R

R

R&D n. Acronym for research and development.

race condition n. 1. A condition in which a feedback circuit interacts with internal circuit processes in a way that produces chaotic output behavior. 2. A condition in which data propagates rapidly through a logic circuit far ahead of the clock signal intended to control its passage.

rack-mounted adj. Built for installation in a metal frame or cabinet of standard width (typically 19 inches or 23 inches) and mounting arrangements.

RAD n. Acronym for rapid application development. A method of building computer systems in which the system is programmed and implemented in segments, rather than waiting until the entire project is completed for implementation. Developed by programmer James Martin, RAD uses such tools as CASE and visual programming. See also CASE, visual programming.

radian n. The angle between two radii of a circle such that the length of the arc between them is equal to the radius. The circumference of a circle is equal to 2p times the radius, so one radian contains 360/(2p) = 180/p = approximately 57.2958 degrees. Conversely, multiplying the number of degrees by p/180 gives the number of radians; 360 degrees equals 2p radians. See the illustration.

Radian.

radio n. 1. Electromagnetic waves longer than about 0.3 mm (frequencies lower than about 1 THz). Radio is used to transmit a wide variety of signals, using various frequency ranges and types of modulation, such as AM and FM broadcasts, microwave relays, and television broadcasts. See also hertz, radio frequency. 2. Audio signals transmitted over the Internet of quality comparable to those broadcast by commercial radio stations. See also Internet Talk Radio, MBONE, RealAudio.

radio button n. In graphical user interfaces, a means of selecting one of several options, usually within a dialog box. A radio button appears as a small circle that, when selected, has a smaller, filled circle inside it. Radio buttons act like the station selector buttons on a car radio. Selecting one button in a set deselects the previously selected button, so one and only one of the options in the set can be selected at any given time. In contrast, check boxes are used when more than one option in the set can be selected at the same time. Compare check box.

radio clock n. A device that receives a broadcast containing a standard time signal. Radio clocks are used in network communications to synchronize the host s hardware clock to the Universal Time Coordinate format in accordance with the Network Time Protocol (NTP). See also NTP, Universal Time Coordinate.

radio frequency n. The portion of the electromagnetic spectrum with frequencies between 3 kilohertz and 300 gigahertz. This corresponds to wavelengths between 30 kilometers and 0.3 millimeter. Acronym: RF. See also radio (definition 1).

radio frequency interference n. See RFI.

radiosity n. A method used in computer graphics to render photographic-quality, realistic images. Radiosity is based on dividing an image into smaller polygons, or patches, for purposes of calculating the global illumination emitted by sources of light and reflected from surfaces. Unlike ray tracing, which follows rays of light between a light source and the objects it illuminates, radiosity takes into account both the light emitted from a light source and the light reflected by all objects in the image environment. Radiosity thus accounts not only for a source of illumination (such as a lightbulb) but also for the effects of that illumination as it is absorbed by, and reflected from, every object in the picture. See also form factor. Compare ray tracing.

RADIUS n. Acronym for Remote Authentication Dial-In User Service protocol. A proposed Internet protocol in which an authentication server provides authorization and authentication information to a network server to which a user is attempting to link. See also authentication, communications protocol, server (definition 2).

radix n. The base of a number system for example, 2 in the binary system, 10 in the decimal system, 8 in the octal system, and 16 in the hexadecimal system. See also base (definition 2).

radix-minus-1 complement n. In a system for representing numbers using a fixed number of possible digits (radix) and a fixed number of positions for them, the number obtained from another number by subtracting each of the digits of the other number from the largest possible digit (equal to the radix minus 1). For example, in a system of five-digit decimal numbers, the radix-minus-1 complement of 1,234 is 98,765. Adding any number to its radix-minus-1 complement produces the largest possible number in the system (in the example, 99,999). Adding another 1 to this number produces, in our example, 100,000 but since only the lower five digits are used, the result is zero. Thus, the negative of any number in the system is its radix-minus-1 complement plus 1, because a + a = 0. In the binary system, the radix-minus-1 complement is the one s complement, which is easily formed electronically by inverting all bits.

radix point n. The period or other character that separates the integer portion of a number from the fractional portion. In the decimal system, the radix point is the decimal point, as in the number 1.33.

radix sort n. See digital sort.

radix sorting algorithm n. A sorting algorithm that sorts by grouping elements according to successive parts of their keys. A simple example is sorting a list of numbers in the range 0 999. First the list is sorted by the hundreds digit into a set of (up to) 10 lists; then each list, one at a time, is sorted into a set of (up to) 10 lists based on the tens digit; and finally each of those lists is sorted by the ones digit. This algorithm is usually most efficient when the sorting is done using binary values, which simplifies comparisons (is a given bit on or off?) and reduces the number of lists (each pass produces at most two lists).

