systems is that grids tend to be more loosely coupled, heterogeneous, and geographically dispersed. Also, while a computing grid may be dedicated to a specialized application, it is often constructed with the aid of general-purpose grid software libraries and middleware.
GRP Gateway Routing Protocol.
GSM (Global System for Mobile Communications) A 2G digital standard for cellular phone communications that is used in many countries. GSM communications bands range from 900-1800MHz. The GSM initials were initially derived from the French “Groupe de travail Sp�ciale pour les services Mobiles.”
Guest OS The operating system installed inside a virtual machine (or a partition). In a virtualization solution the guest OS can be completely different from the host OS. In a partitioning solution the guest OS must be identical to the host OS.
GUI Stands for "Graphical User Interface," and is pronounced "gooey." It refers to the graphical interface of a computer that allows users to click and drag objects with a mouse instead of entering text at a command line. Two of the most popular operating systems, Windows and the Mac OS, are GUI-based. The graphical user interface was first introduced to the public by Apple with the Macintosh in 1984. However, the idea was actually taken from an earlier user interface developed by Xerox.
GUID Stands for "Globally Unique Identifier." A GUID is a 128-bit (16 byte) number used by software programs to uniquely identify the location of a data object. Some examples of data that include GUIDs are streaming media files, Windows registry entries, database keys, and various file types. GUIDs are typically written in hexadecimal notation, containing 32 digits, and may look something like this: {12345678-9012-3456-7890-123456789012}. Globally unique identifiers are also the basis of the GUID Partition Table (GPT). This is a hard disk partitioning scheme proposed by Intel as part of the Extensible Firmware Interface. It is used by Windows PCs as well as Intel-based Macintosh computers. GPT uses GUIDs to define the different partitions on a hard drive. Some examples include the boot partition, the file system partition, and the data partition. Each operating system that supports the GPT partitioning scheme uses specific GUIDs to label each partition.
Gustafson’s Law In response to Amdahl’s Law on limitation of effectiveness of parallel computing due to a serial (non-parallelizable) component of code, Gustafson’s Law was developed to show that you can achieve over a 1000-fold speed-up using 1024 processors. It states that if the size of most problems is increased sufficiently, you can achieve any given efficiency by increasing the amount of processors.
GZIP GNU ZIP A VRML file compression format similar to ZIP compression. In VRML 2.0, the scene graph file can be "GZIP'd," and the file will automatically decompress for rendering on the client machine. Compressed files reduce download time. See also: scene graph, VRML, ZIP
H.323 n ITU-T standard for transferring multimedia videoconferencing data over packet-switched networks, such as TCP/IP. There is a LAN standard for high-quality video, and an Internet standard for lower-bandwidth video over lines as slow as 28.8Kbits.
Hacker While this term originally referred to a clever or expert programmer, it is now more commonly used to refer to someone who can gain unauthorized access to other computers. A hacker can "hack" his or her way through the security levels of a computer system or network. This can be as simple as figuring out somebody else's password or as complex as writing a custom program to break another computer's security software. Hackers are the reason software manufacturers release periodic "security updates" to their programs. While it is unlikely that the average person will get "hacked," some large businesses and organizations receive multiple hacking attempts a day.
HAL 1. Hardware Abstraction Layer. Part of the Windows kernel responsible for much of the interfacing to hardware devices.
Half Duplex Allowing simultaneous sending and receiving of data, but data is sent at a lower speed than it is received. cf Full Duplex.
handshaking The initial negotiation period immediately after a connection is established between two modems. This is when the modems agree about how the data will be transmitted (e.g., error correction, packet size, etc.). The set of rules they agree on is called the protocol.
Hard Copy A hard copy is a printed document. It may be a text file, photograph, drawing, or any other type of printable file. For example, instead of e-mailing a business memo, it may be sent out as a hard copy, or an actual physical paper containing the memo. When a document is created on a computer, it is typically saved as a file on the the computer's hard drive. This is sometimes referred to as a soft copy. While the file can be easily opened and edited on a computer, it can also be easily deleted. Therefore, sometimes printing a hard copy is done to create a physical backup of the document.
hard disk A storage device that holds large amounts of data, usually in the range of hundreds to thousands of megabytes. Although usually internal to the computer, some types of hard disk devices are attached separately for use as supplemental disk space. "Hard disk" and "hard drive" often are used interchangeably but technically, hard drive refers to the mechanism that reads data from the disk.
Hard Drive The hard drive is what stores all your data. It houses the hard disk, where all your files and folders are physically located. A typical hard drive is only slightly larger than your hand, yet can hold over 100 GB of data. The data is stored on a stack of disks that are mounted inside a solid encasement. These disks spin extremely fast (typically at either 5400 or 7200 RPM) so that data can be accessed immediately from anywhere on the drive. The data is stored on the hard drive magnetically, so it stays on the drive even after the power supply is turned off. The term "hard drive" is actually short for "hard disk drive." The term "hard disk" refers to the actual disks inside the drive. However, all three of these terms are usually seen as referring to the same thing -- the place where your data is stored. Since I use the term "hard drive" most often, that is the correct one to use.
Hard Reset (Hardware Reset) This refers to the forced, immediate shutdown and restart of a PDA or other device by means of hardware. This is typically done by pushing a sequence of buttons or a reset button, and usually only after it has become impossible to do a soft reset.
Hard Token A hard token, sometimes called an "authentication token," is a hardware security device that is used to authorize a user. An common example of a hard token is a security card that gives a user access to different areas of building or allows him to log in to a computer system. Some hard tokens are used in combination with other security measures to further enhance security. For example, a username and password or a fingerprint scan may be required along with the hard token to gain access to a secure system. A hard tag is another type of hard token that is used as a security device on merchandise such as clothing and electronics. You have probably seen these used in several retail stores, where they are used to deter theft. If someone tries to exit the building with merchandise before the hard tag has been deactivated, it causes the security system by the doors to beep. Of course, if the cashier forgets to deactivate the hard tag, you get to experience the unpleasant beeping sound as you exit even if you paid for the merchandise.
Hardening Hardening is the process of identifying and fixing vulnerabilities on a system.
Hardware Computer hardware refers to the physical parts of a computer and related devices. Internal hardware devices include motherboards, hard drives, and RAM. External hardware devices include monitors, keyboards, mice, printers, and scanners. The internal hardware parts of a computer are often referred to as components, while external hardware devices are usually called peripherals. Together, they all fall under the category of computer hardware. Software, on the other hand, consists of the programs and applications that run on computers. Because software runs on computer hardware, software programs often have system requirements that list the minimum hardware required for the software to run.
Hardware Emulation Layer (HEL) This provides software-based emulation of features that are not directly available in hardware.
Harvest Another name for the act of capturing web content as a part of crawling.
Hash Function An algorithm that computes a value based on a data object thereby mapping the data object to a smaller data object.
Hash Functions (cryptographic) hash functions are used to generate a one way "check sum" for a larger text, which is not trivially reversed. The result of this hash function can be used to validate if a larger file has been altered, without having to compare the larger files to each other. Frequently used hash functions are MD5 and SHA1.
Hash table A table that contains “hash values,” generally used for speeding up searching algorithms on sorted data. For example, a hash table for a dictionary might contain all the letters of the alphabet and the page numbers where each letter starts. That way, instead of searching through from start to finish for each word, you just use the hash table and get a big head start.
HCL (Hardware Compatibility List) A list of computers and peripherals that have been tested by Microsoft to work with Windows NT or Windows 2000. If you run those operating systems on equipment that is not listed on the HCL, it is not guaranteed to work, but it might. Basically, if you install NT/2000 on hardware that’s not on the HCL, you are on your own. However, it is done frequently with decent success.
HD 1. Hard Disk. cf FDD, HDD. 2. High Density. 3. High Definition. Normally used in the context of High Definition TV (HDTV).
HDD 1. Hard Disk Drive. Also referred to simply as HD. See also IDE, SCSI, SMART. 2. Hybrid Disk Drive. A (standard) Hard Disk Drive that incorporates flash memory as a buffer (likely minimum of 1GB of flash). When compared to a traditional disk drive, a hybrid disk driver offers: significantly improved start-up times for PCs (because most of the files required at start-up can be read from the flash memory rather than the disk). power savings (and corresponding longer battery life for laptops) because the flash memory will allow most writes to be cached (in non volatile storage) allowing the disk spindle to be powered down for much of the time.
HDTV HDTV High Definition Television. A television display standard providing much better picture quality than a standard (non-HD) television. There are a number of different formats for high-definition, a TV which supports any one of these standards can claim to be high-definition (or HD Ready): 720p 1080i 1080p The number part specifies the number of vertical lines. 720p is 720 vertical lines (and 1280 lines horizontally). 1080i and 1080p are both 1080 vertical lines (and 1920 lines horizontally). HDTV are always widescreen, so having a horizontal to vertical ratio of 16:9 The letter "p" or "i" denotes "progressive" or "interlaced" respectively, which denotes how the picture is built up. With interlaced the image is built up in two passes, with every other line updated on each pass. With progressive scan a complete image is transmitted in each frame. What this means in practice is that progressive gives a smoother picture, especially where there is notion. Occasionally the format may be expressed with an additional number after the "p" or "i". Where this is given this is the frame frame, i.e. the number of frames per second. Typically 720p is 60 frames per second (so 720p60 in full), and 1080i and 1080p are 50 frames per second. cf SDTV, NTSC, PAL, EDTV
HEAD or HEADER The top portion of the HTML source code behind Web pages, beginning with and ending with . It contains the Title, Description, Keywords fields and others that web page authors may use to describe the page. The title appears in the title bar of most browsers, but the other fields cannot be seen as part of the body of the page. To view the portion of web pages in your browser, click VIEW, Page Source. In Internet Explorer, click VIEW, Source. Some search engines will retrieve based on text in these fields.
header The portion of an e-mail message or a network newsgroup posting that precedes the body of the message; it contains information like who the message is from, its subject, and the date. A header also is the portion of a packet that proceeds the actual data and contains additional information the receiver will need.
Heap Most commonly, this is a segment of memory claimed by a program. Within the heap, pieces of memory can be used and freed as needed. Depending on usage, heaps can become fragmented as small pieces of memory are used and freed. In formal computer science terms, a heap is the same as a partially ordered tree.
Heat Sink A computer's CPU may perform millions of calculations every second. As the processor continues to work at a rapid pace, it begins to generate heat. If this heat is not kept in check, the processor could overheat and eventually destroy itself. Fortunately, CPUs include a heat sink, which dissipates the heat from the processor, preventing it from overheating. The heat sink is made out of metal, such as a zinc or copper alloy, and is attached to the processor with a thermal material that draws the heat from away the processor towards the heat sink. Heat sinks can range in size from barely covering the processor to several times the size of the processor if the CPU requires it. Most heat sinks also have "fins," which are thin slices of metal that are connected to the base of the heat sink. These additional pieces of metal further dissipate the heat by spreading it over a much larger area. A fan is often used to cool the air surrounding the heat sink, which prevents the heat sink from getting too hot. This configuration is referred to as a heat sink and fan or HSF combination. While heat sinks are used in nearly all computer CPUs, they have become commonplace in video card processors, or GPUs, as well.
Helper Application A program allowing you to view multimedia files (images, audio, video) that your web browser cannot handle internally. The file must be downloaded before it will be displayed. There are some plug-ins that allow you to view the file over the Internet without downloading it first. See Also: Browser, Plug-in
Heuristic A rule of thumb for solving a problem. A heuristic provides a quick means of solving a problem, utilising a known rule of thumb, trick or simplification to arrive at a solution to a problem in a shorter time than other conventional methods. Heuristics are not guaranteed to solve a problem or to provide the optimal solution. Heuristics are sometimes also referred to as Heuristic Algorithms.
heuristics A method of analyzing outcome through comparison to previously recognized patterns. For example, an antivirus program, familiar with behaviors typical of viruses (such as deleting files in sequence), could use heuristics to identify unknown virus strains by their behavior.
Hewlett-Packard (HP) Hewlett-Packard Company (NYSE: HPQ), commonly referred to as HP, is a consumer electronics corporation headquartered in Palo Alto, California, USA. HP is the world's largest technology company and operates in nearly every country. HP specializes in developing and manufacturing computing, storage, and networking hardware, software and services. Major product lines include personal computing devices, enterprise servers, related storage devices, as well as a diverse range of printers and other imaging products. HP markets its products to households, small to medium size businesses and enterprises both directly, via online distribution, consumer-electronics and office-supply retailers, software partners and major technology vendors.
HEX 1. Hexadecimal. A base 16 numbering system, which uses the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F. So: Hex Decimal Octal Binary 0 0 0 0000 1 1 1 0001 2 2 2 0010 3 3 3 0011 4 4 4 0100 5 5 5 0101 6 6 6 0110 7 7 7 0111 8 8 10 1000 9 9 11 1001 A 10 12 1010 B 11 13 1011 C 12 14 1100 D 13 15 1101 E 14 16 1110 F 15 17 1111 10 16 20 10000 Hexadecimal is used in IT because of its close relationship to Binary - as can be seen from the above table each hexadecimal digit corresponds to 4 bits. This means that the hexadecimal numbers 0 to FF cover all the possible eight bit values of a byte (0 to 255 decimal). Depending on the context, hexidecimal numbers are sometimes prefixed with 0x or # to indicate that the number is hexadecimal and not decimal. 2. Hexagonal. A flat six sided shape.
HFS Stands for "Hierarchical File System." HFS is the file system used for organizing files on a Macintosh hard disk. When a hard disk is formatted for a Macintosh computer, the hierarchical file system is used to create a directory that can expand as new files and folders are added to the disk. Since HFS is a Macintosh format, Windows computers cannot recognize HFS-formatted drives. Windows hard drives are typically formatted using WIN32 or NTFS file systems. Since HFS was not originally designed to handle large hard disks, such as the 100GB+ hard disks that are common today, Apple introduced a updated file system called HFS+, or HFS Extended, with the release of Mac OS 8.1. HFS+ allows for smaller clusters or block sizes, which reduces the minimum size each file must take up. This means disk space can be used much more efficiently on large hard disks. Mac OS X uses the HFS+ format by default and also supports journaling, which makes it easier to recover data in case of a hard drive crash.
Hibernate This allows computer users to save the contents of their computer’s memory to disk before shutting down the PC. When restarted, the contents are read back into RAM and the computer is brought back to the exact state it was in before hibernation was initiated. This is different from sleep mode, where the computer is not fully shut down.
HIDS Host based Intrusion Detection System. A system for detecting unauthorised access to a single computer. A HIDS may monitor logs or activity on network ports, or use other techniques to detect possible intrusions. cf Intrusion Detection System (IDS).
Hijack Attack A form of active wiretapping in which the attacker seizes control of a previously established communication association.
HISTORY, Search History Available by using the combined keystrokes CTRL + H. You can set how many days your browser retains history in Edit | Preferences, or in Tools | Options.
hit As used in reference to the World Wide Web, ?hit? means a single request from a web browser for a single item from a web server; thus in order for a web browser to display a page that contains 3 graphics, 4 ?hits? would occur at the server: 1 for the HTML page, and one for each of the 3 graphics.
Hive A sub-tree of the Windows registry.
HKCR Common abbreviation for the Windows registry root ‘HKEY_CLASSES_ROOT’, one of the Windows registry hives.
HKLM Common abbreviation for the Windows registry root ‘HKEY_LOCAL_MACHINE’, one of the Windows registry hives.
HMI Human Machine Interface. See also MMI.
Homepage A page on the World Wide Web (WWW) that is the first page of a website. Usually it is called index.html or index.htm. When you go to a Web address, this is the first page your browser looks for.
Honey Client see Honeymonkey.
Honey pot Programs that simulate one or more network services that you designate on your computer's ports. An attacker assumes you're running vulnerable services that can be used to break into the machine. A honey pot can be used to log access attempts to those ports including the attacker's keystrokes. This could give you advanced warning of a more concerted attack.
Honeymonkey Automated system simulating a user browsing websites. The system is typically configured to detect web sites which exploit vulnerabilities in the browser. Also known as Honey Client.
Honeypot A system left open and unprotected to entice hackers to break into it. Usually this is done so that system administrators can monitor the methods used to break in, the frequency of attack, or just to throw off attackers from the real goodies.
Hop One piece of the TCP/IP networking protocol route that a computer needs to take in order to send or receive information. Think of all the main computers in the world that are physically connected as stones in a lake. To get from your stone to the stone on the other side you need to “hop” on a certain number of other stones. A similar method is used for communicating over the Internet.
Hops A hop is each exchange with a gateway a packet takes on its way to the destination.
Host Any computer on a network that is a repository for services available to other computers on the network. It is quite common to have one host machine provide several services, such as SMTP (email) and HTTP (web).
Host adapter his term is synonymous with SCSI adapter. It refers to an add-in board, such as a PCI SCSI card, that allows PCs to communicate with SCSI devices.
Host OS The operating system hosting one or more virtual machines (or partitions) and sharing physical resources with them. It's where the virtualization product or the partitioning product is installed.
Host-Based ID Host-based intrusion detection systems use information from the operating system audit records to watch all operations occurring on the host that the intrusion detection software has been installed upon. These operations are then compared with a pre-defined security policy. This analysis of the audit trail imposes potentially significant overhead requirements on the system because of the increased amount of processing power which must be utilized by the intrusion detection system. Depending on the size of the audit trail and the processing ability of the system, the review of audit data could result in the loss of a real-time analysis capability.
Host-only networking A type of network connection between a virtual machine and the host. Under host-only networking, a virtual machine is connected to the host on a private network, which normally is not visible outside the host. Multiple virtual machines configured with host-only networking on the same host are on the same network.
Hosted Environment A virtual environment where the virtualization product is installed on top of a host OS, instead of being installed on physical hardware. The opposite of bare metal environment.
Hot Spare A drive in a RAID configuration that sits idle until one of the RAIDed drives fails. The hot spare then assumes the role of the dead drive. When the dead drive is replaced you can make it the hot spare. (The old hot spare doesn’t revert back because it’s got data on it now.) Hot spares are most often used in RAID 5 configurations, but can also be used in RAID 1 or RAID 10. When a drive fails the hot spare must be populated with information regenerated from the other drives. During this time performance is degraded.
Hot-pluggable Same as hot-swappable, but also connotes a simple plug-in mechanism for easy swapping.
Hot-swappable This type of mechanism implies that you can remove or add things while the system is powered on and running. For example, hard drives and power supplies are often candidates for this term, but more expensive servers may even have hot-swappable memory, PCI cards, and processors. Normally they come in special proprietary form factors in server machines and RAID boxes. If you’ve got mission-critical applications, you want your servers to have as many hot swappable components as possible.
Hotmail free email service, now part of MSN.
Hover When you roll the cursor over a link on a Web page, it is often referred to as "hovering" over the link. This is somewhat like when your boss hovers over you at work, but not nearly as uncomfortable. In most cases, the cursor will change from a pointer to a small hand when it is hovering over a link. Web developers can also use cascading style sheets (CSS) to modify the color and style of link when a user hovers over it. For example, the link may become underlined or change color while the cursor is hovering over it. The term hovering implies your computer screen is a three-dimensional space. In this conception, your cursor moves around on a layer above the text and images. When you click the mouse button while the cursor is hovering over a link, it presses down on the link to activate it. Hovering can also be used in a more general sense such as moving the cursor over icons, windows, or other objects on the screen.
HPC 1. High Performance Computing. HPC is a generic and relative term since the desktop computers of today are capable of the same performance as supercomputers from a few years back. Thus because of progress in computing technology, a computer once deemed capable of high performance computing might no longer be regarded as a HPC a year or two later. HPC is often associated with (so called) super computers, and parallel processing. Parallel processing requiring both suitable hardware and suitable software design. 2. Handheld PC. A HPC is a small portable handheld computer. HPC means that same as "PDA", but is a less popular acronym.
HT Common abbreviation for Hyper-Threading.
HTML Hyper Text Mark-up Language. Used to construct web pages. By convention HTML pages composed on Windows platforms have the .htm file extension, whilst pages composed on other platforms tend to use the .html file extension. See also: http, https.
HTML (HyperText Markup Language) A standard language initially created for typesetting. Although it is a language, it isn’t really a programming language. It is mainly used for creating documents on the World Wide Web. Included in the language are provisions for displaying graphics and links to other pages.
HTTP HTTP Hypertext Transfer Protocol. Network protocol for the transfer of web or intranet pages (for subsequent display or other purpose). HTTP is not a secure protocol. All communications with HTTP occurs in plain text. cf HTTPS and SHTTP. HTTP typically uses port 80 (the default port for HTTP), but the protocol allows for other port numbers to be used. Since some ISPs block port 80, typical alternative ports are port 8080 and 8000, but these are by convention and are not part of the HTTP standard.
HTTP (HyperText Transfer Protocol) The way the data in an HTML document is transferred. A document coming in over the HTTP protocol, usually TCP/IP port 80, is read as an HTML document. You may notice in our Internet browser’s address bar that the address begins with “HTTP://” in order to tell the browser to expect HTML files.
HTTPS Hypertext Transmission Protocol Secure (or Hypertext Transmission Protocol Security) is HTTP over SSL. In reality HTTPS is more often HTTP over TLS. HTTPS is used when web page information needs to be kept secure and private, such as when dealing with private, commercial or financial information across the internet. HTTPS is essential for all e-commerce applications. The default port for HTTPS is port 443, but theoretically there is no reason why a site might not use a different port provided the client was aware of it. HTTPS and SHTTP are not the same, although both provide enhanced security above that of HTTP.
HTTPS (Secure HyperText Transfer Protocol) A secure means of transferring data using the HTTP protocol. Typically HTTP data is sent over TCP/IP port 80, but HTTPS data is sent over port 443. This standard was developed by Netscape for secure transactions, and uses 40-bit encryption (”weak” encryption) or 128-bit (”strong” encryption). If you are at a secure site, you will notice that there is a closed lock icon on the bottom area of your Navigator or IE browser. The HTTPS standard supports certificates. A webserver operator must get a digital certificate from a third-party certificate provider that ensures that the webserver in question is valid. This certificate gets installed on the webserver, and verifies for a period of a year that that server is a proper secure server.
Hub Generic term for any device which connects two or more computers or devices together on a network allowing them to communicate. The term hub is sometimes (incorrectly) used to refer to a switch, the difference being that a hub is a simple unintelligent repeater forwarding all incoming packets to everything on the network. cf router and switch.
HW 1. Common abbreviation for Hardware (Hard-Ware). 2. Abbreviation for Hand-Written.
Hybrid Attack A Hybrid Attack builds on the dictionary attack method by adding numerals and symbols to dictionary words.
Hybrid Encryption An application of cryptography that combines two or more encryption algorithms, particularly a combination of symmetric and asymmetric encryption
Hyper-Threading Intel trademark term for multi-threading in in the Pentium 4 micro-architecture. Hyper-Threading enables the processor to execute multiple threads in parallel on the same processor. Hyper-Threading allows different threads to execute in parallel provided the two threads do not require access to the same execution resource on the CPU at the same time. Hyper-threading can give a significant performance boost to some applications. It is not the same as having physically separate CPUs and performance will not be as good as a dual-CPU arrangement. To take advantage of Hyper-Threading you must be running on an operating system that can take advantage of it (such as Windows XP, Windows 2003 or an appropriate Unix/Linux build) and running with a motherboard and processor that support it. Hyper-Threading has been reported to be incompatible with some applications. Hyper-Threading can often be disabled in the BIOS. Hyper-Threading is commonly abbreviated to HT. The technology is also known more generically as SMT (Simultaneous Multithreading Technology).
Hyperlink In hypertext or hypermedia, an information object (such as a word, a phrase, or an image; usually highlighted by color or underscoring) that points (indicates how to connect) to related information that is located elsewhere and can be retrieved by activating the link.
Hypertext Generally, any text that contains links to other documents - words or phrases in the document that can be chosen by a reader and which cause another document to be retrieved and displayed. See also: HTML, HTTP
HyperThreading Slightly abbreviated term for Hyper-Threading.
Hypervisor The virtualization software layer managing hardware requests from a guest OS, simulating answers from a real hardware. Used as VMM (Virtual Machine Monitor) synonymous.
Hz Hertz, the standard unit for measuring frequency. One hertz is one (complete) cycle per second, 100hz is 100 cycles per second and so on. The Hz unit can be applied to any type of frequency, but is more commonly used when measuring sound or AC electricity. For example, electricity in most of Europe is distributed at 50Hz (whilst some countries distribute electricity at 60Hz). The human ear is generally regarded as being capable of hearing sounds in the frequency range 20hz to 20,000Hz (20khz). Other related units: 1,000Hz = 1KHz 1,000,000Hz = 1MHz 1,000,000,000Hz = 1GHz
Hz (hertz) short for hertz
H_Key (Hive_Key) A part of the Windows registry hive. The hive contains several different pieces, or keys.
I/O Stands for "Input/Output" and is pronounced simply "eye-oh." Computers are based on the fundamental idea that every input results in an output. For example, if you are running a word processor program and type a sentence on your keyboard, the text will appear on the screen. The keyboard is an input device and the screen is an output device. You might also print the text using a printer, which is another output device. The computer's CPU handles all the I/O operations, sending the data it receives to the correct path. The path may be to the video card, to the hard drive, or to the RAM, just to name a few.
I/O Address Each I/O device connected to your computer is mapped to a unique I/O (Input/Output) address. These addresses are assigned to every I/O port on your computer, including USB, Firewire, Ethernet, VGA, and DVI ports, as well as any other ports your computer might have. Having a unique address assigned to each port allows your computer to easily recognize and locate devices attached to your computer. Whether it is a keyboard, mouse, monitor, printer, or any other device, the computer can locate it by its I/O address. Because I/O addresses are controlled by the computer's motherboard, they do not use up any system memory, or RAM.
IA-32 (Intel Architecture-32 bit) Intel’s 32-bit instruction architecture that runs on the company’s 386, 486, Pentium, Pentium Pro/II/III/4, and future consumer chips.
IA-64 (Intel Architecture-64 bit) Intel’s 64-bit instruction architecture that features EPIC and runs on the Itanium processor. It’s a fully 64-bit architecture built new from the ground up.
IANA Internet Assigned Numbers Authority.
ICANN Stands for "Internet Corporation For Assigned Names and Numbers." The ICANN is an non-profit corporation that is responsible for allocating IP addresses and managing the domain name system. Every computer connected to the Internet, from servers to home PCs, has an IP address. However, it would be unrealistic for the ICANN to directly assign each computer an individual IP address. Instead, the ICANN allocates blocks of IP addresses to companies, educational institutions, and Internet service providers. These organizations then allocate IP addresses to computers that use their Internet connections. While the ICANN is a US-based organization, it is also a global Internet community. According to ICANN's website, the organization is "dedicated to preserving the operational stability of the Internet; to promoting competition; to achieving broad representation of global Internet communities; and to developing policy appropriate to its mission through bottom-up, consensus-based processes" (icann.org).
ICF Internet Connection Firewall. Abbreviation used by Microsoft to refer to the firewall built into Windows XP.
ICMP Internet Control Message Protocol. An extension to the Internet Protocol (IP), supporting additional control, error and information messages. The ping command uses ICMP.
ICMP (Internet Control Message Protocol) A TCP/IP messaging protocol that runs specifically over IP (as opposed to UDP). This protocol is used to announce network errors, timeouts, and congestion. PING is based on ICMP.
ICMP Flood A type of Denial of Service attack that sends large amounts of (or just over-sized) ICMP packets to a machine in order to attempt to crash the TCP/IP stack on the machine and cause it to stop responding to TCP/IP requests.
Icon Ever since the Macintosh was introduced in 1984, icons have been the way we view files on computers. An icon on your computer screen represents an object or a program on your hard drive. For example, the folders you see on your desktop or in open windows are icons. The files that you see in those folders are also icons. The trash can on the Macintosh and the recycle bin on Windows are both icons as well. Icons are a visual representation of something on your computer. For example, a blue "e" on your screen most likely repersents the Internet Explorer program. An icon that looks like a sheet of paper is probably a text document. By clicking and dragging icons, you can move the actual files they represent to various locations on your computer's hard drive. By double-clicking an application icon, you can open the program. Icons are one of the fundamental features of the graphical user interface (GUI). They make computing much more user-friendly than having to enter text commands to accomplish anything. Some Unix nerds would beg to differ, but I'm talking about normal people here.
ID 1. Abbreviation for IDentifier. Normally something (typically a number or string) that will uniquely identify an object within a specific context. cf UID, GUID. 2. Abbreviation for IDentification.
IDE 1. Integrated Development Environment. As a minimum, the integration of a source code editor, compiler and debugger for software development. An IDE will often offer more than this, such as on-line help, syntax highlighting and other features. 2. Integrated Drive Electronics. Common and cheap form of disk interface. Superseded by EIDE. Now commonly known as Parallel ATA (PATA). cf SCSI, SATA.
Identity Identity is whom someone or what something is, for example, the name by which something is known.
IDS Intrusion Detection System. A system for detecting (unauthorised) intrusions into a network or individual computer. An Intrusion Detection System will typically either: monitor log files to detect intrusions on a single computer. This is known as a Host based IDS (HIDS). or, will employ a packet sniffer to monitor network traffic to attempt to detect intrusions on a network. This is known as a Network based IDS (NIDS).
IE 1. Microsoft Internet Explorer. cf IE4, IE5, IE6, MSIE.
IE4 Microsoft Internet Explorer (IE), version 4. Superseded by IE5.
IE5 Microsoft Internet Explorer (IE), version 5. Superseded by IE6.
IE6 Microsoft Internet Explorer (IE), version 6.
IE7 Microsoft Internet Explorer (IE), version 7. IE 7 was released for general use in November 2006, although beta versions had been in circulation long before that. IE 7 is the successor to IE 6.
IE8 Microsoft Internet Explorer (IE), version 8. IE 8 was released for general use in May 2008 and is the successor to IE 7.
IEEE Stands for the "Institute of Electrical and Electronics Engineers." This is a non-profit organization that develops, defines, and reviews electronics and computer science standards. Though it is a U.S. based organization, standards developed by the IEEE often become International standards. Some examples of commonly-used products standardized by the organization are the IEEE 1284 interface (a.k.a. Parallel Port), which many printers use, and the IEEE 1394 interface (a.k.a. Firewire), which is a super-fast connection for digital video cameras, hard drives, and other peripherals. The IEEE describes itself as "the world's largest technical professional society -- promoting the development and application of electrotechnology and allied sciences for the benefit of humanity, the advancement of the profession, and the well-being of our members." Perhaps they could standardize a more simplified definition of their organization...
IGMP Internet Group Management Protocol.
IIS Microsoft Internet Information Server (or Services). This is the standard web server available under Windows (from NT4 onwards).
IIS (Internet Information Server) The name for Microsoft’s webserver. It works with server versions of Microsoft’s operating systems, and was first developed for Windows NT Server. Starting with Windows 2000 Server, IIS ships on the CD. With Windows NT 4 Server you had to install additional software to get IIS installed.
IM 1. Instant Messaging. See Instant Messaging. 2. Instant Message.
IMAP Internet Message Access Protocol. A protocol for accessing electronic e-mail (or bulletin boards). IMAP allows e-mails to be read by a client but still be stored on a central server. IMAP is suited to environments where people need to be able to access their e-mail from more than one workstation.
Import The process of pulling data into a program. Normally it refers to taking a plain text file and pulling it into a database format so that you can work with it using a database program. For example, you call a company you need some data from and ask it to send you some data to add to your database. The company sends the data as a text file, and you import it into your database. Now you can run queries on the data in your database program. However, you could import any data format your database program supports. There are hundreds out there.
Impression It is said that you never get a second chance to make a first impression. Well, in the wonderful world of the World Wide Web, publishers have thousands of chances each day. An impression is counted each time a Web page is shown to a visitor. Advertisers measure the reach of their ads by tracking ad impressions, or the number of times their ads are shown. The revenue that publishers generate based on 1,000 impressions is called CPM. Impressions are counted each time a page is visited by a user, so a single user can rack up numerous impressions for one website. However, publishers and advertisers are also interested in unique impressions, which count only the number of unique visits to a website. For example, if Greg views 3 pages on a website, while Mary views 4 and Kathy views 10, their visits would total 17 impressions, but only 3 unique impressions. Unique impressions are usually counted by sending a cookie to visitors' browsers that expire in 24 hours. This way, if Greg visits the site on Tuesday morning and Wednesday evening, it would could as two unique impressions.
IMS 1. Internet Mail Service. The service in Microsoft Exchange server 5.x that is responsible for communicating with internet email systems and other SMTP capable systems to effect the transport of email messages (both to and from the Exchange server). In earlier versions of Exchange this was known as IMC. From Exchange 2000 this has been replaced by the SMTP Connector. 2. Information Management System.
InActive Collection / Seed collections or seeds that are not scheduled for crawling. When a collection and/or seed is marked inactive, the URL's crawled from that seed will not be deleted, and are still searchable and viewable.
Inbox An inbox is the main folder that your incoming mail gets stored in. Whether you check your mail through a webmail interface or use a program like Outlook or Mac OS X Mail, each downloaded message gets stored in your inbox. If you check your mail from a POP3 account using an e-mail program, the messages are downloaded to the inbox on your local hard drive. However, if you use an IMAP mail server, your inbox is created on the server and therefore your messages are stored on the server as well. Because most people receive more mail than they can manage in one folder, it is common to create other folders to store your messages. After reading your messages, you may move them to other folders you have created (such as "Family," "Friends," "Business," etc.) or delete them by moving them to the Trash. However you decide to manage you mail, it is a good idea to keep the number of messages in your inbox from growing too large.
Incident An incident as an adverse network event in an information system or network or the threat of the occurrence of such an event.
Incident Handling Incident Handling is an action plan for dealing with intrusions, cyber-theft, denial of service, fire, floods, and other security-related events. It is comprised of a six step process: Preparation, Identification, Containment, Eradication, Recovery, and Lessons Learned.
Incremental Backup A method of archiving data. Basically, during an incremental backup all data that has changed since the last full (or previous incremental) backup will be archived; data that has not changed will not be backed up. It is possible to take incremental backups after previous incremental backups, but then if you need to restore something fully you will need all of the incremental data (which may be split over several tapes, for example) and the last full backup.
Incremental Backups Incremental backups only backup the files that have been modified since the last backup. If dump levels are used, incremental backups only backup files changed since last backup of a lower dump level.
Index An index is a list of data, such as group of files or database entries. It is typically saved in a plain text format that can be quickly scanned by a search algorithm. This significantly speeds up searching and sorting operations on data referenced by the index. Indexes often include information about each item in the list, such as metadata or keywords, that allows the data to be searched via the index instead of reading through each file individually. For example, a database program such as Microsoft Access may generate an index of entries in a table. When an SQL query is run on the database, the program can quickly scan the index file to see what entries match the search string. Search engines also use indexes to store a large list of Web pages. These indexes, such as those created by Google and Yahoo!, are necessary for quickly generating search results. If search engines had to scan through millions of pages each time a user submitted a search, it would take roughly forever. Fortunately, by using search indexes, Web searches can be performed in less than a second instead of several hours. The term "index" can also be used as a verb, which not surprisingly means to create an index. It may also refer to adding a new item to an existing index. For example, Mac OS X 10.4 and later indexes the hard disk to create a searchable index for Apple's Spotlight search utility. Google's "Googlebot" crawls the Web on a regular basis, adding new Web pages to the Google index. While most database and hard disk indexes are updated on-the-fly, search engine indexes are only updated every few hours, days, or even weeks. This is why newly published Web pages may not show up in search engine results. While it may be a frustration for Web developers, it is a small price to pay for the convenience of super-fast Web searches.
Inetd (xinetd) Inetd (or Internet Daemon) is an application that controls smaller internet services like telnet, ftp, and POP.
Inference Attack Inference Attacks rely on the user to make logical connections between seemingly unrelated pieces of information.
Infiniband A standard created by Intel and other server manufacturers to link servers and network devices externally at high speeds. It should scale as high at 30GB/second, but initially will run at 2.5Gbits/second (0.3 GB/second).
Ingress Filtering Ingress Filtering is filtering inbound traffic.
Initialize Format a disk so it will hold information. Explanation: When you tell your computer to initialize a disk, all information on that disk is erased - the disk is "wiped clean." Then the disk is formatted to hold new information. All kinds of disks - floppy disks, hard disks, zip disks, etc. - must be initialized before they can be used. Sentence: "These floppy disks were initialized at the factory."
Inkjet Inkjet printers are the most common type of consumer printers. The inkjet technology works by spraying very fine drops of ink on a sheet of paper. These droplets are "ionized" which allows them to be directed by magnetic plates in the ink's path. As the paper is fed through the printer, the print head moves back and forth, spraying thousands of these small droplets on the page. While inkjet printers used to lack the quality and speed of laser printers, they have become almost as fast as laser printers and some can even produce higher-quality images. Even low-budget inkjet printers can now print high-resolution photos. The amazing thing is, as the quality of inkjet printers has improved, the prices have continued to drop. However, for most people, refilling the inkjet cartridges a few times will often cost more than the printer.
Input Whenever you enter data into your computer, it is referred to as input. This can be text typed in a word processing document, keywords entered in a search engine's search box, or data entered into a spreadsheet. Input can be something as simple as moving the mouse or clicking the mouse button or it can be as complex as scanning a document or downloading photos from a digital camera. Devices such as the keyboard, mouse, scanner, and even a digital camera are considered input devices. This is because they allow the user to input data into the computer (yes, the word "input" can also be used as a verb). While input generally comes from humans, computers can also receive input from other sources. These include audio and video devices that record movies and sound, media discs that install software, and even the Internet, which is used to download files and receive data such as e-mail or instant messages. The opposite of input is output, which is what the computer produces based on user input. Input and output devices are collectively referred to as I/O devices.
Input Device An input device is any device that provides input to a computer. There are dozens of possible input devices, but the two most common ones are a keyboard and mouse. Every key you press on the keyboard and every movement or click you make with the mouse sends a specific input signal to the computer. These commands allow you to open programs, type messages, drag objects, and perform many other functions on your computer. Since the job of a computer is primarily to process input, computers are pretty useless without input devices. Just imagine how much fun you would have using your computer without a keyboard or mouse. Not very much. Therefore, input devices are a vital part of every computer system. While most computers come with a keyboard and mouse, other input devices may also be used to send information to the computer. Some examples include joysticks, MIDI keyboards, microphones, scanners, digital cameras, webcams, card readers, UPC scanners, and scientific measuring equipment. All these devices send information to the computer and therefore are categorized as input devices. Peripherals that output data from the computer are called output devices.
Input Validation Attacks Input Validations Attacks are where an attacker intentionally sends unusual input in the hopes of confusing an application.
Install Most software programs require that you first install them on your computer before using them. For example, if you buy Microsoft Office, you need to install it on your computer before you can run any of the included programs such as Word or Excel. You can install software from a CD or DVD, an external hard drive, or from a networked computer. You can also install a program or software update from a file downloaded from the Internet. Installing a software program writes the necessary data for running the program on your hard drive. Often the installer program will decompress the data included with the installer immediately before writing the information to your hard drive. Software updates, which are typically downloaded from the Internet, work the same way. When you run the update, the installer file decompresses the data and then updates the correct program or operating system. Installing software is usually a simple process. It involves double-clicking an installer icon and then clicking "I Agree" when the license agreement pops up. You may have to choose what directory on your hard disk you would like to install the software in, but often the installer will even choose that for you. Some software can be installed by simply dragging a folder or application program onto your hard drive. Either way, installing software is a rather simple process and should not be intimidating. If you can cook you dinner in the microwave, you can install your own software.
Installer In order to install new software on your computer, you often need to run an installer program. This program unpacks compressed data included with the installer and writes new information to your hard drive. While some installers do not use compressed data, most use some level of compression since it reduces the size of the files included with the installer. This is especially helpful when downloading programs or software updates from the Internet. An installer can either install a new program on your computer or can update a program currently on your hard drive. It can also update or add files to your operating system. Most installers can be run by simply double-clicking the installer icon and then choosing the folder you want to install the software into. The nice thing about installers is that they do all the work for you, decompressing and writing the data on the hard drive. Once the installer is finished, you can often use the new or updated software right away. If any system files were installed, you will be asked to restart your computer before using the new software. This is because system files can only be loaded during the computer's boot process.
Instruction The simplest direction that you can give to a processor. Programs are made up of these, but usually don’t go down to such nitty-gritty levels unless you are programming in assembly language. An example of what a single instruction would do is increment a piece of data by one, or clear a piece of data out of a register.
Integer An integer is a whole number (not a fraction) that can be positive, negative, or zero. Therefore, the numbers 10, 0, -25, and 5,148 are all integers. Unlike floating point numbers, integers cannot have decimal places. Integers are a commonly used data type in computer programming. For example, whenever a number is being incremented, such as within a "for loop" or "while loop," an integer is used. Integers are also used to determine an item's location within an array. When two integers are added, subtracted, or multiplied, the result is also an integer. However, when one integer is divided into another, the result may be an integer or a fraction. For example, 6 divided by 3 equals 2, which is an integer, but 6 divided by 4 equals 1.5, which contains a fraction. Decimal numbers may either be rounded or truncated to produce an integer result.
Integrity Integrity is the need to ensure that information has not been changed accidentally or deliberately, and that it is accurate and complete.
Intel Corporation (Intel) Intel Corporation (NASDAQ: INTC; SEHK: 4335; Euronext: INCO) is the world's largest semiconductor chip maker, based on revenue.[3] The company is the inventor of the x86 series of microprocessors, the processors found in most personal computers.
Interface An interface is a port on a hardware device that allows it to connect to another device. Common hardware interfaces found on computers include USB, Firewire, and Ethernet connections. Other electronic devices may use different interfaces, such as HDMI connections on a TV or MIDI ports on a digital piano. The term "interface" may also refer to a user interface.
Interlaced A common way to compress video is to interlace it. Each frame of an interlaced video signal shows every other horizontal line of the image. As the frames are projected on the screen, the video signal alternates between showing even and odd lines. When this is done fast enough, i.e. around 60 frames per second, the video image looks smooth to the human eye. Interlacing has been used for decades in analog television broadcasts that are based on the NTSC (U.S.) and PAL (Europe) formats. Because only half the image is sent with each frame, interlaced video uses roughly half the bandwidth than it would sending the entire picture. The downside of interlaced video is that fast motion may appear slightly blurred. For this reason, the DVD and HDTV standards also support progressive scan signals, which draw each line of the image consecutively.
Internet Worldwide system of linked networks, providing data communications services including file transfer, electronic mail, World Wide Web (www) and newsgroups.
internet (Lower case i) Any time you connect 2 or more networks together, you have an internet - as in inter-national or inter-state.
Internet (Upper case I) The vast collection of inter-connected networks that are connected using the TCP/IP protocols and that evolved from the ARPANET of the late 60's and early 70's. The Internet connects tens of thousands of independent networks into a vast global internet and is probably the largest Wide Area Network in the world.
Internet Archive A non-profit digital library seeking to provide universal access to all knowledge. Archive-It is a project of the Internet Archive (www.archive.org).
Internet backbone This superfast network spanning the world from one major metropolitan area to another is provided by a handful of national Internet service providers (ISPs). These organizations (including Net 99 and Alternet) use connections running at approximately 45 mbps (T3 lines) linked up at specified interconnection points called national access points (which are located in major metropolitan areas). Local ISPs connect to this backbone through routers so that data can be carried though the backbone to its destination.
Internet Service Provider (ISP) A company that provides Internet access to people or corporations. Early ISPs generally had pools of modems awaiting dial-up connections, but many ISPs nowadays only deal in high-end business communications. Smaller ISPs buy bandwidth from larger ISPs.
Internet Standard A specification, approved by the IESG and published as an RFC, that is stable and well-understood, is technically competent, has multiple, independent, and interoperable implementations with substantial operational experience, enjoys significant public support, and is recognizably useful in some or all parts of the Internet.
InterNIC Stands for "Internet Network Information Center." The InterNIC is an organization created by the National Science Foundation to provide Internet information and domain name registration services. While the InterNIC was started as a joint effort between Network Solutions and AT&T, it is now run by the Internet Corporation For Assigned Names and Numbers (ICANN). While the InterNIC still monitors domain names and provides WHOIS data, the domain name registration process has been relinquished to commercial domain registrars. Public information regarding domain names, registrars, and other Internet-related data can be accessed at the InterNIC website.
Interrupt An Interrupt is a signal that informs the OS that something has occurred.
Intranet Private network using internet type tools, but available only within an organisation.
Intrusion Detection A security management system for computers and networks. An IDS gathers and analyzes information from various areas within a computer or a network to identify possible security breaches, which include both intrusions (attacks from outside the organization) and misuse (attacks from within the organization).
Inverter A device that changes direct current (DC) into alternating current (AC). For example, that part of a UPS that converts the battery DC output to AC.
IP Internet Protocol. IP specifies the format of packets (called datagrams) containing data and a destination address. IP is often combined with TCP. See also IPv4, IPv6.
IP Address Also known as an "IP number" or simply an "IP," this is a code made up of numbers separated by three dots that identifies a particular computer on the Internet. Every computer, whether it be a Web server or the computer you're using right now, requires an IP address to connect to the Internet. IP addresses consist of four sets of numbers from 0 to 255, separated by three dots. For example "66.72.98.236" or "216.239.115.148". Your Internet Service Provider (ISP), will assign you either a static IP address (which is always the same) or a dynamic IP address, (which changes everytime you log on). ISPs typically assign dial-up users a dynamic IP address each time they sign on because it reduces the number of IP addresses they must register. However, if you connect to the Internet through a network or broadband connection, it is more likely that you have a static IP address. ISPs and organizations usually apply to the InterNIC for a range of IP addresses so that all their clients have similar addresses. There are three classes of IP address sets that can be registered: Class C, which consists of 255 IP addresses, class B, which contains 65,000 IP addresses, and class A, which includes hundreds of thousands of IP addresses. Because there are so many computers now connected to the Internet, the InterNIC is actually running out of IP addresses. Therefore, Class A and Class B address blocks are very hard, if not impossible, to get. Most large companies have to register multiple Class C addresses instead. To resolve this problem, the Internet Engineering Task Force, which created the original IP address standard, is working on a new protocol called "IP Next Generation" or "IPng."
IP Flood A denial of service attack that sends a host more echo request ("ping") packets than the protocol implementation can handle.
IP Forwarding IP forwarding is an Operating System option that allows a host to act as a router. A system that has more than 1 network interface card must have IP forwarding turned on in order for the system to be able to act as a router.
IP Number (Internet Protocol Number) Sometimes called a dotted quad. A unique number consisting of 4 parts separated by dots, e.g. 165.113.245.2 Every machine that is on the Internet has a unique IP number - if a machine does not have an IP number, it is not really on the Internet. Many machines (especially servers) also have one or more Domain Names that are easier for people to remember. See also: Domain Name, Server, TCP/IP
IP packet An IP packet is a chunk of data transferred over the Internet using standard Internet protocol (IP). Each packet begins with a header containing addressing and system control information. Unlike uniform ATM "cells," IP packets vary in length depending on the data being transmitted. See also: IP, IP address, ATM
IP Spoofing The technique of supplying a false IP address.
IPSec Internet Protocol Security (also abbreviated to IP Security). Encrypts TCP/IP traffic to secure communications within an intranet and provide the highest levels of security for VPN traffic across the Internet.
IPSEC (IP Secure) The IETF standard for “secure IP” transport. Typically IPSEC is used in branch-VPN tunnels between routed LAN segments, but it’s destined to become the method for securing IP traffic over IPv6.
IPv4 Internet Protocol version 4. Current IP standard, uses 32 bit (4 byte) addresses. cf IPv6.
IPv4 (Internet Protocol version 4) An outdated version of the IP protocol that is still in use on the Internet. It uses a 32-bit addressing scheme, represented by four 8-bit (0-255) numbers separated by periods, such as 123.3.12.255. The addressing scheme allows for a maximum of about 4.3 billion numbers (256*256*256*256). This gets to be a problem as more and more devices are connected to the Internet. ISPs have taken to using Network Address Translation to get around the problem for now, but IPv6 is the ultimate solution. IPv4 may be with us for a long time, even though it is technically outdated.
IPv6 Internet Protocol version 6. Uses a 128bit (16 byte) address space, compared with the 32 bit (4 byte) address space used by IPv4. IPv6 provides a much larger address space than is available for IPv4 and is intended to overcome the limitation of IPv4 where IP addresses are a finite and exhaustible resource. The use of NAT devices has alleviated the need for an extended IP address range, and this in part has been one of the reasons responsible for the slow take up of IPv6. IPv6 is backwards compatible with IPv4.
IPv6 (Internet Protocol version 6) The current version of the IP protocol that features a 128-bit addressing scheme, as opposed to the 32-bit addressing scheme of IPv4, supporting a much higher number of addresses. It also features other improvements over IPv4, such as support for multicast and anycast addressing.
IPX Internetwork Packet Exchange. Novell Network networking protocol.
IRQ (Interrupt Request) Stands for "Interrupt Request." PCs use interrupt requests to manage various hardware operations. Devices such as sound cards, modems, and keyboards can all send interrupt requests to the processor. For example, when the modem needs to run a process, it sends an interrupt request to the CPU saying, "Hey, hold up, let me do my thing!" The CPU then interrupts its current job to let the modem run its process. It is important to assign different IRQ addresses to different hardware devices is because the interrupt request signals run along single IRQ lines to a controller. This interrupt controller assigns priorities to incoming IRQs and sends them to the CPU. It's kind of like taking a number at the local deli, except the hardware usually only has to wait a couple of nanoseconds instead of like twenty minutes). Since the interrupt controller can control only one device per IRQ line, if you assign the same IRQ address to multiple devices, you are likely to get an IRQ conflict. This can cause a range of errors from not allowing network connections to crashing your computer. So make sure you assign unique IRQs to new hardware you install and avoid the frustration and keyboard throwing that conflicts can cause.
ISA Stands for "Industry Standard Architecture." ISA is a type of bus used in PCs for adding expansion cards. For example, an ISA slot may be used to add a video card, a network card, or an extra serial port. The original 8-bit version of PCI uses a 62 pin connection and supports clock speeds of 8 and 33 MHz. 16-bit PCI uses 98 pins and supports the same clock speeds. The original 8-bit version of ISA was introduced in 1981 but the technology did not become widely used until 1984, when the 16-bit version was released. Two competing technologies -- MCA and VLB -- were also used by some manufacturers, but ISA remained the most common expansion bus for most of the 1980s and 1990s. However, by the end of the twentieth century, ISA ports were beginning to be replaced by faster PCI and AGP slots. Today, most computers only support PCI and AGP expansion cards.
iSCSI Stands for "Internet Small Computer Systems Interface." iSCSI is an extension of the standard SCSI storage interface that allows SCSI commands to be sent over an IP based network. It enables computers to access hard drives over a network the same way they would access a drive that is directly connected to the computer. iSCSI is a popular protocol used by storage area networks, which allow multiple computers to share multiple hard drives. For example, data centers can be spread out over multiple locations using iSCSI and a standard Internet connection. While the data access time may be slower over the Internet than compared to a direct SCSI connection, iSCSI can serve as a helpful means for creating off-site backups and sharing large amounts of data across multiple locations.
ISO image An ISO image is an archive file (also known as a disc image) of an optical disc in a format defined by the International Organization for Standardization (ISO). This format is supported by many software vendors. ISO image files typically have a file extension of .iso. The name ISO is taken from the ISO 9660 file system used with CD-ROM media, but an ISO image can also contain a UDF file system since UDF is backward-compatible with ISO 9660.
ISP Internet Service Provider. A company that provides access to the internet for others, typically via dial-up, ASDL or broadband. ISPs typically (but not always) also provide other services such as e-mail, newsgroup access and web-space.
Issue-Specific Policy An Issue-Specific Policy is intended to address specific needs within an organization, such as a password policy.
IT (Information Technology) A very general term referring to the entire field of Information Technology - anything from computer hardware to programming to network management. Most medium and large size companies have IT Departments.
IVR Stands for "Interactive Voice Response." IVR is a telephony technology that can read a combination of touch tone and voice input. It gives users the ability to access a database of information via phone. A typical IVR system has several menus of prerecorded options that the caller can choose from. While many choices are as basic as choosing a number, some options may require the caller to speak detailed information such as his name or account number. This input is read by the IVR system and is used to access the appropriate information in the database. For example, a bank may have an IVR system that allows members to call in and check their balance or recent transactions. Credit card companies and stock brokerage firms also use IVR systems to allow users to access information from their account. The technology can also be used used for other purposes such as phone surveys, checking movie times, and call center forwarding. Because the caller can vocally respond to prerecorded messages, using an IVR system is almost like talking to another human being. That is, as long as it understands you.
IYO Chat abbreviation: In Your Opinion. Normally qualified with a question or a statement.
IYSWIM Chat abbreviation for: If You See What I Mean.
J2EE Java 2 Enterprise Edition. A development environment which is independent of hardware systems and operating systems. The idea is that software developers need only write applications once and these applications can then be run unchanged on any computer or operating system.
J2SE Java 2 Standard Edition. A Java-based, runtime platform that provides many features for developing Web-based Java applications, including database access (JDBC API), CORBA interface technology, and security for both local network and Internet use. J2SE is the core Java technology platform and is a competitor to the Microsoft .NET Framework.
Java Object oriented programming language developed by Sun Microsystems, designed for platform independence and frequently described as "write once run anywhere" language. Sun Microsystems describe Java as "A simple, object-oriented, distributed, interpreted, robust, secure, architecture neutral, portable, high-performance, multithreaded and dynamic language."
Javabeans An object-oriented API created by Sun Microsystems for developers to create re-useable Java applications or components.
JavaScript A scripting language that is usually run in a viewer's browser. JavaScript is used to create dynamic web pages (i.e. pages that change in some way when viewed in a browser), such as image rollovers and menus. JavaScript was originally developed by Netscape, and is now supported by all major browsers. JavaScript has a similar language syntax to both Java and C.
JBOD Just a Bunch Of Disks, or Just a Bunch of Drives. JBOD is a collection of two or more disks in a system which are managed individually and do not form part of a RAID. (Although disks which are physically part of a RAID but are not configured as part of the array and accessed as separate individual disks would still be included as JBOD.) Unlike a RAID, JBOD provides no performance or fault tolerance benefits.
JDK Java Development Kit. Included as part of J2SE.
Joystick A joystick is an input device commonly used to control video games. Joysticks consist of a base and a stick that can be moved in any direction. The stick can be moved slowly or quickly and in different amounts. Some joysticks have sticks that can also be rotated to the left or right. Because of the flexible movements a joystick allows, it can provide much greater control than the keys on a keyboard. Joysticks typically include several buttons as well. Most joysticks have at least one button on the top of the stick and another button in the front of the stick for the trigger. Many joysticks also include other buttons on the base that can be pressed using the hand that is not guiding the stick. Joysticks typically connect to your computer using a basic USB or serial port connection and often come with software that allows you to assign the function of each button. Since joysticks emulate the controls of planes and other aircraft, they are best suited for flight simulators and flying action games. However, some gamers like to use joysticks for other types of video games, such as first-person shooters and fighting games. Others prefer using the basic keyboard and mouse, with which they are already accustomed to.
JPEG Joint Photographic Experts Group. JPEG represents a compressed image file. The JPEG compression algorithm allows a compromise between final file size and the amount of information which is lost in the compression process. (JPEG is therefore a lossy compressed file.) Be aware that if a JPEG file is opened and re-saved then yet more ... be lost. A JPEG file is normally denoted with either a ".jpeg" or ".jpg" file extension. See also JFIF, JPG.
JPG Abbreviation for Joint Photographic Experts Group. See JPEG for details.
JRE Java Runtime Environment. The JRE contains libraries, java virtual machine and other resources required to enable java applications and applets to run.
JS Abbreviation for JavaScript. cf JavaScript.
JSON JavaScript Object Notation. JASON is a format for exchanging data between systems. It is a text based format (and so human readable), and uses simple data structures and associative arrays. It has been suggested that JASON is more efficient (although perhaps less versatile) than XML. Since both file types require some processing, which is the most suitable or the most efficient should be considered on a per application basis. JSON files require less processing to parse than XML files, and for some applications can be smaller than the XML equivalents. JSON is supported natively by JavaScript and for JavaScript based solutions JSON is therefore a very efficient means of data exchange. JSON files normally use the .json file extension.
JSP Stands for "Java Server Page." This standard was developed by Sun Microsystems as an alternative to Microsoft's active server page (ASP) technology. JSP pages are similar to ASP pages in that they are compiled on the server, rather than in a user's Web browser. After all, they don't call them "server pages" for nothing. However, JSP is Java-based, whereas ASP is Visual Basic-based. JSP pages are useful for building dynamic Web sites and accessing database information on a Web server. Though JSP pages may have Java interspersed with HTML, all the Java code is parsed on the server. Therefore, once the page gets to the browser, it is only HTML. JavaScript, on the other hand, is usually parsed by the Web browser, not the Web server.
Jumper his is a small metal connector that acts as an on/off switch and is used to alter hardware configurations. A jumper is typically made of two wires and a small piece of metal. When the wires are connected by the metal piece, the jumper is turned on, completing the circuit. When the wires are disconnected, the jumper is turned off. Mulitple jumpers, referred to collectively as a jumper block, are often used to tell the computer how a certain device, such as a hard drive or a modem, is configured. They can be found on motherboards, sound cards, graphics cards, I/O cards, CD-ROM interface boards, modems, and hard drive controller boards, and others. Manually setting jumpers can be a confusing process, so most hardware usually comes with the necessary jumpers preset. If they are not preset, there should be documentation with a clear diagram of the jumper settings included with the hardware. Fortunately, a lot of plug-and-play equipment available today does not require any jumpers. These devices can be configured through a user-friendly interface on your computer.
Juniper Produces high speed, reliable switching routers to satisfy ISP level performance
Juniper Networks (Juniper) Juniper Networks, Inc. (NYSE:JNPR) is an information technology and computer networking products multinational company, founded in 1996. It is headquartered in Sunnyvale, California, USA. The company designs and sells high-performance Internet Protocol network products and services. Juniper's products include T-series, M-series, E-series, MX-series, and J-series families of routers, EX-series Ethernet switches, WX-series WAN optimization devices, and SRC Session and Resource Control appliances. JUNOS , Juniper's network operating system runs on most of the Juniper products
justified A word processing format in which text is formatted flush with both the left and right margins. Other options include left justified (text is lined up against the left margin) and right justified (text is lined up against the right margin).
JVM Java Virtual Machine. The Java Virtual Machine runs compiled Java byte code. This enables a Java application to run on any operating system for which the JVM has been implemented.
KB 1. Common abbreviation for kilobyte, 1024 bytes. 2. Knowledge Base. Often used to refer to the Microsoft Knowledge base - for example when referring to a Knowledge Base article, but the abbreviation can be used to refer to any Knowledge Base.
kbps 1. kbps = Kilo-bits per second. A common means of expressing data transfer rates. Strictly 1kbps = 1024 bits per second (bps) = 128 bytes per second. However, it is often taken to mean 1000 bps, i.e. 1kbps=125 bytes per second. As a rule of thumb, when estimating network/modem throughput, a figure of 1kbps=100 bytes per second is probably closer to the real throughput after other networking overheads are taken into consideration. 2. kBps (note the capital B) = kilobytes per second, i.e. the number of bytes of data that can be transferred per second. 1kBps = 8kbps. Also rendered as KBps.
KDE Stands for "K Desktop Environment." KDE is a contemporary desktop environment for Unix systems. It is a Free Software project developed by hundreds of software programmers across the world. Both the KDE source code and the software itself are made freely available to the public. KDE's primary benefit is the modern graphical user interface GUI it provides for Unix workstations. While Unix systems are notoriously difficult for novice users to operate, KDE makes it possible for the average user to work on a Unix system. In addition to the modern interface, KDE also includes several user-friendly features, such as an application help system and standardized menus and toolbars. It also supports the ability to customize the interface with various skins or themes. Another important aspect of the K Desktop Environment is its application development framework, which is what software engineers use to develop programs for KDE. Since a desktop environment is only as useful as the applications available for it, it is important that developing software for the environment is not a tedious process. Therefore, the KDE application development framework has been designed to help programmers develop robust applications in a simple and efficient manner. This has lead to the development of KOffice and hundreds of high-quality programs for KDE.
Kerberos A system developed at the Massachusetts Institute of Technology that depends on passwords and symmetric cryptography (DES) to implement ticket-based, peer entity authentication service and access control service distributed in a client-server network environment.
Kermit This is a protocol for transferring files during direct dial-up communications that's named after a Muppet (seriously). Kermit is sound but old and can be very slow--slower than Xmodem, Ymodem, and much slower than Zmodem.
Kernel This is a term for the computing elite, so proceed at your own risk. To understand what a kernel is, you first need to know that today's operating systems are built in "layers." Each layer has different functions such as serial port access, disk access, memory management, and the user interface itself. The base layer, or the foundation of the operating system, is called the kernel. The kernel provides the most basic "low-level" services, such as the hardware-software interaction and memory management. The more efficient the kernel is, the more efficiently the operating system will run.
Kerning Kerning refers to the spacing between the characters of a font. Without kerning, each character takes up a block of space and the next character is printed after it. When kerning is applied to a font, the characters can vertically overlap. This does not mean that the characters actually touch, but instead it allows part of two characters to take up the same vertical space. For example, when the characters A and V are placed next to each other, they can take up less total space if they overlap. This is because the right part of the A and the left part of the V fit together. If kerning is applied to the two characters, you could draw a vertical line straight down starting from the top left part of the V and it would go through the lower right part of the A. Kerning is useful because it allows more text to be placed within a given amount of space. This allows longer articles to be placed in newspapers and magazines with limited space. It also looks more natural because when writing by hand, people often make characters overlap. Many text editing programs, as well as image editors such as Adobe Photoshop, allow the user to kern characters. These programs often include a kerning setting that enables the user to determine how tightly the characters fit together.
