| Word | Description |
| Race Condition | A race condition exploits the small window of time between a security control being applied and when the service is used. |
| Rack | A metal frame used for holding server computers and networking equipment. A standard rack is 19″ wide. There are wider racks that are 23″ wide, built to hold wider equipment. Racks range in height, but are typically either 24 or 42 rack units, with each unit being 1.75″. |
| Rack Units (U) | This refers to the distance of 1.75″ between screw holes in a rack used to hold server equipment. Most computer equipment racks are between 24 and 42 rack units in height. If you are shopping for rack equipment, keep in mind the height of the rack you have to work with and the “U” rating of the equipment. Heights of 1U indicate equipment that can fit into a 1.75″ tall rack space, and 2U would indicate twice that at 3.5″, and so forth with 3U, 4U, and up. |
| RAD | rapid application development The generic name for tools and techniques designed to make it easy to quickly assemble the skeleton of an application, especially the user interface. For example, programs such as Visual Basic and PowerBuilder, which provide tools for easily creating and linking dialog boxes, are considered RAD tools. |
| Radiation Monitoring | Radiation monitoring is the process of receiving images, data, or audio from an unprotected source by listening to radiation signals. |
| RADIUS | Remote Authentication Dial-In user Service (on W2K). Support for dial-up networking. Provides authorization, identification, authentication and accounting services for distributed dial-up networking. |
| RAID | Redundant Array of Inexpensive Disks. The idea of a RAID is to combine a number of disk drives to give better performance, capacity and reliability than could be achieved by a single disk. For a description of the different types of RAID see RAID level. Sometimes also referred to as a RAID Array. |
| RAID 0 | Also known as disk striping, this form of RAID combines two or more hard drives into a single logical drive. Any data is written in blocks first to one drive, then the next, and so on. A RAID 0 configuration sacrifices redundancy for raw speed. The more drives you use the faster your logical drive will be. The space available on the logical drive is the sum of space on all of the drives used, assuming that all drives are the same size. If drives are of disparate sizes, RAID 0 generally only uses a piece of the drive equal to the smallest drive. Of course, if one drive dies, you lose all of the information on the entire RAID. Use RAID 0 with care. |
| RAID 1 | There are two forms of RAID 1: disk duplexing and disk mirroring. Disk mirroring involves two hard drives that are on the same drive controller. The same data is written to both drives, so write operations are slower because you must write data to two drives. Read operations are the same speed, as if you only had one drive. Disk duplexing is much like disk mirroring, but each drive is on a separate controller. This speeds up the normally slow write operations and also adds an additional level of redundancy, in case one of your controller cards dies. With RAID 1 you get half the space you paid for because you’re writing twice as much data. |
| RAID 10 | This form of RAID was originally called RAID 1+0, and is now commonly referred to as RAID 10. This is basically a bunch of RAID 1 drives linked together with RAID 0. Hence you get the speed benefits of RAID 0 with the redundancy benefits of RAID 1. The only problem is that you use a lot of drives to do it. Like RAID 1, you only get half of the space that you’ve paid for. Of course it may be worth it if you can rest easier at night. RAID 10 is generally a bit faster than RAID 5. |
| RAID 2 | This form of RAID protection stripes data across two or more drives, and also stripes an ECC parity code across one or more drives. This code is used to verify that the data read and written is correct. As more data drives are used, you want to increase the number of parity drives to increase performance. This RAID type is not often used. |
| RAID 3 | A form of RAID protection that uses at least three drives, where one drive holds all of the parity data. The other two or more drives contain data striped across them in bits or bytes. This RAID type is not often used. |
| RAID 4 | This is similar to RAID 3 in that an extra drive is used to store all parity information. However, data is striped by drive sector instead of by bits or bytes, so that read operations are faster. This RAID type is not often used. |
| RAID 5 | A RAID 5 configuration utilizes three or more hard drives and stripes the data across them, much like RAID 0. The difference is that parity information is striped across the drives as well, so if you lose any one drive the information can be reconstructed from the parity information. For example, with three drives the first stripe is data (on drive 1), data (on drive 2), parity (on drive 3); then data, parity, data; then parity, data, data. This pattern continues. If one drive fails, you get a mix of parity and data on the remaining two drives, and you can reconstruct all of the data. Of course, before the data is reconstructed the RAID operates in “degraded mode” and is slow. To reconstruct the data you must remove the failed drive and replace it with another, or use a “hot spare.” During reconstruction the array continues to be slow. Once the RAID is reconstructed performance returns to normal levels. RAID 5 performance is similar to RAID 0 performance, but a bit slower due to the parity information. Performance increases, like RAID 0, when more drives are added. With RAID 5 you get most of the space that you’ve paid for, minus one drive’s worth. A common option with RAID 5 is the hot spare, where a drive sits idle until needed. If you lose a drive, the hot spare takes over and the RAID is rebuilt automatically. Of course you still get the performance penalty during the rebuilding stage, but it can be set to happen automatically. |
| RAID Array | A set of disks arranged as a RAID. See RAID for details. |
| RAID Level | RAID level is a number indicating the type of organisation of disks in the RAID array: RAID 0 Striping. No redundancy. Fastest. Provides maximum storage. No fault tolerance. RAID 1 Disk mirroring. Good performance. Fault tolerant. Only fault tolerant option if using 2 drives. RAID 2 Error correction data written to separate disk. RAID 3 Striping (small stripe size) with one parity disk. RAID 4 Striping (large stripe size) with one parity disk. RAID 5 Striping with parity. Parity information is distributed across all drives. Good performance. Fault tolerant. Slowest to rebuild (if one disk is replaced). Better storage than RAID 1. Requires at least 3 disks. Tolerant of a single disk failure. RAID 6 RAID 5 with an extra parity disk. Tolerant of two disks failing. RAID 0+1 Mirrored array (RAID 1) whose segments are RAID 0 arrays, i.e. mirroring of striped sets. RAID 10 Striped array (RAID 0) of mirrored sets (RAID 1). RAID 53 Combination of RAID 0 and RAID 3. Each stripped set (of RAID 0) are RAID 3 sets. |
| RAM | Random Access Memory. Fast, semi-conductor based memory in a computer. It is called "Random Access" because the computer can access any part of the memory directly. |
| RAMDAC | RAMDAC random access memory digital-to-analog converter This microchip sits on a VGA card or other graphics display board and translates the digital representation of a screenful of information into an analog signal that the monitor can display. The faster the RAMDAC (measured in MHz), the higher the screen refresh rates that the card will support at each given resolution. See also: refresh rate |