RADSL n. Acronym for rate-adaptive asymmetric digital subscriber line. A flexible, high-speed version of ADSL (asymmetric digital subscriber line) that is capable of adjusting transmission speed (bandwidth) based on signal quality and length of the transmission line. As the signal quality improves or deteriorates while a transmission line is being used, the transmission speed is adjusted accordingly. See also ADSL, xDSL.

rag n. Irregularity along the left or right edge of a set of lines of text on a printed page. Rag complements justification, in which one or both edges of the text form a straight vertical line. See the illustration. See also justify, ragged left, ragged right.

Rag.

ragged left adj. Of, relating to, or being lines of text whose left ends are not vertically aligned but form an irregular edge. Text may be right-justified and have a ragged left margin. Ragged-left text is used infrequently typically, for visual effect in advertisements. See also rag, right-justify.

ragged right adj. Of, relating to, or being lines of text whose right ends are not vertically aligned but form an irregular edge. Letters and other word-processed documents are commonly left-justified, with ragged-right margins. See also left-justify, rag.

RAID n. Acronym for redundant array of independent (or inexpensive) disks. A data storage method in which data is distributed across a group of computer disk drives that function as a single storage unit. All the information stored on each of the disks is duplicated on other disks in the array. This redundancy ensures that no information will be lost if one of the disks fails. RAID is generally used on network servers where data accessibility is critical and fault tolerance is required. There are various defined levels of RAID, each offering differing trade-offs among access speed, reliability, and cost. See also disk controller, error-correction coding, Hamming code, hard disk, parity bit, server (definition 1).

RAID array n. See RAID.

RAM n. Acronym for random access memory. Semiconductor-based memory that can be read and written by the central processing unit (CPU) or other hardware devices. The storage locations can be accessed in any order. Note that the various types of ROM memory are capable of random access but cannot be written to. The term RAM, however, is generally understood to refer to volatile memory that can be written to as well as read. Compare core, EPROM, flash memory, PROM, ROM (definition 2).

RAMAC n. 1. Acronym for Random Access Method of Accounting Control. Developed by an IBM team led by Reynold B. Johnson, RAMAC was the first computer disk drive. It was introduced in 1956. The original RAMAC consisted of a stack of 50 24-inch platters, with a storage capacity of 5 megabytes and an average access time of 1 second. 2. A high-speed, high-capacity disk storage system introduced by IBM in 1994. Based on the original RAMAC storage device, it was designed to fulfill enterprise requirements for efficient and fault-tolerant storage.

Rambus DRAM n. See RDRAM.

Rambus dynamic random access memory n. See RDRAM.

RAM cache n. Short for random access memory cache. Cache memory that is used by the system to store and retrieve data from the RAM. Frequently accessed segments of data may be stored in the cache for quicker access compared with secondary storage devices such as disks. See also cache, RAM.

RAM card n. Short for random access memory card. An add-in circuit board containing RAM memory and the interface logic necessary to decode memory addresses.

RAM cartridge n. See memory cartridge.

RAM chip n. Short for random access memory chip. A semiconductor storage device. RAM chips can be either dynamic or static memory. See also dynamic RAM, RAM, static RAM.

RAM compression n. Short for random access memory compression. This technology was an attempt by a number of software vendors to solve the problem of running out of global memory under Windows 3.x. Compression of the usual contents of RAM may lessen the system s need to read or write to virtual (hard disk based) memory and thus speed up the system, as virtual memory is much slower than physical RAM. Because of the falling prices of RAM and the introduction of operating systems that handle RAM more efficiently, such as Windows 9x, Windows NT, and OS/2, RAM compression is generally used only on older PCs. See also compression, RAM, Windows.

RAMDAC n. Acronym for random access memory digital-to-analog converter. A chip built into some VGA and SVGA video adapters that translates the digital representation of a pixel into the analog information needed by the monitor to display it. The presence of a RAMDAC chip generally enhances overall video performance. See also SVGA, VGA.

RAM disk n. Short for random access memory disk. A simulated disk drive whose data is actually stored in RAM memory. A special program allows the operating system to read from and write to the simulated device as if it were a disk drive. RAM disks are extremely fast, but they require that system memory be given up for their use. Also, RAM disks usually use volatile memory, so the data stored on them disappears when power is turned off. Many portables offer RAM disks that use battery-backed CMOS RAM to avoid this problem. See also CMOS RAM. Compare disk cache.