Keyboard As the name implies, a keyboard is basically a board of keys. Along with the mouse, the keyboard is one of the primary input devices used with a computer. The keyboard's design comes from the original typewriter keyboards, which arranged letters and numbers in a way that prevented the type-bars from getting jammed when typing quickly. This keyboard layout is known as the QWERTY design, which gets its name from the first six letters across in the upper-left-hand corner of the keyboard. While the design of computer keyboards may have come from typewriters, today's keyboards have many other keys as well. Modifier keys, such as Control, Alt/Option, and Command (Mac) or the Windows key (Windows) can be used in conjunction with other keys as "shortcuts" to perform certain operations. For example, pressing Command-S (Mac), or Control-S (Windows) typically saves a document or project you are working on. Most of today's computer keyboards also have a row of function keys (F1 through F16) along the top of the keyboard, arrow keys arranged in an upside-down T, and a numeric keypad on the right-hand side. Some keyboards have even more buttons, allowing you to change the system volume, eject a CD, or open programs such as your e-mail or Web browser.
Keyboard Shortcut A keyboard shortcut is a key combination that performs a certain command, such as closing a window or saving a file. For example, pressing "Control-S" in a Windows program or "Command-S" on the Mac is the standard shortcut for saving an open document. You can also usually close a window on the Mac by pressing "Command-W" or by pressing "Alt-F4" in Windows. The shortcut for copying data is usually "Control-C" (Windows) or "Command-C" (Mac) and for pasting data, it is "Control-V" (Windows) or "Command-V" (Mac). Most keyboard shortcuts are shortcuts for commands located in a program's menu bar. For example, most of the commands within the File and Edit menus have standard shortcuts. Each command that has a keyboard shortcut usually has the shortcut listed next to the command in the menu. For example, the Save option in a Windows program will usually have the text "Ctrl+S" next to it, indicating that pressing Control and S together will save the document. While most keyboard shortcuts are located in a program's menu bar, there are many keyboard shortcuts that are sometimes not visible to the user.
Keylogger A keylogger is a program that records the keystrokes on a computer. It does this by monitoring a user's input and keeping a log of all keys that are pressed. The log may saved to a file or even sent to another machine over a network or the Internet. Keylogger programs are often deemed spyware because they usually run without the user knowing it. They can be maliciously installed by hackers to spy on what a user is typing. By examining the keylog data, it may be possible to find private information such as a username and password combination. Therefore, keyloggers can be a significant security risk if they are unknowingly installed on a computer. The best way to protect yourself from keylogger programs is to install anti-virus or security software that warns you when any new programs are being installed. You should also make sure no unauthorized people have access to your computer. This is especially true in work environments. You can also periodically check the current processes running on your computer to make sure no keyloggers or other malware programs are active. While it is unlikely that you have a keylogger programs installed on your computer, it is definitely worth it to check.
keystone jack A keystone jack is a female connector used in data communications, particularly local area networks (LANs). The jack is usually mounted in a wall plate or patch panel. A keystone plug is the matching male connector, usually attached to the end of a cable or cord. A principal advantage of keystone connectors is their versatility. Several types of keystone jack can be mounted on a single patch panel. They are available in unshielded and shielded forms, and can accommodate cords and cables having various numbers of conductors. The term keystone derives from the characteristic shape of the jack, resembling the standard RJ-11 wall jack used to connect telephone sets, fax machines, and dial-up computer modems to conventional telephone lines.
Keystroke A keystroke is typing one character on a keyboard (not stroking your keyboard like a cat). Every time you hit a key, you perform a keystroke. Therefore, 5400 keystrokes in one hour means hitting 5400 keys in one hour, or 90 keys a minute (5400 keystrokes ? 60 minutes). Sometimes keystrokes per hour (KSPH) or keystrokes per minute (KSPM) are used to measure typing speed instead of words per minute (WPM). After all, typing the word "hi" 50 times doesn't take quite as long as typing "Nebuchadnezzar" 50 times.
Keywords Keywords are words or phrases that describe content. They can be used as metadata to describe images, text documents, database records, and Web pages. A user may "tag" pictures or text files with keywords that are relevant to their content. Later on, these files may be searched using keywords, which can make finding files much easier. For example, a photographer may use a program like Extensis Portfolio or Apple iPhoto to tag his nature photos with words such as "nature," "trees," "flowers," "landscape," etc. By tagging the photos, he can later locate all the pictures of flowers by simply searching for the "flowers" keyword. Keywords are used on the Web in two different ways: 1) as search terms for search engines, and 2) words that identify the content of the website. 1) Search Engine Search Terms Whenever you search for something using a search engine, you type keywords that tell the search engine what to search for. For example, if you are searching for used cars, you may enter "used cars" as your keywords. The search engine will then return Web pages with content relevant to your search terms. The more specific keywords you use, the more specific (and useful) the results will be. Therefore, if you are searching for a specific used car, you may enter something like "black Honda Accord used car" to get more accurate results. Many search engines also support boolean operators that can be used along with keywords to further refine the search. For example, you may search for "Apple AND computers NOT fruit" if you only want results related to Apple products and not the kind of apples that grow on trees. 2) Web Page Description Terms Keywords can also describe the content of a Web page using the keyword meta tag. This tag is placed in the section of a page's HTML and contains words that describe the content of the Web page. The purpose of the keywords meta tag is to help search engines identify and organize Web pages, like in the photos example above. However, because webmasters have been known to use inaccurate tags to get higher search engine ranking, many search engines now give little to no weight to the keywords meta tag when indexing pages.
Kibibyte A kibibyte is a unit of data storage that equals 2 to the 10th power, or 1,024 bytes. While a kilobyte can be estimated as 10^3 or 1,000 bytes, a kibibyte is exactly 1,024 bytes. This is to avoid the ambiguity associated with the size of kilobytes. A kibibyte is 1,024 bytes and precedes the mebibyte unit of measurement.
Kilobyte Unit of storage, usually abbreviated to KB. 1 kilobyte = 2 to the tenth power (210) bytes = 1024 bytes.
kilobyte (K, KB, or Kb) 1,024 (2 to the 10th power) bytes; often used to represent one thousand bytes. Example: a 720K diskette can hold approximately 720,000 bytes (or characters).
knowledge base A database where information common to a particular topic is stored online for easy reference; for example, a frequently-asked questions (FAQ) list may provide links to a knowledge base.
KVM Keyboard, Video, Monitor. Usually used either when referring to a set of extension cables (for keyboard, video and monitor) or a KVM Switch.
KVM Switch A switch box allowing one monitor, keyboard and video to be switched between two or more separate computers thereby allowing two or more computers to be controlled from the same keyboard, video, monitor combination. See also KVM.
L1 cache (Level 1 Cache) A small piece of very fast memory that’s almost always on the CPU chip itself. It sits between the CPU registers and the L2 cache. Typically L1 cache has a lower latency than L2 cache, making it more expensive to produce and harder to produce in larger quantities without additional complexity.
L2 cache (Level 2 Cache) A piece of fast memory that sits between the L1 cache of the processor and main memory. It is usually larger than L1 cache, and the L1 cache checks the L2 cache before going to main memory for data (unless the L1 and L2 caches are unified–see unified cache). Nowadays L2 caches are almost always on the same die as the microprocessor, but they can be off-chip.
L3 Cache (Level 3 Cache) This type of cache is becoming more prevalent as microprocessor manufacturers ship more processors with L1 and L2 cache built into the processor. L3 cache is then the extra cache that sits on the motherboard between the processor and main memory, since the processor already contains L1 and L2 cache. Some processors are starting to ship with L3 cache built-in as well to speed up memory operations further. In those cases the L3 cache often sits on a separate area of the die, not built directly into the chip core.
Lag A condition caused by network congestion. When more traffic is flowing than a network or connection can handle, it causes programs waiting to send or receive data over the network to slow down, or lag. This term is often used to describe a slowdown while playing games online, especially over dial-up modems or any connection with high latency.
LAMP Linux, Apache, MySQL and PHP. Also defined as Linux, Apache, MySQL and Pythor or Perl. The term LAMP is used to describe a web based solution produced using PHP (scripting), MySQL (database), Apache (web-server) under Linux (operating system), each of which are free to download. It therefore describes a website using free off-the-shelf components.
LAN Local Area Network. Usually a high speed network, normally confined to a single geographic area, allowing communications at either 10Mbps, 100Mbps or (rarely but up-coming) 1000Mbps. cf WAN. LANs are typically implemented using Ethernet, Token Ring, Fast Ethernet, Fibre Distributed Interface (FDDI), Asynchronous Transfer Mode (ATM) or LocalTalk.
Laptop Laptop computers, also known as notebooks, are portable computers that you can take with you and use in different environments. They include a screen, keyboard, and a trackpad or trackball, which serves as the mouse. Because laptops are meant to be used on the go, they have a battery which allows them to operate without being plugged into a power outlet. Laptops also include a power adapter that allows them to use power from an outlet and recharges the battery. While portable computers used to be significantly slower and less capable than desktop computers, advances in manufacturing technology have enabled laptops to perform nearly as well as their desktop counterparts. In fact, high-end laptops often perform better than low or even mid-range desktop systems. Most laptops also include several I/O ports, such as USB ports, that allow standard keyboards and mice to be used with the laptop. Modern laptops often include a wireless networking adapter as well, allowing users to access the Internet without requiring any wires. While laptops can be powerful and convenient, the convenience often comes at a price. Most laptops cost several hundred dollars more than a similarly equipped desktop model with a monitor, keyboard, and mouse. Furthermore, working long hours on a laptop with a small screen and keyboard may be more fatiguing than working on a desktop system. Therefore, if portability is not a requirement for your computer, you may find better value in a desktop model.
Large Scale Integration (LSI) This refers to chips containing thousands of transistors–but less than a million. See also ULSI, VLSI, MSI, and SSI.
Laser Printer A laser printer is a printer that uses a focused beam or light to transfer text and images onto paper. Though contrary to popular belief, the laser does not actually burn the images onto the paper. Instead, as paper passes through the printer, the laser beam fires at the surface of a cylindrical drum called a photoreceptor. This drum has an electrical charge (typically positive), that is reversed in areas where the laser beam hits it. By reversing the charge in certain areas of the drum, the laser beam can print patterns (such as text and pictures) onto the photoreceptor. Once the pattern has been created on the drum, it is coated with toner from a toner cartridge. The toner is black in most cartridges, but may be cyan, magenta, and yellow in color laser printers. The positively charged toner clings to areas of the drum that have been negatively charged by the laser. When the paper passes through the printer, the drum is given a strong negative charge, which allows the toner to transfer and stick to the paper. The result is a clean copy of the image written on the paper. Because laser printers do not use ink, they have less image smearing problems than inkjet printers and are able to print pages faster. While laser printers and toner cartridges typically cost more than inkjet printers and ink cartridges, most laser toner cartridges last several times longer than ink cartridges, which makes their cost per page about equal. For this reason, businesses tend to use laser printers, while consumers are more likely to use inkjet printers. Laser printers typically have a resolution of 600 dpi (dots per inch) or higher.
Latency This is the amount of time it takes a packet of data to move across a network connection. When a packet is being sent, there is "latent" time, when the computer that sent the packet waits for confirmation that the packet has been received. Latency and bandwidth are the two factors that determine your network connection speed.
Lattice Techniques Lattice Techniques use security designations to determine access to information.
Layer 2 Forwarding Protocol (L2F) An Internet protocol (originally developed by Cisco Corporation) that uses tunneling of PPP over IP to create a virtual extension of a dial-up link across a network, initiated by the dial-up server and transparent to the dial-up user.
Layer 2 Tunneling Protocol (L2TP) An extension of the Point-to-Point Tunneling Protocol used by an Internet service provider to enable the operation of a virtual private network over the Internet.
LCD Liquid Crystal Display. cf CRT.
LDAP Lightweight Directory Access Protocol. An implementation of the industry standard X.500 directory protocol developed for PCs and the internet. Unlike X.500, LDAP is designed for IP, has a small footprint, is simple to implement and is faster and less network-intensive than X.500. Also abbreviated to "LDap". Put simply, LDAP is a protocol for querying directory services (such as the Windows Active Directory or DNS servers) over TCP/IP.
Leased Line Refers to line such as a telephone line or fiber-optic cable that is rented for exclusive 24-hour, 7-days-a-week use from your location to another location. The highest speed data connections require a leased line.
Least Privilege Least Privilege is the principle of allowing users or applications the least amount of permissions necessary to perform their intended function.
LED Light Emitting Diode. Small light found on many items of equipment, typically used to indicate activity or that something is switched on. Cheap and low power. Typically red in colour (because these are cheaper to produce) but available in other colours also. cf OLED.
Legacy device A type of device or peripheral that is not Plug-and-Play-compatible. Such devices often contain jumpers that must be set manually.
Legacy System Any old computer system that was set up before your time and now continues to work and need support. Often legacy systems are problematic to upgrade because the people that put them together aren’t around any more. One great example was the Year 2000 problem. Legacy systems were driving everyone nuts because no one programmed in COBOL anymore, and lots of legacy code was written in COBOL.
License (Software license) Most corporations need multiple copies of software, but do not need the media in which they come, either because they already have it or because they allow users to install software from a server on the network. Companies still need to purchase a copy for each user, however, so they need a way to prove they have actually purchased a copy of each. These companies purchase software licenses with no associated media. Such licenses are typically just sheets of paper that cost a lot of money, but allow you to legally use additional copies of the software.
Lightweight Directory Access Protocol (LDAP) An industry standard open client/server protocol for accessing a directory service, such as Active Directory or Novell Directory Services. It is a simplified version of the X.500 protocol.
Line in An analog I/O port for a sound device that allows a device to receive a line-level audio signal. A line-level signal is a non-amplified sound signal meant to be sent to a device that has a line-in port. Since the line-level signal isn’t amplified it is typically cleaner.
Line out An analog I/O port for a sound device that allows a device to send a line-level audio signal. This is opposed to an amplified signal on a speaker out port.
LINK "ROT" Term used to describe the frustrating and frequent problem caused by the constant changing in URLs. A Web page or search tool offers a link and when you click on it, you get an error message (e.g., "not available") or a page saying the site has moved to a new URL. Search engine spiders cannot keep up with the changes. URLs change frequently because the documents are moved to new computers, the file structure on the computer is reorganized, or sites are discontinued. If there is no referring link to the new URL, there is little you can do but try to search for the same or an equivalent site from scratch.
Link State With link state, routes maintain information about all routers and router-to-router links within a geographic area, and creates a table of best routes with that information.
Links These are the hypertext connections between Web pages. This is a synonym for hotlinks or hyperlinks.
Linksys Linksys by Cisco, commonly known as Linksys, is a major provider of home and small office network products and was founded in 1988 and acquired by Cisco Systems in 2003[1]. Linksys also manufactures broadband and wireless routers, consumer and small business grade Ethernet switching, VoIP equipment, wireless internet video camera, AV products, network storage systems, and other products. Since 2008, all Linksys products sold are now packaged and branded as "Linksys by Cisco".
Linux A widely used Open Source Unix-like operating system. Linux was first released by its inventor Linus Torvalds in 1991. There are versions of Linux for almost every available type of computer hardware from desktop machines to IBM mainframes. The inner workings of Linux are open and available for anyone to examine and change as long as they make their changes available to the public. This has resulted in thousands of people working on various aspects of Linux and adaptation of Linux for a huge variety of purposes, from servers to TV-recording boxes.
Liquid Cooling This form of cooling refers to water cooling, or any other method of cooling where a liquid is used to keep something cool.
List Based Access Control List Based Access Control associates a list of users and their privileges with each object.
LISTSERV, Listserver An electronic mailing list; it provides a simple way of communicating with a large number of people very quickly by automating the distribution of electronic mail. At OSU, mailing lists are used not only for scholarly communication and collaboration, but also as a means of facilitating and enhancing classroom education.
Live Backup The operation of copying a whole virtual machine, while powered on, at the host OS level, for archiving purposes.
Live Migration The operation of moving a virtual machine, while powered on, from a host OS to another host OS, for maintenance or server consolidation purposes.
LMZ Local Machine Zone. One of the default security zones that Microsoft's Internet Explorer uses. It includes anything that exists on the local computer (other than cached pages).
Load Balancing Computer networks are complex systems, often routing hundreds, thousands, or even millions of data packets every second. Therefore, in order for networks to handle large amounts of data, it is important that the data is routed efficiently. For example, if there are ten routers within a network and two of them are doing 95% of the work, the network is not running very efficiently. The network would run much faster if each router was handling about 10% of the traffic. Likewise, if a website gets thousands of hits every second, it is more efficient to split the traffic between multiple Web servers than to rely on a single server to handle the full load. Load balancing helps make networks more efficient. It distributes the processing and traffic evenly across a network, making sure no single device is overwhelmed. Web servers, as in the example above, often use load balancing to evenly split the traffic load among several different servers. This allows them to use the available bandwidth more effectively, and therefore provides faster access to the websites they host. Whether load balancing is done on a local network or a large Web server, it requires hardware or software that divides incoming traffic among the available servers. Networks that receive high amounts of traffic may even have one or more servers dedicated to balancing the load among the other servers and devices in the network. These servers are often called (not surprisingly) load balancers. Clusters, or mulitple computers that work together, also use load balancing to spread out processing jobs among the available systems.
Loadable Kernel Modules (LKM) Loadable Kernel Modules allow for the adding of additional functionality directly into the kernel while the system is running.
Localhost "Localhost" refers to the local computer that a program is running on. For example, if you are running a Web browser on your computer, your computer is considered to be the "localhost." While this does not need to be specified when using a single computer, the localhost does need to be defined when running programs from multiple computers. For example, a network administrator might use his local machine to start a Web server on one system and use a remote access program on another. These programs would run from computers other than the localhost. In the example above, the two non-local computers must be defined by their IP addresses. The local machine is defined as "localhost," which gives it an IP address of 127.0.0.1. This is considered a "loopback" address because the information sent to it is routed back to the local machine. Localhost is often used in Web scripting languages like PHP and ASP when defining what server the code should run from or where a database is located.
Log 1. The act of writing information to a log (see definition 2) or to a log file. The term originates from the practise of a maritime officer maintaining a record of events in a ship's log. 2. A record of what has happened, i.e. a record of events. Historically a written diary, such as a captains log recording events on a voyage. In this context it can also refer to a log file. 3. Abbreviation for logarithm, a mathematical function.
Log Clipping Log clipping is the selective removal of log entries from a system log to hide a compromise.
Log file A file that contains a record of activities that have occurred. An application is said to "log" information to the log file (hence the name "log file"). Log files are generated automatically by some applications as they work and are typically (but not always) text editable files. Text editable (and therefore human readable) log files are typically generated produced to provide a record of what went on and are not normally used again by the application that generated them. Databases in particular will generate log files in a binary format which are intended for its own database recovery purposes and are not intended for human reading. Log files will typically have the file extension of .log, but this is not guaranteed and depends on the application.
log in, log on The process of entering your username and password to gain access to a particular computer; e.g., a mainframe, a network or secure server, or another system capable of resource sharing.
Logic Gate A logic gate is an elementary building block of a digital circuit. Most logic gates have two inputs and one output. As digital circuits can only understand binary, inputs and outputs can assume only one of two states, 0 or 1.
Login Noun or a verb. Noun: The account name used to gain access to a computer system. Not a secret (contrast with Password). Verb: the act of connecting to a computer system by giving your credentials (usually your "username" and "password") See also: Password
Loopback Address The loopback address (127.0.0.1) is a pseudo IP address that always refer back to the local host and are never sent out onto a network.
Lossless ossless compression reduces a file's size with no loss of quality. This seemingly magical method of reducing file sizes can be applied to both image and audio files. While JPEGs and MP3s use lossy compression, newer compression algorithms, such as JPEG 2000 and Apple Lossless compression, can be used to create lossless compressed files. Lossless compression basically rewrites the data of the original file in a more efficient way. However, because no quality is lost, the resulting files are typically much larger than image and audio files compressed with lossy compression. For example, a file compressed using lossy compression may be one tenth the size of the original, while lossless compression is unlikely to produce a file smaller than half of the original size.
Lossy Lossy file compression results in lost data and quality from the original version. Lossy compression is typically associated with image files, such as JPEGs, but can also be used for audio files, like MP3s or AAC files. The "lossyness" of an image file may show up as jagged edges or pixelated areas. In audio files, the lossyness may produce a watery sound or reduce the dynamic range of the audio. Because lossy compression removes data from the original file, the resulting file often takes up much less disk space than the original. For example, a JPEG image may reduce an image's file size by more than 80%, with little noticeable effect. Similarly, a compressed MP3 file may be one tenth the size of the original audio file and may sound almost identical. The keyword here is "almost." JPEG and MP3 compression both remove data from the original file, which may be noticeable upon close examination. Both of these compression algorithms allow for various "quality settings," which determine how compressed the file will be. The quality setting involves a trade-off between quality and file size. A file that uses greater compression will take up less space, but may not look or sound as good as a less compressed file. Some image and audio formats allow lossless compression, which does not reduce the file's quality at all.
LS 1. Location Services. 2. UNIX command line command to list files.
LSI Corporation (LSI) LSI Corporation is an electronics company based in Milpitas, California, that designs ASICs, host bus adapters, RAID adapters, storage systems, and computer networking products.
LUA Limited User Account. A user account that lacks any (or all) administrative rights. cf Administrator Account (AC). It is generally recommended that a Limited User Account be used for day to day activities and an Administrator Account used only when strictly necessary. This reduces the opportunity for a system to be compromised due to the actions of the user.
LUN Stands for "Logical Unit Number." LUNs are used to identify SCSI devices, such as external hard drives, connected to a computer. Each device is assigned a LUN, from 0 to 7, which serves as the device's unique address. LUNs can also be used for identifying virtual hard disk partitions, which are used in RAID configurations. For example, a single hard drive may be partitioned into multiple volumes. Each volume can then be assigned a unique LUN. However, few modern computers use LUNs, since SCSI devices have mostly been replaced by USB and Firewire devices.
LUN (Logical Unit Number) A term used in the context of devices connected to a SCSI controller. Each device on a SCSI controller has a SCSI ID, but each SCSI ID may have several LUNs that translate to several hard disks or removable media.
MAC 1. Media Access Control. See also MAC Address. 2. Apple Macintosh computer
MAC Address Media Access Control address. Hardware serial number that uniquely identifies a device on a local area network (commonly a NIC). (Sometimes also referred to as a NIC's "physical address".) A MAC address is 6 bytes in length (i.e. 48 bits) and is normally written as a 12 digit hexadecimal number, with dashes or colons between each pair of hexadecimal digits. The first three bytes identifies the manufacturer and the second three bytes represent a unique serial number generated by that manufacturer. MAC addresses should therefore always be unique (although some cards and switches allow the MAC address to be cloned).
Mac OS This is the operating system that runs on Macintosh computers. It is pronounced, "mack-oh-es." The Mac OS has been around since the first Macintosh was introduced in 1984. Since then, it has been continually updated and many new features have been added to it. Each major OS release is signified by a new number (i.e. Mac OS 8, Mac OS 9). Since the core of the Mac OS was nearly decades old, Apple decided to completely revamp the operating system. In March of 2001, Apple introduced a completely new version of the Mac OS that was written from the ground up. The company dubbed it "Mac OS X," correctly pronounced "Mac OS 10." Unlike earlier versions of the Mac OS, Mac OS X is based on the same kernel as Unix and has many advanced administrative features and utilities. Though the operating system is much more advanced than earlier versions of the Mac OS, it still has the same ease-of-use that people have come to expect from Apple software.
Mac OS X Mac OS X, pronounced "Mac Oh-Es Ten," is the current version of the operating system used on Apple Macintosh computers. If you happen to pronounce it "Mac OS X," computer nerds and dedicated Mac users will be quick to correct you. While the name may be a bit confusing, Mac OS X is an advanced, user-friendly operating system. Previous versions of the Mac OS, were based on the original Macintosh operating system, released in 1984. In the late 1990's, many computer users felt Windows had "caught up" to the Mac OS and Apple's operating system began to appear a bit dated. So Apple completely revamped the Mac OS and created a new operating system from the ground up. While much of the code used to build Mac OS X was written from scratch, a lot was taken from the NEXTSTEP operating system. NEXTSTEP was a Unix-based system that ran on NeXT computers, which are no longer in production. NeXT was acquired by Apple in 1997 and Steve Jobs was hired as interim CEO. Apple developers took the Unix-based code from NEXTSTEP and combined it with the graphical user interface (GUI) of Mac OS 9. The result was a stable, high-performance operating system that had the stability of Unix and the intuitive interface of the Macintosh. Mac OS X 10.0 was released in 2001. Since the initial release, Apple has released several major updates to Mac OS X, at a pace of roughly one update a year. The list of OS X versions include 10.0 Cheetah, 10.1 Puma, 10.2 Jaguar, 10.3 Panther, and 10.4 Tiger. Mac OS X 10.5 is expected to be called Leopard.
Mac OS X Leopard Mac OS X Leopard (version 10.5) is the sixth major release of Mac OS X, Apple’s desktop and server operating system for Macintosh computers. Leopard was released on 26 October 2007 as the successor of Mac OS X Tiger (version 10.4), and is available in two variants: a desktop version suitable for personal computers, and a server version, Mac OS X Server. Steve Jobs stated at Macworld 2008 that over 20% of Macs use Leopard as their operating system.[1] Leopard was superseded by Mac OS X Snow Leopard (version 10.6). Leopard is the final version of Mac OS X to support the PowerPC architecture as Snow Leopard solely functions on Intel based Macs. With the release of Snow Leopard, Leopard will only be maintained with security updates until the next shipping version of Mac OS X. According to Apple, Leopard contains over 300 changes and enhancements over its predecessor, Mac OS X Tiger,[2] covering core operating system components as well as included applications and developer tools. Leopard introduces a significantly revised desktop, with a redesigned Dock, Stacks, a semitransparent menu bar, and an updated Finder that incorporates the Cover Flow visual navigation interface first seen in iTunes. Other notable features include support for writing 64-bit graphical user interface applications, an automated backup utility called Time Machine, support for Spotlight searches across multiple machines, and the inclusion of Front Row and Photo Booth, which were previously included with only some Mac models. Apple missed Leopard's release time frame as originally announced by Apple’s CEO Steve Jobs. When first discussed in June 2005, Jobs had stated that Apple intended to release Leopard at the end of 2006 or early 2007.[3] A year later, this was amended to Spring 2007;[4] however on 12 April 2007, Apple issued a statement that its release would be delayed until October 2007 because of the development of the iPhone.[5]
Mac OS X Server Mac OS X Server is a Unix[1] server operating system from Apple Inc. The server edition of Mac OS X is architecturally identical to its desktop counterpart, except that it includes work group management and administration software tools. These tools provide simplified access to key network services, including a mail transfer agent, a Samba server, an LDAP server, a domain name server, and others. Also included (particularly in later versions) are numerous additional services and the tools to manage them, such as web server, wiki server, chat server, calendar server, and many others. Mac OS X Server is the operating system of Xserve computers, rack mounted server computers designed by Apple. Also, it is optionally preinstalled on the Mac mini and Mac Pro and is sold separately for use on any Macintosh computer meeting its minimum requirements. Overview Mac OS X Server is a server operating system which enables organizations to collaborate, communicate, and share information. It is based on an open source foundation called Darwin and uses open industry standards and protocols. Mac OS X Server includes services and applications for file sharing, sharing contact information and calendars, schedule events, send secure instant messages, conduct live video conferences, send and receive email, contribute to and comment in wikis, publish a companywide blog, produce and distribute podcasts, and set up websites.
Macintosh This is the name of the computers that are made by Apple Computer. The first Macintosh was introduced in 1984 and was seen as a major innovation in computing ease-of-use. The Macintosh was the first personal computer to use a graphical user interface (GUI), which allowed the user to interact with the operating system by using a mouse to click and drag objects. Since 1984, Apple has continually revised and upgraded the Macintosh product line and now makes both laptop and desktop versions of the Macintosh. Apple also makes other equipment such as displays, MP3 players, and networking hardware, but the Macintosh is the heart and soul of the company. Macintosh computers run the Macintosh operating system, creatively named the "Mac OS."
Macro Macro has two computer-related definitions, both of which involve making your computer experience more efficient. 1. A Keyboard Shortcut The term "macro" is often used synonymously with "keyboard shortcut." Keyboard shortcuts are key combinations that perform commands, such as saving a file, closing a window, or copying and pasting data. 2. A Small Program A macro can also be a small program, or script, that automates common tasks. These scripts are usually run within programs and can often be created by the user. For example, a user might record a macro for Microsoft Word that inserts his entire address when he presses a custom key combination. A Microsoft Excel user might record a macro to format the data in the selected column of a spreadsheet. While Word and Excel both make it easy to create custom macros, many other programs allow users to create macros as well. However, not all programs refer to the automated commands as macros. For example, Photoshop allows users to record changes made to an image and saves the series of steps as an "action." These actions can then by applied to other images. Regardless of what they are called, macros can save you a lot of time by automating repetitive tasks. If you find yourself doing the same thing over and over again when using a certain program, you may want to simplify the process by recording a macro.
Magnetic stripe A piece of plastic coated with ferromagnetic particles to hold a magnetic flux. In human speak: a strip of audiotape glued onto a card to hold a bit of information. Every credit card has one on the back–it’s the black/brown stripe. It usually holds the stuff that’s imprinted on the card, like the account number and the expiration date.
Magnetic stripe unit A device to read and encode cards with a magnetic stripe.
main memory The amount of memory physically installed in your computer. Also referred to as "RAM".
Mainframe A mainframe is an ultra high-performance computer made for high-volume, processor-intensive computing. They are typically used by large businesses and for scientific purposes. You probably won't find a mainframe in any household. In the hierarchy of computers, mainframes are right below supercomputers, the most powerful computers in the world. (Which is why they are aptly named "supercomputers.") Yet a mainframe can usually execute many programs simultaneously at a high speed, whereas supercomputers are designed for a single process. Currently, the largest manufacturers of mainframes are IBM and Unisys.
male connector A cable connector that has pins and plugs into a port or interface to connect one device to another.
Malicious Code Software (e.g., Trojan horse) that appears to perform a useful or desirable function, but actually gains unauthorized access to system resources or tricks a user into executing other malicious logic.
Malware hort for "malicious software," malware refers to software programs designed to damage or do other unwanted actions on a computer system. In Spanish, "mal" is a prefix that means "bad," making the term "badware," which is a good way to remember it (even if you're not Spanish). Common examples of malware include viruses, worms, trojan horses, and spyware. Viruses, for example, can cause havoc on a computer's hard drive by deleting files or directory information. Spyware can gather data from a user's system without the user knowing it. This can include anything from the Web pages a user visits to personal information, such as credit card numbers. It is unfortunate that there are software programmers out there with malicious intent, but it is good to be aware of the fact. You can install anti-virus and anti-spyware utilities on your computer that will seek and destroy the malicious programs they find on your computer. So join the fight against badware and install some protective utilities on your hard drive!
MANET Stands for "Mobile Ad Hoc Network." A MANET is a type of ad hoc network that can change locations and configure itself on the fly. Because MANETS are mobile, they use wireless connections to connect to various networks. This can be a standard Wi-Fi connection, or another medium, such as a cellular or satellite transmission. Some MANETs are restricted to a local area of wireless devices (such as a group of laptop computers), while others may be connected to the Internet. For example, A VANET (Vehicular Ad Hoc Network), is a type of MANET that allows vehicles to communicate with roadside equipment. While the vehicles may not have a direct Internet connection, the wireless roadside equipment may be connected to the Internet, allowing data from the vehicles to be sent over the Internet. The vehicle data may be used to measure traffic conditions or keep track of trucking fleets. Because of the dynamic nature of MANETs, they are typically not very secure, so it is important to be cautious what data is sent over a MANET.
Masking To conceal a web site's URL in some manner, normally by using a domain name. For example, if a URL shows up as "http://www.example.com/" but the web site is actually located at "http://www.somewhere-else.com/example/", that URL is said to be "masked". See Also: Domain Name, URL
Masquerade Attack A type of attack in which one system entity illegitimately poses as (assumes the identity of) another entity.
Master When two IDE or EIDE devices are put on the same cable, one must be master and the other slave. The master/slave configuration is used not only to allow communications to work properly for two devices on one channel, but also so that there is a specific boot order when two or more IDE hard drives are encountered on a system. The master hard drive on the first IDE channel will be the first IDE drive checked for a master boot record when the system attempts to boot from an IDE device.
Max Abbreviation for Maximum. Some programming languages have a "max" function that will return the larger of the values supplied to it. Similarly SQL includes a "max" function that returns the maximum matching value found as part of a query. cf Min.
Maximize aximizing a window makes it larger. In Windows, a maximized window fills the entire screen, while on a Mac, it takes up only as much space as needed. The maximize button in Windows is located in the upper-right corner of the window, next to the close button. If you double-click the title bar, it will also maximize the window. On a Mac, the maximize button is three green button located next to the red and yellow buttons in the upper-left corner of the window. To hide an open window, you can click the minimize button, which is located next to the maximize button on both Macintosh and Windows computers.
MB 1. Megabyte. A unit of storage, 1024 KBs, see megabyte for details. 2. Abbreviation for MotherBoard, the main board in a computer that other boards plug into.
mbps Mega-bits per second. Strictly 1mbps = 128KB per second, but when measuring network/modem throughput a figure of 1mbps = 100 KB per second is probably closer to the real throughput after other networking overheads are taken into consideration. See also bps and kbps.
MBR Master Boot Record. Record located at the beginning of a bootable disk on Intel based systems, containing the boot loader.
MBSA Microsoft Baseline Security Analyzer. Tool from Microsoft to scan for security vulnerabilities.
MCA Stands for "Micro Channel Architecture." It is an expansion bus created by IBM that was used in the company's PS/2 desktop computers. An expansion bus allows additional cards to be connected to the computer's motherboard, expanding the number of I/O ports. These include SCSI, USB, Firewire, AGP, and DVI connections, as well as many others. The MCA standard was designed to take the place of the AT and ISA buses used in previous IBM PC/AT compatible computers. While the MCA bus architecture was an improvement in both size and speed over AT and ISA, it was kept as a proprietary standard by IBM. This discouraged other manufacturers from adopting the standard, since the MCA architecture was not compatible with other standards. Most PC companies incorporated the more universal PCI and AGP expansion buses into their computers, which are both widely used today.
MD Make Directory command. On many operating systems (OS), md is a command-line command to make a sub-directory.
Md5 A one way cryptographic hash function. Also see "hash functions" and "sha1"
MDI 1. Multiple Document Interface. A GUI interface for an application that allows more than one document to be visible at a time. 2. Medium Dependent Interface. Provides the physical connection to a cable. 3. Microsoft Document Imaging Format. A file format based on TIFF that is designed to store images by page layout.
MDI/MDI-X etwork hub crossover switch. An MDI/MDI-X switch on a network hub typically allows a port on a network hub to connect to either a network peripheral (such as a pc) or another hub/switch.
Measures of Effectiveness (MOE) Measures of Effectiveness is a probability model based on engineering concepts that allows one to approximate the impact a give action will have on an environment. In Information warfare it is the ability to attack or defend within an Internet environment.
Mebibyte A mebibyte is a unit of data storage that equals 2 to the 20th power, or 1,048,576 bytes. While a megabyte can be estimated as 10^6 or 1,000,000 bytes, a mebibyte is exactly 1,048,576 bytes. This is to avoid the ambiguity associated with the size of megabytes. A mebibyte is 1,024 kibibytes and precedes the gibibyte unit of measurement. A mebibyte is a unit of data storage that equals 2 to the 20th power, or 1,048,576 bytes. While a megabyte can be estimated as 10^6 or 1,000,000 bytes, a mebibyte is exactly 1,048,576 bytes. This is to avoid the ambiguity associated with the size of megabytes. A mebibyte is 1,024 kibibytes and precedes the gibibyte unit of measurement. For a list of other units of measurements, view this Help Center article. Abbreviation: MiB
Mechanical Control A dial or knob whose physical setting directly affects some measurement. For example, the power button in early PCs was a mechanical control, as were the huge, hand-controlled electrical switches in old horror movies and light switches on your wall. By pushing the power button you used to physically make an electrical contact so that power could flow to your PC. Nowadays most power buttons only send signals to the motherboard and are no longer mechanical controls.
Media In general, "media" refers to various means of communication. For example, television, radio, and the newspaper are different types of media. The term can also be used as a collective noun for the press or news reporting agencies. In the computer world, "media" is also used as a collective noun, but refers to different types of data storage options. Computer media can be hard drives, removable drives (such as Zip disks), CD-ROM or CD-R discs, DVDs, flash memory, USB drives, and yes, floppy disks. For example, if you want to bring your pictures from your digital camera into a photo processing store, they might ask you what kind of media your pictures are stored on. Are they on the flash memory card inside your camera or are they on a CD or USB drive? For this and many other reasons, it is helpful to have a basic understanding of what the different types of media are.
Meg Short for mega, meaning a million. Depending on the context in IT meg is typically used to refer to mega-bytes (MB) or mega-hertz (MHz).
Megabyte Unit of storage, often abbreviated to simply MB. Million bytes. Normally abbreviated to MB. Strictly, 1 megabyte = 2 to the twentieth power (220) bytes = 1,048,576 bytes = 1024 kilobytes. See also gigabyte. Computer memory (RAM) is normally measured in megabytes, as is disk space. Note: Storage devices sold by manufacturers normally assume 1MB = 1,000,000 bytes.
megabyte (Meg or MB) 1,024 x 1,024 (2 to the 20th power) bytes; it's usually sufficient to think of a megabytes as one million bytes.
Megapixel A megapixel is one million pixels. It is commonly used to describe the resolution of digital cameras. For example, a 7.2 megapixel camera is capable of capturing roughly 7,200,000 pixels. The higher the megapixel number, the more detail the camera can capture. Therefore, the megapixel count is a significant specification to look for when buying a digital camera. A camera's megapixel number is calculated by multiplying the number of vertical pixels by the number of horizontal pixels captured by the camera's sensor, or CCD. For example, the original Canon Digital Rebel captures 2048 vertical by 3072 horizontal pixels, for a total of 6,291,456 pixels (2048 x 3072). Therefore, it is estimated to be a 6.3 megapixel camera. The Sony T10 captures 3072 x 2304 pixels, totaling 7,077,888, which makes it a 7.2 megapixel camera (because not all the pixels are used). Megapixels are helpful in marketing digital cameras, because it is easier to say, "6.3 megapixels" than "6,291,456 pixels." It is also a little easier to remember. However, while megapixels are important, it is helpful to know the other specifications of a camera as well. For example, shutter speed, shooting modes, start-up time, flash quality, and color accuracy can also make a big difference in the camera's performance. After all, it doesn't matter how many megapixels your camera has if all your pictures turn out blurry and have poor color. Therefore, while you should check the megapixel count on a camera before buying it, make sure you check the other specs too.
Memory Leak A memory leak is like a virtual oil leak in your computer. It slowly drains the available memory, reducing the amount of free memory the system can use. Most memory leaks are caused by a program that unintentionally uses up increasing amounts of memory while it is running. This is typically a gradual process that gets worse as the program remains open. If the leak is bad enough, it can cause the program to crash or even make the whole computer freeze. The most common reason programs have memory leaks is due to a programming error where unused memory is not allocated back to the system. This means the amount of RAM the program uses is always growing. Therefore, the program is constantly "leaking" memory. A memory leak may also be caused by a program that requests new memory too frequently, instead of using available memory. This means each time more memory is requested, the program takes up additional RAM instead of using memory that has already been made available to the program. Fortunately, memory leaks are not as messy as oil leaks and can be more easily fixed. Software development applications often include debuggers that can check programs for memory leaks. Once the source of the leak is found, the programmer can modify the code so that the program uses memory more efficiently. If you are using a program that has a memory leak, you can temporarily fix the problem by simply quitting the program and opening it again. Once the program has been quit, the memory is automatically allocated back to the system. Of course, if the leak continues to be a problem, the best solution is to let the developer know about the issue so it can be fixed.
Memory Module A memory module is another name for a RAM chip. It is often used as a general term used to describe SIMM, DIMM, and SO-DIMM memory. While there are several different types of memory modules available, they all serve the same purpose, which is to store temporary data while the computer is running. Memory modules come in different sizes and have several different pin configurations. For example, the original SIMMs had 30 pins (which are metal contacts that connect to the motherboard). However, newer SIMM chips have 72 pins. DIMMs commonly come in 168-pin configurations, but some DIMMs have as many as 240 pins. SO-DIMMs have a smaller form factor than standard DIMM chips, and come in 72-pin, 144-pin, and 200-pin configurations. While "memory module" is the technical term used to describe computer memory, the terms "RAM," "memory," and "RAM chip" are just as acceptable. But remember, while memory terms may be interchangeable, the memory itself is not. This is because most computers only accept one type of memory. Therefore, if you decide to upgrade you computer's RAM, make sure the memory modules you buy are compatible with your machine.
Memory Stick Memory Stick is a type of flash memory developed by Sony. It is used to store data for digital cameras, camcorders, and other kinds of electronics. Because Memory Stick is a proprietary Sony product, it is used by nearly all of Sony's products that use flash media. Unfortunately, this also means Memory Stick cards are incompatible with most products not developed by Sony. Memory Stick cards are available in two versions: Memory Stick PRO and Memory Stick PRO Duo. Memory Stick PRO cards are 50mm long by 21.5mm wide and are 2.8mm thick. Memory Stick PRO Duo cards are 31mm long by 20mm wide and are only 1.6mm thick. High-speed versions of Memory Stick media support data transfer rates up to 80Mbps, or 10 MB/sec, which is fast enough record high-quality digital video.
menu In a graphical user interface, a bar containing a set of titles that appears at the top of a window. Once you display the contents of a menu by clicking on its title, you can select any active command (e.g., one that appears in bold type and not in a lighter, gray type).
Menu Bar A menu bar is a horizontal strip that contains lists of available menus for a certain program. In Windows programs, the menu bar resides at the top of each open window, while on the Mac, the menu bar is always fixed on the top of the screen. Despite this major difference, the menu bar serves the same purpose on each platform. Nearly all programs have a menu bar as part of their user interface. It includes menu items and options specific to the particular program. Most menu bars have the the standard File, Edit, and View menus listed first. The File menu includes options such as Save and Open File..., the Edit menu has items such as Undo, Copy, Paste, and Select All, while in the View menu you'll find viewing options such as changing the layout of open windows. Word processing programs, such as Microsoft Word, also include menu options such as Insert, Format, and Font which you will most likely not find in a Web browser's menu bar. But a Web browser may contain menu options such as History and Bookmarks, which you will not find in a word processing program. Many items located within the menu bar often have keyboard shortcuts that enable you to choose menu options by just pressing a key combination. For example, to copy an object or text selection, most programs allow you to press Control-C (Windows) or Command-C (Mac) instead of selecting Copy from the Edit menu. When browsing through the items in a program's menu bar, you should see the keyboard shortcuts located next to each option that has a shortcut available. The menu bar is a fundamental part of the graphical user interface (GUI), so it is worth you time to get familiar with it. You may even discover features you did not know about before.
MER MAC Encapsulated Routing.
Metadata Data (or information) about data. Metadata describes the structure and attributes of data, it may also include any license or copyright terms, origin of the data, cautions about the robustness of the data and perhaps suitability for different types of purpose.
Metafile A device independent file containing both Raster and Vector data, such as a vector plan with a Bitmap embedded.
MHz or mHz Megahertz; a measurement of a microprocessor's speed; one MHz represents one million cycles per second. The speed determines how many instructions per second a microprocessor can execute. The higher the megahertz, the faster the computer.
Micron The length of one millionth of a meter, or 1/1,000,000 meters. This length is also referred to as a micrometer. There is also a microchip company called Micron. See also nanometer.
Microprocessor (MPU) This term is commonly used to describe the CPU. More specifically, it refers to the part of the CPU that actually does the work, since many CPUs now contain L1 and L2 caches on-chip.
Microsoft Servers Microsoft Servers (previously called Windows Server System) is a brand that encompasses a line of Microsoft server products. This includes the server editions of Microsoft Windows operating system itself, as well as products targeted at the wider business market. Unlike Microsoft's Dynamics or Office product lines, most of the products sold under this brand are not intended to be line-of-business services in and of themselves.
Middleware Software that is used to tie an application to a network, thus the “middle” terminology. Often the middleware is a type of network authentication or directory of network resources. When Microsoft bundled Internet Explorer into Windows IE began acting as middleware for many operations, and that was the crux of the Department of Justice’s anti-trust case.
MIDI Musical Instrument Digital Interface.
MIFD Management Information Format Database. See Desktop Management Interface (DMI).
Millisecond (ms) One thousandth of a second. It is often associated with the access speed of hard drives.
MIME (Multipurpose Internet Mail Extensions) Originally a standard for defining the types of files attached to standard Internet mail messages. The MIME standard has come to be used in many situations where one cmputer programs needs to communicate with another program about what kind of file is being sent. For example, HTML files have a MIME-type of text/html, JPEG files are image/jpeg, etc. See also: HTML, JPEG
MIMO Multiple Input, Multiple Output. A technique for faster wireless communication. MIMO allows for the use of multiple transmitter and receiver antennas to increase throughput.
Min Short for Minimum. Some programming languages have a "min" function that will return the smaller of the values supplied to it. Similarly SQL includes a "min" function that returns the minimum matching value found as part of a query. cf Max.
Mini DV Most digital camcorders record video and audio on a Mini DV tape. The cassettes measure 2.6 x 1.9 x 0.5 inches (L x W x H), while the tape itself is only .25 inches thick. A Mini DV tape that is 65 meters long can hold an incredible 11GB of data, or 80 minutes of digital video. The small size of Mini DV tapes has helped camcorder manufacturers reduce the size of their video cameras significantly. Some consumer cameras that use Mini DV tapes are smaller than the size of your hand. Because Mini DV tapes store data digitally, the footage can be exported directly to a computer using a Firewire (IEEE 1394) cable. So if you want to record video and edit it on your computer, avoid the SVHS and Hi-8 options and make sure to get a camera that uses Mini DV.
Minicomputer This term refers to “mini” mainframe computers that are a step smaller than a large corporate mainframe. They were once popular in small businesses that couldn’t afford real mainframes, but now you only find reference to them in free subscription surveys for computer industry print magazines (”Do you work with mini-computers, microcomputers, etc.?”) or in some college campuses or large business networks.
Minimize Minimizing a window temporarily hides it from view without closing it. In Windows, a button for the minimized window is added to the taskbar. In Mac OS X, a small icon for the window is added to the dock. Clicking the window's button or icon will reopen the window. You can then click the maximize button to increase the window's size. To minimize a window in Windows, click the button with a horizontal line icon in the upper-right corner of a window. In Mac OS X, click the yellow button in the upper-left corner of the window or double-click the title bar.
MIPS Stands for "Million Instructions Per Second." It is a method of measuring the raw speed of a computer's processor. Since the MIPS measurement doesn't take into account other factors such as the computer's I/O speed or processor architecture, it isn't always a fair way to measure the performance of a computer. For example, a computer rated at 100 MIPS may be able to computer certain functions faster than another computer rated at 120 MIPS. The MIPS measurement has been used by computer manufacturers like IBM to measure the "cost of computing." The value of computers is determined in MIPS per dollar. Interestingly, the value of computers in MIPS per dollar has steadily doubled on an annual basis for the last couple of decades.
Mirrored Volume A mirrored volume is a hard drive or other form of storage media that stores an exact copy of the data from another volume. It is used for fault tolerance, which means mirrored volume serves as a backup device in case the primary device fails. Companies and organizations that store critical information typically "mirror" the data on another drive. Using a mirrored volume decreases the chance of losing data exponentially. For example, if the odds of a hard drive going bad is 1 out of 200, the odds of two drives going bad at the same time is 1 out of 40,000. Mirroring data can be done using various backup software programs or may be enabled within operating systems that support disk mirroring. While using a mirrored volume helps keep data safe, it also slows down data transfers because the data must always be written twice. It also costs more, since mirroring data requires twice as much disk storage than what would otherwise be required. However, the cost of an extra hard drive is usually well worth the security of having important data backed up. Mirroring may also be referred to as "duplexing" or RAID 1.
Mirroring A fault-tolerance disk strategy in which two identical copies of disk partitions are maintained on different disks (or sets of disks). The theory is that if one disk fails then the system can continue operating because reads and writes to the second disk can continue.
Mission Critical Application Any application that is critical to the proper running of a business. If this application fails for any length of time you may be out of business. For example, an order-entry system may be considered mission critical if your business relies on taking lots of orders. You don’t want your mission critical apps running on junky hardware … or software for that matter.
MMC Microsoft Management Console. The Microsoft Management Console provides an open, extensive, common console framework for management applications. The intent is for it to provide a common style of user interface for administering networks, computers, services and other system components. Snap-ins that can be loaded into the Microsoft Management Console have the .msc file extension.
MME Microsoft Mobile Explorer. Mobile phone/WAP emulator, allowing you to see what a web site would look like on a WAP capable phone.
MMI Man Machine Interface. Same as HMI but an older term and generally regarded as being less politically correct than HMI.
MOBO Abbreviation for Motherboard - the main circuit board in a computer or other electronic system.
Modem Short for Modulator/Demodulator. A modem allows allows data to be transmitted over an analogue stream (typically a phone line) to another modem where the data is reconstituted.
moderator A person who reviews and has the authority to block messages posted to a supervised or "moderated" network newsgroup.
MOM Microsoft Operations Manager. Microsoft Operations Manager provides event management, fault detection, altering, reporting, trend analysis and applications monitoring.
Monitor The term "monitor" is often used synonymously with "computer screen" or "display." The monitor displays the computer's user interface and open programs, allowing the user to interact with the computer, typically using the keyboard and mouse. Older computer monitors were built using cathode ray tubes (CRTs), which made them rather heavy and caused them to take up a lot of desk space. Most modern monitors are built using LCD technology and are commonly referred to as flat screen displays. These thin monitors take up much less space than the older CRT displays. This means people with LCD monitors have more desk space to clutter up with stacks of papers, pens, and other objects. "Monitor" can also be used as a verb. A network administrator may monitor network traffic, which means he watches the traffic to make sure the bandwidth usage is within a certain limit and checks to see what external sources may be attempting to access the network. Software programs may monitor the system's CPU performance as well as RAM and hard disk usage. Finally, monitors also refer to speakers used for monitoring sound. Audio engineers typically use "studio monitors" to listen to recordings. These high-end speakers allow the engineers to accurately mix and master audio tracks. So a sound mixer could be monitoring a recording visually using a computer monitor, while monitoring the sound using audio monitors at the same. As you can tell, "monitor" serves as a rather multipurpose word.
Monoculture Monoculture is the case where a large number of users run the same software, and are vulnerable to the same attacks.
Moore’s Law Former Intel chairman Gordon Moore is credited with predicting the trend that transistor counts in processors double every 18 months. This law has held true since the 1970s. The law can also be applied to other technologies, and works frighteningly well with hard drive and memory chip density, processor speeds, processor power, and processor size (micron process). More than ever the end of Moore’s Law is being discussed, as smaller, more compact designs and electrical leakage threaten to throw Moore’s Law off track.
Morris Worm A worm program written by Robert T. Morris, Jr. that flooded the ARPANET in November, 1988, causing problems for thousands of hosts.
Mount In order for a hard disk or disk partition to be accessible by a computer, it must first be mounted. This is a software process that "activates" the disk, which makes the folders and files on the disk readable by the computer. If a hard drive is physically connected, but not mounted, the computer will not recognize it. Fortunately, most operating systems, such as Windows and Mac OS X, mount newly connected disks by default. In Windows, the disk will appear in the "My Computer" window. In Mac OS X, the disk will appear on the desktop. This is true for all types of disks, such as internal and external hard drives, optical media, such as CDs and DVDs, and USB flash drives. Disk image files may have to be mounted manually using a program like Nero or WinImage (Windows) or Apple Disk Utility (Mac OS X). If a disk is not being used, it can be unmounted. Optical disks are typically unmounted automatically when they are ejected. However, before you disconnect an external hard drive or a USB flash drive, you should unmount the disk to avoid possible data corruption.
Mouse A mouse, along with the keyboard, is one of the two main input devices used by computers. It is a small handheld device that tracks the user's motion and is used for moving the cursor on the screen. It also has buttons that are used for clicking and right-clicking objects. While early mice used a mouse ball to track the movement of the mouse, modern mice use a beam of light or an actual laser. This optical technology is more accurate than the rolling ball method and also keeps mice from getting dirty inside.
Mozilla 1. The original name for Netscape Navigator. The name is derived from "Mosaic" (the dominant browser at the time) + "Godzilla". The term "Mozilla" is still used by both Netscape and Microsoft Internet Explorer to identify the type of browser. Mozilla has been superseded by Firefox.
MP3 Stands for "MPEG-1 Audio Layer-3." MP3 is popular compressed audio file format that helped popularize digital music downloads beginning in the late 1990s. MP3 files are typically about one tenth the size of uncompressed WAVE or AIFF files, but maintain nearly the same CD-quality sound. Because of their small size and good fidelity, MP3 files have become a popular way to store music files on both computers and portable devices like the iPod. Several websites, like MP3.com and GarageBand.com, maintain extensive archives of MP3 files that users can download. To listen to MP3s on your computer, you'll need an MP3 player like Nullsoft Winamp (for Windows) or Apple iTunes (for Mac and Windows). Most MP3 players also allow you to create MP3 files from CD audio tracks or other from other audio file types. Once you have converted your favorite songs to MP3 files, you can transfer them to a portable music player, like the Apple iPod, Microsoft Zune, or a music-enabled cell phone. You can also burn the MP3 files to a CD, which can be played in MP3-compatible CD players. File extension: .MP3
MPEG Stands for "Moving Picture Experts Group." The MPEG organization, which works with the International Organization for Standardization (ISO), develops standards for digital audio and video compression. The group constantly works to develop more efficient ways to digitally compress and store audio and video files. The term MPEG also refers to a type of multimedia file, which is denoted by the file extension ".mpg" or ".mpeg." These files are compressed movies that can contain both audio and video. Though they are compressed, MPEG files maintain most of the original quality of the uncompressed movie. This is why many videos on the Web, such as movie trailers and music videos, are available in the MPEG format. File extensions: .MPG, .MPE, .MPEG
MS 1. Common abbreviation for "Microsoft". 2. Millisecond, 1/1000th of a second. Usually expressed as "ms", i.e. in lower case.
MS-DOS Microsoft DOS (Disk Operating System). A command line operating system produced by Microsoft which pre-dates Windows. See DOS for further information.
MSIE 1. Microsoft Internet Explorer. Abbreviation used to refer to any version of Microsoft's Internet Explorer web browser. Also frequently abbreviated to simply IE.
MSS 1. Microsoft Speech Server. 2. Maximum Segment Size. The maximum amount of data that a single (unfragemented) TCP message may contain. The MSS is the maximum data size, and does not include the size of the header. The relationship between MSS and MTU is: MSS + header ≤ MTU.
MSSQL Microsoft SQL Server. The professional relational database management system from Microsoft.
MTBF Mean Time Between Failures. This is an estimate of the average time between failures of a component. cf MTBR.
MTBR Mean Time Between Repair. Similar in meaning to Mean Time Between Failures (MTBF), and the two terms are sometimes used interchangeably. MTBR is normally quoted for components which are economically viable to repair should they fail. Whereas MTBF is normally quoted for components for which it is not economically viable to repair and which would therefore normally be replaced once they have failed. For example a hard disk would not normally be considered repairable should it fail, and thus manufacturers may quote a MTBF figure. Whilst a RAID array (which consists of multiple individual hard disks) would normally have a MTBR figure quoted, because should any individual disk fail then that disk can be replaced (and thus the array repaired).
MTTR Mean Time To Repair. The average length of time it takes to repair something.
MTU Maximum Transmission Unit. The maximum amount of data that can be sent across an interface without being broken up into more than one message or packet. cf MSS.
MU Microsoft Update. MU refers to the updating and patching of Microsoft Windows, either by automatic updates or from the Microsoft Update website. Over time updates are typically rolled up and included as part of a service pack. Microsoft Update is also referred to as Windows Update.
Multi-Cast Broadcasting from one host to a given set of hosts.
Multi-Homed You are "multi-homed" if your network is directly connected to two or more ISP's.
Multi-tier client server A form of client/server application that uses the multi-tiered architecture.
Multicast IP A form of TCP/IP being proposed that will allow for high-bandwidth transmissions (like television channels) to be broadcast over the Internet to all the routers in the world (possibly) that are connected to someone watching that channel. To see the benefit, think of 1,000 people making separate connections to the USA network (if it were an Internet TV channel–give us some leeway!). Each packet of data sent out would have to be sent to 1,000 people. Thus, you have 1,000 conversations active among the USA network server and people’s machines, each one saying the same thing. That’s poor scalability. Now imagine that in this fantasy network we only have 10 routers with these 1,000 people connected to them. In simplistic terms, you only have to send each packet to 10 places, and each machine downloads packets directly from the router it is connected to. Thus the USA network server doesn’t have to do much work to keep Gary Busey movies going to 1,000 people at once, and the rest of the network isn’t clogged with all 1,000 conversations. However, there are lots of minute details that must be considered, such as how many channels are offered and how much router memory that takes. How about if no one is watching? That’s wasted traffic.
Multimedia As the name implies, multimedia is the integration of multiple forms of media. This includes text, graphics, audio, video, etc. For example, a presentation involving audio and video clips would be considered a "multimedia presentation." Educational software that involves animations, sound, and text is called "multimedia software." CDs and DVDs are often considered to be "multimedia formats" since they can store a lot of data and most forms of multimedia require a lot of disk space. Due to the advancements in computer speeds and storage space, multimedia is commonplace today. Therefore, the term doesn't produce the same excitement is once did. This also means it is not as overused as it was back in the late '90s.
Multiplatform If a software program is developed for mulitple operating systems, it is considered to be "multiplatform." Since Microsoft Word runs on both the Windows and Macintosh platform, it is a mutliplatform application. In the consumer gaming market, mutliplatform games run on more than one gaming machine. For example, a sports game developed for Xbox, Playstation, GameCube, and PC would be a multiplatform game. If a game is developed exclusively for one system, i.e. "The Legend of Zelda," for Nintendo, it is not multiplatform. Gaming hardware manufacturers use exclusive software as a reason for consumers to buy their system.
Multiplexing To combine multiple signals from possibly disparate sources, in order to transmit them over a single path.
Multiprocessing For many years, the speed of computer processors increased through improvements in the architecture and clock speed of processors. However, in recent years, chip manufacturers have reached a limit in how small they can make the transistors inside CPUs without them overheating. Therefore, using multiple processors, or multiprocessing, has become the next step in increasing computing performance. Multiprocessing can be implemented in two different ways: 1) using more than one physical processor, or 2) using a processor with multiple cores. For example, early Power Mac G5 computers had multiple physical processors, each with their own heat sink and frontside bus. When Apple switched to using Intel processors in 2006, they began using dual-core processors. These chips look like a single processor, but act as two. Now, some machines like the Mac Pro, have quad-core processors, which include four processing cores. Some Mac Pros even have two physical quad-core processors, giving the computer a total of eight processors. Most Windows and Linux-based PCs now use multi-core processors as well. While multiprocessing sounds like a logical choice for improving computing performance, it must be supported by the computer's operating system in order to work correctly. Fortunately, current versions of both Windows and Mac OS X fully support multiprocessing. This means they can manage multiple processors as one CPU, dividing the processing load between them. Still, not all tasks can be split equally between two or more processors. Therefore, while multiprocessing may increase a computer's speed, it does not typically improve performance by the exact factor of processors in the machine.
Multitasking Multitasking is processing multiple tasks at one time. For example, when you see someone in the car next to you eating a burrito, taking on his cell phone, and trying to drive at the same, that person is multitasking. Multitasking also refers to the way a computer works. Unlike the phone and burrito juggling driver, a computer's CPU can handle many processes at one time with complete accuracy. However, it will only process the instructions sent to it by the computer's software. Therefore, to make full use of the CPU's capabilities, the software must be able to process more than one task at a time, or multitask. Early operating systems could run multiple programs at one time, but did not fully support multitasking. Therefore, a single program could consume the computer's entire CPU while performing a certain operation. Basic operating system processes, such as copying files, prevented the user from performing other tasks, such as opening or closing windows. Fortunately, since modern operating systems include full multitasking support, multiple programs can run at the same time without affecting each other. Also, multiple operating system processes can take place simultaneously. Since multitasking can handle several tasks at once, it also improves the stability of the computer. For example, if one process crashes, it will not affect the other running programs, since the computer handles each process separately. In other words, if you are in the middle of writing a paper in a word processing program and your Web browser unexpectedly quits, you won't lose your work. That's when you can really be thankful for multitasking.
Multithreading Multithreading is similar to multitasking, but enables the processing of multiple threads at one time, rather than multiple processes. Since threads are smaller, more basic instructions than processes, multithreading may occur within processes. By incorporating multithreading, programs can perform multiple operations at once. For example, a multithreaded operating system may run several background tasks, such as logging file changes, indexing data, and managing windows at the same time. Web browsers that support multithreading can have multiple windows open with JavaScript and Flash animations running simultaneously. If a program is fully multithreaded, the different processes should not affect each other at all, as long as the CPU has enough power to handle them. Similar to multitasking, multithreading also improves the stability of programs. However, instead of keeping the computer from crashing, multithreading may prevent a program from crashing. Since each thread is handled separately, if one thread has an error, it should not affect the rest of the program. Therefore, multithreading can lead to less crashes, which is something we can all be thankful for.
Mung "Mash Until No Good" or "Mung Until No Good". To make changes to to words in a string so that the string is no longer recognisable. The changes may be (but do not have to be) reversible and obvious to a human reader.
MVLS Microsoft Volume Licensing Services.
MX Record MX Record Mail eXchange Record. An MX record indicates which mail server will receive e-mails for an internet domain. Each domain can have more than one MX record, allowing e-mail to be routed to a backup mail server should the primary be unavailable. MX records are assigned a priority number and the one with the lowest number will be the one used, unless it is unavailable in which case the one with the next lowest priority will be used and so on.
MySQL MySQL A very popular open source database system. MySQL is a multi-user, multi-threaded database server, which is suitable for office database uses and for on web-servers. cf LAMP.