| Rar (.rar) | The file extension of a type of compressed file created by the WinRAR program by RarSoft. It is considered by many to be more versatile than other compression programs on the market such as WinZip, has a better compression ratio, and is used by many to send archived data over the Internet due to its superior compression in many circumstances. |
| RARP | Reverse Address Resolution Protocol. A protocol used to resolve an IP address from a hardware address (MAC address). cf ARP. |
| RAS | 1. Remote Access Service. 2. RAS Encryption. Named after its inventors Professors Rivest, Adleman and Shamir. RAS is an asymmetrical encryption technique. cf DES. |
| Raster Graphic | Most images you see on your computer screen are raster graphics. Pictures found on the Web and photos you import from your digital camera are raster graphics. They are made up of grid of pixels, commonly referred to as a bitmap. The larger the image, the more disk space the image file will take up. For example, a 640 x 480 image requires information to be stored for 307,200 pixels, while a 3072 x 2048 image (from a 6.3 Megapixel digital camera) needs to store information for a whopping 6,291,456 pixels. Since raster graphics need to store so much information, large bitmaps require large file sizes. Fortunately, there are several image compression algorithms that have been developed to help reduce these file sizes. JPEG and GIF are the most common compressed image formats on the Web, but several other types of image compression are available. Raster graphics can typically be scaled down with no loss of quality, but enlarging a bitmap image causes it to look blocky and "pixelated." For this reason, vector graphics are often used for certain images, such as company logos, which need to be scaled to different sizes. File extensions: .BMP, .TIF, .GIF, .JPG |
| RAT | Remote Access Trojan. Trojan allowing an attacker to remotely access or control a computer. |
| Raw Data | Raw data is unprocessed computer data. This information may be stored in a file, or may just be a collection of numbers and characters stored on somewhere in the computer's hard disk. For example, information entered into a database is often called raw data. The data can either be entered by a user or generated by the computer itself. Because it has not been processed by the computer in any way, it is considered to be "raw data." To continue the culinary analogy, data that has been processed by the computer is sometimes referred to as "cooked data." |
| Raw disk | A hard disk in a virtual machine that is mapped to a physical disk drive in the host machine. A virtual machine's disk can be stored as a file on the host file system (see Virtual disk) or on a local IDE raw disk device. When a virtual machine is configured to use a raw disk, VMware directly accesses the local disk/partition as a raw device (not as a file on a file system). It is possible to boot a previously installed operating system on an existing partition within a virtual machine environment. The only limitation is that the existing partition must reside on a local IDE or SCSI drive. See also Safe raw disk file, Virtual disk. |
| Raw File | A raw file is a collection of unprocessed data. This means the file has not been altered, compressed, or manipulated in any way by the computer. Raw files are often used as data files by software programs that load and process the data. A popular type of raw file is "Camera RAW," which is generated by a digital camera. Instead of processing the image captured by the camera, the data is left unprocessed and uncompressed until it is opened with a computer program. |
| RBL | Real-time Black-hole List or Real-time Block List. RBLs hold information about blocked sites, typically used to list site that generate spam. RBL is sometimes used as an alternative name to DNSBL, see DNSBL for more details. |
| RC1 | Release Candidate 1, i.e. the first (beta) release of something. cf RC. |
| RC2 | Release Candidate 2, i.e. the second (beta) release of something. cf RC. |
| RDBMS | Relational Database Management System. cf DBMS. |
| RDC | 1. Remote Desktop Connection. RDC is a Windows technology that allows any client running the necessary client software to connect to a Routing and Remote Access server (or terminal server) and then run applications and use the remote server in the same way as if using the local PC - the "desktop" on the remote server is viewed in a window (full screen by default). This technology allows someone to remotely login to either a pc running Windows XP or Windows server. |
| RDF | Stands for "Resource Description Framework." RDF is a specification that defines how metadata, or descriptive information, should be formatted. The RDF model uses a subject-predicate-object format, which is a standardized way of describing something. For example, an RDF expression may read, "The computer has a hard drive that stores 250GB." "The computer" is the subject, "has a hard drive that stores" is the predicate, and "250GB" is the object. RDF formatting is used in RSS feeds, which contain short descriptions of Web pages. The RDF standard helps ensure each description contains the subject, predicate, and object necessary to describe the page's content. While humans do not require descriptions to be formatted in such a specific way (we would actually find it rather monotonous), computers benefit from the standard formatting. For example, it makes it easier for computer systems to sort and index RSS feeds based on the RDF descriptions. The end result is more accurate results when people search for articles using keywords. |
| RDNS | In computer networking, reverse DNS lookup or reverse DNS resolution (rDNS) is the determination of a domain name that is associated with a given IP address using the Domain Name System (DNS) of the Internet. Computer networks use the Domain Name System to determine the IP address associated with a domain name. This process is also known as forward DNS resolution. Reverse DNS lookup is the inverse process of this, the resolution of an IP address to its designated domain name. The reverse DNS database of the Internet is rooted in the Address and Routing Parameter Area (arpa) top-level domain of the Internet. IPv4 uses the in-addr.arpa domain and the ip6.arpa domain is delegated for IPv6. The process of reverse resolving an IP address uses the pointer DNS record type (PTR record). Internet standards documents (RFC 1033, RFC 1912 Section 2.1) specify that "Every Internet-reachable host should have a name" and that such names match with a reverse pointer record. |
| RDP | Remote Desktop Protocol. RDP is the protocol used by (Windows) RDC for communications between a terminal server and terminal server client. |
| Read Only | This means that the object cannot be written to, which means that you can’t save any modifications you make to it. An operating system can have a file set to read-only for security purposes, or certain media, like a CD-ROM or DVD-ROM, is read-only by design and cannot be altered. |
