| Word |
Description |
| 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.
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| 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.
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| 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.
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| 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
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| 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.
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| 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).
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| ADO |
ADO: Microsoft® ActiveX® Data Objects. Encompasses the functionality of both RDO and DAO.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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
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| 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.
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| 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.
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| 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.
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| 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”
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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! =)
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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."
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| Event |
An event is an observable occurrence in a system or network.
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| 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".
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| File Transfer Protocol (FTP) |
A TCP/IP protocol specifying the transfer of text or binary files across the network.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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
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| 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.
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| 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.
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| 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.
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| 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).
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| List Based Access Control |
List Based Access Control associates a list of users and their privileges with each object.
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| 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.
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| 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.
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| 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.
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| 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
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| Md5 |
A one way cryptographic hash function. Also see "hash functions" and "sha1"
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| 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 m |