N/A 1. Abbreviation for "Not Applicable". 2. Abbreviation for "Not Appropriate".
Nagware This is shareware that has screens that pop up and require you to press a button or wait an amount of time. These nag screens go away after you pay for the software and enter a registration code.
Nameserver Alternative name for a DNS Server.
Nano a text editor originally designed to be a clone of Pico
Nanotechnology The purposeful manipulation of matter at the atomic level to achieve a defined goal. Atomic constructs can be measured in nanometers. Someday nanotechnology may be used to send a group of tiny machines into your bloodstream and free up clogged arteries, or a bunch of tiny nano-war machines could be built and unintentionally change the entire earth into a gray blob of nano-devices.
NAPT Network Address and Port Translation. See also NAT.
Narrow SCSI The original form of SCSI, using 50 pins and transmitting data at 5MBps. See also Wide SCSI. Drives and adapters that support Narrow SCSI usually have an “N” in the part number.
NAS Network Attached Storage. Typically a data server on a network that provides file storage accessed via the network. cf DAS and SAN.
NAT 1. Network Address Translation - translates multiple IP addresses on a private LAN to one public address used on the Internet. This allows (for example) and office to operate within a private IP address range and all appear to share a single IP address to the outside world. 2. Network Address Translator - when applied to a device that sits between two network domains and maps addresses from one network domain to another.
NAT/Firewall A NAT device that acts as a firewall, filtering network packets entering or leaving a network.
Native File When you save a file using a certain program, the file is often saved in a proprietary format only that program can recognize. For example, if you save a Microsoft Word document, it is saved as a Word document (i.e. mydocument.doc). This is a native Word file -- that is, the file format is native to the Microsoft Word application and may not be recognized by other programs. When you use the "Save As..." command to save a file, you may be given the option to save the file in a different format. For example, you might be able to save a Word document as a plain text (.txt) file or a rich text (.rtf) file. These formats are not native to Microsoft Word, but can still be opened by the Microsoft Word program. Similarly, Adobe Photoshop saves files as Photoshop documents (.psd files), but can also save them in .jpg and .gif formats, among others. It is usually best to save a file in a program's native file format because you can be sure it will store all the data you have created with the program. While other formats may be more compatible with other programs, they might not save all the information in the file. For example, if you save a Word document as a plain text file, all the text formatting you had added will be removed. Saving a Photoshop document in JPEG format will reduce the image quality and flatten all the image's layers. So if you're planning on editing a file after you've saved it, saving it as a native file is the best choice. If you want to save the most compatible version of the file, saving a copy of the file in a more generic format is a good idea.
Natural Disaster Any "act of God" (e.g., fire, flood, earthquake, lightning, or wind) that disables a system component.
NDR Non Delivery Report. See Non Delivery Notification for details.
NESTING A term used in Boolean searching to indicate the sequence in which operations are to be performed. Enclosing words in parentheses identifies a group or "nest." Groups can be within other groups. The operations will be performed from the innermost nest to the outmost, and then from left to right.
NetBEUI NetBIOS Enhanced User Interface. Network protocol for Windows NT networks. Originally developed by IBM to provide a mechanism for passing NetBIOS packets over Token Ring and Ethernet. Later extended to include support for DECnet, IPX/SPX and TCP/IP.
NetBIOS Network Basic Input Output System. Network protocol for LAN Manager and Windows NT networks.
netiquette Short for network etiquette; refers to using basic good manners in your electronic communications. It's advisable to never write anything you would feel uncomfortable repeating in person.
Netmask A netmask is used to define a range of IP addresses. It is similar to a subnet mask, but is used to define classes of IPs rather than a range of IPs that may be used within a network. For example, IP addresses of class B have a subnet mask of 255.255.0.0. This means the IPs must all have the same first two sections, but may have different numbers for the second two sections. Because a limited number of IP addresses are available, most IP ranges are assigned as Class C, which has a netmask 255.255.255.0. This defines a range of IPs that have identical numbers in the first three sections, but may contain any number between 0 and 255 in the final section. Therefore, a Class C netmask defines a range of 256 different addresses.
Network Any time you connect 2 or more computers together so that they can share resources, you have a computer network. Connect 2 or more networks together and you have an internet. See also: internet (Lower case i)
network adapter A device that connects your computer to a network; also called an adapter card or network interface card.
Network Connectivity Connecting and communicating between two or more computers, typically over a network.
Network Mapping To compile an electronic inventory of the systems and the services on your network.
Network Protocol Standards that allow computers to communicate. Protocols also define ways of handling lost or damaged data packets. The main types of network protocol are: HTTP FTP TCP/IP IPX DECnet AppleTalk NetBIOS/NetBEUI
Network Taps Network taps are hardware devices that hook directly onto the network cable and send a copy of the traffic that passes through it to one or more other networked devices.
Network Topology The different way computers (and network enabled peripherals) are arranged on or connected to a network. The most common network topologies are: Star. All computers are connected to a central hub. Ring. Each computer is connected to two others, such that starting at any one computer you can trace the connection through each computer back on the ring back to the first. Bus. All computers are connected to a central cable, normally termed bus or backbone. Tree. Group of start networks each connected to a linear bus. These topologies can be mixed.
Network-Based IDS A network-based IDS system monitors the traffic on its network segment as a data source. This is generally accomplished by placing the network interface card in promiscuous mode to capture all network traffic that crosses its network segment. Network traffic on other segments, and traffic on other means of communication (like phone lines) can't be monitored. Network-based IDS involves looking at the packets on the network as they pass by some sensor. The sensor can only see the packets that happen to be carried on the network segment it's attached to. Packets are considered to be of interest if they match a signature.Network-based intrusion detection passively monitors network activity for indications of attacks. Network monitoring offers several advantages over traditional host-based intrusion detection systems. Because many intrusions occur over networks at some point, and because networks are increasingly becoming the targets of attack, these techniques are an excellent method of detecting many attacks which may be missed by host-based intrusion detection mechanisms.
Newb Newbie. See noob for details.
NFR Not For Resale. Product that may not be resold, transferred, assigned to a third party or installed at a customer site.
NIB New In Box. Abbreviation sometimes used on auction sites.
Nibble Half a byte or 4 bits.
NIC 1. Network Interface Card. Provides the physical connection between the computer and network. On many modern PCs the NIC is integrated onto the motherboard instead of being a separate card.
NIDS Network based Intrusion Detection System. A system for detecting unauthorised access to a (computer) network. A NIDS will typically use a packet sniffer to monitor network traffic to attempt to detect intrusions on a network. cf Intrusion Detection System (IDS).
NLB Network Load Balancing. A clustering technology from Microsoft allowing network traffic to be evenly distributed across a number of servers. It also helps to provide high availability by detecting host failures and rerouting traffic to one of the available servers.
NNTP Network News Transport Protocol. Protocol used to post and receive UseNet messages.
NOC 1. Network Operations Centre. A site which is responsible for the day to day monitoring and management of a large scale network (i.e. a WAN or part of the Internet possibly also a LAN). 2. No Overall Control. Abbreviation often used when displaying election results to indicate that no party (or individual) has an overall majority.
Node Any single computer connected to a network. See also: Network
Non Delivery Notification An email sent by an email system to indicate that an email has not been delivered. Often referred to as an NDN or NDR. Some email systems are configured not to generate NDNs.
Non-Breaking Space (NBSP) An HTML command that is used to display a single text space without a visible character in that space. The format in HTML for this is and it can be used to position text or to fool a browser into behaving like text is in a space when there is no text visible.
Non-Printable Character A character that doesn't have a corresponding character letter to its corresponding ASCII code. Examples would be the Linefeed, which is ASCII character code 10 decimal, the Carriage Return, which is 13 decimal, or the bell sound, which is decimal 7. On a PC, you can often add non-printable characters by holding down the Alt key, and typing in the decimal value (i.e., Alt-007 gets you a bell). There are other character encoding schemes, but ASCII is the most prevalent.
Non-Repudiation Non-repudiation is the ability for a system to prove that a specific user and only that specific user sent a message and that it hasn't been modified.
Nonpersistent disk mode All disk writes issued by software running inside a virtual machine with a nonpersistent disk appear to be written to disk, but are in fact discarded after the session is powered down. As a result, a virtual disk or raw disk in nonpersistent mode is not modified by VMware.
Noob 1. An abbreviation for newbie. Noob indicates a novice, or someone new or inexperienced. Also rendered Newb. 2. Someone behaving or giving the impression to others that they are a novice (even though they might think otherwise). Often used as an insult or derogatory remark intended to imply that the person is stupid, idiotic or has little or no skill. Also rendered as newb or n00b. 3. Work done by a newbie. A derogative term indicating a poor level of work - especially where a higher level of work would normally be expected. Thus a noob installation is one poorly performed which suffers from problems.
Northbridge The northbridge is a chip inside a computer that connects the central processing unit (CPU) to other primary components in the system. These components include RAM (a.k.a. system memory), the frontside bus (FSB), PCI Express cards, and the AGP card. The northbridge also connects to the southbridge, which controls the remaining components of the computer. While the CPU is the main processor inside the computer, the northbridge is the primary controller. It acts like a traffic cop directing data to and from the CPU. Therefore, the performance of the northbridge chip affects the overall performance of the computer. On Intel systems, the northbridge is also called the Memory Controller Hub (MCH), since it controls the data flow to and from the system memory.
NOS 1. Network Operating System. An operating system that provides control over the network, enabling users to copy and share files and share some peripherals such as printers. 2. Not Otherwise Specified. 3. New Old Stock. Describes stock (typically equipment) that is old (and no longer produced) but which has not been used so is in new (unused) condition.
NSP etwork Service Provider. A company which provides access to a network (such as, but not limited to, the internet). In the internet age, NSPs who provide access to the internet are more commonly known as ISPs.
NSPI Name Service Provider Interface. Facilitates communication between the Active Directory (AD) and Exchange Directory Service (XDS).
NT 1. New Technology. Specifically refers to Microsoft's Windows NT 3.5 and NT 4 Windows operating systems. Later versions of Windows are built on NT, which is why references to NT remain in later versions of Windows.
NT4 Microsoft Windows NT 4 (workstation or server).
NTFS NT File System. File system developed by Microsoft for Windows NT and supported by later Windows operating systems. Supports long file names, journaling, security access restrictions (see DAC), lazy-write (allowing disk writes to be cached).
NTFS (NT File System This alternative file allocation system available first with the Windows NT operating system, and then with Windows 2000. It allows for larger disk drives with smaller cluster sizes, as well as a performance increase and more robust security. NTFS is now the standard file system for Windows XP.
NTLDR NT Loader. NTLDR is the boot loader for Windows NT, and for later versions of Windows. This is the first application run when Windows is booted and is responsible for starting the loading of Windows.
NTLM NT Lan Manager. A Microsoft proprietary network user authentication protocol.
NTP Network Time Protocol. A protocol for ensuring accurate synchronization of time (i.e. the clock) between computers across a network (such as the internet).
NTSC National Television System Committee. NTSC is the name of the analogue TV standard used in the USA, Canada, Mexico and Japan. An NTSC picture is made of 525 scan lines of which 486 are visible. Each horizontal line provides 720 pixels. Thus the viewable area of an NTSC picture is 720 by 486. Whilst NTSC has a conventional non-widescreen aspect ratio of 4:3, each pixel is not square but are slightly narrower than they are tall. An NTSC picture is interlaced, images are transmitted at 59.94Hz, giving approximately 30 complete frames per second. cf SDTV, HDTV, PAL.
Null When a variable has no value, it considered to be null. Having a null value is different than having a value of 0, since 0 is an actual value. However, when used in a boolean test, both null and zero result in a FALSE value. Programmers often use boolean tests to determine whether a variable has been given a value or not.
Null Character A null character is a character with all its bits set to zero. Therefore, it has a numeric value of zero and can be used to represent the end of a string of characters, such as a word or phrase. This helps programmers determine the length of strings. In practical applications, such as database and spreadsheet programs, null characters are used as fillers for spaces.
Null Session Known as Anonymous Logon, it is a way of letting an anonymous user retrieve information such as user names and shares over the network or connect without authentication. It is used by applications such as explorer.exe to enumerate shares on remote servers.
Num Lock Num Lock is a toggle key that toggles the input of the numeric keypad. When Num Lock is on, the keypad can be used to enter numeric values. When Num Lock is off, they keys provide different input. For example, 4 is left arrow, 6 is right arrow, 8 is up arrow, and 2 is down arrow. Since most keyboards now include arrow keys, the Num Lock is rarely used. However, some keyboards still support the Num Lock feature. Therefore, if you cannot enter numbers with the numeric keypad, you may be able to fix the problem by simply pressing the Num Lock key.
Nvidia vidia (NASDAQ: NVDA pronounced /ɛnˈvɪ.di.ə/) is a multinational corporation which specializes in the development of graphics processing units and chipset technologies for workstations, personal computers, and mobile devices.
Object This can refer to the objects in object-oriented programming or the objects in OLE (Object Linking and Embedding). In OLE an object is a piece of a document, a graphic, or some multimedia. In object-oriented programming an object can be a spell checker or a piece of a graphics program used to draw squares or circles. Do you remember the crazy story people used to try to tell about a word processor where you could pick all of your favorite pieces (favorite spell checker, grammar checker, text editor, font manager, etc.) and piece them together to form the ultimate customizable word processor? Well, those pieces are objects.
Object Linking and Embedding (OLE) A standard for sharing data between applications. It has been around since Windows 3.1 and continues to improve. For example, if you cut a picture out of Paint and paste it into a word processor document, you are using OLE to properly put the data into your document. Of course, if it doesn’t work quite right you can blame OLE, or the program’s use of it. OLE allows objects to be linked to and embedded in other documents. Linking creates a link to the actual object; embedding puts a copy of the object into the document. You can usually access the program an object was created with in order to edit the linked or embedded object just by clicking on the object. This is much more advanced than just taking a screenshot of the data you want and pasting it into another program as a graphic that has no relation to the original data.
object-oriented A method of software-development that groups related functions and data into reusable chunks. Properly handled, object-oriented programming can reduce development time on new projects.
Object-oriented technology Technology–usually programming languages–designed to work with objects.
OC-12 (Optical Carrier 12) A fiber optic connection that can handle 622Mbps, often used for the 622Mbps ATM protocol.
OC-192 (Optical Carrier 192) A fiber optic connection that can handle 10Gbps connection speeds.
OC-24 (Optical Carrier 24) A fiber optic connection that can handle 1.244Gbps connection speeds.
OC-255 (Optical Carrier 255) A fiber optic connection that can handle 13.21Gbps connection speeds.
OC-3 (Optical Carrier 3) A fiber optic connection that can handle 155Mbps, often used for the 155Mbps ATM protocol.
OC-48 (Optical Carrier 48) A fiber optic connection that can handle 2.488Gbps connection speeds.
OC-96 (Optical Carrier 96) A fiber optic connection that can handle 4.976Gbps connection speeds.
OCR Stands for "Optical Character Recognition." This technology is what allows you to scan that paper you lost on your hard drive, but fortunately printed out, back into your computer. When a page of text is scanned into a computer without OCR software, all the computer sees is a bunch graphical bits, or an image. In other words, it has no idea that there is text on the page, much less what the text says. However, an OCR program can convert the characters on the page into a text document that can be read by a word processing program. More advanced OCR programs can even keep the formatting of the document in the conversion.
Octet A group of eight bits, also called a byte
ODBC Open Database Connectivity. Open standard developed by Microsoft aiming to provide a consistent interface to relational databases regardless of which database engine is used (e.g. SQL Server, Oracle or MySQL). In theory to migrate to another database should only require the installation of the appropriate ODBC driver for the new database. Whilst ODBC does successfully address many of the issues involved in migrating from one database to another, there are issues outside the scope of ODBC which can (for some applications) have serious implications when migrating databases.
OEM 1. Original Equipment Manufacturer. The manufacturer or producer of computing equipment (hardware or software). 2. OEM software or hardware refers to software or hardware bundled with (or licensed for use with) OEM supplied equipment. OEM software is frequently distributed without a box or a manual, but is cheaper than non-OEM software.
Office Suite The set of software products that are required by an office, most often comprised of a spreadsheet program, a word processor, a scheduler, and a presentation manager. Sometimes the suites will include a financial package and a database program as well. These are put together by a single company, so they are made to work with one another.
Offline When a computer or other device is not turned on or connected to other devices, it is said to be "offline." This is the opposite of being "online," when a device can readily communicate with other devices. For example, if you try to print to your printer and you get one of those frustrating errors saying, "The specified printer could not be found," the printer is probably offline. You should check to see if the printer is connected properly and, yes, turned on as well. Offline can also mean not being connected to the Internet. When you disconnect from your ISP or pull out the Ethernet cable from your computer, your computer is offline. Some programs, such as Web browsers and e-mail programs, have an option to "Work Offline." This option disables the program's network connection, meaning no data can be transmitted to or from the computer. This option was more useful when most people used dial-up connections. They didn't want their computer automatically dialing their ISP whenever a program tried to access the Internet. However, since most people now have "always on" connections such as DSL and cable modems, there usually is no reason to work offline.
OLED Organic Light Emitting Diode (Organic-LED). Low-power LEDs, based on carbon-based molecules instead of semiconductor technology. OLED displays can be brighter, lighter, more flexible and more efficient than traditional LCD displays.
On-die This term is most often used when referring to the L2 cache on a microprocessor. It implies that the L2 cache itself is on the same single piece of silicon as the microprocessor.
One-Way Encryption Irreversible transformation of plaintext to cipher text, such that the plaintext cannot be recovered from the cipher text by other than exhaustive procedures even if the cryptographic key is known.
One-Way Function A (mathematical) function, f, which is easy to compute the output based on a given input. However given only the output value it is impossible (except for a brute force attack) to figure out what the input value is.
Online In general, when a machine is "online," it is turned on and connected to other devices. For example, when a network printer is online, computers connected to that network can print from it. Other devices, such as scanners, video cameras, audio interfaces, and others are said to be online when they are running and connected to a computer system. Recently, however, the term "online" usually means being connected to the Internet. The connection can be through a phone line, using a dial-up or DSL modem, a cable line via a cable modem, or through a wireless connection. A computer can also be online via a connection to a computer network. Technically, computers that are on a network are online even if they are not connected to the Internet. But most networks are routed to a T1 line or other Internet connection anyway. When a computer or other device is not online, it is said to be offline.
online learning Also referred to as distance education; courses offered online that do not require the student to be on campus for most or all class participation. Students can work with course materials at their own convenience or they can work collaboratively on class projects using tools like chat and discussion groups (bulletin boards).
OOP Stands for "Object-Oriented Programming." OOP (not Oops!) refers to a programming methodology based on objects, instead of just functions and procedures. These objects are organized into classes, which allow individual objects to be group together. Most modern programming languages including Java, C/C++, and PHP, are object-oriented languages, and many older programming languages now have object-oriented versions.. An "object" in an OOP language refers to a specific type, or "instance," of a class. Each object has a structure similar to other objects in the class, but can be assigned individual characteristics. An object can also call functions, or methods, specific to that object. For example, the source code of a video game may include a class that defines the structure of characters in the game. Individual characters may be defined as objects, which allows them to have different appearances, skills, and abilities. They may also perform different tasks in the game, which are run using each object's specific methods. Object-oriented programming makes it easier for programmers to structure and organize software programs. Because individual objects can be modified without affecting other aspects of the program, it is also easier to update and change programs written in object-oriented languages. As software programs have grown larger over the years, OOP has made developing these large programs more manageable.
Open Firmware pen Firmware is a type of firmware that some computer systems use when they boot up. It controls the processor and performs system diagnostics before the operating system is loaded. Open Firmware also builds the "device tree," which locates internal and external devices connected to the computer. Each device is then assigned a unique address so it can be used once the computer starts up. Several types of computers use Open Firmware, including PowerPC-based Macintosh systems, Sun Microsystems SPARC-based workstations, and IBM POWER systems. (Most Windows-based PCs use the BIOS for the same purpose.) Because Open Firmware is an "open" standard, devices that support Open Firmware can be typically be used in multiple Open Firmware-based systems. For example, identical PCI cards could be used in both Sun and Macintosh-based computer systems.
Open Relay A mail server that will route e-mail from any originator without the need for authentication. Spammers will often search for open relays as a means to send e-mail because it makes them harder to track down. Most (if not all) mail servers can be configured to prevent them from being used as open relays. cf RNDR.
Open Source Program code that is made available for view, reuse and modification by others, normally with no license fee or restrictions on use.
OpenGL OpenGL, or the Open Graphics Library, is a 3D graphics language developed by Silicon Graphics. Before OpenGL was available, software developers had to write unique 3D graphics code for each operating system platform as well as different graphics hardware. However, with OpenGL, developers can create graphics and special effects that will appear nearly identical on any operating system and any hardware that supports OpenGL. This makes it much easier for developers of 3D games and programs to port their software to multiple platforms. So how exactly does OpenGL work? When programmers write OpenGL code, they specify a set of commands. Each command executes a drawing action or creates a special effect. Using hundreds or even thousands of these OpenGL commands, programmers can create 3D worlds which can include special effects such as texture mapping, transparency (alpha blending), hidden surface removal, antialiasing, fog, and lighting effects. An unlimited amount of viewing and modeling transformations can be applied to the OpenGL objects, giving developers an infinite amount of possibilities.
Operating System Also known as an "OS," this is the software that communicates with computer hardware on the most basic level. Without an operating system, no software programs can run. The OS is what allocates memory, processes tasks, accesses disks and peripherials, and serves as the user interface. Thanks to operating systems, like Windows, Mac OS, and Linux, developers can write code using a standard programming interface, or API. Without an operating system, programmers would have to write about ten times as much code to get the same results. Of course, some computer geniuses have to program the operating system itself.
Optical Drive In the real world, "optical" refers to vision, or the ability to see. In the computer world, however, "optical" refers to lasers, which can "see" and read data on optical discs. These discs include CDs and DVDs, which are made up of millions of small bumps and dips. Optical drives have lasers that read these bumps and dips as ones and zeros, which the computer can understand. Some common types of optical drives include CD-ROM, CD-RW, DVD-ROM, DVD?RW, and Blu-ray drives. CD and DVD writers, such as CD-R and DVD-R drives use a laser to both read and write data on the discs. The laser used for writing the data is much more powerful than the laser that reads the data, as it "burns" the bumps and dips into the disc. While optical drives can spin discs at very high speeds, they are still significantly slower than hard drives, which store data magnetically. However, because optical media is inexpensive and removable, it is the most common format used for distributing computer software.
Optical Media Media, in the computer world, refers to various types of data storage. For example, hard drives, CDs, DVDs, and USB drives are all different types of media. Optical media refers to discs that are read by a laser. This includes CD-ROMs, DVD-ROMs, and all the variations of the two formats -- CD-R, CD-RW, DVD-R, DVD+R, Blu-ray, and many others. Optical media typically does not have as fast of a seek time as hard drives (the time it takes to access information on different parts of the disk), but it has many other advantages. Because optical discs are not based on magnetic charges like hard drives are, the discs are less likely to lose their data and have a longer shelf life -- around seven times longer than magnetic media. The discs are also more durable than hard drives and are much cheaper to produce, making them great for backups and for transferring small amounts of data between different computers.
OS 1. Operating System. For example Unix, Linux, Windows. 2. Open Source.
OSD OSD is short for "On Screen Display." An OSD is an onscreen menu included with most monitors that allows users to make adjustments to the display. Common OSD settings include brightness, contrast, and color calibration adjustments. Some monitors also include positioning settings and tilt control. You can activate the OSD by pressing the MENU button on the side of the monitor. Once the OSD appears, you can navigate through the menu options and make adjustments using the plus (+) and minus (-) buttons.
OSI OSI (Open Systems Interconnection) is a standard description or "reference model" for how messages should be transmitted between any two points in a telecommunication network. Its purpose is to guide product implementers so that their products will consistently work with other products. The reference model defines seven layers of functions that take place at each end of a communication. Although OSI is not always strictly adhered to in terms of keeping related functions together in a well-defined layer, many if not most products involved in telecommunication make an attempt to describe themselves in relation to the OSI model. It is also valuable as a single reference view of communication that furnishes everyone a common ground for education and discussion.
OSI 7 Layer Reference Model A reference model for communication protocols designed to allow open systems interconnection. The seven layers are: Physical Data link Network Transport Session Presentation Application
OSI layers The main idea in OSI is that the process of communication between two end points in a telecommunication network can be divided into layers, with each layer adding its own set of special, related functions. Each communicating user or program is at a computer equipped with these seven layers of function. So, in a given message between users, there will be a flow of data through each layer at one end down through the layers in that computer and, at the other end, when the message arrives, another flow of data up through the layers in the receiving computer and ultimately to the end user or program. The actual programming and hardware that furnishes these seven layers of function is usually a combination of the computer operating system, applications (such as your Web browser), TCP/IP or alternative transport and network protocols, and the software and hardware that enable you to put a signal on one of the lines attached to your computer. OSI divides telecommunication into seven layers. The layers are in two groups. The upper four layers are used whenever a message passes from or to a user. The lower three layers (up to the network layer) are used when any message passes through the host computer or router. Messages intended for this computer pass to the upper layers. Messages destined for some other host are not passed up to the upper layers but are forwarded to another host. The seven layers are: Layer 7: The application layer...This is the layer at which communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. (This layer is not the application itself, although some applications may perform application layer functions.) Layer 6: The presentation layer...This is a layer, usually part of an operating system, that converts incoming and outgoing data from one presentation format to another (for example, from a text stream into a popup window with the newly arrived text). Sometimes called the syntax layer. Layer 5: The session layer...This layer sets up, coordinates, and terminates conversations, exchanges, and dialogs between the applications at each end. It deals with session and connection coordination. Layer 4: The transport layer...This layer manages the end-to-end control (for example, determining whether all packets have arrived) and error-checking. It ensures complete data transfer. Layer 3: The network layer...This layer handles the routing of the data (sending it in the right direction to the right destination on outgoing transmissions and receiving incoming transmissions at the packet level). The network layer does routing and forwarding. Layer 2: The data-link layer...This layer provides synchronization for the physical level and does bit-stuffing for strings of 1's in excess of 5. It furnishes transmission protocol knowledge and management. Layer 1: The physical layer...This layer conveys the bit stream through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier.
OSI Model (Open Systems Interconnection Model) A way of representing the complexities of computer networking in a 7-layer model, ranging from the physical hardware of networking all the way up to how application programs talk to the network. The 7 layers are: physical, data link, network, transport, session, presentation, and application. The 7-layer OSI model can be used to help diagnose network problems. It is also used as a measurement of how well people know their networking. If you’re looking for a job in networking, you should familiarize yourself with the OSI model.
Outbox An outbox is where outgoing e-mail messages are temporarily stored. While you are composing a message, most mail programs automatically save a draft of your message in the outbox. The message is then stored in the outbox until it is successfully sent to the recipient. Once the message has been sent, most e-mail programs move the message to the "Sent" or "Sent Messages" folder. While the terms "Outbox" and "Sent Messages" are often used synonymously, technically they have different meanings. Unlike the inbox, which is often overflowing with e-mail, the outbox often does not contain any messages. This is because all the messages that have been sent have already been transferred to the Sent Messages folder. You can think of an e-mail outbox much like the outbox at an office. Mail that is to be delivered is temporarily placed in the outbox until the mailman (or the designated office mail guy) picks up the mail and brings it to the post office. However, the messages in an e-mail outbox are typically delivered immediately (unless a connection to the outgoing SMTP mail server is not available). If only it was as easy to keep your inbox clean...
Output Device Any device that outputs information from a computer is called, not surprisingly, an output device. Since most information from a computer is output in either a visual or auditory format, the most common output devices are the monitor and speakers. These two devices provide instant feedback to the user's input, such as displaying characters as they are typed or playing a song selected from a playlist. While monitors and speakers are the most common output devices, there are many others. Some examples include headphones, printers, projectors, lighting control systems, audio recording devices, and robotic machines. A computer without an output device connected to it is pretty useless, since the output is what we interact with. Anyone who has ever had a monitor or printer stop working knows just how true this is. Of course, it is also important to be able to send information to the computer, which requires an input device.
Overburning The process of recording more than 74 minutes of audio or more than 650 MB of data onto a CD-R disk. There are software programs that allow you to do this, and now there is media that supports larger storage than the standard CD-R normally holds.
Overclocking For some people, fast is never fast enough. In the world of computers, a fast processor can be made even faster by overclocking it. Overclocking involves increasing the clock speed of the computer's CPU past the rate at which it was originally designed to run. Some ways to overclock a processor include increasing the CPU's operating speed in the system BIOS or changing the hardware jumper settings for the processor. Modifying these settings may allow the processor to run faster than set by the manufacturer, which may increase the overall performance of the computer. However, since other settings, such as the memory speed, frontside and backside bus speeds, and other components are fixed, there may not be a significant increase in performance. Regardless of how overclocking is done, it potentially may cause problems with the computer. After all, when you overclock a computer, you are altering the manufacturer's design of the machine. For example, if there is not enough electrical current to to power the processor at the new rate, it may slow down or stop running completely. Also, if the heat sink cannot sufficiently cool the processor running at the faster rate, it may overheat, causing your computer to freeze or crash. This is actually a preventive measure, since the computer stops functioning when the CPU gets too hot. Otherwise, the CPU may literally fry itself and your overclocked processor may become an overcooked processor. In summary, overclocking a processor can be a risky endeavor. It is best left to computer enthusiasts who understand their hardware and are willing to accept the risks associated with it. Since overclocking voids your computer's warranty, don't expect the manufacturer to replace your cooked CPU for free. If you want a fast machine that is supported by the manufacturer, buying a fast processor to begin with is your best bet.
Overdrive A processor upgrade sold by Intel that is used to upgrade an older processor to a newer, faster processor.
Overflow This is when there is more information than can be properly handled. It is often used to describe the production of a number larger than a variable can handle. For instance, if you are expecting 10 digits but receive 11, that’s overflow.
Overload Hindrance of system operation by placing excess burden on the performance capabilities of a system component.
P2P Stands for "Peer to Peer." In a P2P network, the "peers" are computer systems which are connected to each other via the Internet. Files can be shared directly between systems on the network without the need of a central server. In other words, each computer on a P2P network becomes a file server as well as a client. The only requirements for a computer to join a peer-to-peer network are an Internet connection and P2P software. Common P2P software programs include Kazaa, Limewire, BearShare, Morpheus, and Acquisition. These programs connect to a P2P network, such as "Gnutella," which allows the computer to access thousands of other systems on the network. Once connected to the network, P2P software allows you to search for files on other people's computers. Meanwhile, other users on the network can search for files on your computer, but typically only within a single folder that you have designated to share. While P2P networking makes file sharing easy and convenient, is also has led to a lot of software piracy and illegal music downloads. Therefore, it is best to be on the safe side and only download software and music from legitimate websites.
P2V (Physical to Virtual) migration The operation of migrating an operating system and every application installed on it from a physical computer to a virtual machine (or a partition), without reinstalling anything. The opposite of V2P (Virtual to Physical) migration.
Packet This is a small amount of computer data sent over a network. Any time you receive data from the Internet, it comes to your computer in the form of many little packets. Each packet contains the address of its origin and destination, and information that connects it to the related packets being sent. The process of sending and receiving packets is known as "packet-switching." Packets from many different locations can be sent on the same lines and be sorted and directed to different routes by various computers along the way. It works a lot like the post office, except billions of packets are transferred each day, and most packets take less than a few seconds to reach their destination. Even FedEx same-day delivery can't compete with that.
Packet Filter Anything that filters out network traffic based on a sender’s address, receiver’s address, and the type of protocol being sent. Some routers support packet filtering, all firewalls do, and some proxy servers do as well.
Packet InterNet Gopher (PING) Part of the standard TCP/IP suite of protocols that allows you to check your connectivity with other devices, or to check whether your own TCP/IP stack is working properly. Normally you type in something like “ping 10.250.250.37″ or “ping www.geek.com,” and you either get a response from that IP address or not. PING is extremely useful for debugging network problems
Packet Switched Network A packet switched network is where individual packets each follow their own paths through the network from one endpoint to another.
Packet Switching The method used to move data around on the Internet. In packet switching, all the data coming out of a machine is broken up into chunks, each chunk has the address of where it came from and where it is going. This enables chunks of data from many different sources to co-mingle on the same lines, and be sorted and directed along different routes by special machines along the way. This way many people can use the same lines at the same time. You might think of several caravans of trucks all using the same road system to carry materials. See also: Internet (Upper case I), Router
PACKET, PACKET JAM When you retrieve a document via the WWW, the document is sent in "packets" which fit in between other messages on the telecommunications lines, and then are reassembled when they arrive at your end. This occurs using TCP/IP protocol. The packets may be sent via different paths on the networks which carry the Internet. If any of these packets gets delayed, your document cannot be reassembled and displayed. This is called a "packet jam." You can often resolve packet jams by pressing STOP then RELOAD. RELOAD requests a fresh copy of the document, and it is likely to be sent without jamming.
Page Fault This is not an error, as “fault” would usually indicate. It simply means that the computer had to resort to using the swap file as memory. If you are getting a lot of page faults you should upgrade your system’s memory.
Page Orientation Page orientation describes the way a document is printed or displayed on a screen. The two main types are "Portrait," in which the height is longer than the width, and "Landscape," in which the width is longer than the height. Most printers print in portrait mode by default, which means the page is printed vertically from top to bottom. Some programs allow the user to change the orientation to landscape mode within the "Page Setup" window.
Page View Each time a user visits a Web page, it is called a page view. Page views, also written "pageviews," are tracked by website monitoring applications to record a website's traffic. The more page views a website has, the more traffic it is receiving. However, since a page view is recorded each time a Web page is loaded, a single user can rack up many page views on one website. Therefore, unique page views are commonly tracked to log the number of different visitors a website receives in a given time period. Page views are commonly confused with website hits. While people often use the term "hit" to describe a page view, technically a hit is recorded for each object that loads during a page view. For example, if a Web page contains HTML, two images, and a JavaScript reference, a single page view will record four hits. If a page contains over two hundred images, one page view will record over two hundred hits. Page views are more similar to impressions, which are commonly tracked by online advertisers. Page views and impressions may be identical if one advertisement is placed on each page. However, if multiple ads are positioned on each page, the number of ad impressions will be greater than the number of page views.
Paging The act of moving pages of memory from RAM to virtual memory on a hard drive. Excessive paging is caused by a lack of actual system memory. In this case the system has to use the hard drive as memory frequently, and performance is degraded.
PAL Phase Alternating Line. PAL is the name of the analogue television standard used in Westren Europe, Australisa, New Zealand and parts of Asia. A PAL picture is made of 625 scan lines of which 575 are visible. cf NTSC, SDTV, HDTV
palette The range of colors a computer or an application is able to display. Most newer computers can display as many as 16 million colors, but a given program may use only 256 of them. Also refers to a display box containing a set of related tools within a desktop publishing or graphics design program.
PAN 1. Personal Area Network. A wireless network that covers a few meters around a person's workspace. A PAN is used for communication between personal devices, such as bluetooth devices like wireless keyboards, headphones, cell phones etc. 2. Pan. To turn or rotate a camera horizontally - to give a panorama view, from which the abbreviation "pan" comes. 3. Pan. To move a camera or map vertically or horizontally. Panning a camera would be to move it left, right, up or down. To pan a map (or pan across a map) would be to move the area of view up, down, left or right. Whilst "pan" may technically mean a horizontal movement, it is generally taken to mean movement along any axis.
Para-virtualization An enhancement of virtualization technology, where guest OSes need to be adapted (recompiled) before being ready for installation inside virtual machines. It reduces virtualization overhead and improves performances. It's an alternative approach to Binary Translation (BT).
Parallel ATA Traditionally simply known as IDE. Utilizes 40 parallel signal cables for data transfer between the IDE disk drive and the IDE controller. cf Serial ATA.
Parallel Port This interface is found on the back of older PCs and is used for connecting external devices such as printers or a scanners. It uses a 25-pin connector (DB-25) and is rather large compared to most new interfaces. The parallel port is sometimes called a Centronics interface, since Centronics was the company that designed the original parallel port standard. It is sometimes also referred to as a printer port because the printer is the device most commonly attached to the parallel port. The latest parallel port standard, which supports the same connectors as the Centronics interface, is called the Enhanced Parallel Port (EPP). This standard supports bi-directional communication and can transfer data up to ten times faster than the original Centronics port. However, since the parallel port is a rather dated technology, don't be surprised to see USB or Firewire interfaces completely replace parallel ports in the future.
Parity The use of an extra bit on memory chips that serves as a checksum, and can let the operating system know if single-bit memory errors are occurring.
Parity Memory Memory that contains a summary of its stored information. The parity does not exactly have a copy of the original, but just enough information to verify the integrity of the original.
Parse (v. to parse) The act of separating data into more easily understood chunks.
Parser Strictly speaking, this is something that separates data into more easily understood chunks. More practically, a parser is the part of a compiler that goes through a program and cuts it into identifiable chunks before translation. Assuming that a parser is written reliably, if the parser cannot parse a program then the program contains syntax errors.
Partition A partition is a section of a hard disk. When you format a hard disk, you can usually choose the number of partitions you want. The computer will recognize each partition as a separate disk, and each will show up under "My Computer" (Windows) or on the desktop (Macintosh). So why would you want to create multiple partitions? Well, there are two main reasons. One is if you want to have multiple operating systems on your computer. Typically, an operating system needs to be installed on its own partition so that it won't conflict with other operating systems on the machine. The other reason is that multiple partitions can improve the efficiency of your hard disk. On larger disks, the cluster or block size (which is the minimum amount of space a file can take up), is larger than on small disks. This can result in a waste of disk space if you have a lot of small files. So creating multiple partitions can actually give you more space. Yep, more room for all those MP3s. "Partition" can also be used as a verb, meaning to create multiple partitions.
Partitioning A software technology able to create multiple instances of the same host OS, called partitions, instead of reproducing multiple different physical machines like in virtualization.
Pascal A programming language that was designed to teach computer science students the concepts of programming. It’s almost like C for dummies. In fact, the two languages are very similar, but the stoic brackets of C are changed to happy and fluffy “Begin” and “End” statements. Also, many of the more complex functions of C are missing, but Pascal is still a fully functional language. Borland used Pascal as the basis for its Delphi programming language.
Password A code used to gain access (login) to a locked system. Good passwords contain letters and non-letters and are not simple combinations such as virtue7. A good password might be: 5%df(29) But don't use that one!
Password Authentication Protocol (PAP) Password Authentication Protocol is a simple, weak authentication mechanism where a user enters the password and it is then sent across the network, usually in the clear.
Password Cracking Password cracking is the process of attempting to guess passwords, given the password file information.
Password Sniffing Passive wiretapping, usually on a local area network, to gain knowledge of passwords.
Paste Just like you can paste a note on a sheet of paper, you can paste data into a document on a computer. The paste function can be used to paste copied data into text documents, images, Web browser address fields, and just about any place where you can enter data. However, to paste data, you first need to copy it to the "Clipboard," which is a temporary storage area in your system's memory, or RAM. This is done by first selecting the data you want to copy and then choosing "Copy" from the program's Edit menu. Once you have data copied to the Clipboard, you can paste it within the same document or within a different document in the same program. You can even paste copied data into a document within a different program. However, you can typically only paste data into a document with the same kind of data. For example, you cannot paste an image into your Web browser's address field or an audio file into image editing program. To paste a copied piece of data, select "Paste" from the Edit menu in the program you wish to paste the data in. Text documents or programs with text fields will typically paste the data wherever the flashing cursor is. You can also use the keyboard shortcut "Control-V" for Windows or "Command-V" for the Mac OS to paste the data. The reason the "V" key is used is because the "P" key is usually reserved for the "Print" shortcut and "V" is right next to the "C" key, which is used for copying. So it might not be that intuitive at first, but it makes sense when you think about it. =)
PATA Abbreviation for Parallel ATA. PATA is the term now commonly used for what historically was termed simply IDE. PATA has a maximum data transfer rate of 133MB/sec. See ATA for details. cf SATA.
Patch Minor updates to programs that are distributed with only the changes and not the whole program. Imagine an instruction manual that has an extra page stapled in it with a correction of some text for that page. That is what would be considered a patch.
Patch cable The common name for any network cable that is used to connect, or “patch,” any two network ports.
Patch panel A group of network ports stuck together for easy accessibility. Usually this panel resides in a wiring closet or server room. Connections are made between this panel and ports on a hub to enable a network connection at a remote port. Each port on the patch panel is connected by a longer cable (often run through the ceiling) to a remote port anywhere in an office that needs a computer hooked up to the network.Patch panels offer the convenience of allowing technicians to quickly change the path of select signals, without the expense of dedicated switching equipment. This was first used by early telephone exchanges, where the telephone switchboard (a massive array of patch panels) and a large room full of telephone operators running it was ubiquitous.
Patching Patching is the process of updating software to a different version.
Path A path, also known as a "file path" or "directory path," defines the location of a file or folder. Paths can either be relative or absolute. Relative paths describe file and folder locations from the current directory, such as "pdfs/instructions.pdf." Absolute paths define locations of files and folders from the root directory, such as "/Users/[username]/Documents/pdfs/instructions.pdf." Both relative and absolute paths are useful in describing the location of files and folders within a computer's file system.
Pay-Per-Click Fraud Pay-Per-Click Fraud The repetitive clicking on ads on a website in order to generate revenue for the website. Websites which run advertisements on the pay-per-click model are paid an amount each time someone clicks on an advertisement, with pay-per-click fraud the website arranges for clicks to be made on those advertisements purely for the purposes of raising revenue for the website. This is a fraud because the advertisers receive no benefit but see their advertising budget fraudulently eaten away.
Payload The eventual action taken by a virus once it has installed itself on a system. This action may be immediate, or it could wait for some trigger in the future, such as a specific date or a certain amount of time, to take action. The possible actions of a virus are limited to your imagination, although some payloads include deletion of files, formatting hard drives, or simply displaying a message to the user.
PB 1. Abbreviation for Petabyte. 250) bytes. 2. Abbreviation for Play Back.
PBR Policy Based Routing.
PBX Private Branch Exchange.
PC 1. Personal Computer. A computer designed for use by one person at a time. 2. Abbreviation for pieces. For example 2 pc means 2 piece (or 2 pieces).
PC Card A newer synonym for PCMCIA Card.
PC100 (PC100 SDRAM) The standard that SDRAM makers adhere to to be sure that SDRAM running at 100MHz works properly. PC100 SDRAM normally works fine in 66MHz SDRAM motherboards.
PC100 SDRAM The standard that SDRAM makers adhere to to be sure that SDRAM running at 100MHz works properly. PC100 SDRAM normally works fine in 66MHz SDRAM motherboards.
PC1066 RDRAM Rambus RDRAM that runs at a speed of 533MHz double-pumped to an effective speed of 1.06GHz. Memory throughput in systems featuring this type of DRAM is 2.1GB/second per 16-bit channel, or 4.2GB/second per 32-bit channel.
PC133 (PC133 SDRAM) A type of SDRAM that is designed to be run at 133MHz operation. It is pin-compatible with PC100 SDRAM and 66MHz SDRAM, and comes in a DIMM form factor.
PC133 SDRAM A type of SDRAM that is designed to be run at 133MHz operation. It is pin-compatible with PC100 SDRAM and 66MHz SDRAM, and comes in a DIMM form factor.
PC1600 (PC1600 DDR SDRAM) DDR SDRAM running at 100MHz double-pumped to an effective speed of 200MHz. It has a maximum data transfer rate of 1.6GB/second for one PC1600 channel.
PC200 DDR SDRAM The DDR memory chips used to assemble PC1600 DDR memory modules.
PC2100 DDR SDRAM A type of DDR SDRAM running at 133MHz double-pumped to an effective speed of 266MHz. It is referred to as PC2100 because systems featuring DDR SDRAM at 266MHz have a maximum data transfer rate of 2.1GB/second.
PC266 DDR SDRAM The DDR memory chips used to assemble PC2100 DDR memory modules.
PC2700 (PC2700 DDR SDRAM) A type of DDR SDRAM running at 166MHz double-pumped to an effective speed of 333MHz. It is referred to as PC2600 because of its maximum data transfer rate of 2.7GB/second.
PC3200 (PC3200 DDR SDRAM) A type of DDR SDRAM running at 200MHz double-pumped to an effective speed of 400MHz. It is referred to as PC3200 because of its maximum data transfer rate of 3.2GB/second in a single 64-bit channel.
PC333 DDR SDRAM The DDR memory chips used to assemble PC2700 DDR memory modules.
PC400 DDR SDRAM The DDR memory chips used to assemble PC3200 DDR memory modules.
PC600 RDRAM Rambus RDRAM that runs at a speed of 266MHz double-pumped to an effective speed of 532MHz. Memory throughput in systems featuring this type of DRAM is about 1.06GB/second.
PC700 RDRAM Rambus RDRAM that runs at a speed of 356MHz double-pumped to an effective speed of 712MHz. Memory throughput in systems featuring this type of DRAM is about 1.42GB/second.
PC800 RDRAM Rambus RDRAM that runs at a speed of 400MHz double-pumped to an effective speed of 800MHz. Memory throughput in systems featuring this type of DRAM is 1.6GB/second.
PCB Printed Circuit Board. See also PWB.
PCI 1. Peripheral Computer Interface. A 32 or 64 bit bus architecture described by the PCI Local Bus Specification. cf ISA. 2. Payment Card Industry. 3. Payment Card Industry (PCI) Data Security Standard. See PCI DSS
PCI Express First came PCI, then PCI-X, then PCI Express. PCI Express can be abbreviated as PCIe or, less commonly and more confusingly, PCX. Unlike earlier PCI standards, PCI Express does not use a parallel bus structure, but instead is a network of serial connections controlled by a hub on the computer's motherboard. This enables PCI Express cards to run significantly faster than previous PCI cards. Because the PCI Express interface is a serial connection, it does not have a speed measured in Megahertz, like PCI or PCI-X. Instead, its performance is measured in data throughput speeds, which are several times faster than PCI-X. Furthermore, PCI Express is available in x1, x4, x8, and x16 implementations, which increases the bandwidth by the corresponding amount. However, larger implementations require longer PCI Express slots. For example, a x4 slot is larger than a x1 slot and a x16 slot is larger than a x8 slot. A PCI Express card can be inserted in any slot that is large enough for it. For example, a x8 card could be inserted into a x16 slot, but a not a x1 or x4 slot. Since PCI Express connections can support such fast data transfer rates, they can be used to connect high-speed devices such as Gigabit Ethernet cards and high-end video cards. For this reason, PCI Express is expected to replace both PCI and AGP connections. Fortunately, PCI Express was designed to be backwards compatible with both PCI hardware and software. However, to use a PCI Express card, your computer must have at least one available PCI Express slot.
PCI-X Stands for "Peripheral Component Interconnect Extended." Once again, "Ex" is abbreviated with an "X" instead of an "E." Most desktop computers include one or more PCI slots for expanding the computer's I/O capabilities. Common PCI cards include network cards, sound cards, and video cards. In the early 1990s, when PCI was first introduced, the 66 MHz speed of PCI was more than sufficient for PCI cards available at the time. However, a decade later, expansion cards supported much faster data transfer rates and therefore became faster than the PCI bus would support. To prevent the interface from becoming a bottleneck, PCI-X was introduced. The first version of PCI-X supported data transfer rates of 133 MHz, which is more than twice as fast as the original PCI standard. Then along came PCI-X 2.0, which can run at speeds of 266 or 533 MHz. These speeds are fast enough to support Gigabit Ethernet cards and video capture devices without slowing them down. PCI-X cards can only be installed in PCI-X slots, but the slots themselves are backwards compatible with PCI cards.
PCMCIA Stands for "Personal Computer Memory Card International Association." It can also mean, perhaps more appropriately, "People Can't Memorize Computer Industry Acronyms." This way-to-long acronym stands for an association founded in 1989 which develops standards for expansion cards for portable computers. However, the term is most commonly associated with the actual cards standardized by the organization. These cards are referred to as "PCMCIA cards," or simply "PC cards." There are three types of PCMCIA cards, all of which are rectangular and measure 8.56 by 5.4 cm., but have different widths: Type I: up to 3.3 mm. thick, mainly used to add additional ROM or RAM. Type II: up to 5.5 mm. thick, typically used for fax/modem cards. Type III: up to 10.5 mm. thick, often used to attach portable disk drives. PCMCIA slots also come in three sizes -- a Type I slot can hold one Type I card, a Type II slot can hold one Type II card or two Type I cards, and a Type III slot can hold one Type III card or one Type I and one Type II card. PC Cards can be removed or inserted "on the fly," which means you don't have to turn your computer off to exchange them and you don't have to restart for your computer to recognize them.
PDA Personal Digital Assistant. A generic term used to describe any small portable hand-held electronic device that provides a minimum of storage and retrieval functions, such as calendar and address book. PDAs are also referred to as hand-held computers.
PDF Portable Document Format (file). A document format developed by Adobe, for storing and formatting published documents. PDF files are recognised by the file extension .pdf.
peer-to-peer A type of connection between two computers; both perform computations, store data, and make requests from each other (unlike a client-server connection where one computer makes a request and the other computer responds with information).
Penetration Gaining unauthorized logical access to sensitive data by circumventing a system's protections.
Penetration Testing Penetration testing is used to test the external perimeter security of a network or facility.
Peripheral A computer peripheral is any external device that provides input and output for the computer. For example, a keyboard and mouse are input peripherals, while a monitor and printer are output peripherals. Computer peripherals, or peripheral devices, are sometimes called "I/O devices" because they provide input and output for the computer. Some peripherals, such as external hard drives, provide both input and output for the computer.
Perl Practical Extraction and Reporting Language. A common scripting language used on both Windows and UNIX platforms. It was originally popular on UNIX platforms but is now common on Windows systems, particularly for server scripting. Commonly used for creating CGI programs to generate dynamic pages on web servers. Perl was first developed back in 1986 by Larry Wall, and first released the following year. Other names were considered before "Perl" was adopted as the name (including his wife's name "Gloria", and Pearl). The definition "Practical Extraction and Reporting Language" came after the language was first developed.
Permalink A "permanent link" to a particular posting in a blog. A permalink is a URI that points to a specific blog posting, rather than to the page in which the posting original occured (which may no longer contain the posting.)
Permutation Permutation keeps the same letters but changes the position within a text to scramble the message.
Persistent disk mode All disk writes issued by software running inside a virtual machine are immediately and permanently written to a persistent virtual disk. As a result, a virtual disk or raw disk in persistent mode behaves like a conventional disk drive on a real computer.
PERSONAL PAGE A web page created by an individual (as opposed to someone creating a page for an institution, business, organization, or other entity). Often personal pages contain valid and useful opinions, links to important resources, and significant facts. One of the greatest benefits of the Web is the freedom it as given almost anyone to put his or her ideas "out there." But frequently personal pages offer highly biased personal perspectives or ironical/satirical spoofs, which must be evaluated carefully. The presence in the page's URL of a personal name (such as "jbarker") and a ~ or % or the word "users" or "people" or "members" very frequently indicate a site offering personal pages.
Petabyte Unit of storage. Sometimes abbreviated to PB. 1 petabyte = 2 to to the fiftieth power (250) bytes = 1,125,899,906,842,624 bytes = 1024 terabytes.
PFW Personal Firewall. A firewall intended to protect a single PC. Usually a software firewall.
Pharming Pharming is yet another way hackers attempt to manipulate users on the Internet. While phishing attempts to capture personal information by getting users to visit a fake website, pharming redirects users to false websites without them even knowing it. While a typical website uses a domain name for its address, its actual location is determined by an IP address. When a user types a domain name into his or her Web browser's address field and hits enter, the domain name is translated into an IP address via a DNS server. The Web browser then connects to the server at this IP address and loads the Web page data. After a user visits a certain website, the DNS entry for that site is often stored on the user's computer in a DNS cache. This way, the computer does not have to keep accessing a DNS server whenever the user visits the website. One way that pharming takes place is via an e-mail virus that "poisons" a user's local DNS cache. It does this by modifying the DNS entries, or host files. For example, instead of having the IP address 17.254.3.183 direct to www.apple.com, it may direct to another website determined by the hacker. Pharmers can also poison entire DNS servers, which means any user that uses the affected DNS server will be redirected to the wrong website. Fortunately, most DNS servers have security features to protect them against such attacks. Still, they are not necessarily immune, since hackers continue to find ways to gain access to them. While pharming is not as common as phishing scams are, it can affect many more people at once. This is especially true if a large DNS server is modified. So, if you visit a certain website and it appears to be significantly different than what you expected, you may be the victim of pharming. Restart your computer to reset your DNS entries, run an antivirus program, then try connecting to the website again. If the website still looks strange, contact your ISP and let them know their DNS server may have been pharmed.
Phishing A type of scam which attempts to steal an individual's identity and/or financial account credentials. Phishing attacks include sending spoof e-mails to lead the recipient to websites designed to trick the recipient into entering financial data such as credit card numbers, account usernames, passwords etc.
Phone Switch These are generally large cabinets with groups of phone port cards plugged into them. On one end the cards connect to the phone company via T1 or larger line; on the other end they usually connect to a punch-down block on the wall, which is in turn connected to groups of ports at people’s desks. Thus, people can plug phones into these ports and be connected to the phone company. The phone switch manages the connections between you and the outside world. Many offices have their own dedicated switches that they can maintain and control (within certain guidelines). In residential areas the phone company controls the switches.
PHP A general purpose (server side) scripting language for web development that can be embedded in HTML. PHP is a popular alternative to ASP and ASP.NET, because it is cross platform, free and open source. PHP is a recursive acronym for "PHP: Hypertext Preprocessor".
PHRASE More than one KEYWORD, searched exactly as typed in (all words required, in the order specified). Enclosing keywords in "double quotation marks" forms a phrase in most search engines. Sometimes a phrase is called a "character string."
Phreak A person who breaks into phone systems, generally to get free phone or voicemail service–thus the “ph” at the beginning of the term, similar to “phone.” It can be expanded to apply to anyone who breaks into systems to get free goods or services.
Physical Address For Physical Address of a network card see MAC Address.
Pico a text editor originally designed for composing e-mail for Pine
PIN 1. Personal Identification Number. A general term used to refer to any number used to authenticate a person. For example a PIN number for bank withdrawals is used to authenticate the use of a cash-card, and the cash-card cannot be used without entering the correct PIN number. 2. Performance Improvement Network. A social network where members can share information and ideas to enable individuals, organisations or communities to improve their performance. 3. Prior Information Notice. A published notice providing an indication of future needs, which eventually may be manifest in an ITT. A Prior Information Notice is intended to provide interested parties with advanced warning of a possible ITT.
pincushioning On computer screens, lines that should be straight don't always appear that way. Lines that look bowed or curved are evidence of a pincushion error. Such problems are common at the right and left edges of a displayed image, resulting in a screen that appears to be bowed inward at the centers (thus the source of the name). Better monitors include controls to help you compensate for this error.
Ping 1. Ping is a widely available network utility for performing a simple network connectivity test between the current network location and a remote one. It works by generating an ICMP echo-request packet, and then listening for the reply from the remote end. A ping test is used to establish that communications can be successfully established between two computers on a TCP/IP network. Ping was originally named after the "ping" from sonar. The idea was later introduced that it stood for "Packet INternet Groper".
Ping of Death An attack that sends an improperly large ICMP echo request packet (a "ping") with the intent of overflowing the input buffers of the destination machine and causing it to crash.
Ping Scan A ping scan looks for machines that are responding to ICMP Echo Requests.
Ping Sweep An attack that sends ICMP echo requests ("pings") to a range of IP addresses, with the goal of finding hosts that can be probed for vulnerabilities.
Pinging Using ping to check basic network connectivity.
Pipeline Computer processors can handle millions of instructions each second. Once one instruction is processed, the next one in line is processed, and so on. A pipeline allows multiple instructions to be processed at the same time. While one stage of an instruction is being processed, other instructions may be undergoing processing at a different stage. Without a pipeline, each instruction would have to wait for the previous one to finish before it could even be accessed. To understand the benefit of a pipeline, imagine that a car manufacturing plant had to wait for each car to be fully completed before starting on the next one. That would be horribly inefficient, right? It makes much more sense to work on many cars at once, completing them one stage at a time. This is what a pipeline in a computer allows. Pipelining, as it is called, often keeps around six instructions at once in the processor at different stages of processing. Pipelines can be used for the CPU as well as for accessing memory (DRAM).
pipeline burst cache This type of secondary cache is an advanced type of SRAM installed on the motherboard to boost computer performance. Pipeline burst SRAM is commonplace now in motherboard market, where it replaced the older Sync Burst cache, which works less efficiently with fast processors.
Pipeline Burst Cache (Pipeburst Cache) A form of L2 cache that uses pipelining to speed data access by being able to feed data to the CPU at the same time as it pulls data from memory. The burst mode also allows the cache to fetch additional data from main memory before the CPU requests it. This type of cache was used back in the Pentium days when L2 cache was separate from the processor.
Piracy When someone installs and uses commercial software without paying for the program, it is called "pirating" the software. This name comes from the traditional meaning of the word "pirate," which is a sea-faring criminal that steals and loots belongings from others. But far from the stereotypical sea pirate, a software pirate can be anyone who owns a computer. Software piracy is committed by simply downloading or copying a program that a user has not paid for. Since computer programs are stored in a digital format, they are easy to copy and reproduce. For example, a game may be burned to a CD and transferred to the computer of an individual who has not paid for the program. Software programs can also be illegally downloaded from the Internet from unauthorized sources. Since pirating software does not require many resources, it has grown into a major problem for the computer industry. While it may seem like an innocuous act, pirating software is the same as stealing. Software companies often invest thousands or even millions of dollars into creating the programs they sell. The income from selling these programs is what allows companies to produce the software and to continue improving the programs we use. Just because it is possible to copy a software program does not mean it is OK. Installing a commercial program from an illegal copy is the same thing as walking out of a store with the program and not paying for it. While there are some programs that are free to use (such as shareware and freeware programs), it is important to pay for commercial software. You can avoid software piracy by only downloading software from authorized sources and making sure that you have valid software licenses for all the programs you use. Remember that paying for software programs supports the software industry, which is good for all of us!
Pixel The term "pixel" is actually short for "Picture Element." These small little dots are what make up the images on computer displays, whether they are flat-screen (LCD) or tube (CRT) monitors. The screen is divided up into a matrix of thousands or even millions of pixels. Typically, you cannot see the individual pixels, because they are so small. This is a good thing, because most people prefer to look at smooth, clear images rather than blocky, "pixelated" ones. However, if you set your monitor to a low resolution, such as 640x480 and look closely at your screen, you will may be able to see the individual pixels. As you may have guessed, a resolution of 640x480 is comprised of a matrix of 640 by 480 pixels, or 307,200 in all. That's a lot of little dots. Each pixel can only be one color at a time. However, since they are so small, pixels often blend together to form various shades and blends of colors. The number of colors each pixel can be is determined by the number of bits used to represent it. For example, 8-bit color allows for 2 to the 8th, or 256 colors to be displayed. At this color depth, you may be able to see "graininess," or spotted colors when one color blends to another. However, at 16, 24, and 32-bit color depths, the color blending is smooth and, unless you have some kind of extra-sensory vision capability, you should not see any graininess.
PKI (Public Key Infrastructure) The infrastructure needed to support public key encryption. It requires a certificate authority to issue and verify the public keys, a registration authority that verifies the identity of a person or organization before a key is issued, a certificate directory of the public keys, and a certificate management system. Public key encryption can be used to verify an identity or to encrypt data or messages.
Plain Text Text documents come in to flavors - "rich text" and "plain text." Plain text, as you might have guessed, is rather plain. While it supports standard ASCII characters, including numbers, symbols, and spaces, it does not support any type of text formatting. Therefore you cannot use bold, italics, underlining, or different font sizes in a plain text document. Because plain text does not contain information about text sizes or styles, it is the most efficient way to store text. Plain text documents often take up less than half the size of rich text documents containing the same number of characters. You can use a basic text editor such as Windows Notepad to create a plain text document. If you want to copy text from a formatted document without copying the style, you can also use Notepad. Just copy the text from the original document, paste it into Notepad, then copy it again. The unformatted text will be copied from Notepad to your clipboard. The next time you paste the text, it will be pasted as plain text.
Plaintext Ordinary readable text before being encrypted into ciphertext or after being decrypted.
Platform A means of generically grouping like computers. Macintosh computers are a platform; so are PCs running Windows. It’s not very specific, and multi-platform support can mean many things. If someone says to you “this application supports multiple platforms,” ask that person which ones he or she is talking about.
Platter One of the rigid disks inside a hard drive used to store information. Hard drives typically contain between one and 5 platters apiece, but can contain more. Platters have been historically made out of aluminum, and more recently glass.
Plesk The Parallels® Plesk Panel (ex: Parallels Plesk Control Panel, Plesk Server Administrator, PSA) software package is a commercial web hosting automation program. Originally released under the U.S. company Plesk Inc. and designed in Novosibirsk, Russia, Plesk became an SWsoft product when SWsoft acquired Plesk Inc. in July 2003.[1] Parallels Plesk Panel is now shipped under Parallels, Inc. since Swsoft rebranded itself as Parallels (an existing namebrand in its portfolio) in January 2008.[2] At that time, Plesk was rebranded as Parallels Plesk Panel.[3] Overview Parallels Plesk Panel allows a server administrator to set up new websites, reseller accounts, e-mail accounts, and DNS entries through a web-based interface. The administrator can create client and site templates, which predetermine resource allocation parameters for the domains and/or clients. Parallels Plesk Panel for Linux/UNIX supports multiple POSIX platforms, including Debian, Fedora, FreeBSD, Red Hat Linux, SUSE and Ubuntu. Parallels Plesk Panel for Windows supports Windows Server 2003 and Windows Server 2008 operating systems. Parallels Plesk Panel installs custom versions of or manages versions of MySQL and PostgreSQL databases (Microsoft SQL Server and Microsoft SQL Server Desktop Engine under Windows), Apache Tomcat Java platform server, ColdFusion server, as well as CounterStrike and Battlefield 1942 game servers. Add-ons Parallels Plesk Panel has several software packs that are not part of the main Parallels Plesk Panel code base. These add-ons are designed to fully interact with Parallels Plesk Panel. These Parallels Plesk Panel software packs include functionality for billing, website building, and multiple server support. They include: Parallels Plesk Billing Parallels Plesk Sitebuilder Parallels Plesk Expand
Plug and Play Technology where adapters can be automatically configured by the system without user intervention. This removes the need for a user to worry about IRQ and DMA settings. Plug and Play used to also be referred to as "Plug and Pray". This was when the technology was new and not always reliable.