| Readme | A readme file, often named "READ ME" to get the user's attention, is a text file containing useful information about a software program. It often accompanies the program's installer or is installed with the program. A typical readme file contains instructions on how to install the program, how to use the basic functions of the program, and what the program does. It may also include a list of recent updates made to the program. Sometimes the readme file will include warnings and other important notices regarding the operation of the program. So when you see a readme file accompanying a new software program, it is best to do what the file says and read it! |
| Real-Time | When an event or function is processed instantaneously, it is said to occur in real-time. To say something takes place in real-time is the same as saying it is happening "live" or "on-the-fly." For example, the graphics in a 3D action game are rendered in real-time by the computer's video card. This means the graphics are updated so quickly, there is no noticeable delay experienced by the user. While some computer systems may be capable of rendering more frames per second than other systems, the graphics are still being processed in real-time. While video games often require real-time rendering, not all graphics are rendered in real-time. For example, some complex 3D models and animations created for movies are not rendered in real-time, but instead are pre-rendered on a computer system so they can be played back in real-time. As graphics cards get increasingly faster, they are capable of rendering some 3D animations in real-time that previously would need to be pre-rendered. Real-time also describes the way streaming media is processed. Instead of waiting for a file to completely download, the information is played back as it is downloaded. This allows for news broadcasts, sound clips, and other streaming audio and video data to be played live from the Internet. Thanks to real-time processing, people can access information without having to wait for it. This is an important benefit since these days, anything that takes longer than 5 seconds seems like a long time. |
| RealPlayer | A program or plug-in that gives you access to multimedia files, both on the Internet and those stored locally on your computer. With the program you can find and play clips (e.g., video, audio, video with audio, etc.) without having to launch your web browser first. The plug-in works in conjunction with your web browser to allow you to access streaming media files. |
| Realtek | Realtek Semiconductor Corp Products Realtek manufactures and sells a wide variety of products throughout the world, and its product lines can be broadly categorized into two subdivisions: Communications Network ICs, and Computer Peripheral and Multimedia ICs. Included among the communications network IC products manufactured and provided by Realtek are: network interface controllers (both the traditional 10/100M Ethernet controllers and the more advanced Gigabit Ethernet controllers), physical layer controllers (PHYceivers), network switch controllers, gateway controllers, wireless LAN ICs, as well as ADSL router controllers. In particular, the RTL8139 series 10/100M Fast Ethernet controllers met their height during the late 90’s, and continued to take up a significant, and eventually predominant share in the worldwide market in the following years. Those devices categorized as Realtek’s computer peripheral and multimedia IC products consist of the traditional AC97 audio codecs, the High Definition audio codecs, card reader controllers, clock generators, IEEE 1394 ICs, and LCD controllers. Realtek Headquarters in Hsinchu Science Park The most notable Realtek products are 10/100M Ethernet controllers, with a global market share of 70% as of 2003, and AC97 audio codecs, where Realtek's market share is 50%, primarily concentrated in the integrated OEM on-board audio market segment. Presently the ALC850 and RTL8139 are particular OEM favorites, offering low prices, and basic feature sets. RTL8139-based NICs are dubbed "crab cards" in Taiwan, alluding to the crab-like appearance of the Realtek logo. It has been announced or projected, on several different occasions, that Realtek will, in the future, focus its R&D resources in the field of digital television technologies, as well as more advanced wireless communications technologies such as ultra-wide band (UWB) communications and the yet-to-be-realized 802.11n standard. It seems clear that Realtek has been setting its eye on pursuing the Holy Grail of the anticipated new applications and needs derived from the concept of Digital home |
| Reboot | To restart a computer. It comes from “boot,” which is a term that means starting the operating system on the computer. When you are using your computer and have weird problems, the tech guy comes over and says, “Time to reboot.” If you are the tech guy you’ll find yourself saying this far too often. |
| Reconnaissance | Reconnaissance is the phase of an attack where an attackers finds new systems, maps out networks, and probes for specific, exploitable vulnerabilities. |
| record | A set of fields that contain related information; in database type systems, groups of similar records are stored in files. Example: a personnel file that contains employment information. |
| Recursion | Recursion is a process in which a function calls itself as a subroutine. This allows the function to be repeated several times, since it calls itself during its execution. Functions that incorporate recursion are called recursive functions. Recursion is often seen as an efficient method of programming since it requires the least amount of code to perform the necessary functions. However, recursion must be incorporated carefully, since it can lead to an infinite loop if no condition is met that will terminate the function. |
| Recursive Function | A recursive function is a function that calls itself during its execution. This enables the function to repeat itself several times, outputting the result and the end of each iteration. Below is an example of a recursive function. function Count (integer N) if (N <= 0) return "Must be a Positive Integer"; if (N > 9) return "Counting Completed"; else return Count (N+1); end function The function Count() above uses recursion to count from any number between 1 and 9, to the number 10. For example, Count(1) would return 2,3,4,5,6,7,8,9,10. Count(7) would return 8,9,10. The result could be used as a roundabout way to subtract the number from 10. Recursive functions are common in computer science because they allow programmers to write efficient programs using a minimal amount of code. The downside is that they can cause infinite loops and other unexpected results if not written properly. For example, in the example above, the function is terminated if the number is 0 or less or greater than 9. If proper cases are not included in the function to stop the execution, the recursion will repeat forever, causing the program to crash, or worse yet, hang the entire computer system. |
| Recycle Bin | The Recycle Bin in used by Windows computers to store deleted items. It temporarily stores files and folders before they are permanently deleted. You can open the Recycle Bin by double-clicking the icon on the Windows desktop. The Recycle Bin window allows you to delete items individually or restore them to their original location. If you want to permanently remove all items in the Recycle Bin, select "Empty the Recycle Bin" in the left sidebar of the window. |