RAM refresh n. See refresh (definition 2).

RAM resident adj. See memory-resident.

RAM-resident program n. See terminate-and-stay- resident program.

random adj. Specifically, a reference to an arbitrary or unpredictable situation or event. The term is also given an extended, pejorative or semi-pejorative meaning, however, in which it is used in the sense of nonspecific, incoherent, poorly organized, loser, and so on.

random access n. The ability of a computer to find and go directly to a particular storage location without having to search sequentially from the beginning location. The human equivalent of random access would be the ability to find a desired address in an address book without having to proceed sequentially through all the addresses. A computer s semiconductor memory (both RAM and ROM) provides random access. Certain types of files stored on disk under some operating systems also allow random access. Such files are best used for data in which each record has no intrinsic relationship to what comes physically before or after it, as in a client list or an inventory. Also called: direct access. See also RAM, ROM (definition 2). Compare indexed sequential access method, sequential access.

random access memory n. See RAM.

random noise n. A signal in which there is no relationship between amplitude and time and in which many frequencies occur randomly, without pattern or predictability.

random number generation n. Production of an unpredictable sequence of numbers in which no number is any more likely to occur at a given time or place in the sequence than any other. Truly random number generation is generally viewed as impossible. The process used in computers would be more properly called pseudorandom number generation.

range n. 1. A block of cells selected for similar treatment in a spreadsheet. A range of cells can extend across a row, down a column, or over a combination of the two, but all cells in the range must be contiguous, sharing at least one common border. Ranges allow the user to affect many cells with a single command for example, to format them similarly, enter the same data into all of them, give them a name in common and treat them as a unit, or select and incorporate them into a formula. 2. In more general usage, the spread between specified low and high values. Range checking is an important method of validating data entered into an application.

range check n. In programming, a limit check of both the upper and lower limits of a value, thus determining whether the value lies within an acceptable range. See also limit check.

RAPI n. See Remote Application Programming Interface.

RARP n. Acronym for Reverse Address Resolution Protocol. A TCP/IP protocol for determining the IP address (or logical address) of a node on a local area network connected to the Internet, when only the hardware address (or physical address) is known. While RARP refers only to finding the IP address and ARP technically refers to the opposite procedure, ARP is commonly used for both senses. See also ARP.

RAS n. 1. See remote access server, Remote Access Service. 2. Acronym for reliability, availability, serviceability. See high availability.

raster n. A rectangular pattern of lines; on a video display, the horizontal scan lines from which the term raster scan is derived.

raster display n. A video monitor (typically a CRT) that displays an image on the screen as a series of horizontal scan lines from top to bottom. Each scan line consists of pixels that can be illuminated and colored individually. Television screens and most computer monitors are raster displays. See also CRT, pixel. Compare vector display.

raster fonts n. Fonts that are stored as bitmaps. Raster fonts are designed with a specific size and resolution for a specific printer and cannot be scaled or rotated. If a printer does not support raster fonts, it will not print them. The five raster fonts are Courier, MS Sans Serif, MS Serif, Small, and Symbol. Also called: bitmapped fonts. See also font, printer.

raster graphics n. A method of generating graphics that treats an image as a collection of small, independently controlled dots (pixels) arranged in rows and columns. Compare vector graphics.

raster image n. A display image formed by patterns of light and dark or differently colored pixels in a rectangular array. See also raster graphics.

raster image processor n. A device, consisting of hardware and software, that converts vector graphics or text into a raster (bitmapped) image. Raster image processors are used in page printers, phototypesetters, and electrostatic plotters. They compute the brightness and color value of each pixel on the page so that the resulting pattern of pixels re-creates the vector graphics and text originally described. Acronym: RIP.

rasterization n. The conversion of vector graphics (images described in terms of mathematical elements, such as points and lines) to equivalent images composed of pixel patterns that can be stored and manipulated as sets of bits. See also pixel.

raster-scan display n. See raster display.

rate-adaptive asymmetric digital subscriber line n. See RADSL.

raw data n. 1. Unprocessed, typically unformatted, data, such as a stream of bits that has not been filtered for commands or special characters. See also raw mode. Compare cooked mode. 2. Information that has been collected but not evaluated.

raw infrared n. A method of receiving data through an infrared (IR) transceiver. Raw infrared treats the IR transceiver like a serial cable and does not process data in any way. The application is responsible for handling collision detection and other potential problems.

raw mode n. A way in which the UNIX and MS-DOS operating systems see a character-based device. If the identifier for the device indicates raw mode, the operating system does not filter input characters or give special treatment to carriage returns, end-of-file markers, and linefeed and tab characters. Compare cooked mode.

ray tracing n. A sophisticated and complex method of producing high-quality computer graphics. Ray tracing calculates the color and intensity of each pixel in an image by tracing single rays of light backward and determining how they were affected on their way from a defined source of light illuminating the objects in the image. Ray tracing is demanding in terms of processing capability because the computer must account for reflection, refraction, and absorption of individual rays, as well as for the brightness, transparency level, and reflectivity of each object and the positions of the viewer and the light source. Compare radiosity.