Plug-in A (usually small) piece of software that adds features to a larger piece of software. Common examples are plug-ins for the Netscape® browser and web server. Adobe Photoshop® also uses plug-ins.
PNG Portable Network Graphics. A compressed loss-less image format. Image files saved using the PNG format are usually given a .png file extension.
Point to Point Tunneling Protocol (PPTP) A remote access protocol that allows people to make a connection to easily connect to their local network through the Internet or some other large network. Conversations are kept private through encryption. See also Virtual Private Network.
Pointer (1) In programming, think of a pointer as an address. The address can point to just about anything, including another pointer. Ultimately, if you follow the trail of pointers you’ll probably find some data–pointers are most often used to point to data. The purpose of pointers is so that when you are programming you can pass around a small address that points to some data, instead of passing the actual data around. (2) Pointers can also refer to the icon on the screen that you move around with a mouse or other pointing device. In a GUI environment you need a pointer to point to things so that you can select them.
Poison Reverse Split horizon with poisoned reverse (more simply, poison reverse) does include such routes in updates, but sets their metrics to infinity. In effect, advertising the fact that there routes are not reachable.
Policy 1. An adopted plan or course of action. For example, a company may have a written policy on the disposal of equipment. 2. A set of rules that control some aspect of a system's behaviour, often enforced automatically by the system. For example a password policy would specify things like minimum password length and password history. 3. A contract of insurance. This is a document setting out what is and is not covered under an insurance contract and any limitations and responsibilities of the insurance company or the policy holder.
Poll (v. to poll) When one computer, device, or program asks for an answer to a query from another computer or device over a period of time until a condition is met. For example, a program may poll an IP address to see when it is available.
Polyinstantiation Polyinstantiation is the ability of a database to maintain multiple records with the same key. It is used to prevent inference attacks.
Polymorphism Polymorphism is the process by which malicious software changes its underlying code to avoid detection.
POP Post Office Protocol. A protocol for accessing e-mail, allowing e-mails to be downloaded form a server, stored locally and therefore available for off-line reading. cf POP3.
Pop-Up The term "pop-up" has two computer-related meanings. One refers to a window and the other is a type of menu. 1. Pop-Up Window A pop-up window is a type of window that opens without the user selecting "New Window" from a program's File menu. Pop-up windows are often generated by websites that include pop-up advertisements. These ads are produced with JavaScript code that is inserted into the HTML of a Web page. They typically appear when a user visits a page or closes a window. Some pop-up ads show up in front of the main window, while others show up behind the main browser window. Ads that appear behind open windows are also called "pop-under" ads. Regardless of where pop-up advertisements appear on your screen, they can be pretty annoying. Fortunately, browser developers have realized this and most Web browsers now include an option to block pop-up windows. If you are noticing pop-up windows appear on your computer when your browser is not open, you may have an adware program running on your computer. The best solution to this problem is to run an anti-spyware program that will locate and remove the malware from your system. 2. Pop-Up Menu A pop-up menu is a type of menu that pops up on the screen when the user right-clicks a certain object or area. It can be also called a contextual menu since the menu options are relevant to where the user right-clicked on the screen. Pop-up menus provide quick access to common program functions and are used by most operating systems and applications.
POP3 Post Office Protocol version 3. Used for accessing email, see POP for details. The version of POP adopted is version 3, hence the name POP3.
Port Replicator A device that is used to provide laptops–with limited ports and expansion options built-in–with a larger amount of ports and expandability. Most port replicators are proprietary devices that work with one particular model of laptop and add extra ports such as additional USB and PS/2 ports and sound line-in and line-out ports.
Port Scan A port scan is a series of messages sent by someone attempting to break into a computer to learn which computer network services, each associated with a "well-known" port number, the computer provides. Port scanning, a favorite approach of computer cracker, gives the assailant an idea where to probe for weaknesses. Essentially, a port scan consists of sending a message to each port, one at a time. The kind of response received indicates whether the port is used and can therefore be probed for weakness.
Portable Document Format (PDF) A format developed by Adobe. Adobe makes a freeware Adobe Acrobat Reader program that is available for a variety of platforms. Thus, using a variety of operating systems, you can download and read a PDF document with very little hassle. In addition, the PDF format strives for easy printing, viewing, and compact storage. On PCs .pdf is the file extension for this type of file.
Portal While this term can also refer to a matterless vortex used to travel between different dimensions, an Internet portal is a Web site that acts as a starting point for browsing the Web. Portals typically include search engines and large directories of websites. Some popular portals are Yahoo, Excite, Lycos, Netscape, AltaVista, MSN, and AOL.com. There are also many smaller portals, known as "niche portals," for specific interests. These sites include C|net (for computers and technology), Fool.com (for investors), and Garden.com (for gardeners). Most large portals have millions of Web pages indexed for visitors to search though. They also have large directories of Web sites, which are categorized by topic. Though the primary purpose of a portal is to find other sites for you, many now include a lot of information within their own sites.
Portal (Web portal) A term coined to describe the large search engine sites, such as Yahoo! and Lycos, that have branched off to offer a wide variety of services. The idea is that a Web user would peer at the Web by using only one website: the portal. For example, you go to a portal to do searches, get stock quotes, buy things, etc. It would be your everything site. Each portal site wants to offer one of each type of service so that a user never has to leave the site.
POSIX (Portable Operating System Interface) A set of operating system interface standards based on UNIX. The standards were developed so that programs could be written more easily that would work on multiple versions of UNIX from different manufacturers.
Possession Possession is the holding, control, and ability to use information.
POST 1. Power On Self Test. A set of tests performed by a computer's BIOS straight after power up. 2. The act of sending a message to a newsgroup, where others can view and respond to it. The term Post can also be used to refer to that message posted to a newsgroup. 3. To send a message. This usage originates from traditional postal services (snail-mail), but applied to applications, processes and threads. A message can be said to be posted to another process (thread or application).
Post Office Protocol 3 (POP3) A standard for client/server transmission of e-mail. An e-mail server holds the e-mail, and you use a POP3 client to fetch the mail from a server. IMAP is a newer e-mail client/server protocol with more options.
PostScript A standard language for telling printers how to print text and graphics. Most Macs use PostScript to print, while PCs normally default to PCL.
POTS (Plain Old Telephone Service) The regular telephone service that people have in their homes. Newer technologies such as ISDN, digital phones, cellular phones, or DSL are not referred to as POTS.
Power Cycle While the phrase "power cycle" appears to be a noun, it is actually more commonly used as a verb. In simple terms, to power cycle a device means to turn it off and turn it back on again. For example, the user manual of a router may ask you to power cycle the router if it stops responding. This may mean switching the power to OFF and then ON again or may require physically unplugging the device and then plugging it back in again. Power cycling is often synonymous with resetting a device. As we all know, computer equipment can be rather finicky at times. A device that was working fine ten minutes ago may begin acting strangely or may not be responding at all. Often the low-tech solution of simply turning off the device and turning it back on again will fix the problem. This is because information stored in the device's RAM may have gotten corrupted and caused the device to hang up or stall on a certain instruction. Power cycling the device erases the RAM and allows it to boot up with fresh information. Typically it is a good idea to wait 5 to 10 seconds before turning the device back on to make sure it has chance to fully reset. Of course, if you need to power cycle your computer, you should save any work you currently have open, since it will be erased from the RAM once the system is restarted.
Power PC A line of microprocessors developed by Motorola, Apple, and IBM; this chip is used in Power Macintoshes.
Power Supply A device attached to the case that converts 120 AC (in the U.S.) to DC at voltages that a computer needs to run. They come rated by wattage.
PowerNow! AMD’s power saving technology used in some of its mobile processors. It allows the OS and power management to tune down the speed of the processor in order to conserve power.
PowerStep An Apple/Motorola power management technology that allows PowerPC processors to be tuned down in speed when not plugged in so that power can be conserved.
PPM Stands for "Pages Per Minute." PPM is used to measure the printing speed of both inkjet and laser printers. Most printers include a PPM rating for both black and color documents. These speed measurements are typically listed in the printer's technical specifications. While a higher pages per minute rating does indicate a faster printing speed, this measurement can be misleading. This is because manufacturers measure the maximum PPM in the fastest printing mode, a.k.a. "economy mode," which is also the lowest quality. When printing in regular mode, the speed may be twice as slow. When printing in fine or high-quality mode, the speed will likely be reduced even further. Furthermore, a printer's maximum PPM speed is measured using basic text pages, with no graphics, lines, or other objects. Therefore, if you have a text document that includes a picture, the page could take several times longer to print than a plain text document. If you are going to be printing a lot of color photos, make sure to check the printer's photo printing speed, which is often significantly slower than the printer's maximum PPM. Finally, the PPM measurement does not take into account how long it takes the printer to warm up and begin printing. Therefore, if you are only printing one or two pages, the warm up time may be longer than the actual time it takes to print the document. In summary, PPM gives a general idea of how fast a printer is. But since there are several other variables involved that determine a printer's speed, PPM does not always accurately reflect a printer's speed. Therefore, when choosing a printer, it may be helpful to read some reviews about the printer you are interested in. The reviews may give you a better idea of the printer's real-world speed an quality than the numbers on the box do. NOTE: PPM can also be used to measure a scanner's scanning speed. This measurement is particularly important for scanners that use an automatic document feeder ADF, which allows multiple documents to be scanned consecutively.
PPP tands for "Point to Point Protocol." It is the Internet standard for dial-up modem connections. PPP is a set of rules that defines how your modem exchanges packets of data with other systems on the Internet. If you connect to your ISP with a dial-up modem, you are most likely using PPP.
Preamble A preamble is a signal used in network communications to synchronize the transmission timing between two or more systems. Proper timing ensures that all systems are interpreting the start of the information transfer correctly. A preamble defines a specific series of transmission pulses that is understood by communicating systems to mean "someone is about to transmit data". This ensures that systems receiving the information correctly interpret when the data transmission starts. The actual pulses used as a preamble vary depending on the network communication technology in use.
Precision Precision is how well you define a value. For example, if the value you are representing is 4.321 and you say it’s 4.3, you are precise to two places. Numerically, precision is the amount of decimal digits that you are capable of measuring.
Preemptive Multitasking Multitasking operating system strategy in which the operating system scheduler controls which process will run at a given time and for how long before control passes to another process. cf Cooperative Multitasking.
Pretty Good Privacy (PGP) A freeware program that secures e-mail messages by encrypting and/or adding a digital signature to them. There are also commercial versions of PGP available that encrypt data and offer a wider variety of options.
primary cache By caching data in fast, pricey memory, you speed up your system performance. Primary cache is fast, usually integrated into the CPU chip, and not very large (typically 16K). While it's useful for storing some instructions, it usually relies on a secondary (L2) cache for an all-around boost of system performance.
Primary Domain Controller (PDC) In Windows NT and 2000 networking, this machine is the main machine that responds to security authentication requests, such as logging in, within its domain. The PDC may be backed by one or more backup domain controllers that can also handle security authentication.
Primary Key A primary key is a unique identifier for a database record. When a table is created, one of the fields is typically assigned as the primary key. While the primary key is often a number, it may also be a text field or other data type. For example, if a database contains definitions of computer terms, it would make sense that each term is only listed once in the database. By defining the "Term" field as the primary key, it would ensure that no term is listed more than once in the database. While a table's primary key is usually assigned to a specific field, it can also be comprised of multiple values. For example, a database of news articles might use both the title and date fields to uniquely identify each entry. By combining the "Title" and "Date" fields as the primary key, it would ensure no entries have the same title on the same day. If multiple fields in a table cannot have duplicate values, most database management system (DBMS) also allow fields to be defined as "Unique." This is similar to setting a field as the primary key, but is not exactly the same thing. The primary key also acts as a pointer to the record and provides a simple way for the DBMS to search, sort, and access the records. It also helps relate records across multiple tables. Therefore, while multiple fields within a table can be defined as "Unique," each table can only have one primary key. The primary key field must also be defined for each record and not set to null. After all, a undefined identifier is not very useful.
Primary partition A partition that is bootable. You cannot have more than four primary partitions per drive.
Print Screen This button is intended to print whatever is on your screen. If you are using DOS, or you are in your BIOS and have a printer set up, the Print Screen button should do just that. In Windows OSes,hitting the Print Screen button will copy your current desktop so that you can paste it into a graphics program, or a program that will support graphics, such as many word processors today. Additionally, hitting Alt-Print Screen will copy just the window that is active at the time.
Print Server The interface between a printer and a network that allows network clients to connect to the printer and send their print jobs to it. Print servers can be computers, separate hardware devices, or even hardware that resides inside of the printer itself.
Printer Any device that makes an impression on media, usually paper, and is connected to a computer. The invention of the computer with printer has almost made the typewriter obsolete. The simplest printers are located in cash registers printing out receipts, while more advanced printers are capable of magazine-quality photo images. Printers come in several types, including daisy-wheel, dot matrix, inkjet, laser, and dye sublimation.
Printer Control Language (PCL) A set of commands used to communicate with Hewlett Packard printers. Each printer company has its own language, but PCL has become a generic term to describe these languages. See also Postscript.
Private Branch Exchange (PBX) A private phone switch used within a company that allows inter-company phone calls without using outside lines. It also connects to one or more outside POTS lines, which are often partitioned off into outgoing lines, incoming lines, or lines that can be used for both purposes. PBXs today use digital connections for inter-company calls, thus you must use digital phones as opposed to standard analog phones (and modems). A PBX is typically a large and costly piece of machinery maintained and/or supported by the company that sold the PBX. There are various options that can be added onto PBXs for call reporting, call management, and voicemail.
Processor This little chip is the heart of a computer. Also referred to as the "microprocessor," the processor does all the computations such as adding, subtracting, multiplying, and dividing. In PCs, the most popular microprocessor used is the Intel Pentium chip, whereas Macintosh computers use the PowerPC chip (developed by Motorola, IBM, and Apple). The speed of a computer's processor is measured in megahertz, or cycles per second. But higher megahertz doesn't always mean better performance. Though a 600-MHz chip has a clock speed that is twice as fast as a 300-Mhz chip, it doesn't mean that the computer with the 600-Mhz chip will run twice as fast. This is because the speed of a computer is also influenced by other factors, such as the efficiency of the processor, the bus architecture, the amount of memory available, and the software that is running on the computer. Some processors can complete more operations per clock cycle than other processors, making them more efficient than other processors with higher clock speeds. This is why the PowerPC chip is typically faster than Pentium chips at that are clocked at higher megahertz.
Program rogram is a common computer term that can be used as both a noun and a verb. A program (noun) is executable software that runs on a computer. It is similar to a script, but is often much larger in size and does not require a scripting engine to run. Instead, a program consists of compiled code that can run directly from the computer's operating system. Examples of programs include Web browsers, word processors, e-mail clients, video games, and system utilities. These programs are often called applications, which can be used synonymously with "software programs." On Windows, programs typically have an .EXE file extension, while Macintosh programs have an .APP extension. When "program" is used as verb, it means to create a software program. For example, programmers create programs by writing code that instructs the computer what to do. The functions and commands written by the programmer are collectively referred to as source code. When the code is finished, the source code file or files are compiled into an executable program.
Program Infector A program infector is a piece of malware that attaches itself to existing program files.
Program Policy A program policy is a high-level policy that sets the overall tone of an organization's security approach.
Progressive Scan Video signals are generated using horizontal lines. An interlaced picture draws every other line and alternates between drawing odd lines and even lines. A progressive scan picture draws every line in sequence. Therefore, a progressive scan video signal sends twice as much data than an interlaced signal each time it draws an image on the screen. Before DVDs and HDTV became popular, interlaced video was the norm for television. Standard definition broadcasts were interlaced, since it was a more efficient way to send video data. Since the human eye has a hard time detecting video interlacing, an interlaced signal that refreshes at 60 Hz (times per second) is easier on the eyes and produces less flicker than a progressive scan signal that refreshes at 30 Hz. Still, if a progressive scan and interlaced image are both projected at 60 Hz, the progressive scan image will usually appear slightly smoother. Video that contains fast motion makes this difference more noticeable. For this reason, the DVD and HDTV standards were developed to support progressive scan video signals. When you see video formats described as 480p or 720p, the number indicates how many horizontal lines of resolution the video signal uses, while the "p" indicates it is a progressive scan signal. Similarly, the 1080i format contains 1080 lines of resolution, but is interlaced. Both 720p and 1080i are used by HDTV.
PROM (Programmable Read Only Memory) This is a memory device. Once data is written to a PROM it is there forever, unlike with an EPROM. A PROM is also a curious high school ritual involving strangely colored dresses, tuxedos, and sometimes limousines, unconsciously mirroring the wedding rituals most of its participants will undergo at some point in the following 10-15 years. PROMs leave some traumatized and others gleeful, but everyone agrees the post-PROM activities are always better than the PROM itself.
Promiscuous Mode Although it sounds naughty, as it relates to networking promiscuous mode implies that a network card is able to recognize all network traffic with which it comes in contact. Generally you need a promiscuous mode card using a promiscuous mode driver to run any kind of network packet-filtering tool effectively.
Proprietary Information Proprietary information is that information unique to a company and its ability to compete, such as customer lists, technical data, product costs, and trade secrets.
protected mode An operating mode of x86 chips that lets the PC access the largest possible amount of memory. In protected mode, different parts of memory are assigned to different programs. This way, memory is "protected" in the sense that only the assigned program can access it. The phrase is often used to describe device drivers that operate in this mode. Windows and OS/2 run primarily in protected mode, but can switch between the use of protected-mode and real-mode applications.
Protocol A protocol is an agreed set of rules for the communication of information between two or more devices. Whilst the list of protocols is probably near endless, the following are examples of common protocols: HTTP - Hypertext Transport Protocol, used for the transfer of web pages. NNTP - Network News Transport Protocol, used for newsgroups. SMTP - Simple Mail Transfer Protocol, used for sending emails. FTP - File Transfer Protocol, used for transferring files.
Protocol Stacks (OSI) A set of network protocol layers that work together.
Proxy A system (software or hardware) that acts on behalf of another to perform some service. A proxy acts as an interface, hiding the system that ultimately performs the service. Whilst this is not an exhaustive list, a proxy is typically used to provide for any of the following: to bridge separate networks for performance By caching requests - if two or more users are using a cache then there are situations where a single centralised cache will outperform separate caches local to the users. to provide centralised logging of requests to provide anonymous access The user that initiated the request hides behind the proxy and only the proxy is visible to the server that ultimately responds to the request. An HTTP Proxy is a typical example of a proxy.
Proxy Server A server that acts as an intermediary between a workstation user and the Internet so that the enterprise can ensure security, administrative control, and caching service. A proxy server is associated with or part of a gateway server that separates the enterprise network from the outside network and a firewall server that protects the enterprise network from outside intrusion.
PS/2 This is a PC made by IBM that can run OS/2 and DB/2. Of course, it can run anything a normal PC can run, but it’s just a nifty IBM naming convention that caught on.
PS/2 port A standard serial port connector used to plug mice and keyboards into PCs. It’s got 6 pins and is small and round, compared to the larger 9- and 25-pin serial connectors still found on some PCs.
PST Pacific Standard Time. Abbreviated name for the time zone used on the West coast of America. PST = UTC - 8 hours.
PSTN Public Switched Telephone Network.
PSU Power Supply Unit. An electrical device that converts from the mains AC electrical supply into DC voltage (or voltages) required by an electronic device. A PSU may be internal to the device or external. Typically the larger the device to be powered the more likely that the PSU is internal. For example the PSU in a computer is internal to the computer and may be removed and replaced as a unit, whereas the PSU for an external disk drive is normally a completely separate unit.
public domain public domain Of all the kinds of software or information you can download, public domain has the fewest strings attached. With shareware, you're expected to pay a fee. With freeware, you may face other restrictions, and there's still a copyright attached. With public domain downloads (also called downloads in the pubic domain), there are no copyright restrictions whatsoever. See also: shareware, freeware
Public Key The publicly-disclosed component of a pair of cryptographic keys used for asymmetric cryptography.
Public Key Encryption The popular synonym for "asymmetric cryptography".
Public Key Infrastructure (PKI) A PKI (public key infrastructure) enables users of a basically unsecured public network such as the Internet to securely and privately exchange data and money through the use of a public and a private cryptographic key pair that is obtained and shared through a trusted authority. The public key infrastructure provides for a digital certificate that can identify an individual or an organization and directory services that can store and, when necessary, revoke the certificates.
public method In object-oriented languages such as Smalltalk or Java, public is one of several modifiers you use to control access to a method. A public method is available to any class in any file. If you use no modifier, only classes declared in the same file have access to the method. See also: Java, object
Public-Key Forward Secrecy (PFS) For a key agreement protocol based on asymmetric cryptography, the property that ensures that a session key derived from a set of long-term public and private keys will not be compromised if one of the private keys is compromised in the future.
pull Frequently used to describe data sent over the Internet; the act of requesting data from another computer. Example: using your web browser to access a specific page. Contrast to "push" technology when data is sent to you without a specific request being made.
Pull Down 1. To download data or a file from a remote server, typically a file. 2. To remove a file from a public (or publicly accessible) site.
pulldown menu A list of options that "pulls down" when you select a menu at the top of a window. For example, the File menu in most programs is a pulldown menu that reveals commands such as open, new, and save.
Purge (v. to purge) A synonym for deleting something, usually in such a way that it cannot be easily recovered. It is used in several contexts, including the deletion of print jobs from a print queue and the final deletion of files from the NetWare operating system. You can purge print jobs to clean out a print queue that is not behaving, or purge files in NetWare to free up space and fully delete files that were specified for deletion.
Push Push refers to a system in which data is "pushed" to a user's device rather than "pulled" by the user. In other words, the data transfer is initiated by the server rather than the client. Push technology, which is also called "server push," can be used to send news data, stock updates, and other information from the Internet to a user's computer. It is also used to send text messages via SMS to people's cell phones. Push e-mail allows users to receive e-mail messages without having to check their e-mail manually. This means new messages appear on the client's device as soon as they are received by the server. However, in order to receive pushed messages, both the mail server and the user's e-mail client must support push technology. While most information is still "pulled" from the Internet, more kinds of data can now be pushed to users' systems. With push technology, people no longer need to constantly check news sites, e-mail, or other data sources to see if they have been updated. The result is a more efficient means of receiving information.
PWB Printed Wiring Board. Same as PCB, but in Japan is normally referred to as PWB to avoid confusion with "Polychlorinated Biphenyls (PCBs)" which is a poison.
PXE Pre-boot Execution Environment. An Intel standard for booting across a LAN. A workstation boots into the PXE where it can respond to management configuration before loading the operating system.
Python A web scripting language. Python is an open source object oriented programming language.
QA Quality Assurance. The processes (procedure or steps) necessary to give an assurance of quality. QA normally involves some element of testing (which technically is QC) and documentation for audit purposes.
QAZ A network worm.
QBE Stands for "Query By Example." QBE is a feature included with various database applications that provides a user-friendly method of running database queries. Typically without QBE, a user must write input commands using correct SQL (Structured Query Language) syntax. This is a standard language that nearly all database programs support. However, if the syntax is slightly incorrect the query may return the wrong results or may not run at all. The Query By Example feature provides a simple interface for a user to enter queries. Instead of writing an entire SQL command, the user can just fill in blanks or select items to define the query she wants to perform. For example, a user may want to select an entry from a table called "Table1" with an ID of 123. Using SQL, the user would need to input the command, "SELECT * FROM Table1 WHERE ID = 123". The QBE interface may allow the user to just click on Table1, type in "123" in the ID field and click "Search." QBE is offered with most database programs, though the interface is often different between applications. For example, Microsoft Access has a QBE interface known as "Query Design View" that is completely graphical. The phpMyAdmin application used with MySQL, offers a Web-based interface where users can select a query operator and fill in blanks with search terms. Whatever QBE implementation is provided with a program, the purpose is the same – to make it easier to run database queries and to avoid the frustrations of SQL errors.
Quad Abbreviation for Quadruple, meaning 4 or 4 times times.
Queue To avoid any confusion, this term is pronounced exactly like the letter "Q". It is not pronounced "kay" or "kyoo-ee" like some people seem to think it is. A queue is a list of jobs that are awaiting to be processed. When a job is sent to a queue, it is simply added to the list of jobs. Computer programs often work with queues as a way to order tasks. For example, when the CPU finishes one computation, it will process the next one in the queue. A printer queue is a list of documents that are waiting to be printed. When you decide to print a document, it is sent to the printer queue. If there are no jobs currently in the queue, the document will be printed immediately. However, if there are jobs already in the queue, the new document will be added to the list and printed when the others have finished. Most printers today come with software that allows you to manually sort, cancel, and add jobs to the printer queue. While this may not seem like a great benefit for the typical home user, it can be a helpful tool for businesses where many people share one printer.
QuickTime This is a digital video standard developed for Apple Macintosh computers. Special viewing applications are needed to run QuickTime movies.
QWERTY This term is used to describe a standard (Latin alphabet-based) keyboard. Why? Because the first six keys in the upper-left part of the keyboard spell out Q-W-E-R-T-Y. I suppose you could call it a QWERTYUIOP keyboard, but QWERTY is a lot easier to say. In case you are wondering why the QWERTY keyboard is arranged like it is, the original reason was to reduce the jamming of typebars in typewriters as they moved to strike the paper. In 1932, August Dvorak developed what was intended to be a more efficient keyboard, in which he placed the vowels and the five most common consonants in the middle row, based on the idea that an alternating rhythm would be established between the right and left hands. Though the keys on the Dvorak keyboard were more efficienty arranged, it was and still is too much of a pain for people to switch from the familiar QWERTY arrangement.
Race Condition A race condition exploits the small window of time between a security control being applied and when the service is used.
Rack A metal frame used for holding server computers and networking equipment. A standard rack is 19″ wide. There are wider racks that are 23″ wide, built to hold wider equipment. Racks range in height, but are typically either 24 or 42 rack units, with each unit being 1.75″.
Rack Units (U) This refers to the distance of 1.75″ between screw holes in a rack used to hold server equipment. Most computer equipment racks are between 24 and 42 rack units in height. If you are shopping for rack equipment, keep in mind the height of the rack you have to work with and the “U” rating of the equipment. Heights of 1U indicate equipment that can fit into a 1.75″ tall rack space, and 2U would indicate twice that at 3.5″, and so forth with 3U, 4U, and up.
RAD rapid application development The generic name for tools and techniques designed to make it easy to quickly assemble the skeleton of an application, especially the user interface. For example, programs such as Visual Basic and PowerBuilder, which provide tools for easily creating and linking dialog boxes, are considered RAD tools.
Radiation Monitoring Radiation monitoring is the process of receiving images, data, or audio from an unprotected source by listening to radiation signals.
RADIUS Remote Authentication Dial-In user Service (on W2K). Support for dial-up networking. Provides authorization, identification, authentication and accounting services for distributed dial-up networking.
RAID Redundant Array of Inexpensive Disks. The idea of a RAID is to combine a number of disk drives to give better performance, capacity and reliability than could be achieved by a single disk. For a description of the different types of RAID see RAID level. Sometimes also referred to as a RAID Array.
RAID 0 Also known as disk striping, this form of RAID combines two or more hard drives into a single logical drive. Any data is written in blocks first to one drive, then the next, and so on. A RAID 0 configuration sacrifices redundancy for raw speed. The more drives you use the faster your logical drive will be. The space available on the logical drive is the sum of space on all of the drives used, assuming that all drives are the same size. If drives are of disparate sizes, RAID 0 generally only uses a piece of the drive equal to the smallest drive. Of course, if one drive dies, you lose all of the information on the entire RAID. Use RAID 0 with care.
RAID 1 There are two forms of RAID 1: disk duplexing and disk mirroring. Disk mirroring involves two hard drives that are on the same drive controller. The same data is written to both drives, so write operations are slower because you must write data to two drives. Read operations are the same speed, as if you only had one drive. Disk duplexing is much like disk mirroring, but each drive is on a separate controller. This speeds up the normally slow write operations and also adds an additional level of redundancy, in case one of your controller cards dies. With RAID 1 you get half the space you paid for because you’re writing twice as much data.
RAID 10 This form of RAID was originally called RAID 1+0, and is now commonly referred to as RAID 10. This is basically a bunch of RAID 1 drives linked together with RAID 0. Hence you get the speed benefits of RAID 0 with the redundancy benefits of RAID 1. The only problem is that you use a lot of drives to do it. Like RAID 1, you only get half of the space that you’ve paid for. Of course it may be worth it if you can rest easier at night. RAID 10 is generally a bit faster than RAID 5.
RAID 2 This form of RAID protection stripes data across two or more drives, and also stripes an ECC parity code across one or more drives. This code is used to verify that the data read and written is correct. As more data drives are used, you want to increase the number of parity drives to increase performance. This RAID type is not often used.
RAID 3 A form of RAID protection that uses at least three drives, where one drive holds all of the parity data. The other two or more drives contain data striped across them in bits or bytes. This RAID type is not often used.
RAID 4 This is similar to RAID 3 in that an extra drive is used to store all parity information. However, data is striped by drive sector instead of by bits or bytes, so that read operations are faster. This RAID type is not often used.
RAID 5 A RAID 5 configuration utilizes three or more hard drives and stripes the data across them, much like RAID 0. The difference is that parity information is striped across the drives as well, so if you lose any one drive the information can be reconstructed from the parity information. For example, with three drives the first stripe is data (on drive 1), data (on drive 2), parity (on drive 3); then data, parity, data; then parity, data, data. This pattern continues. If one drive fails, you get a mix of parity and data on the remaining two drives, and you can reconstruct all of the data. Of course, before the data is reconstructed the RAID operates in “degraded mode” and is slow. To reconstruct the data you must remove the failed drive and replace it with another, or use a “hot spare.” During reconstruction the array continues to be slow. Once the RAID is reconstructed performance returns to normal levels. RAID 5 performance is similar to RAID 0 performance, but a bit slower due to the parity information. Performance increases, like RAID 0, when more drives are added. With RAID 5 you get most of the space that you’ve paid for, minus one drive’s worth. A common option with RAID 5 is the hot spare, where a drive sits idle until needed. If you lose a drive, the hot spare takes over and the RAID is rebuilt automatically. Of course you still get the performance penalty during the rebuilding stage, but it can be set to happen automatically.
RAID Array A set of disks arranged as a RAID. See RAID for details.
RAID Level RAID level is a number indicating the type of organisation of disks in the RAID array: RAID 0 Striping. No redundancy. Fastest. Provides maximum storage. No fault tolerance. RAID 1 Disk mirroring. Good performance. Fault tolerant. Only fault tolerant option if using 2 drives. RAID 2 Error correction data written to separate disk. RAID 3 Striping (small stripe size) with one parity disk. RAID 4 Striping (large stripe size) with one parity disk. RAID 5 Striping with parity. Parity information is distributed across all drives. Good performance. Fault tolerant. Slowest to rebuild (if one disk is replaced). Better storage than RAID 1. Requires at least 3 disks. Tolerant of a single disk failure. RAID 6 RAID 5 with an extra parity disk. Tolerant of two disks failing. RAID 0+1 Mirrored array (RAID 1) whose segments are RAID 0 arrays, i.e. mirroring of striped sets. RAID 10 Striped array (RAID 0) of mirrored sets (RAID 1). RAID 53 Combination of RAID 0 and RAID 3. Each stripped set (of RAID 0) are RAID 3 sets.
RAM Random Access Memory. Fast, semi-conductor based memory in a computer. It is called "Random Access" because the computer can access any part of the memory directly.
RAMDAC RAMDAC random access memory digital-to-analog converter This microchip sits on a VGA card or other graphics display board and translates the digital representation of a screenful of information into an analog signal that the monitor can display. The faster the RAMDAC (measured in MHz), the higher the screen refresh rates that the card will support at each given resolution. See also: refresh rate
Rar (.rar) The file extension of a type of compressed file created by the WinRAR program by RarSoft. It is considered by many to be more versatile than other compression programs on the market such as WinZip, has a better compression ratio, and is used by many to send archived data over the Internet due to its superior compression in many circumstances.
RARP Reverse Address Resolution Protocol. A protocol used to resolve an IP address from a hardware address (MAC address). cf ARP.
RAS 1. Remote Access Service. 2. RAS Encryption. Named after its inventors Professors Rivest, Adleman and Shamir. RAS is an asymmetrical encryption technique. cf DES.
Raster Graphic Most images you see on your computer screen are raster graphics. Pictures found on the Web and photos you import from your digital camera are raster graphics. They are made up of grid of pixels, commonly referred to as a bitmap. The larger the image, the more disk space the image file will take up. For example, a 640 x 480 image requires information to be stored for 307,200 pixels, while a 3072 x 2048 image (from a 6.3 Megapixel digital camera) needs to store information for a whopping 6,291,456 pixels. Since raster graphics need to store so much information, large bitmaps require large file sizes. Fortunately, there are several image compression algorithms that have been developed to help reduce these file sizes. JPEG and GIF are the most common compressed image formats on the Web, but several other types of image compression are available. Raster graphics can typically be scaled down with no loss of quality, but enlarging a bitmap image causes it to look blocky and "pixelated." For this reason, vector graphics are often used for certain images, such as company logos, which need to be scaled to different sizes. File extensions: .BMP, .TIF, .GIF, .JPG
RAT Remote Access Trojan. Trojan allowing an attacker to remotely access or control a computer.
Raw Data Raw data is unprocessed computer data. This information may be stored in a file, or may just be a collection of numbers and characters stored on somewhere in the computer's hard disk. For example, information entered into a database is often called raw data. The data can either be entered by a user or generated by the computer itself. Because it has not been processed by the computer in any way, it is considered to be "raw data." To continue the culinary analogy, data that has been processed by the computer is sometimes referred to as "cooked data."
Raw disk A hard disk in a virtual machine that is mapped to a physical disk drive in the host machine. A virtual machine's disk can be stored as a file on the host file system (see Virtual disk) or on a local IDE raw disk device. When a virtual machine is configured to use a raw disk, VMware directly accesses the local disk/partition as a raw device (not as a file on a file system). It is possible to boot a previously installed operating system on an existing partition within a virtual machine environment. The only limitation is that the existing partition must reside on a local IDE or SCSI drive. See also Safe raw disk file, Virtual disk.
Raw File A raw file is a collection of unprocessed data. This means the file has not been altered, compressed, or manipulated in any way by the computer. Raw files are often used as data files by software programs that load and process the data. A popular type of raw file is "Camera RAW," which is generated by a digital camera. Instead of processing the image captured by the camera, the data is left unprocessed and uncompressed until it is opened with a computer program.
RBL Real-time Black-hole List or Real-time Block List. RBLs hold information about blocked sites, typically used to list site that generate spam. RBL is sometimes used as an alternative name to DNSBL, see DNSBL for more details.
RC1 Release Candidate 1, i.e. the first (beta) release of something. cf RC.
RC2 Release Candidate 2, i.e. the second (beta) release of something. cf RC.
RDBMS Relational Database Management System. cf DBMS.
RDC 1. Remote Desktop Connection. RDC is a Windows technology that allows any client running the necessary client software to connect to a Routing and Remote Access server (or terminal server) and then run applications and use the remote server in the same way as if using the local PC - the "desktop" on the remote server is viewed in a window (full screen by default). This technology allows someone to remotely login to either a pc running Windows XP or Windows server.
RDF Stands for "Resource Description Framework." RDF is a specification that defines how metadata, or descriptive information, should be formatted. The RDF model uses a subject-predicate-object format, which is a standardized way of describing something. For example, an RDF expression may read, "The computer has a hard drive that stores 250GB." "The computer" is the subject, "has a hard drive that stores" is the predicate, and "250GB" is the object. RDF formatting is used in RSS feeds, which contain short descriptions of Web pages. The RDF standard helps ensure each description contains the subject, predicate, and object necessary to describe the page's content. While humans do not require descriptions to be formatted in such a specific way (we would actually find it rather monotonous), computers benefit from the standard formatting. For example, it makes it easier for computer systems to sort and index RSS feeds based on the RDF descriptions. The end result is more accurate results when people search for articles using keywords.
RDNS In computer networking, reverse DNS lookup or reverse DNS resolution (rDNS) is the determination of a domain name that is associated with a given IP address using the Domain Name System (DNS) of the Internet. Computer networks use the Domain Name System to determine the IP address associated with a domain name. This process is also known as forward DNS resolution. Reverse DNS lookup is the inverse process of this, the resolution of an IP address to its designated domain name. The reverse DNS database of the Internet is rooted in the Address and Routing Parameter Area (arpa) top-level domain of the Internet. IPv4 uses the in-addr.arpa domain and the ip6.arpa domain is delegated for IPv6. The process of reverse resolving an IP address uses the pointer DNS record type (PTR record). Internet standards documents (RFC 1033, RFC 1912 Section 2.1) specify that "Every Internet-reachable host should have a name" and that such names match with a reverse pointer record.
RDP Remote Desktop Protocol. RDP is the protocol used by (Windows) RDC for communications between a terminal server and terminal server client.
Read Only This means that the object cannot be written to, which means that you can’t save any modifications you make to it. An operating system can have a file set to read-only for security purposes, or certain media, like a CD-ROM or DVD-ROM, is read-only by design and cannot be altered.
Readme A readme file, often named "READ ME" to get the user's attention, is a text file containing useful information about a software program. It often accompanies the program's installer or is installed with the program. A typical readme file contains instructions on how to install the program, how to use the basic functions of the program, and what the program does. It may also include a list of recent updates made to the program. Sometimes the readme file will include warnings and other important notices regarding the operation of the program. So when you see a readme file accompanying a new software program, it is best to do what the file says and read it!
Real-Time When an event or function is processed instantaneously, it is said to occur in real-time. To say something takes place in real-time is the same as saying it is happening "live" or "on-the-fly." For example, the graphics in a 3D action game are rendered in real-time by the computer's video card. This means the graphics are updated so quickly, there is no noticeable delay experienced by the user. While some computer systems may be capable of rendering more frames per second than other systems, the graphics are still being processed in real-time. While video games often require real-time rendering, not all graphics are rendered in real-time. For example, some complex 3D models and animations created for movies are not rendered in real-time, but instead are pre-rendered on a computer system so they can be played back in real-time. As graphics cards get increasingly faster, they are capable of rendering some 3D animations in real-time that previously would need to be pre-rendered. Real-time also describes the way streaming media is processed. Instead of waiting for a file to completely download, the information is played back as it is downloaded. This allows for news broadcasts, sound clips, and other streaming audio and video data to be played live from the Internet. Thanks to real-time processing, people can access information without having to wait for it. This is an important benefit since these days, anything that takes longer than 5 seconds seems like a long time.
RealPlayer A program or plug-in that gives you access to multimedia files, both on the Internet and those stored locally on your computer. With the program you can find and play clips (e.g., video, audio, video with audio, etc.) without having to launch your web browser first. The plug-in works in conjunction with your web browser to allow you to access streaming media files.
Realtek Realtek Semiconductor Corp Products Realtek manufactures and sells a wide variety of products throughout the world, and its product lines can be broadly categorized into two subdivisions: Communications Network ICs, and Computer Peripheral and Multimedia ICs. Included among the communications network IC products manufactured and provided by Realtek are: network interface controllers (both the traditional 10/100M Ethernet controllers and the more advanced Gigabit Ethernet controllers), physical layer controllers (PHYceivers), network switch controllers, gateway controllers, wireless LAN ICs, as well as ADSL router controllers. In particular, the RTL8139 series 10/100M Fast Ethernet controllers met their height during the late 90’s, and continued to take up a significant, and eventually predominant share in the worldwide market in the following years. Those devices categorized as Realtek’s computer peripheral and multimedia IC products consist of the traditional AC97 audio codecs, the High Definition audio codecs, card reader controllers, clock generators, IEEE 1394 ICs, and LCD controllers. Realtek Headquarters in Hsinchu Science Park The most notable Realtek products are 10/100M Ethernet controllers, with a global market share of 70% as of 2003, and AC97 audio codecs, where Realtek's market share is 50%, primarily concentrated in the integrated OEM on-board audio market segment. Presently the ALC850 and RTL8139 are particular OEM favorites, offering low prices, and basic feature sets. RTL8139-based NICs are dubbed "crab cards" in Taiwan, alluding to the crab-like appearance of the Realtek logo. It has been announced or projected, on several different occasions, that Realtek will, in the future, focus its R&D resources in the field of digital television technologies, as well as more advanced wireless communications technologies such as ultra-wide band (UWB) communications and the yet-to-be-realized 802.11n standard. It seems clear that Realtek has been setting its eye on pursuing the Holy Grail of the anticipated new applications and needs derived from the concept of Digital home
Reboot To restart a computer. It comes from “boot,” which is a term that means starting the operating system on the computer. When you are using your computer and have weird problems, the tech guy comes over and says, “Time to reboot.” If you are the tech guy you’ll find yourself saying this far too often.
Reconnaissance Reconnaissance is the phase of an attack where an attackers finds new systems, maps out networks, and probes for specific, exploitable vulnerabilities.
record A set of fields that contain related information; in database type systems, groups of similar records are stored in files. Example: a personnel file that contains employment information.
Recursion Recursion is a process in which a function calls itself as a subroutine. This allows the function to be repeated several times, since it calls itself during its execution. Functions that incorporate recursion are called recursive functions. Recursion is often seen as an efficient method of programming since it requires the least amount of code to perform the necessary functions. However, recursion must be incorporated carefully, since it can lead to an infinite loop if no condition is met that will terminate the function.
Recursive Function A recursive function is a function that calls itself during its execution. This enables the function to repeat itself several times, outputting the result and the end of each iteration. Below is an example of a recursive function. function Count (integer N) if (N <= 0) return "Must be a Positive Integer"; if (N > 9) return "Counting Completed"; else return Count (N+1); end function The function Count() above uses recursion to count from any number between 1 and 9, to the number 10. For example, Count(1) would return 2,3,4,5,6,7,8,9,10. Count(7) would return 8,9,10. The result could be used as a roundabout way to subtract the number from 10. Recursive functions are common in computer science because they allow programmers to write efficient programs using a minimal amount of code. The downside is that they can cause infinite loops and other unexpected results if not written properly. For example, in the example above, the function is terminated if the number is 0 or less or greater than 9. If proper cases are not included in the function to stop the execution, the recursion will repeat forever, causing the program to crash, or worse yet, hang the entire computer system.
Recycle Bin The Recycle Bin in used by Windows computers to store deleted items. It temporarily stores files and folders before they are permanently deleted. You can open the Recycle Bin by double-clicking the icon on the Windows desktop. The Recycle Bin window allows you to delete items individually or restore them to their original location. If you want to permanently remove all items in the Recycle Bin, select "Empty the Recycle Bin" in the left sidebar of the window.
Red Hat Linux Red Hat Linux, assembled by the company Red Hat, was a popular Linux based operating system until its discontinuation in 2004.[1] Red Hat Linux 1.0 was released on November 3, 1994. It was originally called "Red Hat Commercial Linux"[2] It was the first Linux distribution to use the RPM Package Manager as its packaging format, and over time has served as the starting point for several other distributions, such as Mandriva Linux and Yellow Dog Linux. Since 2003, Red Hat has discontinued the Red Hat Linux line in favor of Red Hat Enterprise Linux (RHEL) for enterprise environments. Fedora, developed by the community-supported Fedora Project and sponsored by Red Hat, is the free version best suited for home use. Red Hat Linux 9, the final release, hit its official end-of-life on 2004-04-30, although updates were published for it through 2006 by the Fedora Legacy project until that shut down in early 2007.
Red Hat Package Manager (RPM) A packaging system based on files with the .rpm extension that contain dependency information, pre- and post-install scripts, and the actual user runtimes (files/executables) that are part of the package. Windows users might think of this as an .msi file commonly used to hold pre-installation data
Redundancy In a redundant system, if you lose part of the system, you can continue to operate. For example, if you have two power supplies and one takes over if the other one dies, that is a form of redundancy. You can take redundancy to extreme levels, but you spend more money. Redundancy is one reason that high-end server machines cost 10 times more than desktop PCs.
Redundant Array of Inexpensive Drives (RAID) A method of linking storage devices together so that they function as a single logical unit. RAID requires all drives to be of the same size, as compared to JBOD setups. RAID can be used for increased performance, but is also used to increase redundancy.
Reflexive ACLs (Cisco) Reflexive ACLs for Cisco routers are a step towards making the router act like a stateful firewall. The router will make filtering decisions based on whether connections are a part of established traffic or not.
Refresh Refresh is a command that reloads the contents of a window or Web page with the most current data. For example, a window may list files stored within a folder, but may not track their location in real-time. If the files have been moved or deleted since the window was first opened, the folder contents displayed will be inaccurate. By refreshing the window, a current list of files is displayed. Web browsers include a Refresh command, which reloads the contents of a Web page. This is especially useful for dynamic Web pages, which contain content that changes often. For example, a page may include a stock quote, which is updated every few seconds. By refreshing the page, a user can see the latest quote and track how much the stock continues to drop since he bought it. Web developers may also use the Refresh command to view recently published changes to Web pages. Since refreshing a window reloads it with new information, the terms "refresh" and "reload" are often used synonymously. In fact, some Web browsers, such as Firefox and Safari use the term "Reload" instead of "Refresh." In Windows, the shortcut key for the Refresh command is typically "F5," while on the Mac, the shortcut is often "Command-R." The term "Refresh" may also refer to the redrawing process of a computer monitor. This process usually happens many times per second and is called the "refresh rate."
Refresh Rate Computer monitors often have a "maximum refresh rate" listed in their technical specifications. This number, measured in hertz (Hz), determines how many times the screen is redrawn each second. Typical refresh rates for CRT monitors include 60, 75, and 85 Hz. Some monitors support refresh rates of over 100 Hz. The higher the refresh rate, the less image flicker you will notice on the screen. Typically a refresh rate of less than 60 Hz will produce noticeable flicker, meaning you can tell the screen is being redrawn instead of seeing a constant image. If the refresh rate is too slow, this flicker can be hard on your eyes and may cause them to tire quickly. As if sitting at a computer for several hours wasn't hard enough! To avoid flicker, you should set your monitor to use the maximum refresh rate possible. This setting is found in the Monitors control panel in Windows and the Displays system preference in Mac OS X. While 60 Hz is considered a good refresh rate, some people will find that 85 Hz is significantly better. The maximum refresh rate is determined by three factors: 1) The rate your video card supports, 2) the rate your monitor supports, and 3) the resolution your monitor is set at. Lower resolutions (i.e. 800x600) typically support higher refresh rates than higher resolutions (i.e. 1600x1200). If you have an LCD monitor, you may not be able to adjust the refresh rate. This is because most LCD monitors come with a standard refresh rate that is well above the "flicker" point. LCD monitors produce less flicker than CRT monitors because the pixels on an LCD screen stay lit longer than CRT monitors before they noticeably fade.
Registry The central database containing system configuration information on Windows systems. The registry is organised as a hierarchical tree, and allows applications as well as Windows itself to store configuration information in a structured manner.
Regression analysis The use of scripted tests which are used to test software for all possible input is should expect. Typically developers will create a set of regression tests that are executed before a new version of a software is released. Also see "fuzzing".
regular expression A regular expression is a way of expressing a text pattern for the purpose of matching a string. Regular expressions are often used either to extract information from a string or to verify that a string is of the correct format. When referred to, regular expressions are often abbreviated to simply "regex". The following table provides examples of regular expressions: Regex Meaning . A dot matches any single character. c.t Matches "cat", "cbt" ... "c1t" ... "c&t" etc (with anything before the "c" and anything after the "t"). [0-9] Matches anything inside the square brackets against a single character; so in this case any single character in the range 0 to 9. [09] Matches anything inside the square brackets against a single character; in this case the single character 0 or 9 (but not 1 to 8). This can be useful if you don't know the case of something, because [aA] will match either a or A. [0-9a-zA-Z] Matches any single character in the range 0 to 9 or a to z or A to Z. ? Matches the preceding element one time or zero times. This is equivalent to {0,1} * Matches the preceding element zero or more times. *? Matches the preceding element zero or more times, but unlike * will match against the shortest possible match. For example "b[an]*a" when applied to the word "banana" will match the entire word, but "b[an]*?a" will match with just "ban". a[0-9]*z Will match against "az", "a1z" ... "a999z" etc. + Matches the preceding element one or more times. +? Matches the preceding element one or more times, but unlike + will match against the shortest possible substring.. a[0-9]+z Will match against "a1z" ... "a999z" etc (but not "az"). {number} Matches the preceding element the specified number of times. a[0-1]{2}z Will match against "a00z", "a10z", "a01z" and "a11z". {min,max} Matches the preceding element a minimum of "min" times at at most "max" times. a[0-1]{1,2}z Will match against "a0z", "a1z", "a00z", "a10z", "a01z" and "a11z". [^...] Inverts a match - matches anything except. a[^0-1]z Will match against any three letter string starting with "a", ending with "z" that is not "a0z" or "a1z". ^ Matches at the start of the line. $ Matches at the end of the line. \ Escape character. Allows the following character to be treated as a literal rather than having a special meaning. Thus \+ would match against + rather than + having its normal meaning. This also means that to include a \ as a slash you would need to use \\ (to escape the slash). \A Matches at the start of the string. When dealing with a single line expression \A is equivalent to ^. Note: \A is not supported on all implementations. \Z Matches at the end of the string. When dealing with single line expressions \Z is equivalent to $. Note: \Z is not supported on all implementations. \xNN Will match against the single character with the hex code 'NN'. So \x09 will match against a tab character and \x20 will match against a space. See www.cryer.co.uk/brian/misc/ascii_table.htm for a list of hex codes for ASCII characters. \t Match against the TAB character (same as \x09). \n Match against a new-line (same as \x0a). \r Match against a carriage return (same as \x0d). \f Match against a form-feed (same as \x0c). \a Match against a bell character (same as \x07). \b Match against a word boundary. A word boundary will match against any of: (i.) The beginning of the string, (ii.) the end of the string or (iii.) anything which is not [a-zA-Z0-9_] \e Match against an escape character (same as \x16) \r\n Match against a carriage return line feed combination (in that order). \w Match against any alphanumeric character (i.e. 0 to 9, a to z, A to Z and the underscore). \W Match against any non-alphanumeric character. \d Match against any numeric character. \D Match against any non-numeric character. \s Any space (same as [ \t\n\r\f]). \S Match against any non-space. one|two Match everything to the left of the bar ('|') or everything to the right, so in this case "one" or "two". ( … ) Brackets define a group or sub-expression. When a regular expression is used in a situation where the contents of a match need to be extracted then brackets define the group or sub-expression the matching value of which can be retrieved. \b(one|two)\b Match against the whole word "one" or the word "two", specifically it matches against a word boundary, then "one" or "two", followed by another word boundary.
Reimage Reimaging is the process of restoring data to a hard disk from a disk image. When a hard disk is reimaged, the data on the disk is completely erased and rewritten using data from the disk image file. Therefore, reimaging is often done from a recent backup, which allows the user's personal data to be recovered. Reimaging is simpler than reinstalling an operating system since it is performed in a single step, rather than requiring numerous files and programs to be installed.
Relative URL An URL that does not include strict directory information; instead, you give the link directions like “back two directories and up one directory” in standard command line format like “../../imagedir/image.jpg”. This way you can change domain names or IP addresses of your webserver and not have to recode your HTML pages. However, if you change directory names (or depth), you must change even your relative URLs.
Release Engineer The individual whose job it is to oversee the mechanics of the development process of software. The release engineer controls when new code is entered into the current working release, and makes sure the proper pieces of code are compiled and ready when the program has to be sent to a media duplication plant, or simply made live on a network.
RELEVANCY RANKING of search results The most common method for determining the order in which search results are displayed. Each search tool uses its own unique algorithm. Most use "fuzzy and" combined with factors such as how often your terms occur in documents, whether they occur together as a phrase, and whether they are in title or how near the top of the text. Popularity is another ranking system.
Remote Access Remote access is just what it sounds like -- the ability to access your computer from a remote location. Programs like PC Anywhere (Windows), Remote Access (Mac), and Timbuktu (Windows and Mac) allow users to control remote computers from their local machine. In order for a remote access connection to take place, the local machine must have the remote client software installed and the remote machine must have the remote server software installed. Also, a username and password is almost always required to authenticate the connecting user. Remote access is more than just being able to connect to a remote machine -- it is the ability to control the machine once the connection has been made. A remote access program can basically transform your local computer into the the remote computer you connect to. This is great for people who sometimes work from home and for server administrators who frequently need to update and make changes on their server machines. Most remote access programs also allow users to transfer files between the local and remote machines, which can save a lot of commuting time. While remote access can be helpful for many people, don't enable it on your machine unless you absolutely need to. It is just one more security concern you will have to deal with.
Remote Control A means of taking control of a remote computer, usually on a remote network. Programs like Symantec’s pcAnywhere and a host of others offer this ability. Usually you connect to the remote computer via the Internet or a phone line, and control the computer by interacting with your computer while seeing on your screen a representation of what is actually happening on the remote computer. The downside to remote control is that each remote connection requires a separate computer. You can’t easily have multiple people controlling one computer remotely and seeing a useful representation of what is on the remote display. See also remote access.
Remote Desktop Remote desktop technology makes it possible to view another computer's desktop on your computer. This means you can open folders, move files, and even run programs on the remote computer, right from your own desktop. Both Windows and Macintosh computer support remote desktop connections, though they use different implementations. Windows XP and Vista both include Remote Desktop as part of the operating system. The Remote Desktop program uses Microsoft Terminal Services and the Remote Desktop Protocol (RDP) to connect to a remote machine. Remote connections can be opened using Windows' Remote Desktop Connection (RDC), which is also referred to as Terminal Services Client (TSC). This program allows users to configure and manage remote connections to other computers. Of course, to connect to another machine, the remote system must be configured to accept incoming RDC connections. A Windows computer can be configured to accept incoming remote desktop connections by opening the Control Panel and selecting "Performance and Maintenance." Then click the "System" icon and select the "Remote" tab in the System Properties window. Next, check the box that says, "Allow users to connect remotely to this computer." Then click OK. This should enable remote desktop connections to your machine. You can then click "Select Remote Users..." to only provide access to specific users. Of course, if you don't want your computer to be accessed by anyone, leave the "Allow users to connect..." box unchecked. Mac OS X 10.5 and later includes a feature called Screen Sharing that allows other users to remotely access the computer's desktop. To turn on Screen Sharing, open System Preferences and select the Sharing option. Next, check the "Screen Sharing" check box. You can then add access for specific users in the "Allow access for:" section of the window. If the Mac OS X Screen Sharing option feels a bit limited, you may want to try a program called "Apple Remote Desktop." This program, which is developed by Apple, provides more advanced remote access features and is often used for managing several computers on a network.
Remote User A "remote user" is how a woman might refer to her husband while he is watching TV. In the computer world, however, a remote user is someone who works on a computer from a remote location. For example, if Bob leaves work and forgets to bring a file with him from his office computer, he might be able to connect to his work machine from his home computer and grab the file. When Bob accesses his office computer from home, he is considered a remote user.
Removable Canister A removable hard drive casing. There are two parts to the canister: the bay itself, and the casing that goes around the hard drive. These canisters can be used with SCSI or IDE/ATA hard drives, and have the advantage of easy portability of hard drives, especially if you have multiple computers with the same type of bay in them. Integrating a bare hard drive into a removable canister can be an annoying chore, as space is limited and you have lots of extra wires to deal with. This term can also be used to refer to the hard drives that are used in server machines and integrated into cases that can be plugged into servers and removed easily. Removable canisters can be hot pluggable, but usually only in servers with RAID systems.
Removable Storage This type of storage allows you to remove the actual storage media from a drive and replace it with other media. DVD-ROM, CD-ROM, floppy drives, and Zip drives are all forms of removable storage.
Render (v. to render) This synonym for hacking up animals for human consumption determines how colors are used on each triangle displayed in a 3D image. Very complex images take a long time to render; less complex 3D images, such as those in a 3D game, can be rendered in real time. When they make computer animated movies or effects of very high quality, effects companies use many computers to render images.
Repeater A device used to repeat a signal to send it further away or to many more devices. The earliest network hubs are also called repeaters, as they had no switching capabilities but would only repeat the same signal to all ports.
Request for Comment (RFC) A series of notes about the Internet, started in 1969 (when the Internet was the ARPANET). An Internet Document can be submitted to the IETF by anyone, but the IETF decides if the document becomes an RFC. Eventually, if it gains enough interest, it may evolve into an Internet standard.
Reseller Anyone who buys computer equipment or software and sells it. In most states in the U.S. you need a reseller license to purchase goods without paying taxes, and then you are responsible for collecting and paying taxes on the goods you resell. The combined entity of all the resellers makes up the channel. Resellers usually buy goods from large distributors and sell them to companies or consumers.
Resistor A two-terminal electronic component that resists an electrical current and turns the extra current into heat. Resistors are rated in ohms, and can be used to regulate the voltage and current in a circuit. Basically, a resistor resists the flow of electricity. Resistors are used to lower voltages and currents so that components that require smaller voltage/current can function properly. If a power supply puts out 12 volts and you have a chip that runs on three, you need a resistor to cut down the voltage.
Resolution This term can describe either how many pixels a monitor can display or how fine a printer can print. 1. Monitors. A small monitor may have a resolution or 640 x 480, which means there are 640 pixels horizontally across the screen and 480 pixels vertically. Some other common monitor resolutions are 800 x 600, 1,024 x 768, and 1,280 x 1,024. The higher the resolution, the more that can be displayed on the screen. 2. Printers. Printer resolution measures how fine a printer can print. This measurement is known as dots per inch, or "dpi." The greater the dpi, the better the image clarity. Scanner resolution is also measured in dpi.
Resource Exhaustion Resource exhaustion attacks involve tying up finite resources on a system, making them unavailable to others.
Response A response is information sent that is responding to some stimulus.
Restart The process of an operating system on a computer shutting down, and then starting back up automatically. During a restart the user does not need to hit the power switch.
Retention Mechanism This typically refers to the mechanisms attached to a motherboard that hold onto a Slot 1, Slot 2, or Slot A cartridge so that it doesn’t come loose during usage or shipping. The mechanism is usually made of black plastic, and holds the processor cartridge in place.
Reverse Address Resolution Protocol (RARP) RARP (Reverse Address Resolution Protocol) is a protocol by which a physical machine in a local area network can request to learn its IP address from a gateway server's Address Resolution Protocol table or cache. A network administrator creates a table in a local area network's gateway router that maps the physical machine (or Media Access Control - MAC address) addresses to corresponding Internet Protocol addresses. When a new machine is set up, its RARP client program requests from the RARP server on the router to be sent its IP address. Assuming that an entry has been set up in the router table, the RARP server will return the IP address to the machine which can store it for future use.
Reverse DNS lookup In computer networking, reverse DNS lookup or reverse DNS resolution (rDNS) is the determination of a domain name that is associated with a given IP address using the Domain Name System (DNS) of the Internet. Computer networks use the Domain Name System to determine the IP address associated with a domain name. This process is also known as forward DNS resolution. Reverse DNS lookup is the inverse process of this, the resolution of an IP address to its designated domain name. The reverse DNS database of the Internet is rooted in the Address and Routing Parameter Area (arpa) top-level domain of the Internet. IPv4 uses the in-addr.arpa domain and the ip6.arpa domain is delegated for IPv6. The process of reverse resolving an IP address uses the pointer DNS record type (PTR record). Internet standards documents (RFC 1033, RFC 1912 Section 2.1) specify that "Every Internet-reachable host should have a name" and that such names match with a reverse pointer record.
Reverse Engineering The process of understanding a system without knowing how the system actually functions internally, but only judging how the system responds to various inputs. In that way a company can create a product with similar or equivalent behavior to another company’s product without infringing on that company’s patents.
Reverse Lookup Find out the hostname that corresponds to a particular IP address. Reverse lookup uses an IP (Internet Protocol) address to find a domain name.
Reverse Proxy Reverse proxies take public HTTP requests and pass them to back-end webservers to send the content to it, so the proxy can then send the content to the end-user.
Revolutions per Minute (RPM) A measurement that applies commonly to hard drives, and removable drives like CD-ROMs and DVD-ROMs. It also applies to anything that moves in a circular motion. If you are using a drive with higher RPMs, you usually have better performance. Since the disk is spinning faster the drive can usually read data at a faster rate. For example, 5,400 RPM hard drives are generally slower than 7,200 RPM hard drives. The downside to higher RPM rates is that it is harder to stabilize and read data from a disk that is spinning faster, so the mechanism may be more complex and more expensive. Also, faster spinning drives are usually louder and run hotter.
Rewriteable This means that what was written can be erased so that it can be written to again. CD-R media is not rewriteable, but CD-RW media is. It is also more expensive. Floppy disks and hard drives are rewriteable as well.
RFC Request For Comments) The name of the result and the process for creating a standard on the Internet. New standards are proposed and published on the Internet, as a Request For Comments. The proposal is reviewed by the Internet Engineering Task Force (http://www.ietf.org/), a consensus-building body that facilitates discussion, and eventually a new standard is established, but the reference number/name for the standard retains the acronym RFC, e.g. the official standard for e-mail message formats is RFC 822.
RGB Red, Green, Blue. The three primary colours which together make white. Shown using their respective colours: Red, Green and Blue. When displaying colour on computer monitors (or TVs and projectors) colour values are made up of combinations of red, green and blue. Any colour can be represented by the correct proportion of red, green and blue.
Rich Media A type of Internet advertisement that allows for more interaction than a simple click. It may incorporate a useable dropdown menu, radio buttons, or even Flash or Shockwave animation and sound. Some plain graphic ad banners appear to be rich media, but when clicked on they do not interact with the user, merely forwarding the user to a different website using a standard image and link tag.