| Red Hat Linux | Red Hat Linux, assembled by the company Red Hat, was a popular Linux based operating system until its discontinuation in 2004.[1] Red Hat Linux 1.0 was released on November 3, 1994. It was originally called "Red Hat Commercial Linux"[2] It was the first Linux distribution to use the RPM Package Manager as its packaging format, and over time has served as the starting point for several other distributions, such as Mandriva Linux and Yellow Dog Linux. Since 2003, Red Hat has discontinued the Red Hat Linux line in favor of Red Hat Enterprise Linux (RHEL) for enterprise environments. Fedora, developed by the community-supported Fedora Project and sponsored by Red Hat, is the free version best suited for home use. Red Hat Linux 9, the final release, hit its official end-of-life on 2004-04-30, although updates were published for it through 2006 by the Fedora Legacy project until that shut down in early 2007. |
| Red Hat Package Manager (RPM) | A packaging system based on files with the .rpm extension that contain dependency information, pre- and post-install scripts, and the actual user runtimes (files/executables) that are part of the package. Windows users might think of this as an .msi file commonly used to hold pre-installation data |
| Redundancy | In a redundant system, if you lose part of the system, you can continue to operate. For example, if you have two power supplies and one takes over if the other one dies, that is a form of redundancy. You can take redundancy to extreme levels, but you spend more money. Redundancy is one reason that high-end server machines cost 10 times more than desktop PCs. |
| Redundant Array of Inexpensive Drives (RAID) | A method of linking storage devices together so that they function as a single logical unit. RAID requires all drives to be of the same size, as compared to JBOD setups. RAID can be used for increased performance, but is also used to increase redundancy. |
| Reflexive ACLs (Cisco) | Reflexive ACLs for Cisco routers are a step towards making the router act like a stateful firewall. The router will make filtering decisions based on whether connections are a part of established traffic or not. |
| Refresh | Refresh is a command that reloads the contents of a window or Web page with the most current data. For example, a window may list files stored within a folder, but may not track their location in real-time. If the files have been moved or deleted since the window was first opened, the folder contents displayed will be inaccurate. By refreshing the window, a current list of files is displayed. Web browsers include a Refresh command, which reloads the contents of a Web page. This is especially useful for dynamic Web pages, which contain content that changes often. For example, a page may include a stock quote, which is updated every few seconds. By refreshing the page, a user can see the latest quote and track how much the stock continues to drop since he bought it. Web developers may also use the Refresh command to view recently published changes to Web pages. Since refreshing a window reloads it with new information, the terms "refresh" and "reload" are often used synonymously. In fact, some Web browsers, such as Firefox and Safari use the term "Reload" instead of "Refresh." In Windows, the shortcut key for the Refresh command is typically "F5," while on the Mac, the shortcut is often "Command-R." The term "Refresh" may also refer to the redrawing process of a computer monitor. This process usually happens many times per second and is called the "refresh rate." |
| Refresh Rate | Computer monitors often have a "maximum refresh rate" listed in their technical specifications. This number, measured in hertz (Hz), determines how many times the screen is redrawn each second. Typical refresh rates for CRT monitors include 60, 75, and 85 Hz. Some monitors support refresh rates of over 100 Hz. The higher the refresh rate, the less image flicker you will notice on the screen. Typically a refresh rate of less than 60 Hz will produce noticeable flicker, meaning you can tell the screen is being redrawn instead of seeing a constant image. If the refresh rate is too slow, this flicker can be hard on your eyes and may cause them to tire quickly. As if sitting at a computer for several hours wasn't hard enough! To avoid flicker, you should set your monitor to use the maximum refresh rate possible. This setting is found in the Monitors control panel in Windows and the Displays system preference in Mac OS X. While 60 Hz is considered a good refresh rate, some people will find that 85 Hz is significantly better. The maximum refresh rate is determined by three factors: 1) The rate your video card supports, 2) the rate your monitor supports, and 3) the resolution your monitor is set at. Lower resolutions (i.e. 800x600) typically support higher refresh rates than higher resolutions (i.e. 1600x1200). If you have an LCD monitor, you may not be able to adjust the refresh rate. This is because most LCD monitors come with a standard refresh rate that is well above the "flicker" point. LCD monitors produce less flicker than CRT monitors because the pixels on an LCD screen stay lit longer than CRT monitors before they noticeably fade. |
| Registry | The central database containing system configuration information on Windows systems. The registry is organised as a hierarchical tree, and allows applications as well as Windows itself to store configuration information in a structured manner. |
| Regression analysis | The use of scripted tests which are used to test software for all possible input is should expect. Typically developers will create a set of regression tests that are executed before a new version of a software is released. Also see "fuzzing". |
| regular expression | A regular expression is a way of expressing a text pattern for the purpose of matching a string. Regular expressions are often used either to extract information from a string or to verify that a string is of the correct format. When referred to, regular expressions are often abbreviated to simply "regex". The following table provides examples of regular expressions: Regex Meaning . A dot matches any single character. c.t Matches "cat", "cbt" ... "c1t" ... "c&t" etc (with anything before the "c" and anything after the "t"). [0-9] Matches anything inside the square brackets against a single character; so in this case any single character in the range 0 to 9. [09] Matches anything inside the square brackets against a single character; in this case the single character 0 or 9 (but not 1 to 8). This can be useful if you don't know the case of something, because [aA] will match either a or A. [0-9a-zA-Z] Matches any single character in the range 0 to 9 or a to z or A to Z. ? Matches the preceding element one time or zero times. This is equivalent to {0,1} * Matches the preceding element zero or more times. *? Matches the preceding element zero or more times, but unlike * will match against the shortest possible match. For example "b[an]*a" when applied to the word "banana" will match the entire word, but "b[an]*?a" will match with just "ban". a[0-9]*z Will match against "az", "a1z" ... "a999z" etc. + Matches the preceding element one or more times. +? Matches the preceding element one or more times, but unlike + will match against the shortest possible substring.. a[0-9]+z Will match against "a1z" ... "a999z" etc (but not "az"). {number} Matches the preceding element the specified number of times. a[0-1]{2}z Will match against "a00z", "a10z", "a01z" and "a11z". {min,max} Matches the preceding element a minimum of "min" times at at most "max" times. a[0-1]{1,2}z Will match against "a0z", "a1z", "a00z", "a10z", "a01z" and "a11z". [^...] Inverts a match - matches anything except. a[^0-1]z Will match against any three letter string starting with "a", ending with "z" that is not "a0z" or "a1z". ^ Matches at the start of the line. $ Matches at the end of the line. \ Escape character. Allows the following character to be treated as a literal rather than having a special meaning. Thus \+ would match against + rather than + having its normal meaning. This also means that to include a \ as a slash you would need to use \\ (to escape the slash). \A Matches at the start of the string. When dealing with a single line expression \A is equivalent to ^. Note: \A is not supported on all implementations. \Z Matches at the end of the string. When dealing with single line expressions \Z is equivalent to $. Note: \Z is not supported on all implementations. \xNN Will match against the single character with the hex code 'NN'. So \x09 will match against a tab character and \x20 will match against a space. See www.cryer.co.uk/brian/misc/ascii_table.htm for a list of hex codes for ASCII characters. \t Match against the TAB character (same as \x09). \n Match against a new-line (same as \x0a). \r Match against a carriage return (same as \x0d). \f Match against a form-feed (same as \x0c). \a Match against a bell character (same as \x07). \b Match against a word boundary. A word boundary will match against any of: (i.) The beginning of the string, (ii.) the end of the string or (iii.) anything which is not [a-zA-Z0-9_] \e Match against an escape character (same as \x16) \r\n Match against a carriage return line feed combination (in that order). \w Match against any alphanumeric character (i.e. 0 to 9, a to z, A to Z and the underscore). \W Match against any non-alphanumeric character. \d Match against any numeric character. \D Match against any non-numeric character. \s Any space (same as [ \t\n\r\f]). \S Match against any non-space. one|two Match everything to the left of the bar ('|') or everything to the right, so in this case "one" or "two". ( … ) Brackets define a group or sub-expression. When a regular expression is used in a situation where the contents of a match need to be extracted then brackets define the group or sub-expression the matching value of which can be retrieved. \b(one|two)\b Match against the whole word "one" or the word "two", specifically it matches against a word boundary, then "one" or "two", followed by another word boundary. |
| Reimage | Reimaging is the process of restoring data to a hard disk from a disk image. When a hard disk is reimaged, the data on the disk is completely erased and rewritten using data from the disk image file. Therefore, reimaging is often done from a recent backup, which allows the user's personal data to be recovered. Reimaging is simpler than reinstalling an operating system since it is performed in a single step, rather than requiring numerous files and programs to be installed. |
| Relative URL | An URL that does not include strict directory information; instead, you give the link directions like “back two directories and up one directory” in standard command line format like “../../imagedir/image.jpg”. This way you can change domain names or IP addresses of your webserver and not have to recode your HTML pages. However, if you change directory names (or depth), you must change even your relative URLs. |
| Release Engineer | The individual whose job it is to oversee the mechanics of the development process of software. The release engineer controls when new code is entered into the current working release, and makes sure the proper pieces of code are compiled and ready when the program has to be sent to a media duplication plant, or simply made live on a network. |
| RELEVANCY RANKING of search results | The most common method for determining the order in which search results are displayed. Each search tool uses its own unique algorithm. Most use "fuzzy and" combined with factors such as how often your terms occur in documents, whether they occur together as a phrase, and whether they are in title or how near the top of the text. Popularity is another ranking system. |
| Remote Access | Remote access is just what it sounds like -- the ability to access your computer from a remote location. Programs like PC Anywhere (Windows), Remote Access (Mac), and Timbuktu (Windows and Mac) allow users to control remote computers from their local machine. In order for a remote access connection to take place, the local machine must have the remote client software installed and the remote machine must have the remote server software installed. Also, a username and password is almost always required to authenticate the connecting user. Remote access is more than just being able to connect to a remote machine -- it is the ability to control the machine once the connection has been made. A remote access program can basically transform your local computer into the the remote computer you connect to. This is great for people who sometimes work from home and for server administrators who frequently need to update and make changes on their server machines. Most remote access programs also allow users to transfer files between the local and remote machines, which can save a lot of commuting time. While remote access can be helpful for many people, don't enable it on your machine unless you absolutely need to. It is just one more security concern you will have to deal with. |
| Remote Control | A means of taking control of a remote computer, usually on a remote network. Programs like Symantec’s pcAnywhere and a host of others offer this ability. Usually you connect to the remote computer via the Internet or a phone line, and control the computer by interacting with your computer while seeing on your screen a representation of what is actually happening on the remote computer. The downside to remote control is that each remote connection requires a separate computer. You can’t easily have multiple people controlling one computer remotely and seeing a useful representation of what is on the remote display. See also remote access. |
| Remote Desktop | Remote desktop technology makes it possible to view another computer's desktop on your computer. This means you can open folders, move files, and even run programs on the remote computer, right from your own desktop. Both Windows and Macintosh computer support remote desktop connections, though they use different implementations. Windows XP and Vista both include Remote Desktop as part of the operating system. The Remote Desktop program uses Microsoft Terminal Services and the Remote Desktop Protocol (RDP) to connect to a remote machine. Remote connections can be opened using Windows' Remote Desktop Connection (RDC), which is also referred to as Terminal Services Client (TSC). This program allows users to configure and manage remote connections to other computers. Of course, to connect to another machine, the remote system must be configured to accept incoming RDC connections. A Windows computer can be configured to accept incoming remote desktop connections by opening the Control Panel and selecting "Performance and Maintenance." Then click the "System" icon and select the "Remote" tab in the System Properties window. Next, check the box that says, "Allow users to connect remotely to this computer." Then click OK. This should enable remote desktop connections to your machine. You can then click "Select Remote Users..." to only provide access to specific users. Of course, if you don't want your computer to be accessed by anyone, leave the "Allow users to connect..." box unchecked. Mac OS X 10.5 and later includes a feature called Screen Sharing that allows other users to remotely access the computer's desktop. To turn on Screen Sharing, open System Preferences and select the Sharing option. Next, check the "Screen Sharing" check box. You can then add access for specific users in the "Allow access for:" section of the window. If the Mac OS X Screen Sharing option feels a bit limited, you may want to try a program called "Apple Remote Desktop." This program, which is developed by Apple, provides more advanced remote access features and is often used for managing several computers on a network. |