Right Click Most computer mice have at least two mouse buttons. When you press the left one, it is called a left click. When you press the one on the right, it is called a right click. By default, the left button is the main mouse button, and is used for common tasks such as selecting objects and double-clicking. The right mouse button is often used to open contextual menus, which are pop-up menus that change depending where you click. For example, if you right click on the desktop, you may see a menu pop up that includes "Change View Options" and "Change Desktop Background." If you right click on a folder, the menu might include options such as "Open" and "Properties." Certain programs, such as video games, may use the right click to perform other functions, such as firing a secondary weapon in a first-person shooter. Most programs, however, use the right click to open contextual menus.
Ring topology A network that is connected on both ends to one source, with client machines hanging off of the ring. If you break the ring, all computers in the ring lose connectivity.
RIP 1. Routing Information Protocol. A protocol allowing a router to exchange routing information with other gateways and hosts. RIP versions: RIP-1 Universally supported. Defined by RFC 1058. RIP-2 Carries more ...n RIP-1. Defined by RFC 1389. RIP-2B Sends routing information in RIP-2 format using subnet broadcasting. 2. Raster Image Processor.
Ripcording Recording audio with a computer involves capturing an audio signal and saving it digitally on a hard drive. Ripping an audio track is the process of converting an audio file to an MP3 or other compressed audio format. Ripcording is the simultaneous recording and ripping of an audio signal. Ripcording is a popular way to download and archive Internet radio broadcasts, digital cable TV radio, and satellite radio. All you need is ripcording software that will record audio and compress it at the same time. By ripcording live audio, you can save audio streams on your hard drive and listen to them whenever you want.
RIS Remote Installation Services. Enables administrators to install Windows 2000 professional on client computers throughout a network from a central location.
Riser Card A card that plugs into a motherboard and enables other cards to be plugged into it horizontally. Architectures that support riser cards are typically designed to allow tall cards to be plugged into shorter enclosures. Servers often use riser cards, since if they didn’t the motherboard would be too large to fit into a standard sized enclosure.
Risk Risk is the product of the level of threat with the level of vulnerability. It establishes the likelihood of a successful attack.
Risk Assessment A Risk Assessment is the process by which risks are identified and the impact of those risks determined.
Risk Averse Avoiding risk even if this leads to the loss of oportunity. For example, using a (more expensive) phone call vs. sending an e-mail in order to avoid risks associated with e-mail may be considered "Risk Averse"
RJ-11 In the U. S., telephone jacks are also known as registered jacks, sometimes described as RJ-XX, and are a series of telephone connection interfaces (receptacle and plug) that are registered with the U.S. Federal Communications Commission (FCC). They derive from interfaces that were part of AT&T's Universal Service Order Codes (USOC) and were adopted as part of FCC regulations (specifically Part 68, Subpart F. Section 68.502). The term jack sometimes means both receptacle and plug and sometimes just the receptacle.
RJ-45 The standard Ethernet network connector, supporting 8 copper wires. You plug an RJ-45 cable into an RJ-45 port.
RNDR Reverse NDR (spam attack). A technique used by spammers to use email non-delivery reports (NDRs) to deliver spam.
RO Read Only. Anything that can be read from but not written to (or updated).
ROM (Read Only Memory) Memory containing a program, data, or information about the device that has been programmed onto the chip at the factory and cannot be changed. There is no easy mechanism to write to ROM, but it is usually possible to do it. It’s just not made easy, as writing to ROM is not intended to done.
Root Root, or the "root node," refers to the top level of a file system. Since file systems are organized by directories, the root node is also called the root directory. You can imagine the root directory as the top of an upside down tree, with folders and files spanning beneath it. Root is also the name of the "root user," which is user account that has administrative privileges on a computer system. Unlike other users, the root user can access any file or folder on a the main hard disk. For this reason, the root user of a Unix system is often responsible for performing system updates and account modifications.
Root directory The base directory of an operating system. This term is typically used for the UNIX OS, but can apply to a webserver as the directory to which a browser defaults. It refers to the directory represented by a slash, or “/”, character in UNIX, or a “” character in Windows. To change to the root directory use the command “cd /” in UNIX or “cd ” in Windows.
Rootkit A collection of tools (programs) that a hacker uses to mask intrusion and obtain administrator-level access to a computer or computer network.
Rosetta Rosetta is technology included in Mac OS X that allows software written for PowerPC processors to run on Intel processors. It translates the instructions in PowerPC programs into commands that can be recognized by an Intel-based Macintosh. Rosetta runs behind the scenes, so the user does not see it working. However, because dynamically translates commands from PowerPC to Intel, users may notice some slowdown when running PowerPC programs on Intel-based Macintosh computers.
Router Network device connecting two networks that selectively forwards network packets according to their IP address. cf hub and switch.
Routing Information Protocol (RIP) Routing Information Protocol is a distance vector protocol used for interior gateway routing which uses hop count as the sole metric of a path's cost.
Routing Loop A routing loop is where two or more poorly configured routers repeatedly exchange the same packet over and over.
RPC Stands for "Remote Procedure Call." Most computer programs run procedures, or sets of instructions, using the computer's CPU. In other words, the instructions are processed locally on the same computer that the software is running from. Remote procedure calls, however, run procedures on other machines or devices connected to a network. Once the instructions have been run, the results of the procedure are usually returned to the local computer. For example, a computer without a hard drive may use an RPC to access data from a network file system (NFS). When printing to a network printer, a computer might use an RPC to tell the printer what documents to print. A client system connected to a database server may execute an RPC to process data on the server. Remote procedure calls are based on the client-server model, where multiple client computers may connect to a server and retrieve data from it. RPCs are typically written in a standard format, such as XML, so that the procedures can be understood by multiple computer platforms. For example, an XML-RPC sent by a Windows computer could be recognized by a Macintosh or Unix-based system.
RPC Scans RPC scans determine which RPC services are running on a machine.
RPM Stands for "Revenue Per 1,000 Impressions." RPM is similar to CPM, but measures the revenue from 1,000 ads impressions instead of the cost of the ads. Therefore, while CPM is typically measured by advertisers, RPM is monitored by publishers. For example, a publisher has a website that gets 5,000 page views each day. If the advertisements on the website generate a total of $25.00 of daily revenue, the website has an RPM of $5.00 ($25 ? 5). Web publishers use RPM as a way of measuring how effective advertisements are at generating revenue. If certain advertisements generate a low RPM, publishers will likely switch to different ads that provide higher RPM rates and higher revenue. RPM is not only used in online advertising, but is measured in several other types of advertising mediums as well. Though it somewhat confusing, RPM and CPM are often interchangeably. While CPM stands for "Cost Per 1,000 Impressions," it is commonly used synonymously with RPM to describe the average revenue from the publisher's perspective.
RSS (Rich Site Summary or RDF Site Summary or Real Simple Syndication) A commonly used protocol for syndication and sharing of content, originally developed to facilitate the syndication of news articles, now widely used to share the contents of blogs. Mashups are often made using RSS feeds. RSS is an XML-based summary of a web site, usually used for syndication and other kinds of content-sharing. There are RSS "feeds" which are sources of RSS information about web sites, and RSS "readers" which read RSS feeds and display their content to users. RSS is being overtaken by a newer, more complex protocol called Atom.
RTE Stands for "Runtime Environment." As soon as a software program is executed, it is in a runtime state. In this state, the program can send instructions to the computer's processor and access the computer's memory (RAM) and other system resources. When software developers write programs, they need to test them in the runtime environment. Therefore, software development programs often include an RTE component that allows the programmer to test the program while it is running. This allows the program to be run in an environment where the programmer can track the instructions being processed by the program and debug any errors that may arise. If the program crashes, the RTE software keeps running and may provide important information about why the program crashed. When you see the name of a software program with the initials "RTE" after it, it usually means the software includes a runtime environment. While developers use RTE software to build programs, RTE programs are available to everyday computer users as well. Software such as Adobe Flash Player and Microsoft PowerPoint Viewer allow Flash movies and PowerPoint presentations to be run within the player software. These programs provide a runtime environment for their respective file formats. The most common type of RTE, however, is the Java RTE (or JRE), which allows Java applets and applications to be run on any computer with JRE installed.
RTF Rich Text File. An ASCII file format for the transfer of word processed documents across different types of system while still maintaining their formatting.
RTM Online speak for “Read The Manual.”
RTSP (Real Time Streaming Protocol) RTSP is an official Internet standard (RFC 2326) for delivering and receiving streams of data such as audio and video.
Ruby An object oriented scripting language. It has a similar syntax and design philosophy to Perl.
Rule Set Based Access Control (RSBAC) Rule Set Based Access Control targets actions based on rules for entities operating on objects.
Runtime When a program is running, or executing, it is said to be in runtime. The term is mostly used by software developers to specify when errors in a program occur. A "runtime error" is an error that happens while the program is executing. For example, if a program told you that 2 + 2 was 5000, that would be a runtime error. A memory leak, where the program sucks up excessive amounts of system memory is also a runtime error. The other major type of program error is a compile-time error, where the application will not even compile into an executable program. Examples of compile-time errors are syntax errors in the program code and file linking errors. Runtime is a good term to know, but you most likely won't hear it used very often unless you like to hang out with computer nerds.
Runtime Error An error that happens when a program is executed. When you run/execute a program and get a runtime error, that means that there is as error in the program that was not or could not be detected by the compiler when the program was initially compiled.
Runtime Library A group of programming functions that are called when a program is run, as opposed to being embedded into the program when it is compiled.
RX (reception) The act of downloading or receiving data. Often, the term “RX” is used on indicator lights on modems or network cards to indicate that data is flowing into the device.
S/Key A security mechanism that uses a cryptographic hash function to generate a sequence of 64-bit, one-time passwords for remote user login. The client generates a one-time password by applying the MD4 cryptographic hash function multiple times to the user's secret key. For each successive authentication of the user, the number of hash applications is reduced by one.
SA 1. System Administrator. 2. The system administrator account installed with Microsoft SQL Server. This system administrator account has the username "sa". 3. Software Assurance. Specifically the Software Assurance for Volume Licensing scheme run by Microsoft.
Safe Mode Safe Mode is a way for the Windows operating system to run with the minimum system files necessary. It uses a generic VGA display driver instead of the vendor-specific driver, which means you will likely be working with only 16 colors in a resolution of 640x480. Safe Mode also turns off all third-party drivers for other peripherals such as mice, keyboards, printers, and scanners. In basic Safe Mode, networking files and settings are not loaded, meaning you won't be able to connect to the Internet or other computers on a network. So why would I ever want to boot in Safe Mode? Well, that's a good question. Sometimes, Windows may not fully load after an unexpected crash and the only way to get the computer to boot is to use Safe Mode. Once you have successfully booted the computer in Safe Mode, you can run a disk utility program to repair corrupted files or directories on the hard drive. You can also reboot into Safe Mode to see your display when you get a "Sync Out of Range" message on your screen. There may also be times when your computer is performing sluggishly and becomes annoyingly slow. Booting into Safe Mode will allow you to diagnose the problem and determine which files are slowing down the computer. When calling technical support, the support person may ask you to boot into Safe Mode to begin the troubleshooting. To boot your Windows computer into Safe Mode, hold down the F8 key while the computer is starting up. Then select Safe Mode from the list of boot options.
Safe raw disk file A file containing access privilege information that controls a virtual machine's read/write access to partitions on a raw disk. Proper use of this file prevents dual-boot users from accidentally trying to run the host operating system again as a guest or from another guest operating system that the virtual machine was not configured for. Safe raw disk files can also prevent accidental writes to raw disk partitions from badly behaved operating systems or applications. Safe raw disk files can be created by the Configuration Wizard or the Configuration Editor.
SAM Security Accounts Manager.
Samba Most people know of samba as a type of rhythmic dance music from Brazil that uses a 2/4 time signature. In the computer world, samba has a different meaning but is no less exciting (if you are a computer nerd). Samba is an open-source software implementation of the SMB networking protocol used by Windows computers. (If you look closely, you can see the correlation between the two names.) Samba allows other computer platforms, such as Mac OS X, Unix, Linux, IBM System 390, and OpenVMS to interact with Windows computers on the same network. This includes sharing files and using shared devices such as printers connected to other computers within the local network. Because SMB was developed only for Windows, without Samba, other computer platforms would be isolated from Windows machines, even if they were part of the same network. Fortunately, Samba helps different types of computers work together as if they were all based on the same platform. This gives network administrators the freedom to choose multiple types of computers systems when setting up a network.
Sample A sample is a digital representation of an analog signal. Both digital video and digital audio files are created using samples. The quality of the sample is determined by the sampling rate, or the bit rate the signal is sampled at. What we see and hear in the real world is in analog format (our bodies process analog information). Computers, on the other hand, can only understand digital information. Therefore, audio and video signals must be converted to a digital format in order to be stored on a computer or saved to a CD or DVD. The converted data is called a sample. The term "sample" is often used to refer to short audio clips used for playing back sounds. For example, a violin sound or a bird chirp may be sampled and then played back from a digital keyboard (or synthesizer). However, samples can refer to entire songs or movies, since the information is technically one long sample. To learn more about how samples are created, view the definition of sampling, which is the process of recording and creating digital samples.
Sampling Before digital recording took over the audio and video industries, everything was recorded in analog. Audio was recorded to devices like cassette tapes and records. Video was recorded to Beta and VHS tapes. The media was even edited in analog format, using multichannel audio tapes (such as 8-tracks) for music, and film reels for video recordings. This method involved a lot of rewinding and fast-forwarding, which resulted in a time-consuming process. Fortunately, digital recording has now almost completely replaced analog recording. Digital editing can be done much more efficiently than analog editing and the media does not lose any quality in the process. However, since what humans see and hear is in analog format (linear waves of light and sound), saving audio and video in a digital format requires converting the signal from analog to digital. This process is called sampling. Sampling involves taking snapshots of an audio or video signal at very fast intervals ? usually tens of thousands of times per second. The quality of the digital signal is determined largely by the sampling rate, or the bit rate the signal is sampled at. The higher the bit rate, the more samples are created per second, and the more realistic the resulting audio or video file will be. For example, CD-quality audio is sampled at 44.1 kHz, or 44,100 samples per second. The difference between a 44.1 kHz digital recording and the original audio signal is imperceptible to most people. However, if the audio was recorded at 22 kHz (half the CD-quality rate), most people would notice the drop in quality right away. Samples can be created by sampling live audio and video or by sampling previously recorded analog media. Since samples estimate the analog signal, the digital representation is never as accurate as the analog data. However, if a high enough sampling rate is used, the difference is not noticeable to the human senses. Because digital information can be edited and saved using a computer and will not deteriorate like analog media, the quality/convenience tradeoff involved in sampling is well worthwhile.
SAN 1. Storage Area Network. cf. DAS and NAS. 2. Standard Address Number. A unique seven digit number used to identify a specific address of an organisation in the publishing industry.
Sandbox In computer security, a sandbox is a security mechanism for separating running programs. It is often used to execute untested code, or untrusted programs from unverified third-parties, suppliers and untrusted users. The sandbox typically provides a tightly-controlled set of resources for guest programs to run in, such as scratch space on disk and memory. Network access, the ability to inspect the host system or read from input devices are usually disallowed or heavily restricted. In this sense, sandboxes are a specific example of virtualization. Some examples of sandboxes are: Applets are self-contained programs that run in a virtual machine or scripting language interpreter that does the sandboxing. In application streaming schemes, the applet is downloaded onto a remote client and may begin executing before it arrives in its entirety. Applets are common in web browsers, which use the mechanism to safely execute untrusted code embedded in web pages. Three common applet implementations—Adobe Flash, Java applets and Silverlight—provide (at minimum) a rectangular window with which to interact with the user and some persistent storage (at the user's permission). A jail is a set of resource limits imposed on programs by the operating system kernel. It can include I/O bandwidth caps, disk quotas, network access restrictions and a restricted filesystem namespace. Jails are most commonly used in virtual hosting. Rule-based Execution gives users full control over what processes are started, spawned (by other applications), or allowed to inject code into other apps and have access to the net. It also can control file/registry security (What programs can read and write to the file system/registry) As such, viruses and trojans will have a less likely chance of infecting your PC. The SELinux and Apparmor security frameworks are two such implementations for Linux. Virtual machines emulate a complete host computer, on which a conventional operating system may boot and run as on actual hardware. The guest operating system is sandboxed in the sense that it does not run natively on the host and can only access host resources through the emulator. Sandboxing on native hosts: Security researchers rely heavily on sandboxing technologies to analyse malware behaviour. By creating an environment that mimics or replicates the targeted desktops, researchers can evaluate how malware infects and compromises a target host. Capability systems can be thought of as a fine-grained sandboxing mechanism, in which programs are given opaque tokens when spawned and have the ability to do specific things based on what tokens they hold. Capability based implementations can work at various levels, from kernel to user-space. An example of capability-based user-level sandboxing would be HTML rendering in Google Chrome.
SAS Serial Attached SCSI.
SATA SATA Serial ATA (Serial AT Attachment). See Serial ATA.
satellite transmission A method of data transmission; the sender beams data up to an orbiting satellite and the satellite beams the data back down to the receiver.
Scalability The ability to grow with your needs. A scalable software package means that you only buy the parts you need, and that it has the ability to grow by adding on as you do.
Scalable Applications or systems that are able to scale to large amounts of users. For example, a database that completely locks out every other user when someone is using it is NOT scalable. The computer system that runs ATM and bank transactions must be highly scalable. It is often misspelled as “Scaleable,” and is used in many product names.
Scalable Link Interface (SLI) For other uses, see SLI. Scalable Link Interface Manufacturer Nvidia Type Multi-GPU Scalable Link Interface (SLI) is a brand name for a multi-GPU solution developed by Nvidia for linking two or more video cards together to produce a single output. SLI is an application of parallel processing for computer graphics, meant to increase the processing power available for graphics. The name SLI was first used by 3dfx under the full name Scan-Line Interleave, which was introduced to the consumer market in 1998 and used in the Voodoo2 line of video cards. After buying out 3dfx, Nvidia acquired the technology but did not use it. Nvidia later reintroduced the SLI name in 2004 and intended for it to be used in modern computer systems based on the PCI Express (PCIe) bus. However, the technology behind the name SLI has changed dramatically.
SCANDISK SCANDISK or ScanDisk is a utility in MS-DOS and Microsoft Windows systems which checks and repairs file systems and bad clusters on the hard drive. It was introduced in MS-DOS version 6.2. Previous versions of MS-DOS supplied only the simpler, purely text-based program CHKDSK. ScanDisk included a more user-friendly interface than MS-DOS CHKDSK, more command-line and other configuration options,[1][2] and the ability to detect and sometimes recover from physical errors on the disk.[3] Unlike CHKDSK, ScanDisk would also repair crosslinked files.[4] In Windows 95 onwards, SCANDISK also had a graphical user interface, although the text interface continued to be available for use in single-tasking ("DOS") mode.[5][6] SCANDISK can't check NTFS disk drives and therefore isn't available for computers running NT based (including Windows 2000, Windows XP, etc.) versions of Windows: a newer CHKDSK is provided instead (not to be confused with the older MS-DOS CHKDSK). On Unix-like systems there are tools like "fsck_msdosfs" to do the same task.[7]
Scanner A scanner is an input device that scans documents and images, which can be imported into a computer. They are available in flatbed or sheet-fed versions and are usually connected via a high-speed USB port. OCR software can be used to recognize text documents imported from a scanner.
Scavenging Searching through data residue in a system to gain unauthorized knowledge of sensitive data.
scene graph scene graph The scene graph is the data structure defined in VRML. Files using a WRL extension describe the three-dimensional world, including the objects it contains, their properties, and how they interact. As in HTML, developers can link external media--such as graphic textures or sound files. Also like HTML, scene graph files are simple text files. Work is under way to create a binary (nontext) file format for VRML that should dramatically decrease scene-graph file sizes. See also: VRML
screen reader A software program that translates text on a Web page into audio output; typically used by individuals with vision impairment.
Screensaver A program that displays an image, animation, or just a blank screen on a computer after no input has been received for a certain length of time. Screensavers were originally designed so that images would not be burned into the phosphors of older CRT screens, but soon turned into a source of entertainment. Complex screensavers can use a good deal of CPU power to run, and should be kept off of servers. Screensavers are largely unnecessary today as CRT screens are much more resistant to burn-in.
Screenshot A screenshot, or screen capture, is a picture taken of your computer's desktop. This may include the desktop background, icons of files and folders, and open windows. It may also include whatever is being displayed by currently running programs. Screenshots are and easy way to save something you see on the screen, such as an open window, image, or text article. However, because screenshots are saved in an image format, the text saved in a screenshot will not be editable.
Script A computer script is a list of commands that are executed by a certain program or scripting engine. Scripts may be used to automate processes on a local computer or to generate Web pages on the Web. For example, DOS scripts and VB Scripts may be used to run processes on Windows machines, while AppleScript scripts can automate tasks on Macintosh computers. ASP, JSP, and PHP scripts are often run on Web servers to generate dynamic Web page content. Script files are usually just text documents that contain instructions written in a certain scripting language. This means most scripts can be opened and edited using a basic text editor. However, when opened by the appropriate scripting engine, the commands within the script are executed. VB (Visual Basic) scripts, for example, will run when double-clicked, using Windows' built-in VB scripting support. Since VB scripts can access and modify local files, you should never run a VB script that you receive as an unknown e-mail attachment.
Scroll Bar When the contents of a window are too large to be displayed entirely within the window, a scroll bar will appear. For example, if a Web page is too long to fit within a window, a scroll bar will show up on the right-hand side of the window, allowing you to scroll up and down the page. If the page is too wide for the window, another scroll bar will appear at the bottom of the window, allowing you to scroll to the left and right. If the window's contents fit within the current window size, the scroll bars will not appear. The scroll bar contains a slider that the user can click and drag to scroll through the window. As you may have noticed, the size of the slider may change for different windows. This is because the slider's size represents what percentage of the window's content is currently being displayed within the window. For example, a slider that takes up 75% of the scroll bar means 75% of the content fits within the current window size. A slider that fills only 10% of the scroll bar means only 10% of the window's contents are being displayed within the current window size. Therefore, if two windows are the same size, the one with the smaller slider has more content than the one with the larger slider. Most scroll bars also contain up and down or left and right arrows that allow the user to scroll in small increments by clicking the arrows. However, clicking and dragging the slider is much faster, so the arrow keys are typically not used as often. Also, some mice have a scroll wheel that allows the user to scroll by dragging the wheel instead of clicking and dragging within the scroll bar.
Scroll Lock The scroll lock key is, for most, a way to turn the “scroll lock” light on and off on your keyboard and nothing more. The scroll lock key was intended to function as a third “state” key, such as the Caps Lock and Num Lock keys. Some software makes use of it, but most does not. Some people mock the scroll lock key, but we seek ways to unleash its power!
Scroll Wheel Computer windows are often not large enough to display the entire contents of the window at one time. Therefore, you may need to scroll through the window to view all the contents. Traditionally, this has been done by clicking and dragging the slider within the scroll bar. However, many mice now come with scroll wheels that make the scrolling process even easier. The scroll wheel typically sits between the left and right buttons on the top of a mouse. It is raised slightly, which allows the user to easily drag the wheel up or down using the index finger. Pulling the scroll wheel towards you scrolls down the window, while pushing it away scrolls up. Most modern mice include a scroll wheel, since it eliminates the need to move the cursor to the scroll bar in order to scroll through the window. Therefore, once you get accustomed to using a scroll wheel, it can be pretty difficult to live without. Most scroll wheels only allow the user to scroll up and down. However, some programs allow the user to use a modifier key, such as Control or Shift, to change the scrolling input to left and right. Some mice even have a tilting scroll wheel that allows the user to scroll left and right. The Apple Mighty Mouse has a spherical scrolling mechanism (called a scroll ball) that allows the user to also scroll left and right and even diagonally. Whatever the case, any type of scroll wheel is certainly better than nothing.
Scrolling Most computer programs display their content within a window. However, windows are often not large enough to display their entire content at once. Therefore, you may have to scroll through the window to view the rest of the contents. For example, on some monitors, a page from a word processing document may not fit within the main window when viewed at 100%. Therefore, you may have to scroll down the window to view the rest of the page. Similarly, many Web pages do not fit completely within a window and may require you to scroll both vertically and horizontally to see all the content. To scroll up or down within a window, simply click the scroll bar on the right-hand side of the window and drag the slider up or down. If the window requires horizontal scrolling as well, click the scroll bar at the bottom of the window and drag the slider to the right or left. Some computer mice also include a scroll wheel that allows you to scroll through the window by rolling the wheel back and forth.
SCSI Small Computer Systems Interface. cf IDE. SCSI can be used to interface to any device that has a SCSI interface, this includes devices such as printers and scanners as well as the more traditional disk and tape drives. SCSI adapters typically support one or two SCSI buses, each of which can support up to eight units. Each device on the SCSI bus is identified by a SCSI ID, which ranges from 0 to 7 (or sometimes 0 to 15). The SCSI adapter itself will occupy one of these SCSI IDs leaving 6 (or 14) available for other devices. There are a number of different types of SCSI, reflecting its continuing development, and these are summarised in the following table: SCSI Type Data Width Transfer Rate Max devices Max cable length (metres) SCSI-1 8 bits 5MB/sec 7 6 m (SE) or 12 m (LVD) SCSI-2 Fast (Narrow) 8 bits 10MB/sec 7 3 m (SE) or 12 m (LVD) Fast Wide 16 bits 20MB/sec 15 3 m (SE) or 12 m (LVD) SCSI-3 Ultra (narrow) 8 bits 20MB/sec 7 1.5 m (SE) or 12 m (LVD) Ultra Wide 16 bits 40MB/sec 7 (SE) or 15 (LVD) 1.5m (SE) or 12m (LVD) SCSI-4 Ultra 2 (narrow) 8 bits 40MB/sec 7 12m (LVD) Ultra 2 Wide 16 bits 80MB/sec 15 12m (LVD) Ultra 3 (narrow) 8 bits 80MB/sec 15 12m (LVD) Ultra 3 (wide) 16 bits 160MB/sec 15 12m (LVD) Ultra 320 (wide) 16 bits 320MB/sec 16 12m (LVD) Note: The transfer rate is the maximum throughput of data on the bus, it does not indicate the maximum throughput of a device connected to the bus (for example the bus might be capable of 80MB/sec but a disk drive connected to it might be cable of only a fraction of that.) The maximum cable length (which is the length from the adapter to the last device or terminator) may reduce as devices are added.
SCSI-2 This version of SCSI originally came in two varieties: Fast-SCSI 2 and Fast-Wide SCSI 2. Recent extensions to the SCSI 2 specification include Ultra SCSI and Ultra2 SCSI. Ultra3 SCSI is now called Ultra 160M.
SCSI-3 The SCSI 3 specification doesn’t technically exist, but SCSI-3 is often used to describe the Ultra SCSI standard. Before the time of Ultra SCSI, SCSI-3 was a misnomer for Fast Wide SCSI-2.
SD Stands for "Secure Digital." It is a type of memory card used for storing data in devices such as digital cameras, PDAs, mobile phones, portable music players, and digital voice recorders. The card is one of the smaller memory card formats, measuring 24mm wide by 32mm long and is just 2.1mm thick. To give the cards some orientation, the top-rght corner of each SD card is slanted. Even though the cards are extremely small, as of late 2004, they can hold up to 8GB of data. Part of the reason the cards are called "Secure Digital" cards is because the cards have a copyright protection feature built in. The security feature, called "key revocation" means protected data on the card can only be read by specific devices. The cards can have both secured and unsecured areas on them for copyrighted and non-copyrighted data.
SDK 1. Software Development Kit. 2. Often taken to refer to any of the Microsoft SDKs.
SDR Single Data Rate SDRAM. The first generation SDRAM, which ran at the same speed as the system bus. cf DDR SDRAM, which allows data to be read twice as fast as SDR SDRAM.
SDRAM Synchronous DRAM (Synchronous Dynamic RAM). A type of computer memory which is synchronized with the system clock and runs at the same speed as the system bus. For this reason SDRAM is also sometimes referred to as SDR SDRAM - Single Data Rate SDRAM. cf DDR.
SDTV Standard Definition Television. A television standard providing lower quality images than those provided by HDTV. SDTV includes both the NTSC and PAL television standards. cf HDTV.
SDX (Storage Data Acceleration) This technology was introduced by Western Digital. The idea behind it is that slower drives such as CD and DVD drives would attach directly to larger, faster hard drives. There would be a 10-pin connector between the hard drive and the other peripheral, as opposed to the 40-pin IDE connector. A portion of the hard drive would be used as cache for the CD drive or other device. This was touted to speed up CD-ROM drives by 50%-300% depending on what operations are being performed. You would have had to buy specialized hard drives and CD drives to take advantage of this technology, but it flopped, so don’t worry about it.
SEARCH You can search any individual web page using the CTRL-F command (CMD-F on a Macintosh). Many websites also offer search boxes that let you search all the pages in the site, or records in its database. Searching is usually the most efficient way to find information, but sometimes you can find things by browsing that you might miss otherwise because you might not think of the "right" term to search by.
Search Engine A (usually web-based) system for searching the information available on the Web. Some search engines work by automatically searching the contents of other systems and creating a database of the results. Other search engines contains only material manually approved for inclusion in a database, and some combine the two approaches. See also: WWW
Seat (v. to seat, or n. seat) The installation of memory or other accessories into a computer. It can also be used as a noun to describe a single license, or a single client workstation for licensing purposes.
Sector A sector is the smallest unit that can be accessed on a hard disk. Each platter, or circular disk of a hard disk is divided into tracks, which run around the disk. These tracks get longer as they move from the middle towards the outside of the disk, so there are more sectors along the tracks near the outside of the disk than the ones towards the center of disk. This variance in sectors per track is referred to as "zoned-bit recording." Large files can take up thousands of sectors on a disk. Even if one of these sectors becomes corrupted, the file will most likely be unreadable. While a disk utility program may be able to fix corrupted data, it cannot fix physical damage. Physically damaged sectors are called "bad sectors." While your computer may recognize and bypass bad sectors on your hard disk, certain bad sectors may prevent your disk from operating properly. Yet another good reason to always back up your data!
Secure Electronic Transactions (SET) Secure Electronic Transactions is a protocol developed for credit card transactions in which all parties (customers, merchant, and bank) are authenticated using digital signatures, encryption protects the message and provides integrity, and provides end-to-end security for credit card transactions online.
Secure HyperText Transfer Protocol (HTTPS) A secure means of transferring data using the HTTP protocol. Typically HTTP data is sent over TCP/IP port 80, but HTTPS data is sent over port 443. This standard was developed by Netscape for secure transactions, and uses 40-bit encryption (”weak” encryption) or 128-bit (”strong” encryption). If you are at a secure site, you will notice that there is a closed lock icon on the bottom area of your Navigator or IE browser. The HTTPS standard supports certificates. A webserver operator must get a digital certificate from a third-party certificate provider that ensures that the webserver in question is valid. This certificate gets installed on the webserver, and verifies for a period of a year that that server is a proper secure server.
Secure Shell (SSH) A program to log into another computer over a network, to execute commands in a remote machine, and to move files from one machine to another.
Secure Sockets Layer (SSL) A protocol specified by Netscape that allows for “secure” passage of data. It uses public key encryption, including digital certificates and digital signatures, to pass data between a browser and a server. It is an open standard and is supported by most modern browsers.
Security Certificate A chunk of information (often stored as a text file) that is used by the SSL protocol to establish a secure connection.
Security Policy A set of rules and practices that specify or regulate how a system or organization provides security services to protect sensitive and critical system resources.
Segment Segment is another name for TCP packets.
Self-Monitoring Analysis and Reporting Tool (SMART) This technology reports on a variety of hard drive attributes. You need a compliant BIOS and SCSI and/or IDE controller, a hard drive that supports SMART, and some sort of software package that reports on these conditions. Once you have that you should be able to receive system warnings about your hard drive. Many hard drive manufacturers have added onto the SMART technology or changed it around so that it has proprietary features for their drives. The good news about SMART is that having SMART is much better than not having it, and you can be warned of hard drive failure before it happens and backup your drive while it still works. Thus, your data is safer with SMART around.
Semiconductor A substance (usually silicon doped with germanium or arsenic) that selectively conducts electricity. The selection usually occurs by running another current through a different axis to turn current flow on or off. Microprocessors are made of semiconductive materials.
Separation of Duties Separation of duties is the principle of splitting privileges among multiple individuals or systems.
Serial A means of operation meaning in series, or one after the other. It refers to connection standards that use a single wire. See also parallel.
Serial ATA Serial ATA is a disk-interface technology developed by a group of the industry's leading vendors to replace parallel ATA. It is the natural successor to IDE. Serial ATA only requires seven wires per device (4 data and 3 ground) and the cables can be up to 1m long. SATA I (the first version of SATA) supports data transfer speeds of up to 150mbps. SATA II supports data transfer speeds of up to 300mbps. Whilst the SATA interface supports these transfer rates it does not mean that the disk drive is capable of reading/writing at that rate. SATA also supports hot-swap of devices.
Serial Port A data port/connection standard that is usually used to connect modems and mice. It comes in 9- and 25-pin varieties, both of which effectively function the same way. Serial ports are largely being eliminated in favor of much faster USB and FireWire connection standards.
Server A computer, or a software package, that provides a specific kind of service to client software running on other computers. The term can refer to a particular piece of software, such as a WWW server, or to the machine on which the software is running, e.g. "Our mail server is down today, that's why e-mail isn't getting out." A single server machine can (and often does) have several different server software packages running on it, thus providing many different servers to clients on the network. Sometimes server software is designed so that additional capabilities can be added to the main program by adding small programs known as servlets.
Server Consolidation The operation of mitigating the so called server sprawl by optimizing resource usage and simplifying management of available computers. Consolidation can be logical (managing distributed computers with central management) physical (moving several computers in a central location) or rationalized (migrate several computers in virtual machines or partitions, hosted by a single physical computer).
Server Farm A group of servers usually located in a secure area, and sometimes collocated at an ISP. These servers all serve a single purpose (such as serving Web pages, for example) and have some sort of load balanced across them. If one server in the farm dies, business carries on as usual. If performance is slow, you add more servers. This term is popular when dealing with Web-based applications, where a group of webservers all serve up the same content or pull data from a database server or group of database servers.
Server Sprawl The irrational proliferation of multiple computers inside a company infrastructure.
SERVER-SIDE Something that operates on the "server" computer (providing the Web page), as opposed to the "client" computer (which is you or someone else viewing the Web page). Usually it is a program or command or procedure or other application causes dynamic pages or animation or other interaction.
Servlet A small computer program designed to be add capabilities to a larger piece of server software. Common examples are "Java servlets", which are small programs written in the Java language and which are added to a web server. Typically a web server that uses Java servlets will have many of them, each one designed to handle a very specific situation, for example one servlet will handle adding items to a "shopping cart", while a different servlet will handle deleting items from the "shopping cart."
Session A session is a virtual connection between two hosts by which network traffic is passed.
Session Hijacking Take over a session that someone else has established.
Session Key In the context of symmetric encryption, a key that is temporary or is used for a relatively short period of time. Usually, a session key is used for a defined period of communication between two computers, such as for the duration of a single connection or transaction set, or the key is used in an application that protects relatively large amounts of data and, therefore, needs to be re-keyed frequently.
SFF Small Form Factor. Small Form Factor refers to a small sized case for a PC, much smaller than a standard ATX tower or mini/midi tower case. Whilst there does not appear to be a strict definition of what constitutes a small form factor case, it would normally occupy a footprint not much larger than that of the motherboard it contains (which are often but not always standard ATX motherboards), but would be high enough to accommodate some expansion cards (normally no more than two), as well as power supply and disk drives. SFF has the advantage that it occupies much less space than a standard PC, but has the disadvantage that the lack of internal space means there are fewer upgrade options.
SFTP 1. Secure FTP (File Transfer Protocol). Also known as "SSH File Transfer Protocol". A network protocol providing file transfer and manipulation over a secure data stream. 2. FTP over SSH. Running FTP over a secure SSH connection. 3. Simple File Transfer Protocol. A protocol (defined by RFC 913) for an unsecured file transfer protocol that was less complicated and easier to implement than FTP. SFTP was not widely adopted and is generally regarded as obsolete.
SHA1 A one way cryptographic hash function. Also see "MD5"
Shadow Password Files A system file in which encryption user password are stored so that they aren't available to people who try to break into the system.
Share A share is a resource made public on a machine, such as a directory (file share) or printer (printer share).
Shareware Software that is distributed on a try-before-you-buy basis. Typically you are allowed to use the software for a period of 30 days before needing to purchase a license, but terms and conditions will vary. Strictly shareware is a marketing method rather than a type of software, but the name is normally applied to software which is distributed and sold under the heading of shareware.
Shell Most people know of shells as small protective coverings for certain animals, such as clams, crabs, and mollusks. You may also find a shell on the outside of an egg, which I highly recommend you remove before eating. In the computer science world, however, a shell is a software program that interprets commands from the user so that the operating system can understand them and perform the appropriate functions. The shell is a command-line interface, which means it is soley text-based. The user can type commands to perform functions such as run programs, open and browse directories, and view processes that are currently running. Since the shell is only one layer above the operating system, you can perform operations that are not always possible using the graphical user interface (GUI). Some examples include moving files within the system folder and deleting files that are typically locked. The catch is, you need to know the correct syntax when typing the commands and you may still be prompted for a password in order to perform administrative functions. Shells are most commonly associated with Unix, as many Unix users like to interact with the operating system using the text-based interface. Two common Unix shells are the Bourne shell and the C Shell, which is used by BSD. Most Unix systems have both of these shells available to the user. Windows users may be more familiar with DOS, the shell that has long been included with the Windows operating system. Most computer users have no need to use the shell interface, but it can be a fun way to perform functions on your computer, as well as impress your friends.
Shell Account A term used with Internet dial-up accounts that can access a UNIX system at the command line instead of just connecting to the Internet through a browser. Shell accounts were at one time offered by many ISPs, but have fallen out of favor as the larger ISPs now cater mainly to volume users instead of more technical users.
Shift Key Shift is a modifier key that allows you to capitalize lowercase letters and enter various symbols and punctuation marks. To use the Shift key, simply press and hold Shift while typing another key on the keyboard. The Shift key can be used in conjunction with the Command (Mac) or Control (PC) keys to perform various keyboard shortcuts. Many programs also allow the Shift key to be used with the mouse button in order to select multiple objects. For example, to select more than one object, click on the first object, then hold the Shift key while clicking on the other objects you want to select.
Shockwave A technology that enables web pages to include multimedia objects such as audio, animation, and video; you use an authoring tool by Macromedia called "Director" to create a shockwave object and a program called "Afterburner" to compress the object. A plug-in available from Macromedia's web site is required to see a Shockwave object included on a web page.
Shortcut A file on Windows system that serves as a pointer to another file or folder. Shortcuts are similar in concept to a symbolic link on Unix systems, but are not as versatile - for instance a shortcut cannot be used by scripts.
SHTTP Secure Hypertext Transmission Protocol (Secure-HTTP). An extended version of HTTP providing security through encryption. SHTTP encrypts data transfers, but does not authenticate the client. The responsibility for authentication remains with the website (i.e. the responsibility for determining whether the visitor should be shown the information in the first place). cf HTTPS.
SID Security Identifier, or Security ID. A SID uniquely identifier a user, group or computer.
Signals Analysis Gaining indirect knowledge of communicated data by monitoring and analyzing a signal that is emitted by a system and that contains the data but is not intended to communicate the data.
Signature 1. A file containing a bit of personal information that you can set to be automatically appended to your outgoing e-mail messages; many network newsreaders also have this capability. Large signatures over five lines generally are frowned upon. 2. A Signature is a distinct pattern in network traffic that can be identified to a specific tool or exploit.
SIMM Stands for "Single In-Line Memory Module." This is an older type of computer memory. A SIMM is a small circuit board with a bunch of memory chips on it. SIMMs use a 32-bit bus, which is not as wide as the 64-bit bus dual in-line memory modules (DIMMs) use. Newer processors require a 64-bit memory bus, so it is best to use DIMMs. Sometimes you can get away with installing SIMMS, but they have to be installed in pairs.
Simple Integrity Property In Simple Integrity Property a user cannot write data to a higher integrity level than their own.
SIP 1. Session Initiation Protocol. Used for setting up communications sessions on the internet, such as instant messaging, conferencing, telephony or whiteboarding. 2. Single in-line package.
Site Map A site map, sometimes written "sitemap," is an overview of the pages within a website. Site maps of smaller sites may include every page of the website, while site maps of larger sites often only include pages for major categories and subcategories of the website. While site maps can be organized in a variety of ways, most use an outline form, with pages arranged by topic. This gives visitors a good overall picture of how the site is organized and clearly defines all the resources the website has to offer. While a properly designed website should allow visitors to navigate the entire site without using the site map, incorporating a site map gives users another means of locating pages. For this reason, each page listed in a site map is typically linked to the page it represents. This allows visitors to quickly jump to any section of a website listed in the site map.
SKU (Stock Keeping Unit) Stands for "Stock Keeping Unit," and is conveniently pronounced "skew." A SKU is a number or string of alpha and numeric characters that uniquely identify a product. For this reason, SKUs are often called part numbers, product numbers, and product identifiers. SKUs may be a universal number such as a UPC code or supplier part number or may be a unique identifier used by a specific a store or online retailer. For example, one company may use the 10 character identifier supplied by the manufacturer as the SKU of an external hard drive. Another company may use a proprietary 6-digit number as the SKU to identify the part. Many retailers use their own SKU numbers to label products so they can track their inventory using their own custom database system. When shopping online or at retail stores, knowing a product's SKU can help you locate the exact product at a later time. It will help you identify a unique product when there are many similar options, such as a TV model that comes in different colors, sizes, etc. If you know a product's SKU, you can typically locate the product online by typing the SKU in the online retailer's search box. If you visit a retail store and have questions about product you saw in an ad, knowing the SKU will help the salesperson find the exact product you are asking about. SKUs are typically listed in small print below the product name and are often preceded by the words "SKU," "Part Number," "Product ID," or something similar.
SLA (Service Level Agreement) An agreement between a service provider and a customer regulating offered service in several aspects, from amount of resources available to time availability, up to faults recovery timeframe.
Slashdot Effect This describes what happens when a highly trafficked website links to a smaller website, and sends such a large amount of traffic towards the smaller website over a short period of time that the website becomes inaccessible, or at least very slow. The phrase was first used to describe the effect that Slashdot.org had when it linked to small sites in its daily news items.
Slave This usually refers to an IDE setting on a hard drive or other IDE device. When two devices are used on a single IDE channel, one is set to master and the other to slave. See also master.
Sleep mode The placement of a computing device into an inoperable mode, where less power is consumed by shutting down unnecessary devices, but leaving all data in RAM. Typically you return from sleep mode by using the keyboard or mouse, and devices are switched back on. Sleep mode in its early incarnations was very problematic in some PCs, and would often crash programs and operating systems that were not completely compatible with the sleep mode in the PC’s BIOS.
SMART 1. Self Monitoring Analysis and Reporting Technology. A HDD diagnostic technology that monitors device performance and attempts to predict device failure. SMART software on the HDD monitors the internal performance of motors, media, heads and electronics of the drive. SMART software on the host monitors the overall reliability status of the drive.
SMART (Self-Monitoring Analysis and Reporting Tool) This technology reports on a variety of hard drive attributes. You need a compliant BIOS and SCSI and/or IDE controller, a hard drive that supports SMART, and some sort of software package that reports on these conditions. Once you have that you should be able to receive system warnings about your hard drive. Many hard drive manufacturers have added onto the SMART technology or changed it around so that it has proprietary features for their drives. The good news about SMART is that having SMART is much better than not having it, and you can be warned of hard drive failure before it happens and backup your drive while it still works. Thus, your data is safer with SMART around.
Smartcard A smartcard is an electronic badge that includes a magnetic strip or chip that can record and replay a set key.
SmartMedia A type of Flash memory card that is roughly one-third the size of a PC Card (PCMCIA card) and less than 1 mm thick. It is used to store data from and exchange data among PDAs, digital cameras, and other devices. SmartMedia has largely given way to the even smaller MMC MultiMedia Card standard.
SMB Server Message Block. File sharing protocol used in DOS, OS/2 and early versions of Windows.
SMS 1. Short Message Service - mobile phone text messaging. 2. (Microsoft) Systems Management Server.
SMT 1. Simultaneous Multithreading Technology. See also: Hyper-Threading. 2. Surface Mount Technology. A manufacturing technique where components are design for direct mounting on the surface of a PC board or substrate. 3. Senior Management Team. Typically used to refer to heads of department in a company which direct company policy.
SMTP Simple Mail Transfer Protocol. A protocol for sending (or relaying) e-mail to a server. See also: IMAP, POP, MX Record.
Smurf The Smurf attack works by spoofing the target address and sending a ping to the broadcast address for a remote network, which results in a large amount of ping replies being sent to the target.
Smurf Attack A network-based attack where the attacker(s) send out false ICMP echo requests that appear to originate from the IP address of the machine or network under attack. This type of attack can be used to flood a network or device with “responses” to the false ICMP requests.
Snail Mail A derogatory term for the traditional postal mail service, where physical items (typically letters) are posted, transported and delivered to their destination. It is called snail mail only when being compared email, because it is very slow in comparison.
Snapshot While the term "snapshot" is often used in photography, it is also a computing term that refers to a copy made of a disk drive at a specific moment in time. Snapshots are useful for backing up data at different intervals, which allows information to be recovered from different periods of time. A hard drive snapshot includes the full directory structure of a hard disk, including all folders and files on the disk. This type of backup may also be referred to as a "disk image." Disk images allow the full disk to be restored in case the primary disk fails. Many backup programs that create snapshots also allow specific files to be recovered from the snapshot, instead of having to restore the complete backup. Since snapshots are mainly used for backup purposes, it is wise to save the snapshot to a secondary hard drive, removable drive, or optical media, such as CDs or DVDs.
Sniffer A sniffer is a tool that monitors network traffic as it received in a network interface.
Sniffing A synonym for "passive wiretapping."
SNMP A set of standards for communication with devices connected to a TCP/IP network. Examples of these devices include routers, hubs, and switches. SNMP is defined in RFC 1089 See also: Network, RFC, Router, TCP/IP
SNTP Simple Network Time Protocol.
SOAP Simple Object Access Protocol. A protocol that describes a model for packing XML enquiries and responses. SOAP messaging is used to enable exchange of a variety of XML information. The SOAP standard takes on the job of transporting service requests and replies between service users and service providers. SOAP is a way to encapsulate object calls to XML sent via HTTP.
Social Engineering A euphemism for non-technical or low-technology means - such as lies, impersonation, tricks, bribes, blackmail, and threats - used to attack information systems.
Socket 1. An IP address and port number. Applications communicate by sockets - the ip address indicates the network address of the machine to which messages should be sent and the port number is the logical destination on that machine. 2. A receptacle into which a component can be fitted. The socket is the female component of any plug and socket arrangement. For example on the motherboard of a computer the CPU will be fitted into a matching socket (which may sometimes take the form of a slot), or for with a portable CD player the headphones will plug into the headphone socket.
Socket Pair A way to uniquely specify a connection, i.e., source IP address, source port, destination IP address, destination port.
SOCKS A protocol that a proxy server can use to accept requests from client users in a company's network so that it can forward them across the Internet. SOCKS uses sockets to represent and keep track of individual connections. The client side of SOCKS is built into certain Web browsers and the server side can be added to a proxy server.
Soft Copy soft copy is a document saved on a computer. It is the electronic version of a document, which can be opened and edited using a software program. The term "soft copy" is most often used in contrast to hard copy, which is the printed version of a document. Soft copies can be sent via e-mail or over a network connection, which makes them a more efficient and cost effective option than using hard copies for communications. The downside to using soft copies is that they require a computer and software to open and can be accidentally deleted. Of course, some people have so many papers on their desks, a soft copy may be less likely to disappear.
Soft Token A soft token is a software version of a hard token, which is a security device used to give authorized users access to secure locations or computer systems. For this reason, soft tokens can be called "virtual tokens," since they are a virtual version of hardware keys and other physical security devices. Soft tokens are typically generated by a central server that runs security software. They are sent to users' devices, such as cell phones, PDAs, and laptops. Once the soft token has been received by the device, the user can use the device within a secure network or can gain access to the sever as an authorized user. To add an extra measure of security, most soft token authentication also requires a username and password to make sure the correct user is using the authorized device.
Software Computer software is a general term that describes computer programs. Related terms such as software programs, applications, scripts, and instruction sets all fall under the category of computer software. Therefore, installing new programs or applications on your computer is synonymous with installing new software on your computer. Software can be difficult to describe because it is "virtual," or not physical like computer hardware. Instead, software consists of lines of code written by computer programmers that have been compiled into a computer program. Software programs are stored as binary data that is copied to a computer's hard drive, when it is installed. Since software is virtual and does not take up any physical space, it is much easier (and often cheaper) to upgrade than computer hardware. While at its most basic level, software consists of binary data, CD-ROMs, DVDs, and other types of media that are used to distribute software can also be called software. Therefore, when you buy a software program, it often comes on a disc, which is a physical means of storing the software.
Software bug A software bug is the common term used to describe an error, flaw, mistake, failure, or fault in a computer program or system that produces an incorrect or unexpected result, or causes it to behave in unintended ways. Most bugs arise from mistakes and errors made by people in either a program's source code or its design, and a few are caused by compilers producing incorrect code. A program that contains a large number of bugs, and/or bugs that seriously interfere with its functionality, is said to be buggy. Reports detailing bugs in a program are commonly known as bug reports, fault reports, problem reports, trouble reports, change requests, and so forth. Effects Main article: List of software bugs Bugs trigger Type I and type II errors that can in turn have a wide variety of ripple effects, with varying levels of inconvenience to the user of the program. Some bugs have only a subtle effect on the program's functionality, and may thus lie undetected for a long time. More serious bugs may cause the program to crash or freeze leading to a denial of service. Others qualify as security bugs and might for example enable a malicious user to bypass access controls in order to obtain unauthorized privileges. The results of bugs may be extremely serious. Bugs in the code controlling the Therac-25 radiation therapy machine were directly responsible for some patient deaths in the 1980s. In 1996, the European Space Agency's US$1 billion prototype Ariane 5 rocket was destroyed less than a minute after launch, due to a bug in the on-board guidance computer program. In June 1994, a Royal Air Force Chinook crashed into the Mull of Kintyre, killing 29. This was initially dismissed as pilot error, but an investigation by Computer Weekly uncovered sufficient evidence to convince a House of Lords inquiry that it may have been caused by a software bug in the aircraft's engine control computer. [1] In 2002, a study commissioned by the US Department of Commerce' National Institute of Standards and Technology concluded that software bugs, or errors, are so prevalent and so detrimental that they cost the US economy an estimated $59 billion annually, or about 0.6 percent of the gross domestic product.
Solaris A UNIX-based operating system developed by Sun Microsystems and used widely for enterprise-class servers. It is designed to work with Sun’s own SPARC chips as well as Intel’s x86 microprocessors.
Solid State Solid state, at its most basic level, means "no moving parts." Therefore, solid state electronic devices are made up of solid components that do not move. Some examples include computer motherboards and integrated circuits. Devices that use only solid state parts, such as television sets, speakers, and digital watches, are often referred to as solid state products. Flash memory devices are solid state products, while hard drives are not. This is because hard drives use a spinning disk and moving drive head to read and write data, while flash memory uses electric charges to perform the same functions. For this reason, flash memory devices are seen as more durable than hard drives. This is why flash memory is often used in products such as portable MP3 players and digital cameras. Because solid state devices have no moving parts, they are less likely to break down than devices that have mobile mechanisms. For this reason, it is often more worthwhile to buy an extended warranty on electronics that have moving parts than those that do not. That is something you may want to think about next time you are shopping.
Sound Card The sound card is a component inside the computer that provides audio input and output capabilities. Most sound cards have at least one analog line input and one stereo line output connection. The connectors are typically 3.5 mm minijacks, which are the size most headphones use. Some sound cards also support digital audio input and output, either through a standard TRS (tip-ring-sleeve) connection or via an optical audio port, such as Toslink connector. While there are many types of sound cards, any type that produces an analog output must include a digital-to-analog converter (DAC). This converts the outgoing signal from digital to analog, which can be played through most speaker systems. Sounds cards that support analog input also require an analog-to-digital converter (ADC). This digitizes the incoming analog signal, so the computer can process it. In some computers, the sound card is part of the motherboard, while other machines may have an actual card that reside in a PCI slot. If you want to more audio capabilities to your computer, such as additional input or output channels, you can install a new sound card. Professional sound cards often support higher sampling rates (such as 192 kHz instead of 44.1 kHz) and may have more inputs and outputs. Some cards may also have 1/4 in. connectors instead of 3.5 mm, which accommodates most instrument outputs. While professional sound cards can add more audio capabilities to your computer, another popular option for multi-channel recording is a breakout box. This is an external box that typically includes a built-in sound card and multiple audio connections. For example, a breakout box may support 16 channels of audio, which would be impossible to fit on a single card. Most breakout boxes connect to a Firewire or USB port, though some connect to a sound card specifically designed to communicate with the box.
Source Code Every computer program is written in a programming language, such as Java, C/C++, or Perl. These programs include anywhere from a few lines to millions of lines of text, called source code. Source code, often referred to as simply the "source" of a program, contains variable declarations, instructions, functions, loops, and other statements that tell the program how to function. Programmers may also add comments to their source code that explain sections of the code. These comments help other programmers gain at least some idea of what the source code does without requiring hours to decipher it. Comments can be helpful to the original programmer as well if many months or years have gone by since the code was written. Short programs called scripts can be run directly from the source code using a scripting engine, such as a VBScript or PHP engine. Most large programs, however, require that the source code first be compiled, which translates the code into a language the computer can understand. When changes are made to the source code of these programs, they must be recomplied in order for the changes to take effect in the program. Small programs may use only one source code file, while larger programs may reference hundreds or even thousands of files. Having multiple source files helps organize the program into different sections. Having one file that contains every variable and function can make it difficult to locate specific sections of the code. Regardless of how many source code files are used to create a program, you will most likely not see any of the original files on your computer. This is because they are all combined into one program file, or application, when they are compiled.
Source Port The port that a host uses to connect to a server. It is usually a number greater than or equal to 1024. It is randomly generated and is different each time a connection is made.
Southbridge The southbridge is a chip that connects the northbridge to other components inside the computer, including hard drives, network connections, USB and Firewire devices, the system clock, and standard PCI cards. The southbridge sends and receives data from the CPU through the northbridge chip, which is connected directly to the computer's processor. Since the southbridge is not connected directly to the CPU, it does not have to run as fast as the northbridge chip. However, it processes data from more components, so it must be able to multitask well. On Intel systems, the southbridge is also referred to as the I/O Controller Hub, since it controls the input and output devices.
SP1 Service Pack 1. The first service pack (SP) released for a given product. Not all products will have service packs released for them. The existence of SP1 does not imply the existence of SP2 for the same produce.
SP2 Service Pack 2. The second service pack (SP) for a given product. Depending on the service pack, SP2 may require SP1 to have been pre-installed or (more likely) it may include everything contained in SP1.
SP3 Service Pack 3.
SPAM 1. Unsolicited e-mail (or newsgroup posting) sent out in bulk, usually for commercial gain. SPAM is typically promoting something. It may be advertising for a product, website or other service, it may be promoting ideologies (such as political or religious ones), or it may be to precipitate a fraud. Whist most SPAM is sent out for purposes of commercial gain, not all is spam has a financial motive. SPAM can cause considerable problems because it is generated in large volume - both the volume generated by a single spammer and because there are lots of spammers generating email. The large volume of spam clogs up network resources and wastes a considerable amount of time.
Spam (v. to spam, n. spam) Besides being a canned meat (”spiced ham” made by Hormel) spam has taken on a new meaning. Spam is the common term for unsolicited e-mail. Some common types of spam include ads for pornographic sites, pyramid schemes, and advertisements for products that allow you to send spam. Other types of spam are messages that claim that you will win a prize or help a dying child by sending messages to all of your friends. In addition to being a noun, spam is also a verb, as in “Don’t spam me!” Often spammers will take the list of addresses that reply to them asking them to stop sending their messages, and will then compile new lists to spam further.
Spammer A person or organisation that sends out spam. Spammers tend to go to extreme lengths to hide their identity because they are generally despised and hated by the internet community because spam is unwanted, clogs up network resources and wastes a considerable amount of time.
Spanning Port Configures the switch to behave like a hub for a specific port.
SpeedStep SpeedStep is a trademark for a series of dynamic frequency scaling technologies (including SpeedStep, SpeedStep II, and SpeedStep III) built into some Intel microprocessors that allow the clock speed of the processor to be dynamically changed by software. This allows the processor to meet the instantaneous performance needs of the operation being performed, while minimizing power draw and heat dissipation. Explanation Running a processor at high clock speeds allows for better performance. However, when the same processor is run at a lower frequency (speed), it generates less heat and consumes less power. In many cases, the core voltage can also be reduced, further reducing power consumption and heat generation. This can conserve battery power in notebooks, extend processor life, and reduce noise generated by variable-speed fans. By using SpeedStep, users can select the balance of power conservation and performance that best suits them, or even change the clock speed dynamically as the processor burden changes.
SPF Sender Policy Framework. SPF records indicate which mail servers are permitted to send email with a given "from" address. SPF is an attempt to counter "e-mail address spoofing", where a sender (typically a spammer) uses someone else's e-mail address as the apparent sender of an e-mail.
SPI Stateful Packet Inspection. A firewall mechanism which examines each incoming network packet and only allows through those packets which are for a known open connection.
Spider A spider is a software program that travels the Web (hence the name "spider"), locating and indexing websites for search engines. All the major search engines, such as Google and Yahoo!, use spiders to build and update their indexes. These programs constantly browse the Web, traveling from one hyperlink to another. For example, when a spider visits a website's home page, there may be 30 links on the page. The spider will follow each of the links, adding all the pages it finds to the search engine's index. Of course, the new pages that the spider finds may also have links, which the spider continues to follow. Some of these links may point to pages within the same website (internal links), while others may lead to different sites (external links). The external links will cause the spider to jump to new sites, indexing even more pages. Because of the interwoven nature of website links, spiders often return to websites that have already been indexed. This allows search engines to keep track of how many external pages link to each page. Usually, the more incoming links a page has, the higher it will be ranked in search engine results. Spiders not only find new pages and keep track of links, they also track changes to each page, helping search engine indexes stay up to date.
Spindle The centerpiece of a hard drive which holds one or more hard drive platters. Often the term spindle is used to differentiate hard drives from hard disk platters in discussion when referring to large RAID subsystems holding many hard drives, such as “We’ll be using 50 spindles instead of 10 spindles in the new RAID box.” Basically a spindle is seen as a limiting factor in performance; generally, more spindles in a system mean higher possible performance.
Split Horizon Split horizon is a algorithm for avoiding problems caused by including routes in updates sent to the gateway from which they were learned.
Split Key A cryptographic key that is divided into two or more separate data items that individually convey no knowledge of the whole key that results from combining the items.
SPONSOR (of a Web page or site) Many Web pages have organizations, businesses, institutions like universities or nonprofit foundations, or other interests which "sponsor" the page. Frequently you can find a link titled "Sponsors" or an "About us" link explaining who or what (if anyone) is sponsoring the page. Sometimes the advertisers on the page (banner ads, links, buttons to sites that sell or promote something) are "sponsors." WHY is this important? Sponsors and the funding they provide may, or may not, influence what can be said on the page or site -- can bias what you find, by excluding some opposing viewpoint or causing some other imbalanced information. The site is not bad because of sponsors, but you they should alert you to the need to evaluate a page or site very carefully.
Spoof A generic term for misleading a computer system into believing that you are not who you say you are. Most commonly, it refers to a TCP/IP trick that allows you to get around network security by impersonating a TCP/IP address inside of the network.
Spoofing The word "spoof" means to hoax, trick, or deceive. Therefore, in the IT world, spoofing refers tricking or deceiving computer systems or other computer users. This is typically done by hiding one's identity or faking the identity of another user on the Internet. Spoofing can take place on the Internet in several different ways. One common method is through e-mail. E-mail spoofing involves sending messages from a bogus e-mail address or faking the e-mail address of another user. Fortunately, most e-mail servers have security features that prevent unauthorized users from sending messages. However, spammers often send spam messages from their own SMTP, which allows them to use fake e-mail addresses. Therefore, it is possible to receive e-mail from an address that is not the actual address of the person sending the message. Another way spoofing takes place on the Internet is via IP spoofing. This involves masking the IP address of a certain computer system. By hiding or faking a computer's IP address, it is difficult for other systems to determine where the computer is transmitting data from. Because IP spoofing makes it difficult to track the source of a transmission, it is often used in denial-of-service attacks that overload a server. This may cause the server to either crash or become unresponsive to legitimate requests. Fortunately, software security systems have been developed that can identify denial-of-service attacks and block their transmissions. Finally, spoofing can be done by simply faking an identity, such as an online username. For example, when posting on an Web discussion board, a user may pretend he is the representative for a certain company, when he actually has no association with the organization. In online chat rooms, users may fake their age, gender, and location. While the Internet is a great place to communicate with others, it can also be an easy place to fake an identity. Therefore, always make sure you know who you are communicating with before giving out private information.
Spool A spool is a temporary storage area within the computer's RAM that contains input or output data. When a job or process is initiated on a computer, but cannot be run immediately, it is often placed in a spool. This process is called spooling. The spool holds the data until the appropriate device is ready to use it. The most common type of spool is a print spool, which stores print jobs that are sent to a printer. Since the printer may need to warm up before printing a document, the document may be held in the spool during the printer's warm up process. If there are multiple documents that have been sent to the printer, the print spool may contain a queue of jobs. You can think of a print spool as a spool of yarn that is connected from the computer to the printer. Of course, the print spool contains computer data, rather than yarn. As the the data is transmitted to the printer, it is removed from the computer, just like unraveling a spool. Once the spool is empty, no more data is transmitted to the printer.