| Remote User | A "remote user" is how a woman might refer to her husband while he is watching TV. In the computer world, however, a remote user is someone who works on a computer from a remote location. For example, if Bob leaves work and forgets to bring a file with him from his office computer, he might be able to connect to his work machine from his home computer and grab the file. When Bob accesses his office computer from home, he is considered a remote user. |
| Removable Canister | A removable hard drive casing. There are two parts to the canister: the bay itself, and the casing that goes around the hard drive. These canisters can be used with SCSI or IDE/ATA hard drives, and have the advantage of easy portability of hard drives, especially if you have multiple computers with the same type of bay in them. Integrating a bare hard drive into a removable canister can be an annoying chore, as space is limited and you have lots of extra wires to deal with. This term can also be used to refer to the hard drives that are used in server machines and integrated into cases that can be plugged into servers and removed easily. Removable canisters can be hot pluggable, but usually only in servers with RAID systems. |
| Removable Storage | This type of storage allows you to remove the actual storage media from a drive and replace it with other media. DVD-ROM, CD-ROM, floppy drives, and Zip drives are all forms of removable storage. |
| Render (v. to render) | This synonym for hacking up animals for human consumption determines how colors are used on each triangle displayed in a 3D image. Very complex images take a long time to render; less complex 3D images, such as those in a 3D game, can be rendered in real time. When they make computer animated movies or effects of very high quality, effects companies use many computers to render images. |
| Repeater | A device used to repeat a signal to send it further away or to many more devices. The earliest network hubs are also called repeaters, as they had no switching capabilities but would only repeat the same signal to all ports. |
| Request for Comment (RFC) | A series of notes about the Internet, started in 1969 (when the Internet was the ARPANET). An Internet Document can be submitted to the IETF by anyone, but the IETF decides if the document becomes an RFC. Eventually, if it gains enough interest, it may evolve into an Internet standard. |
| Reseller | Anyone who buys computer equipment or software and sells it. In most states in the U.S. you need a reseller license to purchase goods without paying taxes, and then you are responsible for collecting and paying taxes on the goods you resell. The combined entity of all the resellers makes up the channel. Resellers usually buy goods from large distributors and sell them to companies or consumers. |
| Resistor | A two-terminal electronic component that resists an electrical current and turns the extra current into heat. Resistors are rated in ohms, and can be used to regulate the voltage and current in a circuit. Basically, a resistor resists the flow of electricity. Resistors are used to lower voltages and currents so that components that require smaller voltage/current can function properly. If a power supply puts out 12 volts and you have a chip that runs on three, you need a resistor to cut down the voltage. |
| Resolution | This term can describe either how many pixels a monitor can display or how fine a printer can print. 1. Monitors. A small monitor may have a resolution or 640 x 480, which means there are 640 pixels horizontally across the screen and 480 pixels vertically. Some other common monitor resolutions are 800 x 600, 1,024 x 768, and 1,280 x 1,024. The higher the resolution, the more that can be displayed on the screen. 2. Printers. Printer resolution measures how fine a printer can print. This measurement is known as dots per inch, or "dpi." The greater the dpi, the better the image clarity. Scanner resolution is also measured in dpi. |
| Resource Exhaustion | Resource exhaustion attacks involve tying up finite resources on a system, making them unavailable to others. |
| Response | A response is information sent that is responding to some stimulus. |
| Restart | The process of an operating system on a computer shutting down, and then starting back up automatically. During a restart the user does not need to hit the power switch. |
| Retention Mechanism | This typically refers to the mechanisms attached to a motherboard that hold onto a Slot 1, Slot 2, or Slot A cartridge so that it doesn’t come loose during usage or shipping. The mechanism is usually made of black plastic, and holds the processor cartridge in place. |
| Reverse Address Resolution Protocol (RARP) | RARP (Reverse Address Resolution Protocol) is a protocol by which a physical machine in a local area network can request to learn its IP address from a gateway server's Address Resolution Protocol table or cache. A network administrator creates a table in a local area network's gateway router that maps the physical machine (or Media Access Control - MAC address) addresses to corresponding Internet Protocol addresses. When a new machine is set up, its RARP client program requests from the RARP server on the router to be sent its IP address. Assuming that an entry has been set up in the router table, the RARP server will return the IP address to the machine which can store it for future use. |
| Reverse DNS lookup | In computer networking, reverse DNS lookup or reverse DNS resolution (rDNS) is the determination of a domain name that is associated with a given IP address using the Domain Name System (DNS) of the Internet. Computer networks use the Domain Name System to determine the IP address associated with a domain name. This process is also known as forward DNS resolution. Reverse DNS lookup is the inverse process of this, the resolution of an IP address to its designated domain name. The reverse DNS database of the Internet is rooted in the Address and Routing Parameter Area (arpa) top-level domain of the Internet. IPv4 uses the in-addr.arpa domain and the ip6.arpa domain is delegated for IPv6. The process of reverse resolving an IP address uses the pointer DNS record type (PTR record). Internet standards documents (RFC 1033, RFC 1912 Section 2.1) specify that "Every Internet-reachable host should have a name" and that such names match with a reverse pointer record. |
| Reverse Engineering | The process of understanding a system without knowing how the system actually functions internally, but only judging how the system responds to various inputs. In that way a company can create a product with similar or equivalent behavior to another company’s product without infringing on that company’s patents. |
| Reverse Lookup | Find out the hostname that corresponds to a particular IP address. Reverse lookup uses an IP (Internet Protocol) address to find a domain name. |
| Reverse Proxy | Reverse proxies take public HTTP requests and pass them to back-end webservers to send the content to it, so the proxy can then send the content to the end-user. |
| Revolutions per Minute (RPM) | A measurement that applies commonly to hard drives, and removable drives like CD-ROMs and DVD-ROMs. It also applies to anything that moves in a circular motion. If you are using a drive with higher RPMs, you usually have better performance. Since the disk is spinning faster the drive can usually read data at a faster rate. For example, 5,400 RPM hard drives are generally slower than 7,200 RPM hard drives. The downside to higher RPM rates is that it is harder to stabilize and read data from a disk that is spinning faster, so the mechanism may be more complex and more expensive. Also, faster spinning drives are usually louder and run hotter. |
| Rewriteable | This means that what was written can be erased so that it can be written to again. CD-R media is not rewriteable, but CD-RW media is. It is also more expensive. Floppy disks and hard drives are rewriteable as well. |
| RFC | Request For Comments) The name of the result and the process for creating a standard on the Internet. New standards are proposed and published on the Internet, as a Request For Comments. The proposal is reviewed by the Internet Engineering Task Force (http://www.ietf.org/), a consensus-building body that facilitates discussion, and eventually a new standard is established, but the reference number/name for the standard retains the acronym RFC, e.g. the official standard for e-mail message formats is RFC 822. |
| RGB | Red, Green, Blue. The three primary colours which together make white. Shown using their respective colours: Red, Green and Blue. When displaying colour on computer monitors (or TVs and projectors) colour values are made up of combinations of red, green and blue. Any colour can be represented by the correct proportion of red, green and blue. |
| Rich Media | A type of Internet advertisement that allows for more interaction than a simple click. It may incorporate a useable dropdown menu, radio buttons, or even Flash or Shockwave animation and sound. Some plain graphic ad banners appear to be rich media, but when clicked on they do not interact with the user, merely forwarding the user to a different website using a standard image and link tag. |
| Right Click | Most computer mice have at least two mouse buttons. When you press the left one, it is called a left click. When you press the one on the right, it is called a right click. By default, the left button is the main mouse button, and is used for common tasks such as selecting objects and double-clicking. The right mouse button is often used to open contextual menus, which are pop-up menus that change depending where you click. For example, if you right click on the desktop, you may see a menu pop up that includes "Change View Options" and "Change Desktop Background." If you right click on a folder, the menu might include options such as "Open" and "Properties." Certain programs, such as video games, may use the right click to perform other functions, such as firing a secondary weapon in a first-person shooter. Most programs, however, use the right click to open contextual menus. |
| Ring topology | A network that is connected on both ends to one source, with client machines hanging off of the ring. If you break the ring, all computers in the ring lose connectivity. |
| RIP | 1. Routing Information Protocol. A protocol allowing a router to exchange routing information with other gateways and hosts. RIP versions: RIP-1 Universally supported. Defined by RFC 1058. RIP-2 Carries more ...n RIP-1. Defined by RFC 1389. RIP-2B Sends routing information in RIP-2 format using subnet broadcasting. 2. Raster Image Processor. |
| Ripcording | Recording audio with a computer involves capturing an audio signal and saving it digitally on a hard drive. Ripping an audio track is the process of converting an audio file to an MP3 or other compressed audio format. Ripcording is the simultaneous recording and ripping of an audio signal. Ripcording is a popular way to download and archive Internet radio broadcasts, digital cable TV radio, and satellite radio. All you need is ripcording software that will record audio and compress it at the same time. By ripcording live audio, you can save audio streams on your hard drive and listen to them whenever you want. |
| RIS | Remote Installation Services. Enables administrators to install Windows 2000 professional on client computers throughout a network from a central location. |
| Riser Card | A card that plugs into a motherboard and enables other cards to be plugged into it horizontally. Architectures that support riser cards are typically designed to allow tall cards to be plugged into shorter enclosures. Servers often use riser cards, since if they didn’t the motherboard would be too large to fit into a standard sized enclosure. |
| Risk | Risk is the product of the level of threat with the level of vulnerability. It establishes the likelihood of a successful attack. |
| Risk Assessment | A Risk Assessment is the process by which risks are identified and the impact of those risks determined. |
| Risk Averse | Avoiding risk even if this leads to the loss of oportunity. For example, using a (more expensive) phone call vs. sending an e-mail in order to avoid risks associated with e-mail may be considered "Risk Averse" |
| RJ-11 | In the U. S., telephone jacks are also known as registered jacks, sometimes described as RJ-XX, and are a series of telephone connection interfaces (receptacle and plug) that are registered with the U.S. Federal Communications Commission (FCC). They derive from interfaces that were part of AT&T's Universal Service Order Codes (USOC) and were adopted as part of FCC regulations (specifically Part 68, Subpart F. Section 68.502). The term jack sometimes means both receptacle and plug and sometimes just the receptacle. |
| RJ-45 | The standard Ethernet network connector, supporting 8 copper wires. You plug an RJ-45 cable into an RJ-45 port. |
| RNDR | Reverse NDR (spam attack). A technique used by spammers to use email non-delivery reports (NDRs) to deliver spam. |
| RO | Read Only. Anything that can be read from but not written to (or updated). |
| ROM (Read Only Memory) | Memory containing a program, data, or information about the device that has been programmed onto the chip at the factory and cannot be changed. There is no easy mechanism to write to ROM, but it is usually possible to do it. It’s just not made easy, as writing to ROM is not intended to done. |
| Root | Root, or the "root node," refers to the top level of a file system. Since file systems are organized by directories, the root node is also called the root directory. You can imagine the root directory as the top of an upside down tree, with folders and files spanning beneath it. Root is also the name of the "root user," which is user account that has administrative privileges on a computer system. Unlike other users, the root user can access any file or folder on a the main hard disk. For this reason, the root user of a Unix system is often responsible for performing system updates and account modifications. |
| Root directory | The base directory of an operating system. This term is typically used for the UNIX OS, but can apply to a webserver as the directory to which a browser defaults. It refers to the directory represented by a slash, or “/”, character in UNIX, or a “” character in Windows. To change to the root directory use the command “cd /” in UNIX or “cd ” in Windows. |