Spooling Sending a print job to a print queue, from where it is sent to a printer, rather than directly to the printer.
spread spectrum Spread spectrum is a type of modulation that scatters data transmissions across the available frequency band in a pseudorandom pattern. Spreading the data across the frequency spectrum makes the signal resistant to noise, interference, and snooping. Spread-spectrum modulation schemes are commonly used with personal communication devices such as digital cellular phones, as well as with wireless local area networks (LANs) and cable modems.
Spreadsheet A spreadsheet is a document that stores data in a grid of horizontal rows and vertical columns. Rows are typically labeled using numbers (1, 2, 3, etc.), while columns are labeled with letters (A, B, C, etc). Individual row/column locations, such as C3 or B12, are referred to as cells. Each cell can each store a unique instance of data. By entering data into a spreadsheet, information can be stored in a more structured way than using plain text The row/column structure also allows the data to be analyzed using formulas and calculations. For example, each row of a spreadsheet may store information about a person who has an account with a certain company. Each column may store a different aspect of the person's information, such as the first name, last name, address, phone number, favorite food, etc. The spreadsheet program can analyze this data by counting the number of people who live in a certain zip code, listing all the people who's favorite food is fried veal, or performing other calcuations. In this way, a spreadsheet is similar to a database. However, spreadsheets are more streamlined than databases and are especially useful for processing numbers. This is why spreadsheets are commonly used in scientific and financial applications. For example, a spreadsheet may store bank account data, including balance and interest information. A column that stores the account balances of several clients can easily be summed to produce the total value of all the clients' balances. These amounts can be multiplied by the interest rate from another cell to see what the value of the accounts will be in a year. Once the formula has been created, modifying the value of just the interest rate cell will also change the projected value of all the accounts. The most commonly used spreadsheet application is Microsoft Excel, but several other spreadsheet programs are available including IBM Lotus 1-2-3 for Windows and AppleWorks and Numbers for Mac OS X.
SPS Stand-by Power Supply. A cheaper form of UPS (see UPS for comparison).
Spyware Spyware Software that monitors the activities of a user (such as their browsing habits) or gathers information about a user (such as stored credit card details) without the user's knowledge or permission. This information is collected so that it can be relayed to a third party. Spyware is typically used as a prelude to theft or fraud. Once credit card or personal information has been collected and relayed to a third party that third party is able to use the information to commit a theft or fraud.
SQL Structured Query Language. Standard query language is a standard language available on virtually all database systems for quering, adding and updating information from database systems
SQL Injection An attack technique where an attacker tries to make an application execute unauthorised (or unintended) SQL.
SRAM Stands for "Static Random Access Memory." I know it is tempting to pronounce this term as "Sram," but it is correctly pronounced "S-ram." SRAM is a type of RAM that stores data using a static method, in which the data remains constant as long as electric power is supplied to the memory chip. This is different than DRAM (dynamic RAM), which stores data dynamically and constantly needs to refresh the data stored in the memory. Because SRAM stores data statically, it is faster and requires less power than DRAM. However, SRAM is more expensive to manufacture than DRAM because it is built using a more complex structure. This complexity also limits the amount of data a single chip can store, meaning SRAM chips cannot hold as much data as DRAM chips. For this reason, DRAM is most often used as the main memory for personal computers. However, SRAM is commonly used in smaller applications, such as CPU cache memory and hard drive buffers. It is also used in other consumer electronics, from large appliances to small children's toys. It is important to not confuse SRAM with SDRAM, which is a type of DRAM.
sRGB Stands for "Standard RGB" (and RGB stands for Red-Green-Blue"). All the colors you see on your computer display are made up various mixtures of red, green, and blue light. While this works great for individual displays, the same colors are often displayed differently on different screens. For example, dark red on one screen may look like red-orange on another. When you add printers, scanners, and digital cameras to the mix, the problem is magnified even more. To help achieve a greater color consistency between hardware devices, the sRGB standard was created in 1999. It defines a gamut of colors that represents each color well and can be used by CRT monitors, LCD screens, scanners, printers, and digital cameras. It also has been incorporated into many Web browsers to make sure the colors on Web pages match the color scheme of the operating system. Because of the color consistency sRGB creates, most hardware devices that work with images now use it as the default setting.
SSD Solid State Drive. A disk drive technology which stores data to solid state devices (flash) without the need for any moving parts.
SSD (Solid State Drive) This type of storage is basically a huge block of RAM chips that functions like a hard drive. Solid state drives are extremely expensive, but offer very high data speeds that are necessary in some applications. They can also be used as large caches on huge RAID subsystems, but due to the volatile nature of the DRAM used as storage solid state drives should be used carefully.
SSH Secure Shell. A set of applications and protocols to provide secure encrypted message transmission between two computers on an insecure (e.g. public) network.
SSI Server Side Include or Server Side Includes.
SSI commands SSI stands for "server-side include," a type of HTML instruction telling a computer that serves Web pages to dynamically generate data, usually by inserting certain variable contents into a fixed template or boilerplate Web page. Used especially in database searches.
SSID Service Set Identification. Sometimes referred to as the name of a wireless network. The two types of SSID are ESSID (for wireless networks with an access point) and BSSID (for ad-hoc wireless networks).
SSL Secure Sockets Layer. Protocol for transmitting documents over the internet using a private key to encrypt the data. Originally developed by Netscape and now an industry standard. cf TLS, SHTTP, HTTPS. SSL is used in e-commerce websites for accepting credit card details on-line and for any site where it is important that the information cannot be gleaned by someone using a protocol analyzer. SSL ensures that data sent between a server and client is encrypted. On a web server, the SSL protocol (and corresponding encryption and decryption) occurs before the processing of the HTTP header information. For this reason a web server can only host a single secure website per unique IP address. The default TCP/IP port for SSL is port 443.
SSL (Secure Sockets Layer) A protocol specified by Netscape that allows for “secure” passage of data. It uses public key encryption, including digital certificates and digital signatures, to pass data between a browser and a server. It is an open standard and is supported by most modern browsers.
SSMP (Simple Screen Management Protocol) A communications protocol for text-based terminals.
Stack A stack is a type of data structure -- a means of storing information in a computer. When a new object is entered in a stack, it is placed on top of all the previously entered objects. In other words, the stack data structure is just like a stack of cards, papers, credit card mailings, or any other real-world objects you can think of. When removing an object from a stack, the one on top gets removed first. This method is referred to as LIFO (last in, first out). The term "stack" can also be short for a network protocol stack. In networking, connections between computers are made through a series of smaller connections. These connections, or layers, act like the stack data structure, in that they are built and disposed of in the same way.
Stack Mashing Stack mashing is the technique of using a buffer overflow to trick a computer into executing arbitrary code.
Standalone A standalone device is able to function independently of other hardware. This means it is not integrated into another device. For example, a TiVo box that can record television programs is a standalone device, while a DVR that is integrated into a digital cable box is not standalone. Integrated devices are typically less expensive than multiple standalone products that perform the same functions. However, using standalone hardware typically allows the user greater customization, whether it be a home theater or computer system. Standalone can also refer to a software program that does not require any software other than the operating system to run. This means that most software programs are standalone programs. Software such as plug-ins and expansion packs for video games are not standalone programs since they will not run unless a certain program is already installed.
Standby When electronic devices are receiving power but are not running, they are in standby mode. For example, a television is in standby mode when it is plugged in, but turned off. While the TV is not "on," it is ready to receive a signal from the remote control. An A/V receiver is also in standby mode when it is plugged in and turned off. This is because the receiver may be activated by receiving input from a connected device or by being turned on directly with the remote control. In other words, these devices are "standing by," waiting to receive input from the user or another device. When a computer is in standby mode, it is not completely turned off. Instead, it has already been turned on, but has gone into "sleep" mode. Therefore, when referring to computers, "Sleep" and "Standby" may be used synonymously. A computer in standby mode requires a small amount of current, called a "trickle charge," that keeps the current state of running software saved in the computer's RAM. However, because the computer is in sleep mode, the CPU, video card, and hard drive are not running. Therefore, the computer uses very little power in standby mode. Since standby mode saves energy, it is a good idea to put your computer to sleep if you are going to be away from it for more than 15 or 20 minutes. You can also use the Power Options control panel (in Windows) or the Energy Saver System Preference (in Mac OS X) to automatically put your computer to sleep after it has been inactive for a specific amount of time. Then, when you take a break from your computer, your computer can take a break as well.
Star Property In Star Property, a user cannot write data to a lower classification level without logging in at that lower classification level.
start bit Ancient modems alternated between two tones. One tone represented 0 and the other represented 1, which covered the entire binary language. Silence was not an option: to a modem, silence meant the phone call had been cut off. So when a modem had nothing to say, it continuously transmitted the 1 tone to tell the other modem that it was in an idle state. When there was more data to send, the modem would send a single 0 bit to say there was real data on the way. The next eight bits the receiving modem heard were the real data. Then the line went back to idle for at least one more bit. The 0 just before the data is called the start bit. The 1 at the end is the stop bit.
State Machine A system that moves through a series of progressive conditions.
Stateful Inspection The ability of a firewall to retain “state” information about ongoing network sessions. When a packet goes out through a stateful firewall (TCP/UDP/ICMP) it will only permit expected return traffic that would normally be returned in response to that packet from the remote site. This prevents spoofed packet attacks and other nasty things.
stateless A stateless server (for example, a World Wide Web server) considers each page request independently. A request specifies the entire document, without requiring any context or memory of previous requests. Unless a cookie is set, no information is carried across requests. See also: cookie, state
Static Host Tables Static host tables are text files that contain hostname and address mapping.
Static IP Address An IP address that does not change. Most IP addresses for client machines are handed out by a method such as a DHCP server that manages a range of IP addresses. Static IP addresses are typically reserved for servers or routers, but some companies still use them for all their PCs. Most IP addresses handed out by an ISP are not static, but you can find ISPs that offer static IP addresses.
Static Routing Static routing means that routing table entries contain information that does not change.
Static Website A static website contains Web pages coded in HTML. The content of each page is fixed and does not change unless it is edited and republished by the webmaster. Static websites are usually small and only contain a few brochure-style Web pages. Large sites are typically designed as dynamic websites, since they are easier to maintain.
Status Bar A status bar is a small area at the bottom of a window. It is used by some applications to display helpful information for the user. For example, an open folder window on the desktop may display the number of items in the folder and how many items are selected. Photoshop uses the status bar to display the size of the current image, the zoom percentage, and other information. Web browsers use the status bar to display the Web address of a link when the user moves the cursor over it. It also shows the status of loading pages, and displays error messages. If you don't see the status bar in your Web browser or another program, you may be able to enable it by selecting "Show Status Bar" from the application's View menu. If this option is not available in the View menu, the program may not use a status bar. Some programs use a "status window" instead to show the current activity in the application. The option for displaying this window is usually found in the "Window" menu.
Stealthing Stealthing is a term that refers to approaches used by malicious code to conceal its presence on the infected system.
Steganalysis Steganalysis is the process of detecting and defeating the use of steganography.
Steganography Methods of hiding the existence of a message or other data. This is different than cryptography, which hides the meaning of a message but does not hide the message itself. An example of a steganographic method is "invisible" ink.
STEMMING In keyword searching, word endings are automatically removed (lines becomes line); searches are performed on the stem + common endings (line or lines retrieves line, lines, line's, lines', lining, lined). Not very common as a practice, and not always disclosed. Can usually be avoided by placing a term in " ".
Stepping The version of a particular chip. Microprocessors typically have many different steppings where performance is increased or minor bugs are fixed. The steppings are usually not touted as a new release of the chip because chips are not as easily upgradeable as software. You would have to buy a whole new chip to upgrade it.
Stimulus Stimulus is network traffic that initiates a connection or solicits a response.
stop bit The opposite of the start bit. See also: start bit
STOP WORDS In database searching, "stop words" are small and frequently occurring words like and, or, in, of that are often ignored when keyed as search terms. Sometimes putting them in quotes " " will allow you to search them.
Storage Capacity Storage capacity is another term for "disk space." It measures how much data a computer system may contain. For example, a computer with two 750GB hard drives has a storage capacity of 1.5TB. Storage capacity is commonly included in the technical specifications of a system, along with processing power and memory. It is possible to increase the storage capacity of most systems by adding additional internal or external hard drives.
Storage Device A computer storage device is any type of hardware that stores data. The most common type of storage device, which nearly all computers have, is a hard drive. The computer's primary hard drive stores the operating system, applications, and files and folders for users of the computer. While the hard drive is the most ubiquitous of all storage devices, several other types are common as well. Flash memory devices, such as USB keychain drives and iPod nanos are popular ways to store data in a small, mobile format. Other types of flash memory, such as compact flash and SD cards are popular ways to store images taken by digital cameras. External hard drives that connect via Firewire and USB are also common. These types of drives are often used for backing up internal hard drives, storing video or photo libraries, or for simply adding extra storage. Finally, tape drives, which use reels of tape to store data, are another type of storage device and are typically used for backing up data.
Store-and-Forward Store-and-Forward is a method of switching where the entire packet is read by a switch to determine if it is intact before forwarding it.
Straight-Through Cable A straight-through cable is where the pins on one side of the connector are wired to the same pins on the other end. It is used for interconnecting nodes on the network.
Stream Cipher A stream cipher works by encryption a message a single bit, byte, or computer word at a time.
Streaming Data streaming, commonly seen in the forms of audio and video streaming, is when a multimedia file can be played back without being completely downloaded first. Most files, like shareware and software updates that you download off the Internet, are not streaming data. However, certain audio and video files like Real Audio and QuickTime documents can be streaming files, meaning you can watch a video or listen to a sound file while it's being downloaded to your computer. With a fast Internet connection, you can actually stream live audio or video to your computer.
streaming audio Streaming audio solves a problem that used to discourage the use of sound on the Internet. Before streaming audio, Web users had to download an entire sound file before they could hear it. Because sound files tend to be fairly large, users had to wait a long time before they could hear the file. Web browsers can begin playing streaming audio files a few seconds after the download begins. In other words, you hear the file as it streams into your computer, rather than after it arrives. Streaming video does the same thing for digital movies, which are even bigger than digital sound files.
String A string is a data type used in programming, such as an integer and floating point unit, but is used to represent text rather than numbers. It is comprised of a set of characters that can also contain spaces and numbers. For example, the word "hamburger" and the phrase "I ate 3 hamburgers" are both strings. Even "12345" could be considered a string, if specified correctly. Typically, programmers must enclose strings in quotation marks for the data to recognized as a string and not a number or variable name. For example, in the comparison: if (Option1 == Option2) then ... Option1 and Option2 may be variables containing integers, strings, or other data. If the values are the same, the test returns a value of true, otherwise the result is false. In the comparison: if ("Option1" == "Option2") then ... Option1 and Option2 are being treated as strings. Therefore the test is comparing the words "Option1" and "Option2," which would return false. The length of a string is often determined by using a null character.
Striping Storing data across multiple disks in such a way that I/O read and write operations can proceed in parallel. Striping can give significant performance gains. cf RAID.
Strong Star Property In Strong Star Property, a user cannot write data to higher or lower classifications levels than their own.
Sub Network A separately identifiable part of a larger network that typically represents a certain limited number of host computers, the hosts in a building or geographic area, or the hosts on an individual local area network.
SUB-SEARCHING Ability to search only within the results of a previous search. Enables you to refine search results, in effect making the computer "read" the search results for you selecting documents with terms you sub-search on. Can function much like RESULTS RANKING.
Subdirectory A subdirectory, or subfolder, is a folder that is nested within another folder. Subdirectories are used to organize files and folders, which makes it easy to navigate to different files stored on a computer. While each operating system creates its own series of predefined subdirectories, you can also create new folders, which can be used to organize data in whatever way makes sense to you.
SUBJECT DIRECTORY An approach to Web documents by a lexicon of subject terms hierarchically grouped. May be browsed or searched by keywords. Subject directories are smaller than other searchable databases, because of the human involvement required to classify documents by subject.
Subnet Mask A subnet mask is a number that defines a range of IP addresses that can be used in a network. (It is not something you wear on your head to keep subnets out.) Subnet masks are used to designate subnetworks, or subnets, which are typically local networks LANs that are connected to the Internet. Systems within the same subnet can communicate directly with each other, while systems on different subnets must communicate through a router. Therefore, subnetworks can be used to partition multiple networks and limit the traffic between them. A subnet mask hides, or "masks," the network part of a system's IP address and leaves only the host part as the machine identifier. A common subnet mask for a Class C IP address is 255.255.255.0. Each section of the subnet mask can contain a number from 0 to 256, just like an IP address. Therefore, in the example above, the first three sections are full, meaning the IP addresses of computers within the subnet mask must be identical in the first three sections. The last section of each computer's IP address can be anything from 0 to 255. For example, the IP addresses 10.0.1.201 and 10.0.1.202 would be in the same subnet, while 10.0.2.201 would not. Therefore, a subnet mask of 255.255.255.0 allows for close to 256 unique hosts within the network (since not all 256 IP addresses can be used). If your system is connected to a network, you can typically view the network's subnet mask number in the Network control panel (Windows) or System Preference (Mac OS X). Most home networks use the default subnet mask of 255.255.255.0. However, some office networks may use a different subnet mask such as 255.255.255.128, which can be used to split a network into two subnets. Large networks with several thousand machines may use a subnet mask of 255.255.0.0. This is the default subnet mask used by Class B networks. The largest Class A networks use a default subnet mask of 255.0.0.0.
Subroutine A mini program that resides inside another program and is called within that program. Typically you put together a subroutine when you have to do similar repetitive tasks in different areas of your program and you don’t want to code the same thing over and over again.
subscribe Commonly refers to the act of selecting a network newsgroup as one you want to read on a regular basis or of sending a request to join a mailing list (discussion group) that interest you. The opposite action is called "unsubscribing".
Super Bypass A means of reducing memory latency in the AMD 750 chipset, the first chipset designed to work with the AMD Athlon. It was implemented in all versions of the AMD 750, but did not function properly in early versions. AMD corrected this problem with a new revision of the AMD 750 chipset. It is possible to identify the Super Bypass-capable chipsets electronically or through software, but the enabling or disabling of Super Bypass is done automatically by the motherboard BIOS.
Super VGA (SVGA) An extension to the original VGA standard which allows resolutions of 800×600. See also VGA.
Super XGA (SXGA) A display with 1280×1024 pixel resolution.
Super XGA+ (SXGA+) A display with 1400×1050 pixel resolution. It is a hybrid resolution between SXGA and UXGA found on some LCD screens in laptop PCs.
Supercomputer As the name implies, a supercomputer is no ordinary computer. It is a high performance computing machine designed to have extremely fast processing speeds. Supercomputers have various applications, such as performing complex scientific calculations, modeling simulations, and rendering large amounts of 3D graphics. They may also be built to simply showcase the leading edge of computing technology. If you are hoping to have a supercomputer on your desk, you may be out of luck. Supercomputers are typically several times the size of a typical desktop computer and require far more power. A supercomputer may also consist of a series of computers, which may fill an entire room. Examples of single machine supercomputers include the early Cray-1 and Cray X-MP systems developed by Cray Research as well as the more recent Blue Gene and Roadrunner systems developed by IBM. System X is an example of a multi-system supercomputer, which was developed by Virginia Tech and is comprised of 1,100 Apple Xserve G5s. Supercomputers cost a fortune to build and are expensive to maintain, which is why only a few exist in the entire world. Furthermore, computing power continues to advance each year, meaning it isn't too long before a ground-breaking supercomputer isn't so super. The good news is that the supercomputers of the past eventually become the personal computers of today. Therefore, your home PC most likely has more computing power than many supercomputers from previous decades. Now that's super cool.
Supermicro Super Micro Computer, Inc. or Supermicro (NASDAQ: SMCI) designs, develops, manufactures and sells servers based on the modular and open-standard x86 architecture. The company's solutions include rackmount server and blade server systems, high-end workstations, storage server systems, motherboards, chassis, and server components called Server Building Block Solutions®.
Surf (v. to surf) This term is synonymous with browsing, as in browsing the Web with a Web browser.
Surge Protector The surge protector is an important, yet often overlooked part of a computer setup. It allows multiple devices to plugged in to it at one time and protects each connected device from power surges. For example, a home office may have a computer, monitor, printer, cable modem, and powered speakers all plugged into one surge protector, which is plugged into a single outlet in the wall. The surge protector allows many devices to use one outlet, while protecting each of them from electrical surges. Surge protectors, sometimes called power strips, prevent surges in electrical current by sending the excess current to the grounding wire (which is the round part of the plug below the two flat metal pieces on U.S. outlet plugs). If the surge is extra high, such as from a lightning strike, a fuse in the surge protector will blow and the current will prevented from reaching any of the devices plugged into the surge protector. This means the noble surge protector will have given its life for the rest of the equipment, since the fuse is destroyed in the process. While surge protectors all perform the same basic function, they come in many shapes and sizes with different levels of protection. Some may look like basic power strips, while others may be rack mounted or fit directly against the wall. Most surge protectors offer six to ten different outlets. Cheaper surge protectors offer limited protection for surges (under 1000 joules), while more expensive ones offer protection for several thousand joules and include a monetary guarantee on connected devices if a power surge happens. Typically, you get what you pay for, so if you have an expensive computer system, it is wise to buy a quality surge protector that offers at least 1000 joules of protection. Some surge protectors also include line conditioning, which uses an electromagnet to maintain a consistent level of electricity when there are slight variations in current. For example, you might notice your computer monitor or television fade for a moment when you turn on a high-powered device, like a vacuum or air conditioner. A surge protector with line conditioning should prevent connected devices from being affected by these slight variances in current. While you may be able to hook up your computer system without a surge protector, it is important to protect your equipment by using one. You may not need a large, expensive surge protector with line conditioning, but using a quality surge protector for all your electronic devices is a smart choice.
SUS Software Update Services. SUS is a Windows server add-on that makes it easier to deploy patches and other updates to a group of managed computers. Set to be superseded by WUS.
SVGA (Super VGA) An extension to the original VGA standard which allows resolutions of 800×600. See also VGA.
Swap file A file stored on the computer hard disk drive that is used as a temporary location to store information that is not currently being used by the computer RAM. By using a swap file a computer has the ability to use more memory than what is physically installed in the computer. However, users who are low on hard disk space may notice that the computer runs slower because of the inability of the swap file to grow in size. It is perfectly normal for the swap file or page file to grow in size, sometimes growing several hundred megs in size. Below is a listing of common Microsoft operating system swap file information; however, it is important to realize that this information may vary. Finally, by default the swap files are hidden.
Switch 1. In a network, a switch is similar to a hub, in that it provides a central connection between two or more computers on a network, but with some intelligence. (A switch operates on Layer 2 (or above) of the OSI 7 layer model and a hub operates at Layer 1.) Whereas for a hub any message received at the hub is broadcast to all the attached computers, with a switch it is sent only to the destination computer and is not visible to other attached devices. This does not prevent "broadcast" messages from being sent to all attached devices. cf hub and router. 2. An electrical device used to turn current on and off. For example a light switch. 3. In software development languages, a switch statement is a control statement which allows one of a set of statements to be selected based on the value of some parameter. In some development languages a switch statement is known by the alternative name of a select statement (but do not confuse this with select in SQL which is not related.)
Switched Network A communications network, such as the public switched telephone network, in which any user may be connected to any other user through the use of message, circuit, or packet switching and control devices. Any network providing switched communications service.
SXGA (Super XGA) A display with 1280×1024 pixel resolution.
Symbolic Links Special files which point at another file.
Symmetric Cryptography A branch of cryptography involving algorithms that use the same key for two different steps of the algorithm (such as encryption and decryption, or signature creation and signature verification). Symmetric cryptography is sometimes called "secret-key cryptography" (versus public-key cryptography) because the entities that share the key.
Symmetric Key A cryptographic key that is used in a symmetric cryptographic algorithm.
SYN Abbreviation for Synchronize.
SYN Flood A denial of service attack that sends a host more TCP SYN packets (request to synchronize sequence numbers, used when opening a connection) than the protocol implementation can handle.
Sync When you "sync" a device, you synchronize it with your computer. Syncing is commonly done with iPods, PDAs, cell phones, and other electronic devices. The syncing process is also called "merging" the data because it copies the most recently entered information to each device. Therefore, when a device is synced with a computer, typically both the device and the computer are updated. Syncing may also refer to merging the data on two or more computer systems, which is often done over a network.
Synchronization Synchronization is the signal made up of a distinctive pattern of bits that network hardware looks for to signal that start of a frame.
synchronous communication Synchronous communication is the technique of choice for ISDN lines because it handles data more efficiently than the typical modem's asynchronous technique. While asynchronous communication sends smallish blocks of data with lots of control bits for error correction, synchronous techniques use big blocks of data with control bits only at the start and end of the entire transmission. But because of the minimal error checking, synchronous communicating devices must be timed to perfection, and they need a clean line. A modem used over an analog line won't handle synchronous communication well because a crackle on the line would throw everything out of sync. ISDN routers and internal adapters use synchronous communication. This allows them to transfer data up to 30 percent faster than ISDN modems, which must convert the data they receive synchronously so that it can be transmitted asynchronously through the computer's serial interface. See also: asynchronous communication
Synonym A synonym is an alias for any table, view, snapshot, sequence, procedure, function or package contained within a database.
Syntax Each spoken language has a general set of rules for how words and sentences should be structured. These rules are collectively known as the language syntax. In computer programming languages, syntax serves the same purpose, defining how declarations, functions, commands, and other statements should be arranged. Each computer programming language uses a different syntax. Many languages share similar syntax rules, while others have a very unique syntax design. For example, C and Java use a highly similar syntax, while Perl has many characteristics that are not seen in either the C or Java languages. Regardless of the rules, a program's source code must have the correct syntax in order to compile correctly and be made into a program. In fact, it must have the exact right syntax, or the program will fail to compile and produce a "syntax error." A syntax error can be as simple as a missing parenthesis or a forgotten semicolon at the end of a statement. Even these small errors will keep the source code from compiling. Fortunately, most software development programs include a debugger, which helps find the exact location of syntax errors within the source code. Imagine a program that has over ten thousand lines of code and a syntax error is caused by one missing semicolon. Finding a needle in a haystack would be preferred over manually locating the error. Needless to say, the debugger makes the debugging process much easier for the programmer.
synthesizer An electronic musical instrument capable of generating sound using real-time control over the key parameters of sound: frequency, timbre, amplitude, and duration. Today most synthesizers include a MIDI interface. Also may refer to an internal sound card or external box for use with multimedia sequencing software.
Syslog Syslog is the system logging facility for Unix systems.
System Analyst A system analyst is the person who selects and configures computer systems for an organization or business. His or her job typically begins with determining the intended purpose of the computers. This means the analyst must understand the general objectives of the business, as well as what each individual user's job requires. Once the system analyst has determined the general and specific needs of the business, he can choose appropriate systems that will help accomplish the goals of the business. When configuring computer systems for a business, the analyst must select both hardware and software. The hardware aspect includes customizing each computer's configuration, such as the processor speed, amount of RAM, hard drive space, video card, and monitor size. It may also involve choosing networking equipment that will link the computers together. The software side includes the operating system and applications that are installed on each system. The software programs each person requires may differ greatly between users, which is why it is important that the system analyst knows the specific needs of each user. To summarize, the system analyst's job is to choose the most efficient computer solutions for a business, while making sure the systems meet all the company's needs. Therefore, the system analyst must have a solid understanding of computer hardware and software and should keep up-to-date on all the latest technologies. He must also be willing to listen to the constant needs and complaints of the users he builds systems for.
System Bus The path between a microprocessor and the chipset on the motherboard. This bus may or may not run at the same speed as the memory bus.
System Hardening Most computers offer network security features to limit outside access to the system. Software such as antivirus programs and spyware blockers prevent malicious software from running on the machine. Yet, even with these security measures in place, computers are often still vulnerable to outside access. System hardening, also called Operating System hardening, helps minimize these security vulnerabilities. The purpose of system hardening is to eliminate as many security risks as possible. This is typically done by removing all non-essential software programs and utilities from the computer. While these programs may offer useful features to the user, if they provide "back-door" access to the system, they must be removed during system hardening. Advanced system hardening may involve reformatting the hard disk and only installing the bare necessities that the computer needs to function. The CD drive is listed as the first boot device, which enables the computer to start from a CD or DVD if needed. File and print sharing are turned off if not absolutely necessary and TCP/IP is often the only protocol installed. The guest account is disabled, the administrator account is renamed, and secure passwords are created for all user logins. Auditing is enabled to monitor unauthorized access attempts. While these steps are often part of operating system hardening, system administrators may choose to perform other tasks that boost system security. While both Macintosh and Windows operating systems can be hardened, system hardening is more often done on Windows machines, since they are more likely to have their security compromised.
System Requirements Whenever you purchase software or hardware for your computer, you should first make sure your computer supports the system requirements. These are the necessary specifications your computer must have in order to use the software or hardware. For example, a computer game may require you computer to have Windows XP or later, a 2.0 GHz processor, 512 MB or RAM, a 64 MB graphics card, and 500 MB or hard drive space. If your computer does not meet all of these requirements, the game will not run very well or might not run at all. It is just as important to check system requirements for hardware devices. For example, if you buy a printer, it may require either Windows XP or Mac OS X 10.3 or later. It may also require a USB port and 80 MB of available hard drive space. If your computer does not have any USB ports, you will not be able to physically connect the printer. If your machine does not have Windows XP or Mac OS X 10.3 or later, the printer drivers may be incompatible with your operating system. This means you computer will be unable to recognize the printer. Most hardware and software products have the system requirements printed on the side or bottom of the product packaging. When you are shopping for computer software or hardware, it is a good idea to first find out exactly what your system's specifications are and write them down on a piece of paper. The important information to record includes: Operating System (i.e. Windows XP, SP 2 or Mac OS X 10.3.8) Processor Speed (i.e. Pentium 4, 3.2 GHz or Power PC G5, 2.0 GHz) Memory, a.k.a. RAM (i.e. 512 MB) Graphics Card (i.e. ATI Radeon 9800 w/ 256 MB video memory) Hard Disk Space (i.e. 80 GB available) I/O Ports (i.e. USB, Firewire, Serial, Parallel, SCSI, VGA, DVI ports) By recording these specifications from your computer, you will be able to make sure your computer supports the products you are buying.
System Resources Your computer has many types of resources. They include the CPU, video card, hard drive, and memory. In most cases, the term "system resources" is used to refer to how much memory, or RAM, your computer has available. For example, if you have 1.0 GB (1024 MB) of RAM installed on your machine, then you have a total of 1024 MB of system resources. However, as soon as your computer boots up, it loads the operating system into the RAM. This means some of your computer's resources are always being used by the operating system. Other programs and utilities that are running on your machine also use your computer's memory. If your operating system uses 300 MB of RAM and your active programs are using 200 MB, then you would have 524 MB of "available system resources." To increase your available system resources, you can close active programs or increase your total system resources by adding more RAM. System resources can also refer to what software is installed on your machine. This includes the programs, utilities, fonts, updates, and other software that is installed on your hard drive. For example, if a file installed with a certain program is accidentally removed, the program may fail to open. The error message may read, "The program could not be opened because the necessary resources were not found." As you can see, the term "system resources" can be a bit ambiguous. Just remember that while it usually refers to your computer's memory, it can be used to describe other hardware or software as well.
System Security Officer (SSO) A person responsible for enforcement or administration of the security policy that applies to the system.
System Software System software refers to the files and programs that make up your computer's operating system. System files include libraries of functions, system services, drivers for printers and other hardware, system preferences, and other configuration files. The programs that are part of the system software include assemblers, compilers, file management tools, system utilites, and debuggers. The system software is installed on your computer when you install your operating system. You can update the software by running programs such as "Windows Update" for Windows or "Software Update" for Mac OS X. Unlike application programs, however, system software is not meant to be run by the end user. For example, while you might use your Web browser every day, you probably don't have much use for an assembler program (unless, of course, you are a computer programmer). Since system software runs at the most basic level of your computer, it is called "low-level" software. It generates the user interface and allows the operating system to interact with the hardware. Fortunately, you don't have to worry about what the system software is doing since it just runs in the background. It's nice to think you are working at a "high-level" anyway.
System Unit This is the technical term that refers to the box that houses your computer. The system unit refers to the computer itself but does not include the monitor, the keyboard, the mouse, or any other peripherals. I suppose most people will probably know what you mean when you refer to "the box," but saying "system unit" will definitely make you sound more sophisticated.
System-Specific Policy A System-specific policy is a policy written for a specific system or device.
Systray The systray, short for "system tray," is located on the right side of the Windows toolbar. It is the collection of small icons on the opposite side of the Start Menu. The volume control and the date & time are default items in the systray and many more can be added. Some common icons that get placed in the systray are virus-scan, mouse, and instant messenger icons. They usually get put in the systray (whether you like it or not) when their respective programs are installed. The nice thing about the systray is that it allows quick and easy access to programs and control settings. Most systray icons will open a control panel or program when double-clicked. However, if you install too many of them, the area can get so cluttered, you may find it easier to just browse your hard drive and open the program.
T&C Terms and Conditions. A stated list of terms and conditions that must be agreed to by a user of a service as a condition of use of that service. Sometimes also referred to as TOS or TOU.
T-1 A leased-line connection capable of carrying data at 1,544,000 bits-per-second. At maximum theoretical capacity, a T-1 line could move a megabyte in less than 10 seconds. That is still not fast enough for full-screen, full-motion video, for which you need at least 10,000,000 bits-per-second. T-1 lines are commonly used to connect large LANs to theInternet.
T-3 A leased-line connection capable of carrying data at 44,736,000 bits-per-second. This is more than enough to do full-screen, full-motionvideo.
T1 Two pairs of copper wire that carry data at a rate of 1.544Mbps. T1 lines are used to carry 24 DS-0 signals. They can be used to carry 24 phone lines or an Internet connection capable of 1.544Mbps data transfer. See also fractional T1.
T2 Four T1 lines which can carry 96 voice channels or up to 6.312Mbps worth of data.
T3 28 T1 lines together make up a T3, which can carry 672 separate voice channels or up to 44.736Mbps data throughput.
T4 6 T3 lines make up a T4, which carries data at 274Mbps.
T5 240 T1 lines, which can carry 5760 voice channels or up to 400.352Mbps worth of data.
table With reference to web design, a method for formatting information on a page. Use of tables and the cells within also provide a way to create columns of text. Use of tables vs frames is recommended for helping to make your web site ADA-compliant.
Tag On clothes, tags usually indicate the brand, size of the garment, fabrics used, and the washing instructions. In Web pages, tags indicate what should be displayed on the screen when the page loads. Tags are the basic formatting tool used in HTML (hypertext markup language) and other markup languages, such as XML. For example, to create a table on a Web page, the tag is used. The data that should be inside the table follows the
tag, and the table is closed with a
tag. If you want something to show up in bold on a Web page, you would use the bold tag. For example, the line: This site is the best website ever! would show up as: This site is the best website ever! Since there is often a need to format content within more general tags, the tags can be "nested," meaning one tag can enclose one or more other tags. For example: This is the Times font, and this is in italics. Pretty exciting, huh? would should up as: This is the Times font, and this is in italics. Pretty exciting, huh? Tags are a fundemental part of HTML and they are pretty simple to understand.
Tamper To deliberately alter a system's logic, data, or control information to cause the system to perform unauthorized functions or services.
Tape Drive This is a removable storage device mainly used for backing up data. It is similar to a Zip Drive, but instead of Zip disks, it uses small tapes. The drive acts like a tape recorder, reading data from the computer and writing it onto the tape. Since tape drives have to scan through lots of tape to read small amounts of scattered data, they are not practical for most storage purposes. That is why they are used almost exclusively for data backup. The benefit of tape drives is that they typically have large capacities for storing data, for a lower cost than hard drives similar in size. Also, multiple tapes can be used to make incremental backups (daily, weekly, monthly, etc.), which is much cheaper than using multiple hard drives.
tar (file format) In computing, tar (derived from tape archive and commonly referred to as "tarball") is both a file format (in the form of a type of archive bitstream) and the name of a program used to handle such files. The format was created in the early days of Unix and standardized by POSIX.1-1988 and later POSIX.1-2001. Initially developed to be written directly to sequential I/O devices for tape backup purposes, it is now commonly used to collect many files into one larger file for distribution or archiving, while preserving file system information such as user and group permissions, dates, and directory structures.
Target Disk Mode Target disk mode is a way of booting a Macintosh computer so that it acts as an external hard drive on another computer. When a Mac is booted in target disk mode, the typical boot sequence is bypassed and the operating system is not loaded. Instead, the computer's internal and external hard drives are simply mounted on a connected computer. Target disk mode can be used to manually transfer files between two machines or to copy data from one computer to another using Apple's Migration Assistant. In order for target disk mode (TDM) to work, two Macintosh computers must be attached to each other via a Firewire cable. One computer should be on and the computer designated for TDM should be off. To boot into target disk mode, hold the "T" key on the keyboard immediately after turning on or restarting the computer. After a few seconds, the screen should display the Firewire icon, which will move around the screen as long as the machine is in target disk mode. You should then see the hard drive(s) of the computer in TDM appear on the Desktop of the connected computer. Booting a computer in target disk mode makes it easy to transfer files between two machines. Since the hard drives of the computer in TDM automatically mount on the other Mac's desktop, you can simply drag and drop files between them. Also, the computer in target disk mode is not seen as a boot disk, so you don't have to worry about file permissions. You can also run more comprehensive disk diagnostics and repairs. Just be sure not to remove or copy over any important system files on the TDM hard drive(s), since there are no safeguards to protect you from doing so. Since the hard drives of the TDM machine are mounted on the connected computer, you should make sure to unmount or "eject" the hard drives before you turn off the computer. This can be done by selecting the hard drive on the desktop and choosing "Eject" from the File menu. Once the hard drives are ejected, you can safely turn off the TDM computer. When you turn on the computer again, it should boot normally (as long as you don't hold down the "T" key). Any files you copied to the computer's hard drives should appear in the directories you copied them to.
Task Bar The task bar was introduced with Windows 95 and has been part of every version of Windows since then. It is the bar that spans the bottom of the screen and contains the Start button on the left side and the systray on the right. The task bar also includes the current time on the far right side and can hold shortcuts to programs directly to the right of the Start button. Most of the task bar, however, contains shortcuts to open windows. Whenever you open a program or window, it shows up in the task bar. So if you have Internet Explorer and Microsoft Word open, there will be at least two items in the middle area of the task bar. Since each window gets its own location in the task bar, if there are two Microsoft Word documents open and three Internet Explorer windows open, there will be a total of five items in the task bar. When you click on a window title in the task bar, that window will become active and show up in front of other open windows. You can also cycle through the task bar items by holding the Alt key and pressing Tab a few times.
TB 1. Abbreviation for terabyte, a unit of storage. 2. Chat abbreviation for: Text Back. This abbreviation simply asks for a text response and in essence is a way of texting "please respond".
TBD 1. To Be Done. 2. To Be Determined. 3. Technical Background Document. 4. To Be Decided. 5. To Be Developed.
Tcl Tool Command Language. A scripting language originating from Unix. Tcl can be extended by users and is suited for creating GUIs, and other tools. It can be used in mixed environments, including Windows, Mac and Unix platforms. See also Tcl/Tk.
Tcl/Tk Tool Command Language/Tool Kit. Tcl (Tool Command Language) with a set of graphical user components (originally developed as a Tcl extension) which has collectively become known as Tcl/Tk.
TCP Transmission Control Protocol. Connection-Oriented protocol for establishing a connection between two computers and for managing the delivery of data packets between the those computers. TCP is often used in conjunction with IP, which it is referred to as TCP/IP.
TCP Fingerprinting TCP fingerprinting is the user of odd packet header combinations to determine a remote operating system.
TCP Full Open Scan TCP Full Open scans check each port by performing a full three-way handshake on each port to determine if it was open.
TCP Half Open Scan TCP Half Open scans work by performing the first half of a three-way handshake to determine if a port is open.
TCP Wrapper A software package which can be used to restrict access to certain network services based on the source of the connection; a simple tool to monitor and control incoming network traffic.
TCP/IP Transmission Control Protocol/Internet Protocol. Transmission Control Protocol (TCP) used in conjunction with Internet Protocol (IP). cf CAT5, CAT5e, CAT6.
TCPDump TCPDump is a freeware protocol analyzer for Unix that can monitor network traffic on a wire.
Tebibyte A tebibyte is a unit of data storage that equals 2 to the 40th power, or 1,099,511,627,776 bytes. While a terabyte can be estimated as 10^12 or 1,000,000,000,000 bytes, a tebibyte is exactly 1,099,511,627,776 bytes. This is to avoid the ambiguity associated with the size of terabytes. A tebibyte is 1,024 gibibytes and precedes the pebibyte unit of measurement. For a list of other units of measurements, view this Help Center article. Abbreviation: TiB
Technology Refresh echnology Refresh (sometimes abbreviated to simply TR) is the periodic replacement of equipment to ensure continuing reliability of equipment and/or improved speed and capacity. cf evergreening, technology replacement.
Technology Replacement The policy for the periodic replacement of equipment to ensure the lowest cost of replacement technology that continuously satisfies the speed and capacity requirements over the life of the replacement. See also "Technology Refresh" and "evergreening".
Technology Services Technology services are services that make use of modern technology. Examples include Internet service providers (ISPs), Web hosts, and technical support companies. Since many technology services are related to information technology, they are sometimes called "information technology services," or ITS. However, other services like graphic design, audio/video production, and scientific engineering also fall under the scope of technology services. Therefore, while technology services are often related to IT, they may be associated with other forms of technology as well.
Telecom Refers to the industry and hardware involved with telephones and the transmission of voice data.
Telecommunications Telecommunications is the transmission of analog or digital signals over a long distance. This includes telephone calls, radio and television broadcasts, and data transfers over the Internet. Thanks to telecommunications, people can communicate instantly regardless of where they are located. The term "telecom" may also refer to a telecommunications company.
Telnet The command and program used to login from one Internet siteto another. The telnet command/program gets you to the login: prompt of another host.
TEMP File TEMP File A temporary file. This may be written as "TEMP file" or "temp file", case is not significant other than that TEMP is a system variable that indicates the folder in which temporary files should be generated. Temporary files are generated by applications and should be deleted automatically by the application that created them when they are no longer required. Unfortunately this frequently does not happen so temporary files can tend to build up over time. Temporary files can be deleted if they are no longer in use. Temporary files are commonly denoted by the file extension ".tmp" (or less commonly ".$$$") but this is not always the case. They are typically created in a directory designated as a temporary directory (meaning that the files in the directory are temporary files not that the directory itself is temporary), but some applications may create temporary files elsewhere.
Template A template is a file that serves as a starting point for a new document. When you open a template, it is pre-formatted in some way. For example, you might use template in Microsoft Word that is formatted as a business letter. The template would likely have a space for your name and address in the upper left corner, an area for the recipient's address a little below that on the left site, an area for the message body below that, and a spot for your signature at the bottom. When you save a file created with a template, you are usually prompted to save a copy of the file, so that you don't save over the template. Templates can either come with a program or be created by the user. Most major programs support templates, so if you find yourself creating similar documents over and over again, it might be a good idea to save one of them as a template. Then you won't have to format your documents each time you want to make a new one. Just open the template and start from there.
Temporary File A file which is generated by an application on a temporary basis and which the application should delete after use. Temporary files are generated by applications and should be deleted automatically by the application that created them when they are no longer required - unfortunately this frequently does not happen so temporary files can tend to build up over time. Temporary files can be deleted if they are no longer in use. Temporary files are commonly denoted by the file extension ".tmp" (or .$$$), but this is not always the case. They typically are created in a directory designated as a temporary directory (meaning that the files in the directory are temporary files not that the directory itself is temporary), but some applications may create temporary files elsewhere. Temporary files are often abbreviated to simply Temp file or TMP file.
Terabyte Unit of storage. Often abbreviated to TB. 1 terabyte = 2 to the fortieth (240) bytes = 1,099,511,627,776 bytes = 1024 gigabytes. See also petabyte.
Terminal 1. End point. For example the end point on a journey would be its terminal. Similarly the end point on a line (or polyline) would be the terminal point. 2. An electronic input/output device for communicating with a computer. Normally consisting of at least a keyboard and monitor. 3. Deadly. 4. An electrical connection point, such as on a circuit board.
Terminal Adapter An electronic device that interfaces a PC with a host computer via an ISDN phone line. They are often called "ISDN modems"; however, because they are digital, Terminal Adapters are not modems at all. See Also: Modem
Terminal Server A special purpose computer that has places to plug in many modemson one side, and a connection to a LAN or host machine onthe other side. Thus the terminal server does the work of answering the calls and passes the connections on to the appropriate node. Most terminal servers can provide PPP or SLIP services if connected to the Internet.
Text Editor A text editor is any word processing program that you can use to type and edit text. Hey, they don't call it a text editor for nothing... Word Pad and NotePad for Windows and SimpleText and TextEdit for the Mac are common text editors. Larger programs such as Microsoft Word and Word Perfect are also text editors, but they have many more features. You can actually write HTML code and create HTML pages with a simple text editor, as long as you know the correct HTML syntax.
Thermal Compound A paste that is applied between a microprocessor and heatsink. This paste fills in any tiny gaps that may be present on the visibly flat surfaces of the microprocessor package and heatsink. Without thermal compound cooling may be less efficient, as the heatsink and microprocessor package may have air gaps between them. Thermal compound has much more efficient heat exchange properties than air.
Thermal Paper A type of paper that displays a mark on it when heat is applied. Some older printers and fax machines used thermal paper, as it allowed for a very cheap printing mechanism.
Thermal Paste Synonymous with thermal compound. A paste that is applied between a microprocessor and heatsink. This paste fills in any tiny gaps that may be present on the visibly flat surfaces of the microprocessor package and heatsink. Without thermal compound cooling may be less efficient, as the heatsink and microprocessor package may have air gaps between them. Thermal compound has much more efficient heat exchange properties than air.
Thermal Tape Like thermal compound, thermal tape fits between a microprocessor package and heatsink and gives greater heat conductivity than air. Thermal tape is typically less efficient than thermal compound.
ThickNet The type of cabling on which 10Base5 Ethernet runs. It can transfer data at up to 10Mbps using the 10Base5 Ethernet standard. It is thicker than 10Base2 cabling, and thus the name.
Thin Client 1. A client/server application that is designed to minimize the amount of data (including the application itself) that needs to be transferred from the server to the client. Thin client applications are therefore small and perform most of the work on the server. cf Fat Client. 2. When applied to a computer rather than an application it refers to a client computer which is intended only to be used as a network client with no local storage and minimal processing capability. A thin client computer runs applications (such as word-processing, internet browser etc) on the server, using the thin client only as a display device. Thin client computers include network computers and X-terminals
ThinNet This refers to the type of cabling on which 10Base2 Ethernet runs. It can transfer data at up to 10Mbps using the 10Base2 Ethernet standard. It is thinner than 10Base5 cabling.
Thread An ongoing message-based conversation on a single subject. See Also: Mailing List, Newsgroup, Posting
Threat A potential for violation of security, which exists when there is a circumstance, capability, action, or event that could breach security and cause harm.
Threat Assessment A threat assessment is the identification of types of threats that an organization might be exposed to.
Threat Model A threat model is used to describe a given threat and the harm it could to do a system if it has a vulnerability.
Threat Vector The method a threat uses to get to the target.
Throughput Throughput refers to how much data can be transferred from one location to another in a given amount of time. It is used to measure the performance of hard drives and RAM, as well as Internet and network connections. For example, a hard drive that has a maximum transfer rate of 100 Mbps has twice the throughput of a drive that can only transfer data at 50 Mbps. Similarly, a 54 Mbps wireless connection has roughly 5 times as much throughput as a 11 Mbps connection. However, the actual data transfer speed may be limited by other factors such as the Internet connection speed and other network traffic. Therefore, it is good to remember that the maximum throughput of a device or network may be significantly higher than the actual throughput achieved in everyday use.
TIA Chat abbreviation: Thanks In Advance. Sometimes used in newsgroup postings where someone asks a question of the newsgroup, and ends it with the polite comment "TIA" ("Thanks In Advance").
TIFF Tagged Image File Format. A common image file format developed by Adobe. TIFF files are usually identified with a ".tif" or ".tiff" file extension.
Tiger This ferocious cat is the code name for Mac OS X 10.4, released April 29, 2005. Tiger follows a list of other felines in the Mac OS X lineup, including Panther (10.3), Jaguar (10.2), Puma (10.1), and Cheetah (10.0). Apple originally used the cat names as internal names for the operating system development, but actually started to market the names with the release of Jaguar. According to Apple, Tiger includes over 200 improvements from Mac OS X 10.3. A few of the most notable additions include an enhanced search feature called "Spotlight," an internal scripting program called "Automator," and quick information access via widgets from the new "Dashboard." Mac OS X 10.4 Tiger is a feature-rich operating system that some may consider as a serious alternative to Windows.
Time to Live A value in an Internet Protocol packet that tells a network router whether or not the packet has been in the network too long and should be discarded.
Time Zone Time Zone A North-South strip along the surface of the Earth which uses the same time standard, where notionally at 12 noon the sun is at its highest point in the sky. The Earth is divided into 24 time zones and within each time zone the same time standard is used (i.e. all the clocks in a given time zone should agree). Each time zone is roughly 15 degrees wide, but there are some variations because time zones are often bounded by country or administrative borders and it is often easier to follow these borders than the strict 15 degree boundary. Time zones are defined by the number of hours difference from UTC: UTC Offset Abbreviation Full Name Used Where UTC - 12 Eniwetok, Kwajalein UTC - 11 Midway Island, Somoa UTC - 10 Hawaii-Aleutian Standard Time Hawaii UTC - 9 AKST Alaska Standard Time Alaska UTC - 8 AKDT Alaska Daylight Time Alaska UTC - 8 PST Pacific Standard Time West coast of America and Canada UTC - 7 Arizona UTC - 7 Mountain Time America and Canada UTC - 6 Central America, Mexico City UTC - 6 CST Central Standard Time America and Canada UTC - 5 Bogota, Lima, Quito, East Indiana UTC - 5 EST Eastern Standard Time East coast of America and Canada UTC - 4 Atlantic Time Canada UTC - 4 Caracas, La Paz, Santiago UTC - 3 Newfoundland, Brasilia, Buenos Aires, Georgetown, Greenland UTC - 2 Mid-Atlantic UTC -1 Azores, Cape Verde Islands UTC UTC Coordinated Universal Time London UTC GMT Greenwich Meridian Time London UTC London, Casablanca, Monrovia UTC + 1 BST British Summer Time London UTC + 1 Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna, Belgrade, Bratislava, Budapest, Ljubljana, Prague, Brussels, Copenhagen, Madrid, Paris, Sarajevo, Skopje, Sofija, Vilnius, Warsaw, Zagreb, West Central Africa UTC + 2 Athens, Istanbul, Minsk, Bucharest, Cairo, Harare, Pretoria, Helsinki, Riga, Tallinn, Jerusalem UTC + 3 Baghdad, Kuwait, Riyadh, Moscow, St. Petersburg, Volgograd, Nairobi UTC + 4 Abu Dhabi, Muscat, Baku, Tbilisi, Yerevan UTC + 5 Ekaterinburg, Islamabad, Karachi, Tashkent UTC + 6 Almaty, Novosibirsk, Astana, Dhaka UTC + 7 Bangkok, Hanoi, Jakarta, Krasnoyarsk UTC + 8 Beijing, Chongqing, Hong Kong, Urumqi, Irkutsk, Ulaan Bataar, Kuala Lumpur, Singapore, Perth, Taipei UTC + 9 Osaka, Sapporo, Tokyo, Seoul, Yakutsk UTC + 10 Brisbane, Canberra, Melbourne, Sydney, Guam, Port Moresby, Hobart, Vladivostok UTC + 11 Magadan, Solomon Islands, New Caledonia UTC + 12 Auckland, Wellington, Fiji, Kamchatka, Marshall Islands UTC + 13 Muku'alofa As a further complication some countries observe daylight saving, which means that their local time is adjusted by one or two hours at certain times of the year to make best use of the available daylight.
Tiny Fragment Attack With many IP implementations it is possible to impose an unusually small fragment size on outgoing packets. If the fragment size is made small enough to force some of a TCP packet's TCP header fields into the second fragment, filter rules that specify patterns for those fields will not match. If the filtering implementation does not enforce a minimum fragment size, a disallowed packet might be passed because it didn't hit a match in the filter. STD 5, RFC 791 states: Every Internet module must be able to forward a datagram of 68 octets without further fragmentation. This is because an Internet header may be up to 60 octets, and the minimum fragment is 8 octets.
TITLE The official title of a document from the "meta" field called title. The text of this meta title field may or may not also occur in the visible body of the document. It is what appears in the top bar of the window when you display the document and it is the title that appears in search engine results. The "meta" field called title is not mandatory in HTML coding. Sometimes you retrieve a document with "No Title" as its supposed title; this is caused when the meta-title field is left blank. In Alta Vista and some other search tools, title: search also matches on the "meta" field, which contains document descriptors not displayed on the Web. See also LIMITING TO A FIELD.
Title Bar A title bar is the section at the top of a window that contains the name or description of the window. Nearly all windows displayed on your computer have a title bar. Therefore, if several windows are tiled across the screen at one time, a user can identify each window by just glancing at the title bar. Windows makes this even easier by placing the information from each window's title bar in the Task Bar. Mac OS X displays the title bar information in the middle of each window when the Expos? function is active. The title bar is a standard user interface GUI convention used by many applications, as well as the operating system itself. For example, in a Web browser window, the title bar typically is the title of the current Web page. In a word processor window, the title bar is usually the name of the document itself. If the document has not been named or saved yet, the title bar may read "Document 1" or "Untitled." When folders are opened on the Desktop, the folder window typically displays the name of the active folder in the title bar. In Windows, the title bar can also be set to display the full path to the folder's location by selecting "Folder Options" in the Tools menu. While the title bar serves as an identifier for each window, it also has another important function. By clicking and dragging the title bar, you can move a window to another location on the screen. This is important to know, since the title bar is often the only place you can click to move the window. Also, double-clicking the title bar will minimize the window, placing the window in the Task Bar (Windows) or the Dock (Mac OS X).
TLD Top Level Domain) The last (right-hand) part of a complete Domain Name. For example in the domain name www.matisse.net ".net" is the Top Level Domain. There are a large number of TLD's, for example .biz, .com, .edu, .gov, .info, .int, .mil, .net, .org, and a collection of two-letter TLD's corresponding to the standard two-letter country codes, for example, .us, .ca, .jp, etc. See also: Domain Name
TLS 1. Transport Layer Security. A protocol which is intended to enhance SSL.
TM 1. Trade Mark. Often represented as ™. The trademark symbol shows that a name is used by a business to exclusively identify itself or a specific product. Trade marks do not need to be registered, but under UK law (and the law in this respect may vary from country to country) it is the first person who registers the trademark who can legally prevent others from using it.
TMP File A temporary file. Temporary files are generated by applications and should be deleted automatically by the application that created them when they are no longer required - unfortunately this frequently does not happen so temporary files can tend to build up over time. Temporary files can be deleted if they are no longer in use. Temporary files are commonly denoted by the file extension ".tmp", but this is not always the case. They typically are created in a directory designated as a temporary directory (meaning that the files in the directory are temporary files not that the directory itself is temporary), but some applications may create temporary files elsewhere.
TOC Table of Contents. A list of section headings for a document, normally providing page numbers.
Token A token is a group of bits that are transferred between computers on a token-ring network. Whichever computer has the token can send data to the other systems on the network. This ensures that only one computer can send data at a time. A token may also refer to a network security card, also known as a hard token.
Token Ring A token ring network is a local area network in which all computers are connected in a ring or star topology and a binary digit or token-passing scheme is used in order to prevent the collision of data between two computers that want to send messages at the same time.
Token-Based Access Control Token based access control associates a list of objects and their privileges with each user. (The opposite of list based.)
Token-Based Devices A token-based device is triggered by the time of day, so every minute the password changes, requiring the user to have the token with them when they log in.
Tomcat a web server from the Jakarta Project
Tooltip As computer users, we have become accustomed to icons that represent files, folders, programs, and other objects on the computer. Many software programs also use icons to represent tools, which are often found in the program's toolbar. While these icons can save screen space and make the program's interface more attractive, it can sometimes be difficult to tell what all the tool icons mean. While some tool icons are obvious (such as a printer icon to print and a scissors icon to cut a text selection), others are a bit more ambiguous. For this reason, programs often include tooltips that explain what each tool icon represents. Tooltips are displayed when you roll over an icon with the cursor. It may take a second or two to display the tooltip, but when it does appear, it usually is a small box with a yellow background explaining what the icon represents. For example, in Microsoft Word, when you roll over the disk icon, the tooltip "Save" appears. This means clicking on the disk icon will save your document. In Photoshop, when you roll over the wand icon, the text "Magic Wand Tool (W)" appears. This indicates that clicking the the wand icon or pressing the W key will activate the magic wand selection tool. Not all programs incorporate tooltips, but most modern programs include them as part of a user-friendly interface. Operating systems also support them in different ways. For example, Mac OS X will show the full text of a long filename when you place the cursor over the filename. Windows includes tooltips for the systray icons and also tells you information about each file and folder you place the cursor over. If you drag your cursor over different icons on your computer, you may find tooltips you never knew were there!
Topology The geometric arrangement of a computer system. Common topologies include a bus, star, and ring. The specific physical, i.e., real, or logical, i.e., virtual, arrangement of the elements of a network. Note 1: Two networks have the same topology if the connection configuration is the same, although the networks may differ in physical interconnections, distances between nodes, transmission rates, and/or signal types. Note 2: The common types of network topology are illustrated
Torrent A torrent is a file sent via the BitTorrent protocol. It can be just about any type of file, such as a movie, song, game, or application. During the transmission, the file is incomplete and therefore is referred to as a torrent. Torrent downloads that have been paused or stopped cannot be opened as regular files, since they do not contain all the necessary data. However, they can often be resumed using a BitTorrent client, as long as the file is available from another server. Torrents are different from regular downloads in that they are usually downloaded from more than one server at a time. The BitTorrent protocol uses multiple computers to transfer a single file, thereby reducing the bandwidth required by each server. When a torrent download is started, the BitTorrent system locates multiple computers with the file and downloads different parts of the file from each computer. Likewise, when sending a torrent, the server may send the file to multiple computers before it reaches the recipient. The result is a lower average bandwidth usage, which speeds up file transfers. File Extension: .TORRENT
Torx A type of indent in a screw head that looks like a 6-pointed star. Compaq used torx screws for all of its computer equipment at one point. Torx screws are also used in some automotive applications for body trim that should not be easily removed, such as to hold in the headlights on a ‘79 Chevy Malibu. Because a Torx driver is rarer than a Phillips-head or flat-head screwdriver, Torx screws are used as a simple security method.
TOS 1. Terms Of Service. Sometimes also referred to as T&C 2. Top Of Stack. 3. The Other Service. 4. Abbreviation for TOSLink. 5. Type of Service. TOS refers to the Type of Service field in a ping generated ICMP packet.
Total Cost of Ownership (TCO) This phrase was coined by the creators of the Network Computer (NC) to describe the benefits of using a system that is more mainframe and less client/server. Their logic states that NCs, although they may cost the same up front as cheap PCs, have a lower TCO than a network built on PCs.
TOU Terms Of Use. More commonly referred to as T&C
Touchpad A pad that is electrically sensitive to touch, often used as the pointing device in laptops. You can also tap on it for clicks, but some people find that annoying if they bump the pad while typing.
Tower Case An improvement to the standard desktop case, a tower case is flipped 90 degrees to accommodate more inside and to make it more convenient by allowing the case to be placed on the floor instead of on the desk.
TR 1. Abbreviation for Transmit/Receive. 2. Abbreviation for Technology Refresh. 3. Abbreviation for Token-Ring. 4. Abbreviation for Top-Right
Traceroute When computers communicate over the Internet, there are often many connections made along the way. This is because the Internet is made up of a network of networks, and two different computers may be on two separate networks in different parts of the world. Therefore, if a computer is to communicate with another system on the Internet, it must send data through a series of small networks, eventually getting to the Internet backbone, and then again traveling to a smaller network where the destination computer resides. These individual network connections, called "hops," typically go unnoticed by the average user. After all, why bother tracking all the various connections when you are only interested in communicating with the destination computer? However, if a connection cannot be made or is taking a unusually long time, tracing the path of connections along the way can prove to be helpful. This is exactly what the traceroute command does. Traceroute is a TCP/IP utility that allows a user to trace a network connection from one location to another, recording every hop along the way. The command can be run from a Unix or DOS command line by typing tracert [domain name], where [domain name] is either the domain name or the IP address of the system you are trying to reach. A traceroute can also be done using various networking utilities, such as Apple's Network Utility for Mac OS X. When a traceroute is run, it returns a list of network hops and displays the host name and IP address of each connection. It also returns the amount of time it took for each connection to take place (usually in milliseconds). This shows if there were any delays in establishing the connection. Therefore, if a network connection is slow or unresponsive, a traceroute can often explain why the problem exists and also show the location of the problem.
Traceroute (Tracert) A command that displays PING results for each router encountered between a source and a destination TCP/IP address. Traceroute is useful for getting some information along the entire path between two TCP/IP addresses. Firewalls or other security measures that block PING traffic also block traceroutes. The command itself is typed “tracert” on the command line of most operating systems.
Tracert (Traceroute) A command that displays PING results for each router encountered between a source and a destination TCP/IP address. Traceroute is useful for getting some information along the entire path between two TCP/IP addresses. Firewalls or other security measures that block PING traffic also block traceroutes. The command itself is typed “tracert” on the command line of most operating systems.
Trackback Trackback is a protocol for notifying websites that other websites have linked to it. When a trackback link is added to a Web page, the linked website is notified that the link has been added. However, both websites must support the trackback protocol in order for the system to work. For this reason, trackback is most commonly used by blogging websites to share links and responses to blog entries.
Trackball A trackball is an input device that has a ball which is held in a socket and can be rolled in any direction. Most trackballs perform the same functions as a mouse and are used primarily to control the cursor on a computer screen. However, unlike a mouse, a trackball device remains stationary when the user move the ball. This makes trackballs ideal for areas with limited space.