| Rootkit | A collection of tools (programs) that a hacker uses to mask intrusion and obtain administrator-level access to a computer or computer network. |
| Rosetta | Rosetta is technology included in Mac OS X that allows software written for PowerPC processors to run on Intel processors. It translates the instructions in PowerPC programs into commands that can be recognized by an Intel-based Macintosh. Rosetta runs behind the scenes, so the user does not see it working. However, because dynamically translates commands from PowerPC to Intel, users may notice some slowdown when running PowerPC programs on Intel-based Macintosh computers. |
| Router | Network device connecting two networks that selectively forwards network packets according to their IP address. cf hub and switch. |
| Routing Information Protocol (RIP) | Routing Information Protocol is a distance vector protocol used for interior gateway routing which uses hop count as the sole metric of a path's cost. |
| Routing Loop | A routing loop is where two or more poorly configured routers repeatedly exchange the same packet over and over. |
| RPC | Stands for "Remote Procedure Call." Most computer programs run procedures, or sets of instructions, using the computer's CPU. In other words, the instructions are processed locally on the same computer that the software is running from. Remote procedure calls, however, run procedures on other machines or devices connected to a network. Once the instructions have been run, the results of the procedure are usually returned to the local computer. For example, a computer without a hard drive may use an RPC to access data from a network file system (NFS). When printing to a network printer, a computer might use an RPC to tell the printer what documents to print. A client system connected to a database server may execute an RPC to process data on the server. Remote procedure calls are based on the client-server model, where multiple client computers may connect to a server and retrieve data from it. RPCs are typically written in a standard format, such as XML, so that the procedures can be understood by multiple computer platforms. For example, an XML-RPC sent by a Windows computer could be recognized by a Macintosh or Unix-based system. |
| RPC Scans | RPC scans determine which RPC services are running on a machine. |
| RPM | Stands for "Revenue Per 1,000 Impressions." RPM is similar to CPM, but measures the revenue from 1,000 ads impressions instead of the cost of the ads. Therefore, while CPM is typically measured by advertisers, RPM is monitored by publishers. For example, a publisher has a website that gets 5,000 page views each day. If the advertisements on the website generate a total of $25.00 of daily revenue, the website has an RPM of $5.00 ($25 ? 5). Web publishers use RPM as a way of measuring how effective advertisements are at generating revenue. If certain advertisements generate a low RPM, publishers will likely switch to different ads that provide higher RPM rates and higher revenue. RPM is not only used in online advertising, but is measured in several other types of advertising mediums as well. Though it somewhat confusing, RPM and CPM are often interchangeably. While CPM stands for "Cost Per 1,000 Impressions," it is commonly used synonymously with RPM to describe the average revenue from the publisher's perspective. |
| RSS | (Rich Site Summary or RDF Site Summary or Real Simple Syndication) A commonly used protocol for syndication and sharing of content, originally developed to facilitate the syndication of news articles, now widely used to share the contents of blogs. Mashups are often made using RSS feeds. RSS is an XML-based summary of a web site, usually used for syndication and other kinds of content-sharing. There are RSS "feeds" which are sources of RSS information about web sites, and RSS "readers" which read RSS feeds and display their content to users. RSS is being overtaken by a newer, more complex protocol called Atom. |
| RTE | Stands for "Runtime Environment." As soon as a software program is executed, it is in a runtime state. In this state, the program can send instructions to the computer's processor and access the computer's memory (RAM) and other system resources. When software developers write programs, they need to test them in the runtime environment. Therefore, software development programs often include an RTE component that allows the programmer to test the program while it is running. This allows the program to be run in an environment where the programmer can track the instructions being processed by the program and debug any errors that may arise. If the program crashes, the RTE software keeps running and may provide important information about why the program crashed. When you see the name of a software program with the initials "RTE" after it, it usually means the software includes a runtime environment. While developers use RTE software to build programs, RTE programs are available to everyday computer users as well. Software such as Adobe Flash Player and Microsoft PowerPoint Viewer allow Flash movies and PowerPoint presentations to be run within the player software. These programs provide a runtime environment for their respective file formats. The most common type of RTE, however, is the Java RTE (or JRE), which allows Java applets and applications to be run on any computer with JRE installed. |
| RTF | Rich Text File. An ASCII file format for the transfer of word processed documents across different types of system while still maintaining their formatting. |
| RTM | Online speak for “Read The Manual.” |
| RTSP | (Real Time Streaming Protocol) RTSP is an official Internet standard (RFC 2326) for delivering and receiving streams of data such as audio and video. |
| Ruby | An object oriented scripting language. It has a similar syntax and design philosophy to Perl. |
| Rule Set Based Access Control (RSBAC) | Rule Set Based Access Control targets actions based on rules for entities operating on objects. |
| Runtime | When a program is running, or executing, it is said to be in runtime. The term is mostly used by software developers to specify when errors in a program occur. A "runtime error" is an error that happens while the program is executing. For example, if a program told you that 2 + 2 was 5000, that would be a runtime error. A memory leak, where the program sucks up excessive amounts of system memory is also a runtime error. The other major type of program error is a compile-time error, where the application will not even compile into an executable program. Examples of compile-time errors are syntax errors in the program code and file linking errors. Runtime is a good term to know, but you most likely won't hear it used very often unless you like to hang out with computer nerds. |
| Runtime Error | An error that happens when a program is executed. When you run/execute a program and get a runtime error, that means that there is as error in the program that was not or could not be detected by the compiler when the program was initially compiled. |
| Runtime Library | A group of programming functions that are called when a program is run, as opposed to being embedded into the program when it is compiled. |
| RX (reception) | The act of downloading or receiving data. Often, the term “RX” is used on indicator lights on modems or network cards to indicate that data is flowing into the device. |