Transactions Per Minute (TPM) The amount of database transactions a server can do in a minute’s time. This method of measurement is often used to compare high-powered database servers with multiple processors. Often the ratio of money per transactions is used to show the cost-effectiveness of a particular server.
transistor One of the most important inventions in history, the transistor can be found in nearly every common electronic device manufactured today--radios, TV sets, cellular phones, computers, and so on. Originally created in the late 1940s by Bell Labs, the transistor was hailed as a smaller, less-expensive, and cooler-running replacement for the vacuum tubes then commonly used to amplify current in electronic devices. Today, millions of transistors are often packed into silicon chips to create the processors used in modern computers.
Transmission Control Protocol (TCP) The part of the TCP/IP suite of protocols that is responsible for forming data connections between nodes that are reliable, as opposed to UDP, or IP, which TCP is based on, and which is by default connectionless and potentially unreliable.
Transmission Control Protocol/Internet Protocol (TCP/IP) The TCP/IP suite first saw use on the original Department of Defense Internet in 1983. Its first implementation was amazingly successful, and it is still THE protocol of the Internet. In fact, it has grown even more, and is being used in private networks around the world. TCP/IP is a suite of communications protocols that allows communication between groups of dissimilar computer systems from a variety of vendors. It scales better than NetBEUI because NetBEUI is not routable, and beat out IPX/SPX as it was easier to route than that once-dominant protocol.
Transport Layer Security (TLS) A protocol that ensures privacy between communicating applications and their users on the Internet. When a server and client communicate, TLS ensures that no third party may eavesdrop or tamper with any message. TLS is the successor to the Secure Sockets Layer.
Trawl To search for, specifically to search through a large amount of information for, such as trawling (i.e. searching) the web for information.
Tree A means of organizing data that starts with a single node, or data element, that has any number of child elements. Each of these child elements or nodes can also have its own child elements. Trees are an important part of understanding programming and data structures.
Triple DES Encryption A form of DES encryption that uses three separate 56-bit keys to encrypt and decrypt messages. This basically compounds the number of possible key combinations (72 quadrillion) three times, and makes it even harder to crack an encrypted message.
Triple-Wrapped S/MIME usage: data that has been signed with a digital signature, and then encrypted, and then signed again.
Trivial File Transfer Protocol (TFTP) A network transfer protocol that allows you to connect to a device and download code onto it. For example, it can be used to shove boot code onto a diskless workstation, or connect and download firmware updates to networking devices.
Trojan A harmful application (or routine) that hides it malicious activities by masquerading as a more useful, harmless and desirable application. In many respects a Trojan is like a virus, except that it does not provide a means to copy itself. A Trojan instead relies upon the fact that it masquerades as something useful that people will recommend or copy-on the application. Trojan's are often found in software that is freeware, although it must be stressed that most freeware is free of viruses and Trojans. Anti-virus applications will typically scan for many known Trojans. Anti-virus writers tend to classify a Trojan as one of the following depending on what the Trojan does: Trojan Downloader - downloads and installs new software on the computer. Trojan Dropper - installs new software on the computer. Trojan Proxy - turns the computer into a proxy server providing anonymous access to the internet for the Trojan writer. Trojan PSW - password stealer, hunts the computer for stored usernames and passwords and forwards these to the Trojan writer. Trojan Spy - any form of spyware application, such as keyloggers, password stealers etc. Trojans get their name from the classical Greek story of the Trojan horse, used in the Trojan war. The Trojan horse was a large wooden horse left as a gift from the Greeks to the Trojans, the Greeks then sailed away (apparently admitting defeat). The Trojans moved the horse inside their city walls and then celebrated their apparent victory. Unfortunately for the Trojans the Trojan Horse contains a number of Greek soldiers who then killed the guards and let the remainder of the Greek army into the city who then sacked Troy. A Trojan is also known as a Trojan horse.
Trojan Horse A harmful application (or routine) that hides it malicious activities by masquerading as a more useful, harmless and desirable application. A Trojan horse is also referred to simply as a "Trojan", see Trojan for details.
Troubleshooting Troubleshooting is the process or identifying and fixing problems. Computer troubleshooting may involve hardware or software and can sometimes involve both at the same time. The basic process of troubleshooting is to check the most general possible problems first, and then gradually check for more specific problems. This provides a logical approach to problem solving and can apply to multiple types of products.
True Color The name given to 32-bit, 16.7 million color representation.
True Parity This term has come about with the advent of logical parity memory. It simply means that the parity memory actually does something useful instead of just issuing positives over and over.
TrueType This is a font standard developed by Apple and used in Mac OS version 7. Later, Apple licensed the technology to Microsoft, which used it in Windows 3.1 and continues to use it today. However, Apple and Microsoft TrueType fonts are not compatible.
Truncate To truncate something is to shorten it, or cut part of it off. In computer science, the term is often used in reference to data types or variables, such as floating point numbers and strings. For example, a function may truncate the decimal portion of a floating point number to make it an integer. If the number 3.875 is truncated, it becomes 3. Note that this is different than if the number had been rounded to the nearest integer, which would be 4. Strings may also be truncated, which can be useful if a string exceeds the maximum character limit for a certain application. Several programming languages use the function trunc() to truncate a variable. PHP uses strlen() to truncate a string to a set limit of characters.
TRUNCATION In a search, the ability to enter the first part of a keyword, insert a symbol (usually *), and accept any variant spellings or word endings, from the occurrence of the symbol forward. (E.g., femini* retrieves feminine, feminism, feminism, etc.)
Trunking Trunking is connecting switched together so that they can share VLAN information between them.
Trust Trust determine which permissions and what actions other systems or users can perform on remote machines.
Trusted Ports Trusted ports are ports below number 1024 usually allowed to be opened by the root user.
Tunnel A communication channel created in a computer network by encapsulating a communication protocol's data packets in (on top of) a second protocol that normally would be carried above, or at the same layer as, the first one. Most often, a tunnel is a logical point-to-point link - i.e., an OSI layer 2 connection - created by encapsulating the layer 2 protocol in a transport protocol (such as TCP), in a network or inter-network layer protocol (such as IP), or in another link layer protocol. Tunneling can move data between computers that use a protocol not supported by the network connecting them.
Tunneling The term "tunneling" probably brings to mind images of digging tunnels underground, perhaps for a subway system, or for you more technically-minded, a fiber optic cable connection. In the virtual world of computers world, however, tunneling refers to a protocol in which one protocol is encapsulated within another. Tunneling protocols are often used for establishing various types of connections over common protocols, such as HTTP. For example, a peer-to-peer (P2P) file sharing program may mask data as HTTP to allow the data to be transferred through a firewall. Since most firewalls allow HTTP (port 80) connections, the connection would likely be allowed, since this is the same port that the Web uses. If the program used its own protocol and port number, the connection may be blocked. Tunneling can also be used to establish secure connections through protocols that are typically not secure. For example, the point-to-point tunneling protocol (PPTP) establishes a secure connection over a standard PPP connection, and can used to create a virtual private network (or VPN) between two remote locations. PPTP allows a user to "tunnel" to another location with a secure password-protected connection using the standard or PPP protocol.
Turnkey This usually refers to a server or a complex system that can basically be shipped from the manufacturer, turned on, and work right away. Many VARs pride themselves on providing turnkey servers on which their customers don’t need to do any configuration. If you think of it in terms of an engine, a turnkey engine comes with all the parts and can be tossed into a car and work immediately. An engine that isn’t turnkey will need additional parts and integration before it will run.
Tutorial A computer tutorial is an interactive software program created as a learning tool. Tutorials help people learn new skills by using a step-by-step process that ensures the user is following along and comprehending the material. For example, a Web development tutorial may begin with instructions on how to create a basic Web page. This page might only include the words "Welcome to my website" on it and use the minimum HTML required in order for the page to load in a Web browser. Once the user is able to create a working Web page, the tutorial may explain how to add other features, such as styled text, table layouts, and images, to the page. Then the tutorial may provide instructions on how to publish the Web page to the Internet. Some software tutorials provide testing features to ensure comprehension of the material, while others may be simple walkthroughs of a software program. Tutorials can be used for both school and business purposes and are written for basic, intermediate, and advanced users. Even smart computer programmers use tutorials. Most software development programs include a tutorial for creating a "Hello World!" program, which is the most basic program that can be created with the software. Since tutorials offer a gradual approach to learning, they can be helpful to people at many different skill levels. If a computer programmer can benefit from a tutorial, just about anybody can.
TWAIN The TWAIN working group (www.twain.org) is a non-for-profit organisation which represents the imaging industry, whose purpose is to provide and foster a universal public standard which links applications and image acquisition devices. TWAIN is often loosely referred to as an interface standard for image acquisition devices.
Tweak When you modify a certain piece of hardware for better performance, it is often referred to as "tweaking" it. Overclocking the computer's CPU or changing jumper settings on the motherboard are common examples of hardware tweaking. Removing system limitations and adding plug-ins or extensions to a computer's operating system are types of software tweaking. Tweaking a computer is much like "tuning" a car (you know, the ones with the huge mufflers, big spoilers, and pimped out rims). It may increase performance, but is best left in the hands of the technically savvy. For example, overclocking your computer's processor may cause it to crash frequently, or worse yet, overheat and destroy the CPU. So, for most people, it is best to leave well enough alone.
twisted pair Telephone companies commonly run twisted pairs of copper wires to each customer household. The pairs consist of two insulated copper wires twisted into a spiral pattern. Although originally designed for plain old telephone service (POTS), these wires can carry data as well as voice. New services such as ISDN and ADSL also use twisted-pair copper connections. See also: ISDN, ADSL, POTS
two-factor authentication An extra level of security achieved using a security token device; users have a personal identification number (PIN) that identifies them as the owner of a particular token. The token displays a number which is entered following the PIN number to uniquely identify the owner to a particular network service. The identification number for each user is changed frequently, usually every few minutes.
TXT File A text file is one which holds just text with no document formatting information. They are the most basic type of file and so can be opened with any text editor or word processor. Also known as an "ASCII Text File" or "Plain Text File". A TXT file is often denoted by a file extension of ".txt", but there are many other file types which can also be classified as text files (for example a ".ini" file, which is normally an initialisation file, is normally a text file).
Typeface A typeface is a set of characters of the same design. These characters include letters, numbers, punctuation marks, and symbols. Some popular typefaces include Arial, Helvetica, Times, and Verdana. While most computers come with a few dozen typefaces installed, there are thousands of typefaces available. Because they are vector-based (not bitmaps), typefaces can be scaled very large and still look sharp. The term "typeface" is often confused with "font," which is a specific size and style of a typeface. For example, Verdana is a typeface, while Verdana 10 pt bold is a font. It's a small difference, but is good to know.
U U is the standard unit of measurement for rack-mounted equipment. Racks can be used to house servers, hard drives, switches, routers, and other computer hardware. They are also used for mounting audio and video equipment. Standard racks are 24 inches wide, but vary in height. For this reason, the U unit measures how tall a rack-mountable hardware device is. 1U is equal to 1.75 inches. Therefore, a 1U piece of equipment is 1.75 inches tall and takes up one unit of rack space. A 2U device is 3.5 inches tall and takes up 2 units of rack space. Racks themselves are also measured in U. For example, a 10U rack could store 10 1U devices or 5 2U devices.
UAC User Account Control. A system built into Windows Vista where the operating system warns the user if an application tries to install or overwrite installed programs, and requests authorisation from the user before allowing the activity to go ahead. UAC is intended to increase the security of Windows Vista by making the user (administrator) aware each time an application performs something which has the potential to compromise security. Whilst UAC can be disabled (which administrators may be tempted to to to avoided the repeated prompting it generates) it is generally advised to leave it enabled.
UART (Universal Asynchronous Receiver Transmitter) A chip that standardized serial communications. Its function is to change a byte into a standard sequence of electrical impulses.
UBE Unsolicited Broadcast E-mail. Unsolicited e-mail - otherwise more commonly known as spam.
UBR 1. Unspecified Bit Rate. No guarantee of available bandwidth. 2. Universal Bandwidth Router.
Ubuntu (operating system) Ubuntu (pronounced /uːˈbuːntuː/),[3][4] is a computer operating system based on the Debian GNU/Linux distribution. It is named after the Southern African ethical ideology Ubuntu ("humanity towards others")[5] and is distributed as free and open source software. Ubuntu provides an up-to-date, stable operating system for the average user, with a strong focus on usability and ease of installation. Ubuntu has been selected by readers of desktoplinux.com as the most popular Linux distribution for the desktop, claiming approximately 30% of Linux desktop installations in both 2006 and 2007.[6][7] Web statistics from late 2009 suggest that Ubuntu's share is between 40 and 50%.[8][9] Ubuntu is composed of multiple software packages, of which the vast majority are distributed under a free software license (also known as open source). The main license used is the GNU General Public License (GNU GPL) which, along with the GNU Lesser General Public License (GNU LGPL), explicitly declare that users are free to run, copy, distribute, study, change, develop and improve the software. Ubuntu is sponsored by the UK-based company Canonical Ltd., owned by South African entrepreneur Mark Shuttleworth. By keeping Ubuntu free and open source, Canonical is able to utilize the talents of community developers in Ubuntu's constituent components. Instead of selling Ubuntu for profit, Canonical creates revenue by selling technical support and from creating several services tied to Ubuntu. Canonical endorses and provides support for three additional Ubuntu-derived operating systems: Kubuntu, Edubuntu and Ubuntu Server Edition. There are several other derivative operating systems including local language and hardware-specific versions.[10] Canonical releases new versions of Ubuntu every six months and supports Ubuntu for eighteen months by providing security fixes, patches to critical bugs and minor updates to programs. LTS (Long Term Support) versions, which are released every two years,[11] are supported for three years on the desktop and five years for servers.
UCE Unsolicited Commercial E-mail, i.e. Spam distributed with the aim of commercial gain.
UDDI Universal Description, Discovery and Integration. A method for finding new Web Services by referring to a central directory. The specification for an index of all available Web services which is comparable to a global Yellow-Pages directory. UDDI helps businesses to produce descriptions of the services they offer, pass on details to the registry and thus appear to be a services provider. Using the UDDI method, Web services users can send enquiries in the form of SOAP messages to the central registration point to ascertain suppliers of a particular service.
UDF 1. Universal Disc Format. A disc format for optical media (such as cds and dvds) which is designed to be supportable by any operating system and not be tied to a single operating system. UDF is defined by ISO/IEC 13346 (also known as ECMA-167) and is widely viewed as a successor to ISO 9660 (which defined the file system for CD-ROMs).
UDMA (Ultra DMA) short for Ultra DMA
UDP 1. User Datagram Protocol. Like TCP, UDP sits above IP, but unlike TCP it is a connectionless communications protocol (meaning there is no handshaking between the sender and receiver). It provides a "best-effort" delivery, and neither the arrival or correct sequencing of datagrams is guaranteed. Datagrams can therefore go missing without any form of notification. UDP is used by applications that do not require an acknowledgement and which send only small amounts of data. It is typically used to broadcast information over a network.
UDP (User Datagram Protocol) Part of the TCP/IP suite of protocols. UDP is the part of the TCP/IP suite used by applications to transfer datagrams. It is also the part of TCP/IP responsible for port addresses. UDP got the short end of the stick in some ways in that its name isn’t included in TCP/IP.
UDP Scan UDP scans perform scans to determine which UDP ports are open.
UID Unique Identifier or Unique ID. A generic term used to refer to any form of unique identifier - which can be used to uniquely identify something within the system or context in which it was generated. UID is sometimes used as an abbreviation for an account user name.
ULSI (Ultra Large Scale Integration) A microchip with over one million transistors. Most popular chips today fit this description. Maybe in 10 years we will have the SDULSI, for Super-Duper Ultra Large Scale Integration. For now this is at the top of the heap. See also VLSI, LSI, MSI, and SSI.
Ultra 160M (160M) A form of SCSI that supercedes Ultra2 SCSI. It runs at up to 160 megabytes per second and uses 80-pin connections over copper wires.
Ultra 320M (320M) A form of SCSI that doubles the potential performance of Ultra 160M SCSI and offers throughput of up to 320 megabytes per second per channel.
Ultra ATA/100 Another extension to the ATA interface that adds a 50% increase in top speed over ATA/66, getting to 100MB/second, up from 66MB/second. This standard also adds some additional error-checking not found in earlier ATA standards. Like Ultra ATA/66, ATA/100 requires an 80-conductor cable to work at full speed.
Ultra ATA/133 This refers to what is most probably the final extension to the parallel ATA connection standard. The proposal was created by Maxtor, and allows a top data transfer rate of 133 megabytes per second. Intel didn’t support this standard in its chipsets, instead opting to wait for Serial ATA. See Serial ATA for further details.
Ultra ATA/33 An extension to the ATA interface (IDE) that effectively doubles the top data transfer speed of IDE from 16.6MBytes/second up to 33 MBytes/second. Also known as Ultra-IDE.
Ultra ATA/66 An extension to the ATA interface (IDE) proposed by Quantum that effectively doubles the data transfer speed of the Ultra ATA/33 interface to 66MBps. To achieve the increase in speed you must use a special 80-conductor cable with 40 data lines and 40 ground lines to keep the signal stable.
Ultra DMA This technology for transferring data between a computer's hard disk and memory was developed by Quantum and Intel. The maximum burst rate of an Ultra DMA hard drive is 33.3 MBps. The original DMA (Direct Memory Access) protocol could only transfer data at half that speed. Thanks to Ultra DMA, programs can open faster and run more smoothly. This is because Utlra DMA can send more data to the memory in less time than the original DMA. Ultra DMA also has a built-in utility called Cyclical Redundancy Checking (CRC) that helps protect data integrity. So if you want a nice, fast hard drive, look for one that supports Ultra DMA.
Ultra DMA (Ultra ATA/33) An extension to the ATA interface (IDE) that effectively doubles the top data transfer speed of IDE from 16.6MBytes/second up to 33 MBytes/second. Also known as Ultra-IDE.
Ultra SATA (Serial ATA) A specification for consumer hard drive connections that boosts the data transfer rate up to 150MB/second. In addition, it changes IDE/ATA from a parallel interface requiring 40 separate wires to connect components to a serial interface requiring only 6 wires. 2x and 4x versions of Serial ATA double and quadruple the speed of Serial ATA.
Ultra SCSI This is SCSI that communicates twice as fast as standard SCSI-2. Normal Ultra-SCSI transfers data at 20MBps, and Wide Ultra-SCSI transfers data at 40MBps. Similar to Ultra-IDE, Ultra-SCSI works its magic by transferring data on the up AND the down stroke of a clock cycle, doubling throughput.
Ultra XGA (UXGA) A display with 1600×1200 pixel resolution.
Ultra2 SCSI (LVD) This standard doubles the maximum transmission speed of Ultra SCSI. Almost all devices made to this standard support the 80MBps transfer rate of Ultra2 Wide SCSI. See also LVD.
Ultra3 SCSI Ultra3 SCSI doubles the maximum transfer rate of Ultra2 SCSI up to 160MBps. This is synonymous with 160M SCSI.
UNC Stands for "Universal Naming Convention," not just the home of the North Carolina Tar Heels. UNC is a filename format that is used to specify the location of files, folders, and resources on a local-area network (LAN). The UNC address of a file may look something like this: \\server-name\directory\filename UNC can also be used to identify peripheral devices shared on the network, including scanners and printers. It provides each shared resource with a unique address. This allows operating systems that support UNC (such as Windows) to access specific resources quickly and efficiently.
Undoable disk mode All writes to an undoable disk issued by software running inside the virtual machines appear to be written to the disk, but are in fact stored in a temporary file (.REDO) on the host file system for the duration of the session. When the virtual machine is powered down, the user is given three choices: (1) permanently apply all changes to the disk; (2) discard the changes, thus restoring the disk to its previous state; or (3) keep the changes, so that further changes from future sessions can be added to the log.
Unicast Broadcasting from host to host.
uniformity An ideal monitor will deliver equal brightness across the entire screen. In practice, however, many monitors have darker areas or appear patchy, demonstrating a lack of uniformity. These problems are particularly easy to spot on a white background.
Unix A computer operating system (the basic software running on a computer, underneath things like word processors and spreadsheets). Unix is designed to be used by many people at the same time (it is multi-user) and has TCP/IP built-in. It is the most common operating system for servers on the Internet. Apple computers' Macintosh operating system, as of version 10 ("Mac OS X"), is based on Unix. See also: Linux, Server, TCP/IP
Unmount Unmounting a disk makes it inaccessible by the computer. Of course, in order for a disk to be unmounted, it must first be mounted. When a disk is mounted, it is active and the computer can access its contents. Since unmounting a disk prevents the computer from accessing it, there is no risk of the disk being disconnected in the middle of a data transfer. Therefore, before removing an external data storage device, such as a USB flash drive, the disk should be unmounted to avoid possible data corruption. Several types of disks can be unmounted, including external hard drives, USB flash drives, iPods, flash memory cards, and disk images. In order to unmount a disk in Windows, open "My Computer," select the disk, and click the "Eject this disk" option in the left sidebar. In Mac OS X, select the disk on the desktop and either drag the disk to the trash (which changes to an Eject icon), or select "File->Eject" from the Finder's menu bar. Once a removable disk has been unmounted, it can safely be disconnected from the computer.
Unprotected Share In Windows terminology, a "share" is a mechanism that allows a user to connect to file systems and printers on other systems. An "unprotected share" is one that allows anyone to connect to it.
UP 1. Unified Process. 2. In computing "Up" is usually used to mean "On and working". For example "is the server up?" is a question asking whether the server is working and available. cf Down.
Upgrade This normally refers to a newer version of software, or a version with an enhanced feature set. If you already own a previous version of the software, you can often purchase an upgrade version for a lower price than a new version. In terms of hardware, you can upgrade your system by adding more memory, or any component that makes your system better or faster. Some graphics cards let you upgrade them by plugging more memory onto the board.
Uplink Port A special networking port on a hub or switch that is used to connect it to a larger network. Often you need a special crossover cable to make this connection function properly. If you think of a network as a tree, the hub (or switch) on top connects to the uplink ports of the hubs (or switches) below it, and so on.
Upload To transmit (or copy) data from a local computer to a remote computer via a network, modem, serial or parallel cable. For example to copy a file from a local computer to a server via FTP you would be said to be uploading the file (in this case by FTP). cf Download.
UPnP Stands for "Universal Plug and Play." Plug and Play describes devices that work with a computer system as soon as they are connected. UPnP is an extension of this idea that expands the range of Plug and Play devices to networking equipment. Universal Plug and Play uses network protocols to allow a wide range of devices to be interconnected and work seamlessly with each other. UPnP devices can be connected via wired (i.e. Ethernet and Firewire) or wireless (i.e. Wi-Fi and Bluetooth) connections. As long as a product supports UPnP, it can communicate with other UPnP devices within a network. The connections are typically created using the DHCP networking protocol, which assigns each connected device a unique IP address. While UPnP is helpful for setting up networks, it also can be used to set up compatible audio and video (AV) devices. UPnP AV is a group of standards based on UPnP that allows audio and video components to be connected via network connections. This enables media files and streaming data to be sent between devices. For example, a movie stored on a hard drive in a bedroom could be played back on the TV screen in the living room. The central controller of a UPnP AV network is called a MediaServer and can be run from a Macintosh, Windows, or Linux computer or from a hardware device specifically designed to manage the network. Since most UPnP devices support zero-configuration setup (like ordinary Plug and Play devices), it is simple to add devices to a network and use them immediately. While the networking terms associated with UPnP can be a bit intimidating, setting up a UPnP network is meant to be hassle-free ? and that is a term we can all appreciate.
UPS Uninterruptible Power Supply. A battery backup device that supplies AC power automatically in the event of a power failure. There are two basic types of UPS, "stand-by" and "on-line": Stand-by power supply or SPS. A device powered by an SPS is normally powered directly from the mains, with the battery charging. The batter is the stand-by power supply. Should the power fail then the power supply is switched to the battery (via an inverter). SPS has the advantage of being cheaper than the on-line version but does not provide an instant change over of power nor does it provide any mains filtering and therefore they are not suitable for all applications. On-line. Here the battery to AC inverter is always connected to the output of the UPS. While mains power is available the battery will recharge, and should the mains power fail the switch to batter power is almost instantaneous. Thus there is almost no risk of interruption of supply should the power fail. They normally also provide some form of mains filtering but are generally more expensive than the SPS variety.
Upstream This refers to sending of data from a client machine across the Internet. With cable modems and ADSL, upstream speeds are slower than downstream speeds.
URI Uniform Resource Identifier. A UNI is a way to identify (or address) a name or resource over a network. A URI is expressed as a short string. A URI takes the form of a URN or a URL.
URL Uniform Resource Locator. A URL provides a standard way to address any resource on the internet. URLs are expressed as a text string of the form: protocol://domain-name/pathname Where protocol is any valid protocol, such as http, ftp, gopher etc. One example of a URL that most people are now familiar with is the web address of each site and page. See also: URI, URN. URLs are defined by RFC1738 and RFC1808. Whilst the HTTP specification does not limit the length of a URL, most browsers do have a limiting maximum size. Whilst this limit is far in excess of most browsing requests, current limits are: Browser / Server Limit Source Internet Explorer (browser) 2083 characters Microsoft Knowledge Base Article 208427 Netscape (browser) No limit Apache (web server) 8190 characters (default) www.jetools.com/content/resources/whitepapers/HTTP_GET_Requests.pdf IIS 6.0 (web server) 16KB
URN Uniform Resource Name. A URN provides a standard way to name a resource. URNs are expressed as a text string of the form: urn://nid/nss Where nid indicates the namespace and nss the namespace specific string. For example: urn://isbn/0674362500 refers to a book (on Greek) See also URL.
USB Universal Serial Bus. USB provides a single common interface to peripherals and plug-and-play configuration (at the host/pc). The original standard for USB (occasionally referred to as USB 1.0, but normally simply as USB) supported transfer speeds of 1.5Mbps and 12Mbps. USB 1.1 is a revised version of the USB specification, but the transfer rate remains unchanged. USB 2.0 (also referred to as "USB Hi-Speed) also supports 480Mbps and is otherwise backwards compatible with earlier versions. The USB specification limits maximum cable lengths to 5m for high speed USB devices and 3m to low speed devices USB. USB Version Supported speeds Maximum cable length 1.5Mbps 12Mbps 480Mbps USB 2.0 5m USB 1.1 3m USB 1.0 3m
USB port An interface used for connecting a Universal Serial Bus (USB) device to computer; these ports support plug and play
USENET A world-wide system of discussion groups, with comments passed among hundreds of thousands of machines. Not all USENET machines are on the Internet. USENET is completely decentralized, with over 10,000 discussion areas, called newsgroups.
User Contingency Plan User contingency plan is the alternative methods of continuing business operations if IT systems are unavailable.
User Datagram Protocol (UDP) Part of the TCP/IP suite of protocols. UDP is the part of the TCP/IP suite used by applications to transfer datagrams. It is also the part of TCP/IP responsible for port addresses. UDP got the short end of the stick in some ways in that its name isn’t included in TCP/IP, but would you really want to call it TCP/UDP/IP?
User Interface A user interface is the means in which a user controls a software program or hardware device. For example, a software interface may include windows, icons, menus, and buttons that allow the user to interact with the program. This is also known as a graphical user interface, or GUI. A hardware interface can be a remote control or a video game controller. It may also refer to the controls on a camcorder, digital camera, or iPod. Most modern user interfaces today are designed using a combination of hardware and software. Example: "The Apple iPhone has a touchscreen user interface."
Username A username is a name that uniquely identifies someone on a computer system. For example, a computer may be setup with multiple accounts, with different usernames for each account. Many websites allow users to choose a username so that they can customize their settings or set up an online account. For example, your bank may allow you to choose a username for accessing your banking information. You may need to choose a username in order to post messages to a certain message board on the Web. E-mail services, such as Hotmail require users to choose a username in order to use the service. A username is almost always paired with a password. This username/password combination is referred to as a login, and is often required for users to log in to websites. For example, to access your e-mail via the Web, you are required to enter your username and password. Once you have logged in, your username may appear on the screen, but your password is kept secret. By keeping their password private, people can create secure accounts for various websites. Most usernames can contain letters and numbers, but no spaces. When you choose a username for an e-mail account, the part before the "@" is your username.
UTC Coordinated Universal Time (UTC). It is the current term for what used to be commonly referred to as Greenwich Meridian Time (GMT).
Utility Utility programs, commonly referred to as just "utilities," are software programs that add functionality to your computer or help your computer perform better. These include antivirus, backup, disk repair, file management, security, and networking programs. Utilities can also be applications such as screensavers, font and icon tools, and desktop enhancements. Some utility programs help keep your computer free from unwanted software such as viruses or spyware, while others add functionality that allows you to customize your desktop and user interface. In general, programs that help make your computer better are considered utilities. And unlike water and electric bills, computer utilities don't send you a bill every month!
Utility computing Utility computing is the packaging of computing resources, such as computation and storage, as a metered service similar to a traditional public utility (such as electricity, water, natural gas, or telephone network). This system has the advantage of a low or no initial cost to acquire hardware; instead, computational resources are essentially rented. Customers with very large computations or a sudden peak in demand can also avoid the delays that would result from physically acquiring and assembling a large number of computers. "Utility computing" has usually envisioned some form of virtualization so that the amount of storage or computing power available is considerably larger than that of a single time-sharing computer. Multiple servers are used on the "back end" to make this possible. These might be a dedicated computer cluster specifically built for the purpose of being rented out, or even an under-utilized supercomputer. The technique of running a single calculation on multiple computers is known as distributed computing. The term "grid computing" is often used to describe a particular form of distributed computing, where the supporting nodes are geographically distributed or cross administrative domains. To provide utility computing services, a company can "bundle" the resources of members of the public for sale, who might be paid with a portion of the revenue from clients. One model, common among volunteer computing applications, is for a central server to dispense tasks to participating nodes, on the behest of approved end-users (in the commercial case, the paying customers). Another model, sometimes called the Virtual Organization (VO),[citation needed] is more decentralized, with organizations buying and selling computing resources as needed or as they go idle. The definition of "utility computing" is sometimes extended to specialized tasks, such as web services.
UTP (Unshielded Twisted Pair) Cables that consist of pairs of unshielded wire twisted together. These cables are used for data and telephone networks. They are cheap to produce because they are unshielded, and they get their shielding by being twisted together in pairs.
UXGA (Ultra XGA) A display with 1600×1200 pixel resolution.
V.32 A standard naming convention used in determining modem communications, all starting with “V.” This one is for specifying the Hayes standard of bidirectional 9600 baud transmission.
V.32bis The standard that came after V.32 which increased the speed from 9600 baud to 14.4 Kbits per second.
V.34 This was a dramatic improvement for modem communications. It doubled the top speed of the V.32bis standard to 28.8Kbps.
V.34+ This standard was made by US Robotics to indicate that its modems are superior to a standard V.34 modem in that they run at 33.6 KB baud instead of the slower 28.8 KB baud.
V.42 The name given to the standard for transmitting at 2400 baud.
V.42Bis This is not a speed standard like V.32 and V.34, but an error correction and compression method that is hardware-based. Its major improvement comes from knowing when compression will be beneficial and when it will not be.
V.90 The ITU’s first standard for 56K modem communications. It superceded X2 and 56kflex to become the ultimate 56K standard. Most X2 and 56kflex modems were able to upgrade to V.90 for free.
V.92 An extension to the V.90 modem transmission standard that adds three new features: quick connect, which speeds up the connection handshake; Modem-on-Hold, for receiving incoming calls without breaking your connection; and PCM Upstream, for speeding up upstream data rates to up to 48Kbps. Previously with V.90, upstream rates were limited to 33.6Kbps.
V.Fast This standard was made between the time of V.32bis and V.34. It is also a 28.8 KB baud speed, but was not as reliable as the approved V.34 standard.
V2P (Virtual to Physical) migration The operation of migrating an operating system and every application installed on it from a virtual machine or a partition to one or multiple physical computers, without reinstalling anything. The opposite of P2V (Physical to Virtual).
V2V (Virtual to Virtual) migration The operation of migrating an operating system and every application installed on it from a virtual machine or partition hosted in a virtual infrastructure to another virtual machine or partition hosted in a different virtual infrastructure, without reinstalling anything. Mainly used when working with different virtualization technologies in the same environment.
VA Volt Amps. Used to measure an the maximum load that can be placed on a UPS. VA = Maximum UPS load = Watts/0.7 = Amps x Voltage.
VB (Microsoft) Visual Basic. cf VB6 and VB.Net.
VB.Net (Microsoft) Visual Basic .NET. Touted by Microsoft as the next version of VB after VB6, but regarded by some as a new language in its own right because of the magnitude of the changes between VB6 and VB.Net. Very infrequently referred to as VB7.
VBA (Microsoft) Visual Basic for Applications. VBA is the common (macro) programming language available for Office tools. It is a dialect of VB.
VBScript VBScript Visual Basic Scripting Edition (VBScript) is a programming language developed by Microsoft for creating scripts (miniprograms) that can be embedded in HTML Web pages for viewing with Internet Explorer. These scripts can make Web pages more interactive. VBScript also works with Microsoft ActiveX Controls, allowing Web site developers to create forms, interactive multimedia, games, and other Web-based programs. VBScript is similar in functionality to JavaScript and is a subset of the widely used Microsoft Visual Basic programming language. See also: ActiveX, JavaScript, Visual Basic
Vector Mathematically, a vector is a quantity, defined by both magnitude and direction. For example, a vector could be illustrated by an 1 inch arrow pointing at a 30 degree angle. Another vector may be 2.5 inches and point at a 160 degree angle. In the computer world, vectors are used to define paths in certain types of images, such as EPS files and Adobe Illustrator documents. These images are often called vector graphics since they are comprised of vectors, or paths, instead of dots. Vector graphics can be scaled larger or smaller without losing quality. In computer science, a vector may refer to a type of one dimensional array. For example, a vector called "fibonacci" that stores the first six values of the Fibonacci sequence would be defined as follows: fibonacci[0] = 0, fibonacci[1] = 1, fibonacci[2] = 1, fibonacci[3] = 2, fibonacci[4] = 3, fibonacci[5] = 5 Vectors are similar to arrays, but unlike arrays, vectors use their own memory management mechanisms. Arrays are restricted to the memory structure supplied by the programming language they are created in, typically called a stack. Vectors have a more dynamic structure, often referred to as a heap, which gives them greater flexibility in how they use memory. While an array uses a static amount of memory, the memory used by the vector can be increased or decreased as elements are added or removed from the vector.
Vector Graphic Unlike JPEGs, GIFs, and BMP images, vector graphics are not made up of a grid of pixels. Instead, vector graphics are comprised of paths, which are defined by a start and end point, along with other points, curves, and angles along the way. A path can be a line, a square, a triangle, or a curvy shape. These paths can be used to create simple drawings or complex diagrams. Paths are even used to define the characters of specific typefaces. Because vector-based images are not made up of a specific number of dots, they can be scaled to a larger size and not lose any image quality. If you blow up a raster graphic, it will look blocky, or "pixelated." When you blow up a vector graphic, the edges of each object within the graphic stay smooth and clean. This makes vector graphics ideal for logos, which can be small enough to appear on a business card, but can also be scaled to fill a billboard. Common types of vector graphics include Adobe Illustrator, Macromedia Freehand, and EPS files. Many Flash animations also use vector graphics, since they scale better and typically take up less space than bitmap images. File extensions: .AI, .EPS, .SVG, .DRW
Veronica The name actually stands for "Very Easy Rodent-Oriented Netwide Index to Computerized Archives." Pretty weird, I know. The "rodent" part of the acronym refers to how the Veronica utility allows you to search all of the world's gopher servers using keywords. (That's about 10 million items from over 6,000 gopher servers.) After searching for the terms, Veronica displays a list of gopher menus and articles containing the key words you searched for. The more recent versions of Veronica can also search certain Web pages, newsgroups, and FTP sites. Unlike most search engines, Veronica searches for keywords only in gopher server menu titles, and doesn't look throught the entire text of documents. When searching with Veronica, you can use the logical operators AND, NOT, and OR to help narrow your search. Also, typing an asterisk (*) at the end of a word will match anything starting with that word. Sound familar to any Unix users?
VFAT Stands for "Virtual File Allocation Table." Older Windows operating systems (Windows ME and earlier) used a file system called "FAT" or "FAT32." The file system is what the operating system uses to organize and access files on the hard drive. VFAT, introduced with Windows 95, was an improvement to the basic FAT file system, allowing more information to be stored for each file. While the FAT file system can only store 8 characters for each file name, VFAT allows for file names up to 255 characters in length
VGA Video Graphics Array. An analogue graphics standard which supports a maximum resolution of 640 x 480 pixels. cf video mode.
vi vi is a family of screen-oriented text editors which share certain characteristics, such as methods of invocation from the operating system command interpreter, and characteristic user interface features. The portable subset of the behavior of vi programs, and the ex editor language supported within these programs, is described by (and thus standardized by) the Single Unix Specification[1] and POSIX.
Video Card Most of the processing done on a computer is done via the computer's central processing unit, or CPU. So in order to give the CPU a break and help it run more efficiently, a video card can be used to process the graphics portion of the processing load. Because most of today's programs are graphically oriented, the video card can help almost any program run more efficiently. However, the difference in performance is especially noticeable in image editing applications and 3D games. Video cards, also called graphics accelerators, can speed up both 2D and 3D graphics rendering. Programs such as photo editors and Web browsers may benefit from 2D acceleration, while CAD design programs and video games will most likely benefit from the card's 3D acceleration. Some programs rely so heavily on the video card, that they will not run if a supported video card is not installed. Most video cards support the OpenGL and DirectX libraries. These libraries include commands for manipulating graphics that programmers can include in their code. Some of these commands may include moving or rotating an object, morphing polygons, or casting light and creating shadows. By using standard OpenGL or DirectX functions, it makes it easier for developers to create graphically-oriented programs. Of course, it also makes it necessary for the computer to include a supported video card in order for the program to run. Video cards are typically installed in either the PCI or AGP slots in the back of a computer. Most computers come with a video card installed in one of these slots, which means it can be upgraded at a later time.
Video Mode 1. The current setting of a video adapter. Different video modes support different resolutions (i.e. number of pixels horizontally and vertically) and colour depth (i.e. the number of colours). The following table lists common video graphics adapter abbreviations and the maximum supported resolutions for each: Abbreviation Max resolution Aspect VGA 640 x 480 standard SVGA 800 x 600 standard XGA 1024 x 768 standard SXGA 1280 x 1024 standard SXGA+ 1400 x 1050 widescreen WXGA 1366 x 768 or 1280 x 768 widescreen WSXGA 1440 x 900 widescreen WSXGA+ 1680 x 1050 widescreen UXGA 1600 x 1200 standard WUXGA 1920 x 1200 widescreen QXGA 2048 x 1600 standard WQXGA 2560 x 1600 widescreen These abbreviations are unfortunately not standardized. There may therefore be some variability between two graphics adapters both claiming to support say SXGA. 2. The ability or setting for a digital photo camera to record short video clips.
Vim a text editor, acronym for Vi improved after Vim added several features over the vi editor. Vim however had started out as an imitation of Vi and was expanded as Vi imitation.
Virtual With regard to memory, virtual refers to temporarily storing information on the hard drive. Virtual memory is controlled automatically by the operating system.
virtual classroom An online environment where students can have access to learning tools any time. Interaction between the instructor and the class participants can be via e-mail, chat, discussion group, etc.
Virtual disk A virtual disk is a file on the host file system that appears as a physical disk drive to a guest operating system. This file can be on the host machine as well as on a remote file system. When you configure a virtual machine with a virtual disk, you can install a new operating system onto the disk file without the need to repartition a physical disk or reboot the host. VMware virtual disk devices can also be mapped to partitions on the host machine. See also Raw disk.
Virtual Machine A virtual machine was originally defined by Popek and Goldberg as "an efficient, isolated duplicate of a real machine". Current use includes virtual machines which have no direct correspondence to any real hardware.[1] Virtual machines are separated into two major categories, based on their use and degree of correspondence to any real machine. A system virtual machine provides a complete system platform which supports the execution of a complete operating system (OS). In contrast, a process virtual machine is designed to run a single program, which means that it supports a single process. An essential characteristic of a virtual machine is that the software running inside is limited to the resources and abstractions provided by the virtual machine—it cannot break out of its virtual world. Example: A program written in Java receives services from the Java Runtime Environment (JRE) software by issuing commands to, and receiving the expected results from, the Java software. By providing these services to the program, the Java software is acting as a "virtual machine", taking the place of the operating system or hardware for which the program would ordinarily be tailored. [edit]System virtual machines See also: Platform virtualization and Comparison of platform virtual machines System virtual machines (sometimes called hardware virtual machines) allow the sharing of the underlying physical machine resources between different virtual machines, each running its own operating system. The software layer providing the virtualization is called a virtual machine monitor or hypervisor. A hypervisor can run on bare hardware (Type 1 or native VM) or on top of an operating system (Type 2 or hosted VM). The main advantages of system VMs are: multiple OS environments can co-exist on the same computer, in strong isolation from each other the virtual machine can provide an instruction set architecture (ISA) that is somewhat different from that of the real machine application provisioning, maintenance, high availability and disaster recovery[2] The main disadvantage of system VMs is: a virtual machine is less efficient than a real machine when it accesses the hardware indirectly Multiple VMs each running their own operating system (called guest operating system) are frequently used in server consolidation, where different services that used to run on individual machines in order to avoid interference are instead run in separate VMs on the same physical machine. This use is frequently called quality-of-service isolation (QoS isolation). The desire to run multiple operating systems was the original motivation for virtual machines, as it allowed time-sharing a single computer between several single-tasking OSes. This technique requires a process to share the CPU resources between guest operating systems and memory virtualization to share the memory on the host. The guest OSes do not have to be all the same, making it possible to run different OSes on the same computer (e.g., Microsoft Windows and Linux, or older versions of an OS in order to support software that has not yet been ported to the latest version). The use of virtual machines to support different guest OSes is becoming popular in embedded systems; a typical use is to support a real-time operating system at the same time as a high-level OS such as Linux or Windows. Another use is to sandbox an OS that is not trusted, possibly because it is a system under development. Virtual machines have other advantages for OS development, including better debugging access and faster reboots.[3] Alternate techniques such as Solaris Zones provides a level of isolation within a single operating system. This does not have isolation as complete as a VM.
Virtual machine configuration The specification of what virtual devices (disks, memory size, etc.) are present in a virtual machine, and how they are mapped to host files and devices.
Virtual machine configuration file A file containing a virtual machine configuration. It is created by the Configuration Wizard or the Configuration Editor. It is used by VMware to identify and run a specific virtual machine.
Virtual Memory Memory is hardware that your computer uses to load the operating system and run programs. It consists of one or more RAM chips that each have several memory modules. The amount of real memory in a computer is limited to the amount of RAM installed. Common memory sizes are 256MB, 512MB, and 1GB. Because your computer has a finite amount of RAM, it is possible to run out of memory when too many programs are running at one time. This is where virtual memory comes in. Virtual memory increases the available memory your computer has by enlarging the "address space," or places in memory where data can be stored. It does this by using hard disk space for additional memory allocation. However, since the hard drive is much slower than the RAM, data stored in virtual memory must be mapped back to real memory in order to be used. The process of mapping data back and forth between the hard drive and the RAM takes longer than accessing it directly from the memory. This means that the more virtual memory is used, the more it will slow your computer down. While virtual memory enables your computer to run more programs than it could otherwise, it is best to have as much physical memory as possible. This allows your computer to run most programs directly from the RAM, avoiding the need t
Virtual Private Network (VPN) A restricted-use, logical (i.e., artificial or simulated) computer network that is constructed from the system resources of a relatively public, physical (i.e., real) network (such as the Internet), often by using encryption (located at hosts or gateways), and often by tunneling links of the virtual network across the real network. For example, if a corporation has LANs at several different sites, each connected to the Internet by a firewall, the corporation could create a VPN by (a) using encrypted tunnels to connect from firewall to firewall across the Internet and (b) not allowing any other traffic through the firewalls. A VPN is generally less expensive to build and operate than a dedicated real network, because the virtual network shares the cost of system resources with other users of the real network.
Virtual Reality While the word "virtual" is typically overused in the computer world, it is aptly placed in the phrase "virtual reality." According to the American Heritage Dictionary, virtual means "existing or resulting in essence or effect though not in actual fact, form, or name." It can also mean "created, simulated, or carried on by means of a computer or computer network." Therefore, virtual reality is best described as an illusion of reality created by a computer system. A person may enter a world of virtual reality by putting on special glasses and headphones attached to a computer system running the virtual reality program. These devices immerse the user with the sights and sounds of the virtual world. Some virtual reality systems allow the user to also wear gloves with electronic sensors that can be used to touch or move virtual objects. As the user moves his head or hands, the computer moves the virtual world accordingly in real-time. Virtual reality has been widely used for entertainment purposes, but the technology has found its way into the military and medical fields as well. While virtual reality systems have advanced significantly over the past decade, for the most part they are still more "virtual" than reality.
Virtualization irtualization allows a single computer to run multiple operating systems. For example, using virtualization software, a Mac OS X computer can run Windows and a Windows computer can run Linux. Virtualization software allows multiple operating systems to run at the same time and even interact with each other. When an additional operating system (OS) is running on top of the main OS through virtualization, it is called a virtual machine. Example: "Virtualization allows a Macintosh computer to run Mac OS X and Windows at the same time."
Virus A chunk of computer programming code that makes copies of itself without any concious human intervention. Some viruses do more than simply replicate themselves, they might display messages, install other software or files, delete software of files, etc. A virus requires the presence of some other program to replicate itself. Typically viruses spread by attaching themselves to programs and in some cases files, for example the file formats for Microsoft word processor and spreadsheet programs allow the inclusion of programs called "macros" which can in some cases be a breeding ground for viruses. See also: Trojan Horse, Worm
Visitor When a user arrives on a website, he or she is considered one visitor regardless of how many pages at which he or she looks. If a visitor returns to that website later in the day, he or she may be counted as another visitor by logging programs unless you are looking for “unique” visitors and the visitor is identified by cookies or IP addresses.
Vista Windows Vista. Refers to the Windows Vista operating system from Microsoft. Vista is available in four different editions: Home Basic, Home Premium, Business and Ultimate.
VLAN Virtual Local Area Network (LAN). System for allowing a set of computers to behave and interact as though they were on the same LAN, even though they may be on physically separate and distinct networks.
VLAN (Virtual LAN) This is created when a bunch of physically connected ports are grouped together by network hardware that supports VLANs. These VLANs are each treated as completely separate entities, and can only be joined together by a router. This scheme is useful for grouping departments together for security and minimizing network traffic.
VLK Volume License Key. A single license key which can be used on a number of computers to install a given product. A volume license key is typically issued to an individual company after purchasing a site license for a product.
VMM (Virtual Machine Monitor) The virtualization software layer managing hardware requests from a guest OS, simulating answers from a real hardware. Used as Hypervisor synonymous.
VMware ESX VMware ESX is an enterprise-level virtualization product offered by VMware, Inc. ESX is a component of VMware's larger offering, VMware Infrastructure, which adds management and reliability services to the core server product. The basic server requires some form of persistent storage—typically, an array of hard disk drives—for storing the virtualization kernel and support files. A variant of this design, VMware ESXi, does away with the first requirement by moving the server kernels into a dedicated hardware device. Both variants support the services offered by VMware Infrastructure.[2]
VMware ESXi VMware ESX is an enterprise-level virtualization product offered by VMware, Inc. ESX is a component of VMware's larger offering, VMware Infrastructure, which adds management and reliability services to the core server product. The basic server requires some form of persistent storage—typically, an array of hard disk drives—for storing the virtualization kernel and support files. A variant of this design, VMware ESXi, does away with the first requirement by moving the server kernels into a dedicated hardware device. Both variants support the services offered by VMware Infrastructure.[2]
VMware vSphere VMware vSphere, (formerly developed as VMware Infrastructure 4) is VMware's first cloud operating system, able to manage large pools of virtualized computing infrastructure, including software and hardware. VMware vSphere 4 was originally developed as VMware Infrastructure (VI) 4 then became its own product called vSphere.[1]
Voice Firewall A physical discontinuity in a voice network that monitors, alerts and controls inbound and outbound voice network activity based on user-defined call admission control (CAC) policies, voice application layer security threats or unauthorized service use violations.
Voice Intrusion Prevention System (IPS) Voice IPS is a security management system for voice networks which monitors voice traffic for multiple calling patterns or attack/abuse signatures to proactively detect and prevent toll fraud, Denial of Service, telecom attacks, service abuse, and other anomalous activity.
VoIP Voice over IP. Sending voice data (i.e. human conversations) using IP packets across a network (such as the internet) instead of across a (traditional) telephone network. A number of companies offer VoIP services. Typically these provide free telephone calls between people using the same software, but do not support calls between people using different software. Some provide additional facilities such as VoIP to landline numbers (call-out) or landline numbers to VoIP (call-in), and video.
Volt The standard unit of electric potential. It is defined as the amount of electrical potential between two points on a conductor carrying a current of one ampere while one watt of power is dissipated between the two points.
Voltage A measure of an amount of volts.
Volume The word "volume" has several different meanings. The most common definition is the magnitude or intensity of a certain sound. Volume may also refer to how much space a three-dimensional object takes up. However, in the always ambiguous realm of computers, the word volume can also refer to a specific data storage device. Some examples of volumes include hard disks, DVD drives, and flash memory drives, such as USB keychain drives. Your computer recognizes all these data storage devices as volumes. The only requirement is that each volume has a file system that the computer can recognize. The file system tells the computer how the folders and files are organized on the volume. On a Macintosh, all volumes connected to the computer (either directly or by a network connection) will show up on the desktop. For example, a hard drive will have a hard drive icon and a CD will have a CD icon. In Windows, you will find a list of all available volumes when you open "My Computer." If a volume is connected, but is not showing up on the screen, you can often use a disk utility program to "mount" the volume so that the computer can communicate with it.
VPK Volume Product Key. A volume product key is a single product key issued to a company in respect of a specific product for a specific number of licenses. VPKs are used by Microsoft as a means of electronically selling volume licneses.
VPN Usually refers to a network in which some of the parts are connected using the public Internet, but the data sent across the Internet is encrypted, so the entire network is "virtually" private.
VPS Virtual Private Server. A web server that is administered by a customer as though it were a single dedicated server, but which is one of many virtual servers running on the same physical server. This allows a hosting company to host multiple VPS on the same server. A VPS is therefore much cheaper than a dedicated server, and has many of the advantages of a dedicated server.
VRAM Stands for "Video Random Access Memory" and is pronounced "V-RAM." System RAM is great for loading and running programs, but when you need graphics power, VRAM is where it's at. This is the memory used to store image data that the computer displays; it acts as a buffer between the CPU and the video card. When a picture is to be displayed on the screen, the image is first read by the processor and then written to the VRAM. The data is then converted by a RAM digital-to-analog converter (RAMDAC) into analog signals that are sent to the display. Of course, the whole process happens so quickly, you don't notice it. Unlike most system RAM, VRAM chips are dual-ported, which means that while the display is reading from VRAM to refresh the currently displayed image, the processor is writing a new image to the VRAM. This prevents the display from flickering between the redrawing of images. There are many different types of VRAM. One popular kind is called Synchronous Graphics RAM (SGRAM). It is an inexpensive type of RAM that is clock-synchronized. This means data can be modified in a single operation rather than as a sequence of read, write, and update operations. This allows background, foreground, and image fills to be handled more efficiently. Another type of VRAM is Rambus Dynamic RAM (RDRAM). It is designed by Rambus and includes a proprietary Rambus bus that speeds up the transfer of data through it. Video editing pros like this chip since it is optimized for video streaming. A third type of VRAM is Window RAM (WRAM). This high-performance VRAM is dual-ported, has about 25% more bandwidth than standard VRAM, and typically costs less. Finally, there is Multibank Dynamic RAM (MDRAM). This is also high-performance VRAM, developed by MoSys, which divides the memory into divisions of 32 KB that can be accessed individually. This makes memory transfers more efficient and increases overall performance. Another advantage of MDRAM is that it can be manufactured with just the right amount of memory for a given resolution, so it is cheaper to manufacture than most other types of VRAM.
VRML Stands for "Virtual Reality Modeling Language." If you think this has something to do with HTML, you're right. While HTML is the format for Web page production, VRML is a 3D navigation specification, which enables the creation of interactive 3D Web sites. With VRML, visitors can take virtual tours through buildings and view three-dimensional models of cars directly from their Web browsers. Though the technology was created by Silicon Graphics and Intervista Software a number of years ago, it still is not widely used.
VSAN Virtual Storage Area Network (Virtual SAN). A storage area technology originally developed by Cisco, which allows a SAN to be logically sectioned allowing each section to be viewed and manipulated as though it were a separate SAN. A SAN is composed of a number of "SAN islands" (or fabrics), each of which is physically isolated by a switch or group of switches. This allows SANs to be expanded and changed with minimal disruption to the existing storage infrastructure. VSANs are a logical way of managing the collection of SAN islands, providing too future scalability.
VSMP (Virtual Symmetric Multiprocessing) The feature of mapping two or more virtual processors inside a single virtual machine or partition.
vSphere VMware vSphere, (formerly developed as VMware Infrastructure 4) is VMware's first cloud operating system, able to manage large pools of virtualized computing infrastructure, including software and hardware. VMware vSphere 4 was originally developed as VMware Infrastructure (VI) 4 then became its own product called vSphere.[1]
VT100 A type of terminal emulation required when you open an interactive network connection (telnet) to a UNIX system from your desktop computer.
VxD (Virtual device Driver) A device driver that runs under the Windows operating system. It runs as part of the OS kernel and has access to kernel memory, running processes and hardware. Starting with Windows 95, these files have the file extension .vxd, and before that with Windows 3.x, they had the extension .386.
W2K Microsoft Windows 2000 (workstation or server) operating system. Also known as Windows 2000.
W3C "World Wide Web Consortium (W3C) is an international consortium where Member organizations, a full-time staff, and the public work together to develop Web standards. W3C primarily pursues its mission through the creation of Web standards and guidelines designed to ensure long-term growth for the Web. Over 400 organizations are Members of the Consortium. W3C is jointly run by the MIT Computer Science and Artificial Intelligence Laboratory (MIT CSAIL) in the USA, the European Research Consortium for Informatics and Mathematics (ERCIM) headquartered in France, Keio University in Japan, and has additional Offices worldwide."
W9x Abbreviation for Windows 95 and Windows 98, sometimes also used to include Windows ME. Any software said to run on Windows 9x should run on Windows 95 and Windows 98, and probably Windows ME. W9x is often also expressed as "Windows 9x".
Wafer A flat, round piece of silicon that is used in the manufacture of microprocessors. Fabrication plants, or fabs, typically will take a wafer and carve many microprocessors into it. Over the years wafer size has been increasing so that more chips can be fit on a single wafer, from 6″ to 8″ to 12″ in diameter in some plants today. Wafers are created by taking a cylinder of silicon and slicing it, much like taking a loaf of bread and cutting slices, but to much more precise measurements.
WAIS Stands for "Wide Area Information Server." This is a program that can index enormous amounts of information and make it searchable across large networks (including the Internet). People can search the WAIS index and it will return results by relevance. Searches can then be narrowed down by subsequent searches on the original results. Search engines are a new and improved version of WAIS, specifically for the Web.
Wallpaper An optional background graphic used in a graphical user interface.
WAN Wide Area Network. Typically much slower than a LAN. Typical speeds start at 56kbps but are typically much faster. WANs typically provide connections between LANs that are at different geographical locations.
WAP 1. Wireless Application Protocol.
War Chalking War chalking is marking areas, usually on sidewalks with chalk, that receive wireless signals that can be accessed.
War Dialer A computer program that automatically dials a series of telephone numbers to find lines connected to computer systems, and catalogs those numbers so that a cracker can try to break into the systems.
War Dialing War dialing is a simple means of trying to identify modems in a telephone exchange that may be susceptible to compromise in an attempt to circumvent perimeter security.
War Driving War driving is the process of traveling around looking for wireless access point signals that can be used to get network access.
WatchGuard WatchGuard Technologies is a provider of Internet security solutions for small- to mid-sized enterprises worldwide and a pioneer in security appliances. WatchGuard products include the Firebox line of firewall and VPN appliances.
Water Cooling This type of cooling differs from air cooling in that water is used to remove heat from a heatsink that makes contact with a hot microprocessor or other device. Ultimately the water may actually exchange its heat with metal and air, or it could be cooled by a refrigeration unit. Water cooling is more efficient than air cooling, especially if the water is refrigerated.
Watt The electrical unit of power, which is energy transferred over a unit of time. Often it is used to describe the amount of heat generated by a microprocessor.
Wattage A measure of an amount of watts.
Waveform A waveform is an image that represents an audio signal or recording. It shows the changes in amplitude over a certain amount of time. The amplitude of the signal is measured on the y-axis (vertically), while time is measured on the x-axis (horizontally). Most audio recording programs show waveforms to give the user a visual idea of what has been recorded. If the waveform is very low and not pronounced, the recording was probably very soft. It the waveform almost fills the entire image, the recording may have been too "hot" or recorded with the levels set too high. Changes in a waveform are also good indicators as too when certain parts of a recording take place. For example, the waveform may be small when there is just a vocalist singing, but may become much larger when the drums and guitar come in. This visual representation enables audio producers to locate certain parts of a song without even listening to the recording.
Wavetable synthesis A method of translating digital data into analog sounds; it relies on recordings of real instruments to produce sounds.
Wayback Machine Wayback Machine is also known as Internet Archive's web archive. The Wayback Machine is a piece of software that makes archived websites viewable and browsable.
Web 2.0 Web 2.0 is term that was introduced in 2004 and refers to the second generation of the World Wide Web. The term "2.0" comes from the software industry, where new versions of software programs are labeled with an incremental version number. Like software, the new generation of the Web includes new features and functionality that was not available in the past. However, Web 2.0 does not refer to a specific version of the Web, but rather a series of technological improvements. Some examples of features considered to be part of Web 2.0 are listed below: Blogs - also known as Web logs, these allow users to post thoughts and updates about their life on the Web. Wikis - sites like Wikipedia and others enable users from around the world to add and update online content. Social networking - sites like Facebook and MySpace allow users to build and customize their own profile sand communicate with friends. Web applications - a broad range of new applications make it possible for users to run programs directly in a Web browser. Web 2.0 technologies provide a level user interaction that was not available before. Websites have become much more dynamic and interconnected, producing "online communities" and making it even easier to share information on the Web. Because most Web 2.0 features are offered as free services, sites like Wikipedia and Facebook have grown at amazingly fast rates. As the sites continue to grow, more features are added, building off the technologies in place. So, while Web 2.0 may be a static label given to the new era of the Web, the actual technology continues to evolve and change.
Web Archive A collection of web-published materials that an institution has either made arrangements for or has accepted long-term responsibility for preservation and access in keeping with an archive's user access policies. Some of these materials may also exist in other forms but the web archive captures the web versions for posterity.
Web Archive Service Enables curators to build collections of web-published materials that are stored in either local and/or remote repositories. The service includes a set of tools for selection, curation, and preservation of the archives. It also includes repositories for storage, preservation services (e.g., replication, emulation, and persistent naming), and administrative services (e.g., templates for collection strategies, content provider agreements, repository provider agreements.)
Web farm Web server environment using many servers each hosting the same website (or website application) so any one of the servers can respond to a http (web) request. Web farms are used where either high resilience is required (so web requests can continue to be responded to even though one server has failed) or for hosting busy websites where a single server would not be able to cope with the load. Also known as a server farm or server cluster. cf web garden.
Web garden A web hosting environment which uses a single server but with multiple instances of the web server worker process are used for each application pool. Web gardens are a concept which exists under IIS. Web gardens can provide better performance for web applications which have long running requests (such as database queries) but which are not CPU bound. Web gardens are used where a server has two or more physical processors (but not multiple cores).
Web Host In order to publish a website online, you need a Web host. The Web host stores all the pages of your website and makes them available to computers connected to the Internet. The domain name, such as "sony.com," is actually linked to an IP address that points to a specific computer. When somebody enters your domain name into their browser's address field, the IP address is located and Web site is loaded from your Web host. A Web host can have anywhere from one to several thousand computers that run Web hosting software, such as Apache, OS X Server, or Windows Server. Most websites you see on the Web are accessed from a "shared host," which is a single computer that can host several hundred Web sites. Larger websites often use a "dedicated host," which is a single machine that hosts only one website. Sites with extremely high amounts of traffic, such as apple.com or microsoft.com, use several computers to host one site. If you want to publish your own website, you'll need to sign up for a "Web hosting service." Finding a good Web host shouldn't be too hard, since their are thousands available. Just make sure the Web host you choose offers good technical support and ensures little or no downtime. You'll usually have to pay a monthly fee that varies depending on how much disk space and bandwidth your site will use. So it's a good idea to estimate how big your site will be and how much traffic you expect before signing up for a Web hosting service.
Web Page An HTML document that is accessible on the Web.
Web Ring A Web ring is a way of interlinking related Web sites so that people can visit many similar Web sites by just following the "Web ring" link on each page. Most Web rings allow people to browse backwards or forwards through the sites in the ring, or choose to visit individual sites from a list. The rings are typically run from a main site which uses a Web scripting application to select random sites and keep the ring up to date. This includes getting rid of outdated pages and links, and adding new ones. There are tens of thousands of Web rings for topics like football, cars, celebrities, computers, TV shows, etc. You can tell if a Web page is part of Web ring if on the bottom of the page it has some huge, obtrusive, off-color, button linking to other sites in the ring.
Web Service A Web Service is a means for objects to obtain data from other remote objects over the internet using common internet protocol, normally XML over HTTP. A Web Service publishes what functions it provides (using WSDL). Clients communicate with the Web Service using XML and receive results back in XML form. Web Services typically make use of SOAP to translate objects into XML See also UDDI.
Web-bot Web Robot. A generic term applied to any program which retrieves information from websites. Common examples of web-bots include: Search engines use web-bots (sometimes also called search-bots or simply bots) to gather (trawl) information from websites, which the search engine will then use to respond to search queries. An email-harvester will use a web-bot to gather email addresses from web-pages or from newsgroup postings. These are then used by spammers who then spam the harvested email addresses. A harvester-bot is used spammers to harvest e-mail addresses from web pages. See also bot.
Web-published materials Web-published materials are accessed and presented via the World Wide Web. The materials span the cultural heritage spectrum and include a range of material types from text documents to streaming video to interactive experiences. Web-published materials are both dynamic and transient. They are at risk of disappearing. Web archives preserve web-published materials.
Webcam The term webcam is a combination of "Web" and "video camera." The purpose of a webcam is, not surprisingly, to broadcast video on the Web. Webcams are typically small cameras that either attach to a user's monitor or sit on a desk. Most webcams connect to the computer via USB, though some use a Firewire connection. Webcams typically come with software that allows the user to record video or stream the video on the Web. If the user has a website that supports streaming video, other users can watch the video stream from their Web browsers. Webcams can also be used for video chat sessions with other people. Instead of broadcasting the video on the Web, users can set up a video chat session with one or more friends and have a conversation with live audio and video. For example, Apple's iSight camera, which is built into Apple laptops and iMacs, allows users to video chat using the iChat instant messaging program. Several other chat programs also work with webcams, allowing users to set up video chat sessions with friends. Since streaming video over the Internet requires a lot of bandwidth, the video stream is typically compressed to reduce the "choppiness" of the video. The maximum resolution of a webcam is also lower than most handheld video cameras, since higher resolutions would be reduced anyway. For this reason, webcams are relatively inexpensive compared to most video cameras. And while they may not be ideal for filming a movie, webcams are great for video chat sessions with friends.
Webmail There are two primary ways of checking your e-mail – using an e-mail program like Microsoft Outlook or with a Web-based interface called webmail. When you check or send e-mail via the Web, you are using webmail. Most free e-mail services, such as Gmail, Hotmail, and Yahoo! Mail offer webmail interfaces that allow you to send, receive, and organize your e-mail on the Web. If you own a domain name, many Web hosts also offer a webmail interface to use with your domain name or website. Some common webmail systems supported by Web hosts include Horde, NeoMail, and SquirrelMail. Because webmail is run from a server, the messages downloaded to your inbox are saved on the mail server. This is convenient since you can check your mail and browse old messages from any computer as long as you have an Internet connection. The downside is that, since the messages are not downloaded to your computer, you need an Internet connection to view your messages – even ones that you have already viewed. If you only have one e-mail account, webmail may be the simplest way to check, send, and manage your e-mail. However, if you regularly use multiple e-mail accounts, a software e-mail client like Microsoft Outlook or Mac OS X Mail may be a better choice.
Webmaster The webmaster is the person in charge of maintaining a Web site. The jobs of a webmaster include writing HTML for Web pages, organizing the Web site's structure, responding to e-mails about the Web site, and keeping the site up-to-date
Website A website, or Web site, is not the same thing as a Web page. Though the two terms are often used interchangeably, they should not be. So what's the difference? To put it simply, a Web site is a collection of Web pages. For example, Amazon.com is a Web site, but there are millions of Web pages that make up the site. Knowing the difference between these two terms can save you a lot of embarrassment.
WEP Stands for "Wired Equivalent Privacy." WEP is a security protocol for Wi-Fi networks. Since wireless networks transmit data over radio waves, it is easy to intercept data or "eavesdrop" on wireless data transmissions. The goal of WEP is to make wireless networks as secure as wired networks, such as those connected by Ethernet cables. The wired equivalent privacy protocol adds security to a wireless network by encrypting the data. If the data is intercepted, it will be unrecognizable to system that intercepted the data, since it is encrypted. However, authorized systems on the network will be able to recognize the data because they all use the same encryption algorithm. Systems on a WEP-secured network can typically be authorized by entering a network password.
WFW Windows For Workgroups. Also known as Windows 3.11. Successor to Windows 3.1. Predecessor to Windows 95.
WGA Windows Genuine Advantage (or Windows Genuine Article). A Microsoft programme that will require Windows to be validated as genuine before any windows updates can be downloaded from the Microsoft website.
Wheel Mouse A mouse controller that, besides the usual buttons, also has a wheel device built in that is most often used to scroll up and down windows that are longer than the screen, such as long Web pages or documents.
White hat A hacker with benign intentions. For example, if a hacker encounters a security hole and the first thing he or she does is explain the problem to the people who run the system that allows the security hole–without letting the knowledge out publicly–that hacker would be described as a white hat hacker. This term comes from old cowboy movies where the good guy wore a white hat.
White List 1. List of approved or trusted people or vendors or items etc. cf Blacklist. 2. In the context of e-mail and Spam, a white list is a list of approved e-mail contacts that spam filtering software should allow through.
White Noise This is technically sound with a uniform frequency spectrum over a wide range of frequencies. Non-technically, white noise is any unobtrusive background noise, such as the hum of a fan, the sound of rain, or the sound of a channel that isn’t coming in properly on an old television. Often white noise is imitated and generated to drown out other obtrusive sounds.
White Paper This term has historically been used to describe a report that states the social or political position of an organization. In recent years, however, the IT industry has adopted the term to describe articles that explain a certain technology or product. For example, a company may release a white paper to the public in order to educate consumers about one of their products. The terminology used may be somewhat technical, but the goal of a white paper is usually to describe the technology or product in terms most people can understand. That way nerds don't get to have all the fun each time a new technology is invented.
WHOIS This is an Internet service that finds information about a domain name or IP address. If you enter a domain name in a WHOIS search engine, it will scour a huge database of domains and return information about the one you entered. This information typically contains the name, address, and phone number of the administrative, billing, and technical contacts of the domain name. WHOIS can also be used to simply check if a certain domain name is available or if it has already been registered. To see the WHOIS service in action, check out Allwhois.com or BetterWhois.com.
Wi-Fi (Wireless Fidelity) A popular term for a form of wireless data communication, basically Wi-Fi is "Wireless Ethernet". See also: Ethernet
Wide Area Information Service (WAIS) A client/server method of accessing databases stored on multiple servers. You use a WAIS client to connect to a WAIS server and search the databases that the WAIS server has cataloged. WAIS is not much use to the average Internet user today, but is still used by some to access information that is not readily available in HTML form yet.
Wide SCSI An improvement to the old narrow SCSI that allows for faster throughput by increasing the number of pins used to connect the drive to the controller from 50 to 68. Wide SCSI doubled the throughput of narrow versions of SCSI, but was generally more expensive due to the additional pins and marketing strategies. Of course you were getting twice the performance, so what’s a few bucks?
Wideband CDMA (WCDMA) A 3G standard that increases the throughput of data transmission of CDMA by using a wider 5MHz carrier than standard CDMA, which uses a 200KHz carrier. WCDMA allows for data transfer rates as high as 2Mbps.
Widget A widget is a small program run by the Mac OS X Dashboard or the Yahoo! Widget Engine. Dashboard is only available on Macintosh computers, while the Yahoo! Widget Engine is available for both Windows and Macintosh platforms. Dashboard and Yahoo! widgets are not compatible with each other, so similar widgets must be created separately for each widget engine. Some common widgets include weather guides, stock lists, flight trackers, calendars, and search boxes for various websites. Widgets are convenient tools since they are always only one click or keystroke away. By default, pressing the F12 key brings up Dashboard widgets on the Mac, while pressing the F8 key brings up Yahoo! widgets. When widgets are active, they jump to the front of the screen. When Dashboard widgets are not active, they completely disappear, while Yahoo! widgets move to the background. The idea of widgets started with a program called Konfabulator, which allowed many small programs to run simultaneously on the computer's desktop. Apple introduced a similar program, called Dashboard, with the release of Mac OS X 10.4 Tiger. Shortly after, in 2005, Yahoo! bought Konfabulator and now markets the program as the Yahoo! Widget Engine. While both widget engines come with several standard widgets, there are thousands more available online.
Wiki A wiki is a web site for which the content can be easily edited and altered from the web browser in which you are viewing it. Typically there is an "edit" button on each page and the wiki is configured to allow either anyone or only people with passwords to edit each page. The word "wiki" comes from a Hawaiian word meaning "quick."
wild card A special character provided by an operating system or a particular program that is used to identify a group of files or directories with a similar characteristic. Useful if you want to perform the same operation simultaneously on more than one file. Example: the asterisk (*) that can be used in DOS to specify a groups of files such as *.txt.
WiMAX WiMAX, also known as "IEEE 802.16," is a broadband wireless access (BWA) standard similar to Wi-Fi. However, unlike Wi-Fi, which only has a range of several hundred feet, a WiMAX signal can be broadcast up to 30 miles. Therefore, WiMAX can be used to provide Internet access to large areas, such as corporate buildings or entire cities, with a single wireless station. While WiMAX isn't expected to replace Wi-Fi in small settings, it will provide a new, more efficient way of covering large regions.
WIN32 The Windows API for all 32 bit versions of windows, i.e. from Windows 95 onwards. WIN32 can also indicate the 32bit API on 64bit versions of Windows. cf WIN64.
WIN64 The Windows API for all 64 bit versions of windows. cf WIN32.
Window A window is an area on the screen that displays information for a specific program. This often includes the user interface GUI as well as the program content. Windows are used by most applications as well as the operating system itself. A typical window includes a title bar along the top that describes the contents of the window, followed by a toolbar that contains user interface buttons. Most of the window's remaining area is used to display the content. Examples: Web Browser windows: The top of a typical Web browser window contains a title bar that displays the title of the current page. Below the title is a toolbar with back and forward buttons, an address field, bookmarks, and other navigation buttons. Below the toolbar is the content of the current Web page. The bottom of the window may contain a status bar that displays the page loading status Word Processing windows: A window used by a word processing program, such as Microsoft Word, typically includes buttons for page and text formatting, followed by a ruler that defines the document area. Below the ruler is the main page area used for entering text. Operating System windows: Windows used by the operating system typically include navigation buttons along the top and shortcuts to folders and other locations on the left side of the window. The rest of the window is used to display icons or lists of files and folders. Most windows can be opened, closed, resized, minimized, and moved around the screen. The close, minimize, and zoom buttons are located on the title bar (on the right side on Windows and the left side on Macs). Minimizing a window will close the contents of the window, but store a reference to it in the Taskbar (Windows) or the Dock (Mac). Closing a window will make it disappear completely (so you may be asked to save your changes first). To move a window, click on the title bar and drag the window where you want it. To resize a window, either click the Zoom button in the title bar or click the lower right-hand corner and expand or contract the window to the size you want.
Windowing A windowing system is a system for sharing a computer's graphical display presentation resources among multiple applications at the same time. In a computer that has a graphical user interface (GUI), you may want to use a number of applications at the same time (this is called task). Using a separate window for each application, you can interact with each application and go from one application to another without having to reinitiate it. Having different information or activities in multiple windows may also make it easier for you to do your work. A windowing system uses a window manager to keep track of where each window is located on the display screen and its size and status. A windowing system doesn't just manage the windows but also other forms of graphical user interface entities.
Windows A family of operating systems developed by Microsoft, which uses a graphical user interface (GUI) instead of a command line one. Windows is a generic term encompassing all the different versions of Windows released by Microsoft and includes: Windows 7 (Ultimate, Enterprise, Professional, Home Premium, Home Basic or Starter) Windows Vista (Ultimate, Business, Home Premium or Home Basic) Windows 2003 Server Windows XP (Home or Professional) Windows 2000 (Server or Professional, which are collectively known as Windows 2000) Windows NT 4 (Server or Workstation, which are collectively known as Windows NT) Windows NT 3.5 - collectively known as Windows NT Windows ME - collectively known as Windows 9x Windows 98SE - collectively known as Windows 9x Windows 98SE was a second release of Windows 98 with some additional features not found in the original release. Windows 98 - collectively known as Windows 9x Windows 95 - collectively known as Windows 9x Windows 3.11 - also known as Windows for Workgroups (WFW) Windows 3.1 - Windows 3, 3.1 and 3.11 are also collectively referred to as Windows 3.x Windows 3 (Windows 3.0) Windows 2 Windows 1
Windows 2000 General abbreviation for any Windows 2000 based operating system. This included Windows 2000 Professional and Windows 2000 Server. Windows 2000 is sometimes abbreviated to simply W2K.
Windows 3.x Abbreviation denoting Windows 3, 3.1, 3.11 and WFW. Windows 9x is sometimes abbreviated to W9x.
Windows 95 A 16- and 32-bit operating system that builds on DOS and Windows 3.x to support 32-bit operations, additional hardware, and a more usable interface. This was a true breakthrough product for Microsoft, allowing game developers to run games inside of the Windows OS instead of separately in DOS. It was designed for the consumer market.
Windows 98 This operating system was designed by Microsoft and adds additional hardware support and integrated browsing onto the Windows 95 platform. This OS is still partially 16-bit, a full 15 years after Intel released its first 32-bit processor, the 386.
Windows 9x Abbreviation for Windows 95 and Windows 98, sometimes also used to include Windows ME. Any software said to run on Windows 9x should run on Windows 95 and Windows 98, and probably Windows ME. Windows 9x is sometimes abbreviated to simply W9x.
Windows CE This was initially the name for Microsoft’s mobile operating system designed for PDAs. Initial Windows CE devices offered color screens, and a fairly direct port of the Windows user interface. The Windows CE platform has been renamed by Microsoft to Pocket PC.
Windows Essential Business Server Windows Essential Business Server[1] (code named Centro)[1] is Microsoft's server offering for mid-size businesses (up to a maximum of 300 Users and/or Devices). [2] It was released to manufacturing on 16 September 2008 and was officially launched on the 12th of November 2008. [3] Overview Built from the Windows Server 2008 codebase, two editions are available: Standard and Premium. The Standard edition includes three Windows Server 2008 x64 Standard Servers and on top of those three servers: Microsoft Exchange 2007, Microsoft System Center Essentials, Microsoft Forefront Security for Exchange Server, and Forefront Threat Management Gateway (Medium Business Edition) formerly known as Microsoft Internet Security and Acceleration Server. The Premium edition adds another Windows Server 2008 Standard Edition and the Microsoft SQL Server 2008 Standard database software. According to Microsoft, Essential Business Server features a single administration/management console, through which the collection of managed clients and servers can be monitored and managed. Third party software can also utilize the same console to present an administration interface to their software. Computer Associates Inc. and Symantec will use the management console for their CA ARCserve Backup, Backup Exec and Endpoint Protection products respectively.[2] Essential Business Server also includes Remote Web Workplace, an out-of-the-box feature that enables IT to easily set up security-enhanced remote access to company client computers and Outlook Web Access.
Windows for Workgroups (WFW) Officially this was called Windows 3.11 for Workgroups, and it added some basic networking functionality to the standard Windows 3.1 operating system.
Windows Home Server Windows Home Server, code-named Quattro, is a home server operating system from Microsoft. Announced on 7 January 2007, at the Consumer Electronics Show by Bill Gates, Windows Home Server is intended to be a solution for homes with multiple connected PCs to offer file sharing, automated backups, and remote access.[3][4] It is based on Windows Server 2003 Service Pack 2 Features Centralized Backup - Allows backup of up to 10 PCs,[8] using Single Instance Store technology to avoid multiple copies of the same file, even if that file exists on multiple PCs.[9] Health Monitoring - Can centrally track the health of all PCs on the network, including antivirus and firewall status.[9] File Sharing - Offers network shares for computers to store the files remotely, acting as a network-attached storage device. Separate categories are provided for common file types like Documents, Music, Pictures and Videos.[9] The files are indexed for fast searching.[10] Printer Sharing - Allows a centralized print server to handle print jobs for all users.[9] Shadow Copy - Takes advantage of Volume Shadow Copy Services to take point in time snapshots that allow older versions of files to be recovered.[11] However, after introduction Microsoft has recommended not enabling shadow copies on HomeServer for unspecified reasons, and had not fixed the problem by September 2008.[12] Headless Operation - No monitor or keyboard is required to manage the device.[9] Remote administration is performed by using the Windows Home Server Console client software provided in the bundle. Also supports Remote Desktop[13] connections to the server while connected to the same LAN.[14] Remote Access Gateway - Allows remote access to any connected PC on the network over the Internet.[14] Media Streaming - Can stream media to an Xbox 360 or other devices supporting Windows Media Connect.[9] Selective Data redundancy - Guards against a single drive failure by duplicating selected data across multiple drives.[9] Expandable Storage - Provides a unified single and easily expandable storage space, removing the need for drive letters.[9] Extensibility through Add-Ins - Add-Ins allow third-party developers to extend the features and functionality of the server. Add-Ins can be developed using the Windows Home Server SDK, to provide additional services to the client computers or work with the data already on the server. Add-Ins can also be ASP.NET applications, hosted in IIS 6 running on WHS.[10] Server Backup - Backs up files which are stored within shared folders on the server to an external hard drive.
Windows HPC Server 2008 Windows HPC Server 2008, released by Microsoft in September 2008, is the successor product to Windows Compute Cluster Server 2003. Like WCCS, Windows HPC Server 2008 is designed for high-end applications that require high performance computing clusters. This version of the server is claimed to efficiently scale to thousands of cores. It includes features unique to HPC workloads: a new high-speed NetworkDirect RDMA, highly efficient and scalable cluster management tools, a service-oriented architecture (SOA) job scheduler, and cluster interoperability through standards such as the High Performance Computing Basic Profile (HPCBP) specification produced by the Open Grid Forum (OGF). In June 2008, a system built collaboratively with the National Center for Supercomputing Applications (NCSA) and Microsoft ranked #23 on the Top500 list, a ranking of the world's fastest supercomputers, with a LINPACK score of 68.5 teraflops. In the November 2008 rankings published by Top500.org, a Windows HPC system built by the Shanghai Supercomputer Center achieved 180.6 teraflops, a peak performance that placed the Dawning 5000A system at #10 on the list of the world's fastest supercomputers. However, as of June 2009, Windows HPC only has about 1% of the market of the 500 most powerful supercomputers, with about 1.5% of total gigaflops, with Linux dominating the rankings and Unix second place. The other two systems in the top 100 that can run Windows HPC do so only part of the time[1][2].
Windows Me (Windows Millennium Edition) This Microsoft Windows operating system added many UI enhancements and clutter that actually made it less stable and more hated than Windows 95 and 98. No improvements to the core were made for stability or to enhance the combination 16- and 32-bit mess under the hood. This was Microsoft’s last version of Windows containing pieces of 16-bit DOS guts, and good riddance.
Windows Media Audio (WMA) A Microsoft-developed audio codec that offers sampling rates of 8 to 48KHz. Files of this type typically have the file extension “.wma,” and Microsoft is aggressively pushing WMA as an alternative to the popular MP3 audio format, making WMA the default format for its Media Player, which now ships with Windows by default. WMA can create files that sound similar to MP3 files at a given quality and take up less disk space.
Windows NT General abbreviation for a family of Microsoft Windows operating systems covering Windows NT 3.5 and NT 4 server or workstation. Windows NT is sometimes abbreviated to simply NT.
Windows RAM A type of memory chip, or RAM, that was commonly used at one time in graphics cards on PCs. It is dual-ported so that graphics information can be displayed at the same time that it is being refreshed, much like with VRAM. This can give an increase in display speed over conventional memory.
Windows Server Windows Server is a brand name for server operating systems released by Microsoft Corporation. This name has been used for the following software releases: Windows Server 2003 Windows Server 2008 Windows HPC Server 2008, an edition designed exclusively for high-performance computing Windows Server 2008 R2, the current release of Windows Server 2008 Windows Small Business Server, an operating system based on Windows Server with some integrated Microsoft Servers, for small businesses Windows Essential Business Server, a product similar to Small Business Server, but for medium-sized businesses Windows Home Server, a home server operating system for file sharing and streaming, automated backups, and remote access [edit]See also Microsoft Servers, overview of Microsoft's Server range of products. Windows NT
Windows Server 2003 Windows Server 2003 (also referred to as Win2K3) is a server operating system produced by Microsoft. Introduced on 24 April 2003 as the successor to Windows 2000 Server, it is considered by Microsoft to be the cornerstone of its Windows Server System line of business server products[citation needed]. An updated version, Windows Server 2003 R2, was released to manufacturing on 6 December 2005. Its successor, Windows Server 2008, was released on 4 February 2008. New and updated features Manage Your Server See also: Features new to Windows XP Internet Information Services (IIS) v6.0 - A significantly improved version of IIS. Increased default security over previous versions, due to the built-in firewall and having most services disabled by default. Significant improvements to Message Queuing. Manage Your Server - a role management administrative tool that allows an administrator to choose what functionality the server should provide. Improvements to Active Directory, such as the ability to deactivate classes from the scheme, or to run multiple instances of the directory server (ADAM) Improvements to Group Policy handling and administration Provides a backup system to restore lost files Improved disk management, including the ability to back up from shadows of files, allowing the backup of open files. Improved scripting and command line tools, which are part of Microsoft's initiative to bring a complete command shell to the next version of Windows. Support for a hardware-based "watchdog timer", which can restart the server if the operating system does not respond within a certain amount of time.[3] [edit]Removed features The ability of creating rescue disk. Automated System Recovery (ASR) is used instead.
Windows Server 2008 Windows Server 2008 is one of Microsoft Windows' server line of operating systems. Released to manufacturing on February 4, 2008, and officially released on February 27, 2008, it is the successor to Windows Server 2003, released nearly five years earlier. A second release, named Windows Server 2008 R2, was released to manufacturing on July 22, 2009.[3] Like Windows Vista and Windows 7, Windows Server 2008 is built on Windows NT 6.x. Features See also: Features new to Windows Vista Windows Server 2008 is built from the same code base as Windows Vista; therefore, it shares much of the same architecture and functionality. Since the code base is common, it automatically comes with most of the technical, security, management and administrative features new to Windows Vista such as the rewritten networking stack (native IPv6, native wireless, speed and security improvements); improved image-based installation, deployment and recovery; improved diagnostics, monitoring, event logging and reporting tools; new security features such as BitLocker and ASLR; improved Windows Firewall with secure default configuration; .NET Framework 3.0 technologies, specifically Windows Communication Foundation, Microsoft Message Queuing and Windows Workflow Foundation; and the core kernel, memory and file system improvements. Processors and memory devices are modelled as Plug and Play devices, to allow hot-plugging of these devices. This allows the system resources to be partitioned dynamically using Dynamic Hardware Partitioning; each partition has its own memory, processor and I/O host bridge devices independent of other partitions.[8] [edit]Server Core Default user interface for Server Core Windows Server 2008 includes a variation of installation called Server Core. Server Core is a significantly scaled-back installation where no Windows Explorer shell is installed. All configuration and maintenance is done entirely through command line interface windows, or by connecting to the machine remotely using Microsoft Management Console. However, Notepad and some control panel applets, such as Regional Settings, are available. Server Core does not include the .NET Framework, Internet Explorer, Windows PowerShell or many other features not related to core server features. A Server Core machine can be configured for several basic roles: Domain controller/Active Directory Domain Services, ADLDS (ADAM), DNS Server, DHCP Server, file server, print server, Windows Media Server, IIS 7 web server and Hyper-V virtual server. Server Core can also be used to create a cluster with high availability using Failover Clustering or Network Load Balancing. Andrew Mason, a program manager on the Windows Server team, noted that a primary motivation for producing a Server Core variant of Windows Server 2008 was to reduce the attack surface of the operating system, and that about 70% of the security vulnerabilities in Microsoft Windows from the prior five years would not have affected Server Core.[9] [edit]Active Directory roles Active Directory roles is expanded with identity, certificate, and rights management services. Active Directory, until Windows Server 2003, allowed network administrators to centrally manage connected computers, to set policies for groups of users, and to centrally deploy new applications to multiple computers. This role of Active Directory is being renamed as Active Directory Domain Services (ADDS).[10] A number of other additional services are being introduced, including Active Directory Federation Services (ADFS), Active Directory Lightweight Directory Services (AD LDS), (formerly Active Directory Application Mode, or ADAM), Active Directory Certificate Services (ADCS), and Active Directory Rights Management Services (ADRMS). Identity and certificate services allow administrators to manage user accounts and the digital certificates that allow them to access certain services and systems. Federation management services enable enterprises to share credentials with trusted partners and customers, allowing a consultant to use his company user name and password to log in on a client's network. Identity Integration Feature Pack is included as Active Directory Metadirectory Services. Each of these services represents a server role. [edit]Failover Clustering Main article: Failover Clustering Windows Server 2008 offers high-availability to services and applications through Failover Clustering. Most server features and roles can be kept running with little to no downtime. In Windows Server 2008 and Windows Server 2008 R2, the way that clusters are qualified is changing significantly with the introduction of the cluster validation wizard[11]. The cluster validation wizard is a feature that is integrated into failover clustering in Windows Server 2008 and Windows Server 2008 R2. With the cluster validation wizard, you can run a set of focused tests on a collection of servers that you intend to use as nodes in a cluster. This cluster validation process tests the underlying hardware and software directly, and individually, to obtain an accurate assessment of how well failover clustering can be supported on a given configuration. [edit]Windows PowerShell Screenshot of a sample Windows PowerShell session. Main article: Windows PowerShell Windows Server 2008 is the first Windows operating system to ship with Windows PowerShell, Microsoft's new extensible command line shell and task-based scripting technology.[12] PowerShell is based on object-oriented programming and version 2.0 of the Microsoft .NET Framework and includes more than 120 system administration utilities, consistent syntax and naming conventions, and built-in capabilities to work with common management data such as the Windows Registry, certificate store, or Windows Management Instrumentation. PowerShell's scripting language was specifically designed for IT administration, and can be used in place of cmd.exe and Windows Script Host. [edit]Self-healing NTFS In Windows versions prior to Windows Vista, if the operating system detected corruption in the file system of an NTFS volume, it marked the volume "dirty"; to correct errors on the volume, it had to be taken offline. With self-healing NTFS, an NTFS worker thread is spawned in the background which performs a localized fix-up of damaged data structures, with only the corrupted files/folders remaining unavailable without locking out the entire volume and needing the server to be taken down. The operating system now features S.M.A.R.T. detection techniques to help determine when a hard disk may fail.[13] [edit]Hyper-V Hyper-V architecture Main article: Hyper-V Hyper-V is a hypervisor-based virtualization system, forming a core part of Microsoft's virtualization strategy. It virtualizes servers on an operating system's kernel layer. It can be thought of as partitioning a single physical server into multiple small computational partitions. Hyper-V includes the ability to act as a Xen virtualization hypervisor host allowing Xen-enabled guest operating systems to run virtualized[14]. A beta version of Hyper-V ships with certain x86-64 editions of Windows Server 2008. Microsoft released the final version of Hyper-V on 26 June 2008 as a free download. Also, a standalone version of Hyper-V exists. This version also only supports the x86-64 architecture.[15] While the x86 editions of Windows Server 2008 cannot run the Hyper-V integrations, they can run the Manager Console and Hyper-V tools. [edit]Windows System Resource Manager Main article: Windows System Resource Manager Windows System Resource Manager (WSRM) is being integrated into Windows Server 2008. It provides resource management and can be used to control the amount of resources a process or a user can use based on business priorities. Process Matching Criteria, which is defined by the name, type or owner of the process, enforces restrictions on the resource usage by a process that matches the criteria. CPU time, bandwidth that it can use, number of processors it can be run on, and allocated to a process can be restricted. Restrictions can be set to be imposed only on certain dates as well. [edit]Server Manager Server Manager is a new roles-based management tool for Windows Server 2008[16]. It is a combination of Manage Your Server and Security Configuration Wizard from Windows Server 2003. Server Manager is an improvement of the Configure my server dialog that launches by default on Windows Server 2003 machines. However, rather than serve only as a starting point to configuring new roles, Server Manager gathers together all of the operations users would want to conduct on the server, such as, getting a remote deployment method set up, adding more server roles etc and provides a consolidated, portal-like view about the status of each role. [edit]Other features Other new or enhanced features include: [edit]Core OS improvements Fully multi-componentized operating system. Improved hot patching, a feature that allows non-kernel patches to occur without the need for a reboot. Support for being booted from Extensible Firmware Interface (EFI)-compliant firmware on x86-64 systems. Dynamic Hardware Partitioning Support for the hot-addition of processors and memory, on capable hardware. Support for the hot-replacement of processors and memory, on capable hardware. [edit]Active Directory improvements A new "Read-Only Domain Controller" operation mode in Active Directory, intended for use in branch office scenarios where a domain controller may reside in a low physical security environment. The RODC holds a non-writeable copy of Active Directory, and redirects all write attempts to a Full Domain Controller. It replicates all accounts except sensitive ones. In RODC mode, credentials are not cached by default. Moreover, only the replication partner of the RODC needs to run Windows Server 2008. Also, local administrators can log on to the machine to perform maintenance tasks without requiring administrative rights on the domain. Restartable Active Directory allows ADDS to be stopped and restarted from the Management Console or the command-line without rebooting the domain controller. This reduces downtime for offline operations and reduces overall DC servicing requirements with Server Core. ADDS is implemented as a Domain Controller Service in Windows Server 2008. [edit]Policy related improvements All of the Group Policy improvements from Windows Vista are included. Group Policy Management Console (GPMC) is built-in. The Group Policy objects are indexed for search and can be commented on.[17] Policy-based networking with Network Access Protection, improved branch management and enhanced end user collaboration. Policies can be created to ensure greater Quality of Service for certain applications or services that require prioritization of network bandwidth between client and server. Granular password settings within a single domain - ability to implement different password policies for administrative accounts on a "group" and "user" basis, instead of a single set of password settings to the whole domain. [edit]Disk management and file storage improvements The ability to resize hard disk partitions without stopping the server, even the system partition. This applies only to simple and spanned volumes, not to striped volumes. Shadow Copy based block-level backup which supports optical media, network shares and Windows Recovery Environment. DFS enhancements - SYSVOL on DFS-R, Read-only Folder Replication Member. There is also support for domain-based DFS namespaces that exceed the previous size recommendation of 5,000 folders with targets in a namespace.[18] Several improvements to Failover Clustering (High-availability clusters).[19] Internet Storage Naming Server (iSNS) enables central registration, deregistration and queries for iSCSI hard drives. [edit]Protocol and cryptography improvements Support for 128- and 256-bit AES encryption for the Kerberos authentication protocol. New cryptography (CNG) API which supports elliptic curve cryptography and improved certificate management. Secure Socket Tunneling Protocol, a new Microsoft proprietary VPN protocol. AuthIP, a Microsoft proprietary extension of the IKE cryptographic protocol used in IPsec VPN networks. Server Message Block 2.0 protocol in the new TCP/IP stack provides a number of communication enhancements, including greater performance when connecting to file shares over high-latency links and better security through the use of mutual authentication and message signing. [edit]Improvements due to client-side (Windows Vista) enhancements Searching Windows Server 2008 servers from Windows Vista clients delegates the query to the server, which uses the Windows Search technology to search and transfer the results back to the client. In a networked environment with a print server running Windows Vista, clients can render print jobs locally before sending them to print servers to reduce the load on the server and increase its availability. Event forwarding aggregates and forwards logs of subscribed Windows Vista client computers back to a central console. Event forwarding can be enabled on the client subscribers from the central server directly from the event management console. Offline Files are cached locally so that they are available even if the server is not, with copies seamlessly updating when the client and server are reconnected. [edit]Miscellaneous improvements Windows Deployment Services replacing Automated Deployment Services and Remote Installation Services. Windows Deployment Services (WDS) support an enhanced multicast feature when deploying operating system images.[20] Internet Information Services 7 - Increased security, XCOPY deployment, improved diagnostic tools, delegated administration. Windows Internal Database, a variant of SQL Server Express 2005, which serves as a common storage back-end for several other components such as Windows System Resource Manager, Windows SharePoint Services and Windows Server Update Services. It is not intended to be used by third-party applications. An optional "Desktop Experience" component provides the same Windows Aero user interface as Windows Vista, both for local users, as well as remote users connecting through Remote Desktop. [edit]Removed features See also: Features removed from Windows Vista NT Backup is replaced by Windows Server Backup, and no longer supports backing up to tape drives[21] NNTP (Network News Transfer Protocol) is no longer part of Internet Information Services 7.0 Post Office Protocol component has been deprecated and will no longer be supplied as part of Windows OS Exchange backups. (NTBackup was replaced with VSS-based Windows Server Backup). Microsoft is recommending Data Protection Manager, but it requires a dedicated server. However a plug-in has been included as part of Exchange 2007 SP2 which facilitates Exchange backups using the Windows 2008 Backup tool.[22] Windows Small Business Server and Windows Essential Business Server both include an Exchange backup component. A Windows Backup component for non-SBS installations is forthcoming.
Windows Server 2008 R2 Windows Server 2008 R2 is a server operating system produced by Microsoft. It was launched on October 22, 2009.[2] According to the Windows Server Team blog, the retail availability was September 14, 2009.[3] It is built on Windows NT 6.1, the same core operating system used with the end-user oriented Windows 7. It is the first 64-bit only operating system release from Microsoft. Version enhancements include new functionality for Active Directory, new Virtualization and Management features, the release of IIS 7.5, and support for up to 256 logical processors. New features See also: Features new to Windows 7 A reviewer guide published by the company describes several areas of improvement in version R2.[9] These include new virtualization capabilities (Live Migration, Cluster Shared Volumes using Failover Clustering and Hyper-V), reduced power consumption, a new set of management tools and new Active Directory capabilities such as a "recycle bin" for deleted AD objects. IIS 7.5 has been added to this release which also includes updated FTP server services. Security enhancements include the addition of DNSSEC support for DNS Server Service and encrypted clientless authenticated VPN services through DirectAccess for clients using Windows 7. The DHCP server supports a large number of enhancements [10] such as MAC address-based control filtering, converting active leases into reservations or Link Layer based filters, IPv4 address exhaustion at scope level, DHCP Name protection for non-Windows machines to prevent name squatting, better performance through aggressive lease database caching, DHCP activity logging, auto-population of certain network interface fields, a wizard for split-scope configuration, DHCP Server role migration using WSMT, support for DHCPv6 Option 15 (User Class) and Option 32 (Information Refresh Time). The DHCP server runs in the context of the Network Service account which has less privileges to reduce potential damage if compromised. Windows Server 2008 R2 supports up to 64 physical processors [11] or up to 256 logical processors per system.[12] When deployed in a file server role, new File Classification Infrastructure services allow files to be stored on designated servers in the enterprise based on business naming conventions, relevance to business processes and overall corporate policies.[13] Server Core includes a subset of the .NET Framework, so that some applications (including ASP.NET web sites and Windows PowerShell 2.0) can be used. Performance improvement was a major area of focus for this release; Microsoft has stated that work was done to decrease boot time, improve the efficiency of I/O operations while using less processing power, and generally improve the speed of storage devices, especially iSCSI. Active Directory has several new features when raising the forest and domain functional levels[14] to Windows Server 2008 R2. When raising the domain function level, two added features are Authentication Mechanism Assurance and Automatic SPN Management. When raising the forest functional level, the Active Directory recycle bin feature is available and can be enabled using the Active Directory Module for Powershell.[15]
Windows Small Business Server Windows Small Business Server (SBS) (formerly Microsoft Small Business Server) is an integrated server suite from Microsoft designed for running network infrastructure (both intranet management and Internet access) of small and medium enterprises having no more than 75 workstations or users. Application server technologies are tightly integrated to enable small businesses with targeted solutions such as the Remote Web Workplace, and offer management benefits such as integrated setup, enhanced monitoring, a unified management console, and remote access. Windows Small Business Server is technically not an 'edition' of the Windows Server operating system but rather a customized SKU of server technologies targeted especially to small businesses. As such, the application servers are not merely bundled with the OS but are tightly integrated into the operating system. Since the release of SBS 2008, the same service packs as those for Windows Server or other server products can be used to update the OS. Editions Windows Small Business Server is available in Standard and Premium editions. Both editions are based on the Windows Server codebase and include Microsoft Exchange Server mail server, Internet Information Services (IIS) web server, Windows SharePoint Services for collaboration, Microsoft Office Outlook 2003 email client (not included in 2008), Routing and Remote Access Service (RRAS), Windows Server Update Services for update management across the network, and a Fax server. Up to SBS 2003, the Premium edition also included Microsoft SQL Server, Microsoft Internet Security and Acceleration Server and Microsoft Office FrontPage 2003. SBS 2008 Premium edition will not include ISA Server but will include a Windows Server 2008 license and SQL Server 2008 for running on a second server. Those upgrading to SBS 2008 Premium edition via Software Assurance will be compensated with a free license for the latest version of ISA Server. [1] The version of Windows Server that is part of Small Business Server 2008 and Essential Business Server 2008, Windows Server 2008 for Windows Essential Server Solutions (WinWESS) or Windows Server 2008 Standard FE is available outside the product suite, supporting a maximum of 15 Client Access Licenses. [2] Initially, Small Business Server was marketed as an edition of Microsoft BackOffice Server. When Windows 2000 was released, it was marketed as Microsoft Small Business Server 2000, and finally was rebranded as a member of the Windows Server 2003 family. Microsoft has also introduced a Windows Essential Business Server product aimed at medium-sized businesses, which will now incorporate the next version of ISA Server instead of SBS.
Windows Sockets An API designed to help inconsistent TCP/IP stacks talk together and be accessed properly by Windows 3.x programs.
Windows Task Manager Windows Task Manager is a task manager application included with Microsoft Windows NT family of operating systems that provides detailed information about computer performance and running applications, processes and CPU usage, commit charge and memory information, network activity and statistics, logged-in users, and system services. The Task Manager can also be used to set process priorities, processor affinity, forcibly terminate processes, and shut down, restart, hibernate or log off from Windows. Windows Task Manager was introduced with Windows NT 4.0, previous versions of Windows NT included the Task List application, which had far fewer features. The task list was capable of listing currently running processes and killing them, or creating a new process. The Task Manager can be launched using any of the following four methods: Using the context menu on the taskbar and selecting "Task Manager". Using the key combination Ctrl+Shift+Esc. In Windows NT, Windows 2000, and Windows Vista, use the key combination Ctrl+Alt+Del to open the Windows Security dialog, then click on "Task Manager". In Windows XP, pressing Ctrl+Alt+Del or Ctrl+Shift+Esc directly launches Task Manager, unless you have disabled the Welcome Screen. Starting "Taskmgr.exe" from a command line, GUI (located in C:\Windows\System32\taskmgr.exe) or a shortcut.
Windows Vista Windows Vista is the latest version of Microsoft's Windows operating system. The business version was released at the end of 2006, while the consumer version shipped on January 30, 2007. The Vista operating system includes an updated look from Windows XP, referred to as the "Aero" interface. The desktop, windows, icons, and toolbars have a smoother 3D look, similar to the Mac OS X interface. These graphics are generated using the new Windows Presentation Foundation (WPF) graphics subsystem included with Windows Vista. Other improvements include faster indexed file searching (which can locate text within files), built-in Web services called the Windows Communication Foundation (WCF), support for the new XML Paper Specification (XPS) document format, numerous security improvements, and more multimedia capabilities built into the operating system. Windows Vista was code-named "Longhorn" for much of the development process. The operating system was originally slated to ship in 2003 as an update to Windows XP, but Microsoft decided to make additional updates to the operating system and scheduled it for release in 2005. Several delays pushed back the release date to 2006 and eventually to the beginning of 2007. In order to ship the consumer version by early 2007, the new file system called Windows Future Storage, or WinFS, was left out of the release. Microsoft plans to incorporate the WinFS file system in a future update. Overall, Vista is a major upgrade to the Windows operating system (which is a good thing, since it has been over five years since Microsoft's last major OS release). The interface feels more modern, file navigation has been improved and system security has been designed to be stronger than Windows XP. If you plan to purchase Windows Vista for your system, you can choose one of five options: Business (designed for small business users and streamlined for work-oriented tasks) Enterprise (meant for large, global organizations with complex IT infrastructures) Home Basic (the most basic version of the Vista operating system designed for the average home user) Home Premium (a more robust home version that includes extra security and multimedia features) Ultimate (includes all the features from the Home Premium and Business versions of Vista) The absolute minimum system requirements for Vista are: - 800 MHz processor - 512 MB of RAM - 20 GB hard drive with at least 15 GB of available space - Super VGA graphics support - CD-ROM drive However, Microsoft recommends the following system requirements: - 1 GHz 32-bit (x86) or 64-bit (x64) processor - 1 GB of RAM - 40 GB hard drive with at least 15 GB of available space - DirectX 9 graphics support with a WDDM Driver - 128 MB (minimum) of video RAM - Pixel Shader 2.0 in hardware - 32 bits per pixel - DVD-ROM drive - Audio Output - Internet access Because many of Vista's new features require the recommended system requirements, it may be best to upgrade your operating system only if your computer meets or exceeds the recommended specifications. Otherwise, waiting to buy a new machine with Windows Vista installed is probably the best choice.
Windows XP The friendly-faced, updated version of Windows 2000, with an almost cartoonish interface that will surely be looked back upon with a wince. XP started to take real “advantage” of the Internet by including numerous hooks and links to Microsoft’s website to improve various functionality, and that is part of what made this operating system so controversial. Also, at long last, it moved the Windows NT code-base onto consumer machines, allowing home users to get the benefits of stability that Windows Me didn’t offer. Many hold-outs prefer to stick with Windows 2000.
Windump Windump is a freeware tool for Windows that is a protocol analyzer that can monitor network traffic on a wire.
Wine An implementation of Windows 3.x and Win32 APIs on top of X-Windows. Wine runs on Linux and UNIX, and allows Windows programs to run. Wine was created in 1993 and continues to be updated.
WINS Windows Internet Name Service. Dynamic hostname based addressing scheme used on Microsoft LANs. Integrated with DNS, allowing WINS clients to resolve DNS names.
WINS (Windows Internet Naming Service) A Windows-specific method of name resolution where a WINS server translates a NetBIOS name into an IP address.
Winsock Winsock. "Isn't that one of those tube-like flags that tell which way the wind is blowing?" Actually, that's a "windsock," which was first used by airline pilots to tell how fast and what direction the wind was blowing. To learn how to make your own windsock, click here. Winsock is actually short "Windows sockets," which are files that allow Windows programs to connect to the Internet and other computers. Technically, Winsock is an "Application Programming Interface (API)," that developers use to make their programs network-enabled. 16-bit applications use a file called WINSOCK.DLL and 32-bit applications use a file called WSOCK32.DLL. Both of these files are libraries of networking functions (based on TCP/IP), but they can differ from computer to computer, depending on the vendor. If you use Windows, you probably use Winsock on a regular basis. Fortunately, unless you're a Windows programmer, you don't have to understand exactly how it works.
Wired Equivalent Privacy (WEP) A security protocol for wireless local area networks defined in the standard IEEE 802.11b.
Wireless In the computing world, the term "wireless" can be rather ambiguous, since it may refer to several different wireless technologies. The two most common types of wireless capabilities computers have are Wi-Fi and Bluetooth. Wi-Fi is the technology used for wireless networking. If your computer has a wireless card, it is most likely Wi-Fi compatible. The wireless card transmits to a wireless router, which is also based on the Wi-Fi standard. Wireless routers are often connected to a network, cable modem, or DSL modem, which provides Internet access to anyone connected to the wireless network. Bluetooth is the technology often used for wireless keyboards and mice, wireless printing, and wireless cell phone headsets. In order to use a device such as a Bluetooth keyboard or mouse, your computer must be Bluetooth-enabled or have a Bluetooth adapter installed. Computers may also use other wireless technologies aside from Wi-Fi and Bluetooth. Products such as remote controls and wireless mice may use infrared or other proprietary wireless technologies. Because of the many wireless options available, it is a good idea to check the system requirements of any wireless device you are considering buying.
Wireless Application Protocol A specification for a set of communication protocols to standardize the way that wireless devices, such as cellular telephones and radio transceivers, can be used for Internet access, including e-mail, the World Wide Web, newsgroups, and Internet Relay Chat.
Wiretapping Monitoring and recording data that is flowing between two points in a communication system.
Wizard When most people think of a wizard, they think of an old man with magical powers. This, as with many other computer definitions, has no correlation with the technical term. In computer terminology, a wizard is a part of a program that guides you through certain steps. For example, a wizard in Microsoft Word would help you create and format a new document according to your needs. This is helpful when creating a r?sum?, outline, invoice, etc. Some other examples of wizards are the Finale 2000 wizard, which helps you create a new music composition with your desired instruments, and the PowerPoint wizard, which helps you set up a presentation using a certain theme. Basically, a wizard acts as a guide for creating a new document in a software program. Though wizards can be helpful, sometimes they can be more of a hassle than a help for experienced users. Some users would rather just create a new document from scratch, without using a wizard. This is because wizards typically don't offer as much customization as an experienced user may want. Finally, be sure not to confuse a "wizard" with a "template." A template is a pre-formatted document that has already been created, whereas a wizard is a step-by-step guide that helps you create your own document.
WLAN Wireless LAN.
WMI Windows Management Instrumentation (W2K). Improves administrative control by allowing administrators to correlate data and events from multiple sources and vendors on a local or enterprise basis.
WMS 1. Warehouse Management System. 2. Web Map Service. A technology for downloading map data from servers that are WMS compliant across the internet. WMS is defined by the Open GIS Consortium Inc in Web Map Service Implementation.
WOL Wake On LAN. The ability of a network card to wake up a PC that is powered down or on standby (i.e. sleep or suspected), when a wake-up message is received across the LAN.
Word 1. Technically a word is the number of bits (or bytes) that a CPU can process at a time. At the hardware level a word may therefore be 8, 16, 32 or 64 bits (1, 2, 4 or 8 bytes). It should be noted that in the programming sense the word size is 2 or 4 bytes. The concept originally came into existence because the bus and/or CPU register size is know as the word size. On old 16 bit CPU's this led to a common word size of 2 bytes. The most common CPU these days is 32 bit and therefore the word size is 4 bytes. However in general the word size defined by the compiler or programming language should not be confused with the word size of the hardware. Windows running on a 64 bit platform may or may not still define a word size as 4 bytes. 2. Common abbreviation for Microsoft Word, which is part of Microsoft Office.
WORD VARIANTS Different word endings (such as -ing, -s, es, -ism, -ist,etc.) will be retrieved only if you allow for them in your search terms. One way to do this TRUNCATION, but few systems accept truncation. Another way is to enter the variants either separated by BOOLEAN OR (and grouped in parentheses). In +REQUIRE/-REJECT non-Boolean systems, enter the variant terms preceded with neither + nor -, because this will allow documents containing any of them to retrieved.
Word Wrap Word wrapping is when a line of text automatically "wraps" to the next line when it gets to the end of a page or text field. This is different than a "word rap," which involves rhyming words to a rhythmic beat, though that may be more fun than typing. Most word processing programs use word wrap to keep the text within the default margins of the page. Without the word wrap feature, text would continue on one line until the user pressed "Enter" or "Return" to insert a line break. Most programs that incorporate word wrap take the first word that does not fit on a line of text and move it to the beginning of the next line. Advanced word processing programs can hyphenate long words at appropriate places. While it is uncommon, sometimes a word, or string of characters ,will take up more than one line. In this case, the word wrap feature will simply continue the string of characters onto the next line.
Workload Management The operation of handling computation power demand and computation power unavailability.
Workstation A workstation is a place where work gets done. It refers to a computer (and often the surrounding area) that has been configured to perform a certain set of tasks, such as photo editing, audio recording, or video production. An office may have several workstations for different purposes, which may be assigned to certain employees. For example, one workstation may be used for scanning and importing images, while another is used for editing images. Because workstations often work together like in the example above, they are commonly networked together. This allows them to send files back and forth over the network, which is important for various types of media production. To use another example, a user at a photo-editing workstation may prepare images to be used in a video clip. Once the images are ready, he may send them to another user at a video-editing workstation, where they are incorporated into the video. Once the video has been put together, the video file may be sent to another user at an audio production workstation where the soundtrack and other sound effects are added. While workstations are often part of a network, they can be standalone machines as well. Even a home computer can be a workstation if it is used for certain kinds of work. So if you want to sound professional, the next time you send an e-mail to a friend from your home PC, you can let him know you are sending it from your home workstation.
World-Wide Web Also known as WWW, or W3, is a way that information is moved around the Internet, the world-wide network of computer networks, providing text, files, graphics, sounds and moving pictures. It is a hypertext- based Internet service used for browsing Internet resources.
Worm A worm is a virus that does not infect other programs. It makes copies of itself, and infects additional computers (typically by making use of network connections) but does not attach itself to additional programs; however a worm might alter, install, or destroy files and programs.
WPA 1. Windows Product Activation. An anti-piracy measure from Microsoft where each copy of software can only be used for a limited time before it stops working unless the product is activated - either by phone or across the internet. Activation involves checking that the product key has not already been registered and ties the product to the machine on which it is being registered. The software can then not be activated on anther PC.
WRAM (Windows RAM) A type of memory chip, or RAM, that was commonly used at one time in graphics cards on PCs. It is dual-ported so that graphics information can be displayed at the same time that it is being refreshed, much like with VRAM. This can give an increase in display speed over conventional memory.
Write Protect Tab This phrase was initially coined for older floppy diskettes that needed to be write-protected by placing a tab or sticker over a notch that told a floppy drive that the disk was write-enabled. With the standard 3.5″ floppy disks, the write protect tabs are replaced by small plastic parts that can be enabled by setting them to up or down positions.
WSDL Web Services Description Language. A standard by which a web service can tell clients what messages it accepts and which results it will return. WSDL is an XML language which is used by service interfaces and protocol agreements, among others, for describing access to Web Services. WSDL is independent from the underlying service implementation language or component model.
WSUS Windows Server Update Services.
WUS Windows Update Services. A successor from Microsoft to SUS.
WWW World Wide Web. Often abbreviated to just "Web". The World Wide Web is the collection of all web pages available across the world. It is referred to as a web because each page can contain links to other pages, and these links (links to pages which link to other pages which link to other pages and so forth) making a network or web of pages. Page links may be to pages on the same site, or to other sites - since the network of links ultimately straddles the globe it is truly a world wide web.
WYSIWYG Stands for "What You See Is What You Get," and is pronounced "wihzeewig." WYSIWYG refers to software that accurately represents the final output during the development phase. For example, a desktop publishing program such as Photoshop is a WYSIWYG graphics program because it can display images on the screen the same way they will look when printed on paper. Word processing programs like Microsoft Word and Apple Pages are both WYSIWYG editors, because they include page layout modes that accurately display what the documents will look when printed. While WYSIWYG originally referred to programs that produce physical output, the term is now also used to describe applications that produce software output. For example, most Web development programs are called WYSIWYG editors since they show what Web pages will look like as the developer is creating them. This means that the developer can move text and images around the page to make it appear exactly how he or she wants before publishing the page on the Web. When the page is published, it should appear nearly the same on the Web as the way it looked in the Web development program. Of course, as most Web developers know, there is no guarantee that a Web page will look the same in two different browsers, such as Internet Explorer and Firefox. But at least a WYSIWYG editor can give developers a close approximation of what the published page will look like.
X Window System (X Windows) A consortium-developed, open-standard, device-independent GUI system that is most commonly found on UNIX and Linux operating systems and invoked with the “startx” command. The X Window System was initially developed in 1984 at MIT and called Project Athena. In 1986 the X Consortium was formed to further the development of the GUI. The torch was passed to the Open Group in 1997, and now resides at x.org on the Web. The GUI system works by running an X Server on the client machine that manages the windows, or X Clients. The X Window System uses the client/server architecture in and of itself.
X-Windows (X Window System) A consortium-developed, open-standard, device-independent GUI system that is most commonly found on UNIX and Linux operating systems and invoked with the “startx” command. The X Window System was initially developed in 1984 at MIT and called Project Athena. In 1986 the X Consortium was formed to further the development of the GUI. The torch was passed to the Open Group in 1997, and now resides at x.org on the Web. The GUI system works by running an X Server on the client machine that manages the windows, or X Clients. The X Window System uses the client/server architecture in and of itself.
X2 This is US Robotics’ 56Kbps modem standard that pre-dated V.90. It used the fact that most ISPs were digitally terminated, and this eliminated one analog loop. Due to this fact digital transmissions can remain more intact than previously thought, theoretically allowing for up to 56Kbps data rates, beyond the 33.6Kbps rate that was the earlier ceiling on analog modem transmission speed. See also 56Kflex.
X86 x86 is the generic name for Intel processors released after the original 8086 processor. These include the 286, 386, 486, and 586 processors. As you can see, the "x" in x86 stands for a range of possible numbers. Technically, x86 is short for 80x86 since the full names of the processors are actually 80286, 80386, 80486, and 80586. The "80" is typically truncated to avoid redundancy. If a computer's technical specifications state that is based on the x86 architecture, that means it uses an Intel processor (not AMD or PowerPC). Since Intel's x86 processors are backwards compatible, newer x86 processors can run all the programs that older processors could run. However, older processors may not be able to run software that has been optimized for newer x86 processors. While numbers provide a simple way to distinguish between processor types, they cannot be trademarked. For this reason, Intel's 586 processor is formally known as the Pentium processor. However, software developers still often refer to processors by their number. Of course, what else would you expect from computer nerds?
XDS Exchange Directory Service.
XGA Extended Graphics Array. A video graphics card standard (originally developed by IBM) that supports screen resolutions up to 1024x768x16, i.e. 1024 pixels wide by 768 pixels tall by 16 bit colour (65,536 colours). cf video mode.
XHTML eXtensible HyperText Markup Language (or eXtensible HTML). XHTML is a form of HTML that meets the XML 1.0 specification. It is commonly regarded as the natural successor to HTML. It is defined by a draft specification from W3C. XHTML files often (but not always) have the file extension .xhtml.
XML Extensible Mark-up Language. A specification developed by the W3C and is a mark-up language for structured documents. XML had its roots in specifying and formatting for web documents and web pages, providing a natural development beyond HTML, but it is now also frequently used to provide a common means of data exchange. It supports communication between various companies and applications and is a simplified version of SGML. Despite the various operating system platforms and end devices, data access logic and application logic do not have to be changed. An XML file is a file that is readable using a standard text editor. The file uses tags to indicate the start and end of blocks, with each opening tag having a matching closing tag (although there are exceptions). Since each tag can contain other tags, XML files provide a means of providing a hierarchy of data. Since each tag has a corresponding closing tag it is possible to read an XML file without understanding what each of the tags means, which is why it is possible to build generic XML parsers. See also DTD, JSON and the file extensions .xml and .xsd. Whilst XML files typically have a .xml file extension, they do not have to and many other file extensions are used for specific applications.
Xmodem A protocol for transferring files during direct dial-up communications. Developed by Ward Christensen in 1977, Xmodem has basic error checking to ensure that information isn’t lost or corrupted during transfer. It sends data in 128-byte blocks. Xmodem has undergone a couple of enhancements: Xmodem CRC uses a more reliable error-correction scheme, and Xmodem-1K transfers data faster by sending it in 1,024-byte blocks. See also Ymodem and Zmodem.
XOFF Transmitter off. Used as part of flow control, it is a character (0Fhex, 15dec, ©O) transmitted to suspend output from the sender. cf XON.
XON Transmitter on. Used as part of flow control, it is a character (0Ehex, 14dec, ©N) transmitted to resume output from a sender. cf XOFF.
XP 1. Windows XP. Refers to the Windows XP operating system from Microsoft. Relevant links: www.microsoft.com/windowsxp/default.mspx - Windows XP Home Page 2. XML Protocol.
Xsan Xsan is Apple Inc.'s SAN or clustered file system for Mac OS X. Xsan enables multiple Mac desktop and Xserve systems to access shared block storage over a Fibre Channel network. With the Xsan file system installed, these computers can read and write to the same storage volume at the same time. Xsan is a complete SAN solution which includes the metadata controller software, the file system client software, and integrated setup, management and monitoring tools. Xsan has all the normal features to be expected in an enterprise shared disk file system, which includes support for large files and file systems, multiple mounted file systems, meta data controller failover for fault tolerance, support for multiple operating systems etc. Interoperability Xsan is based on the StorNext File System. [1] The Xsan website claims complete interoperability [2] with the Quantum Corporation StorNext File System: And because Xsan is completely interoperable with Quantum’s StorNext File System, you can even provide clients on Windows, Linux, and other UNIX platforms with direct Fibre Channel block-level access to the data in your Xsan-managed storage pool. [3] Quantum Corporation claims Complete interoperability with Apple’s Xsan and Promise RAID and Allows Xsan and Xserve RAID to support AIX, HP-UX, IRIX, Red Hat Linux, SuSE Linux, Mac OS X, Solaris, and Windows clients, including support for 64 Bit Windows and Windows Vista. [4] This means that the StorNext File System and the Xsan file system must share the same file system layout and the same protocol when talking to the meta data server. They also seem to share a common code base or very close development based on the new features developed for both file systems. All the command line tools for Xsan are beginning with the letters cv which stands for CentraVision - the original name for the file system.
Ymodem A protocol for transferring files during direct dial-up communications. It is so named because it builds on the earlier Xmodem protocol. Ymodem sends data in 1,024-byte blocks and is consequently faster than Xmodem; however, it doesn’t work well on noisy phone lines. Ymodem has undergone a few enhancements: Ymodem-Batch can send several files in one session, and Ymodem-G drops software error-correction, which speeds up the process by removing the overhead used by error-correction. This works because all modems since the V.32 era have error-correction built into the hardware.
Yobibyte A yobibyte is a unit of data storage that equals 2 to the 80th power, or 1,208,925,819,614,629,174,706,176 bytes. While a yottabyte can be estimated as 10^24 or 1,000,000,000,000,000,000,000,000 bytes, a yobibyte is exactly 1,208,925,819,614,629,174,706,176 bytes. This is to avoid the ambiguity associated with the size of yottabytes. A yobibyte is 1,024 zebibytes and is the largest unit of measurement.
Yottabyte Unit of storage. Often abbreviated to YB. 1 yottabyte (YB) = 2 to the eitheth power (280) bytes = 1,208,925,819,614,629,174,706,176 bytes = 1024 zettabytes = 250 gigabytes = 260 megabytes.
Z-Buffering (or Hidden Surface Removal) This tracks the depth of each triangle in a 3D graphics representation, from the perspective of the viewer, to ensure that objects behind other objects in a scene don’t appear until the viewer has them in his or her line of sight. This is why you can’t see through walls to what lies behind, but why you can play multiplayer Quake and have people at many different areas in a level.
Zebibyte A zebibyte is a unit of data storage that equals 2 to the 70th power, or 1,180,591,620,717,411,303,424 bytes. While a zettabyte can be estimated as 10^21 or 1,000,000,000,000,000,000,000 bytes, a zebibyte is exactly 1,180,591,620,717,411,303,424 bytes. This is to avoid the ambiguity associated with the size of zettabytes. A zebibyte is 1,024 exbibytes and precedes the yobibyte unit of measurement.
Zero Administration Kit (ZAK) A software kit from Microsoft originally for Windows NT that can prevent various user actions, such as installing software or changing desktop configurations.
Zero Day Exploit A zero day exploit is a malicious computer attack that takes advantage of a security hole before the vulnerability is known. This means the security issue is made known the same day as the computer attack is released. In other words, the software developer has zero days to prepare for the security breach and must work as quickly as possible to develop a patch or update that fixes the problem. Zero day exploits may involve viruses, trojan horses, worms or other malicious code that can be run within a software program. While most programs do not allow unauthorized code to be executed, hackers can sometimes create files that will cause a program to perform functions unintended by the developer. Programs like Web browsers and media players are often targeted by hackers because they can receive files from the Internet and have access to system functions. While most zero day exploits may not cause serious damage to your system, some may be able to corrupt or delete files. Because the security hole is made known the same day the attack is released, zero day exploits are difficult to prevent, even if you have antivirus software installed on your computer. Therefore, it is always good to keep a backup of your data in a safe place so that no hacker attack can cause you to lose your data.
Zettabyte Unit of storage. Often abbreviated to ZB. 1 zettabyte (ZB) = 2 to the seventieth power (270) bytes = 1,180,591,620,717,411,303,424 bytes = 1024 exabytes = 250 megabytes. 1024 zettabytes = 1 yottabyte.
ZIP 1. To zip a file is to compress a file (or folder) using lossless compression. Correspondingly, to unzip a file is to decompress the file. 2. Zone Improvement Plan. A US postal service code used to facilitate the delivery of mail to the correct location. Where each delivery area is assigned a different code. Many other countries use similar schemes (details are obviously very different) using a code to indicate the area that post needs to be delivered. Elsewhere these are typically referred to as postcodes. A zip code was originally a five digit number, where the first three digits indicated the state or area within a state and the last two digits a specific postal delivery zone. This was later expanded by four digits to become known as ZIP + 4, with the first two additional digits indicating a postal sector and the last two a postal segment. Normally abbreviated to ZIP, ZIP +4 (see above) or ZIP code. 3. A fastening device. Known in British-English as a zip but in US-English as a zipper.
zipped files Zipped files are files that are compressed and must be "unzipped" to be read. Zipped files download faster because they are smaller than an uncompressed equivalent.
Zmodem This protocol has many error-correcting properties. It can detect if a bad block (of 1,024 bytes) has come through and ask to have it resent. If the transfer gets interrupted for any reason, it can resume from where it left off. It is slightly slower than Ymodem-G, but is much more reliable.
Zone A sub-tree of a DNS domain.
Zone File A zone file is stored on a name server and provides information about one or more domain names. Each zone file contains a list of DNS records with mappings between domain names and IP addresses. These records define the IP address of a domain name, the reverse lookup of an IP to other domains, and contain DNS and mail server information. Because zone files are plain text files, they can be edited quickly and easily. However, this also means that if unauthorized users gain access to zone files, the files can be easily modified. This could cause websites to not respond, or worse yet, redirect to the wrong Web server. For this reason, it is important to keep the zone files on a highly secured server and always have a recent backup of zone files on another machine.
Zone of Authority (Zone) A term having to do with DNS. Each top-level domain name, such as Geek.com, is considered a zone, where subdomains such as server1.geek.com or www.geek.com are managed by their own DNS servers. Geek.com’s Zone of Authority is all the subdomains under Geek.com.
Zone Transfer he act of replicating a zone file from one DNS server to another.
zoom The act of enlarging a portion of an onscreen image for fine detail work; most graphics programs have this capability.