RCA connector n. A connector used for attaching audio and video devices, such as stereo equipment or a composite video monitor, to a computer s video adapter. See the illustration. See also composite video display. Compare phono connector.

RCA connector. A female version (left) and a male version (right).

RDBMS n. Acronym for relational data base management system. See relational database.

RDF n. See Resource Description Framework.

RDO n. See Remote Data Objects.

RDRAM n. Acronym for Rambus dynamic random access memory. A type of DRAM designed by Rambus, Inc. In its fastest form, known as Direct RDRAM, this technology provides a 16-bit data path and a peak bandwidth of 1.6 GB per second (approximately eight to ten times faster than synchronous DRAM, or SDRAM). RDRAM has been used in graphics and video chips; Direct RDRAM is expected to replace DRAM and SDRAM in personal computers. Also called: Rambus DRAM. See also dynamic RAM, SDRAM.

read¹ n. The action of transferring data from an input source into a computer s memory or from memory into the CPU (central processing unit). Compare write¹.

read² vb. To transfer data from an external source, such as from a disk or the keyboard, into memory or from memory into the central processing unit (CPU). Compare write².

read-after-write n. A feature of certain data storage devices, such as tape drives, in which the device reads data immediately after it is written as a means of verifying data integrity.

reader n. See card reader.

Reader n. See Microsoft Reader.

read error n. An error encountered while a computer is in the process of obtaining information from storage or from another source of input. Compare write error.

README n. A file containing information that the user either needs or will find informative and that might not have been included in the documentation. README files are placed on disk in plain-text form (without extraneous or program-specific characters) so that they can be read easily by a variety of word processing programs.

read notification n. An e-mail feature providing feedback to the sender that a message has been read by the recipient.

read-only adj. Capable of being retrieved (read) but not changed (written). A read-only file or document can be displayed or printed but not altered in any way. Read-only memory (ROM) holds programs that cannot be changed; a read-only storage medium, such as CD-ROM, can be played back but cannot be used for recording information. Compare read/write.

read-only attribute n. A file attribute, stored with a file s directory entry, indicating whether or not a file may be changed or erased. When the read-only attribute is off, the file can be modified or deleted; when it is on, the file can only be displayed.

read-only memory n. See ROM.

read-only terminal n. See RO terminal.

read/write adj. Able to be both read from and written to. Abbreviation: R/W. Compare read-only.

read/write channel n. See input/output channel.

read/write head n. See head.

read/write memory n. Memory that can be both read from and written to (modified). Semiconductor RAM and core memory are typical read/write memory systems. Compare ROM (definition 2).

real address n. An absolute (machine) address specifying a physical location in memory. See also physical address. Compare relative address, virtual address.

RealAudio n. Streaming audio technology developed by RealNetworks, Inc., for distributing radio and FM-quality sound files over the Internet in real time. RealAudio is based on two components: client software for decompressing the sound on the fly and server software for delivering it. The client software is free, distributed either as a downloadable program or as part of browser software. See also RealPlayer, RealVideo, stream, streaming.

reallocate n. A function in C that allows the programmer to request a larger portion of heap memory than was previously assigned to a particular pointer. See also dynamic memory allocation, heap (definition 1).

reallysafe palette n. A color look-up table (CLUT) consisting of 22 colors from the 216-color websafe palette that are completely consistent when viewed with all Web browsers on all major computer platforms. The reallysafe palette arose from an experiment that indicated that most of the colors of the websafe palette shift to some degree in different viewing environments. See also browser CLUT, websafe palette.

real mode n. An operating mode in the Intel 80x86 family of microprocessors. In real mode, the processor can execute only one program at a time. It can access no more than about 1 MB of memory, but it can freely access system memory and input/output devices. Real mode is the only mode possible in the 8086 processor and is the only operating mode supported by MS-DOS. In contrast, the protected mode offered in the 80286 and higher microprocessors provides the memory management and memory protection needed for multitasking environments such as Windows. See also 8086, privileged mode. Compare protected mode, virtual real mode.

real-mode mapper n. An enhancement for Windows 3.x systems that allows 32-bit file system access. The real-mode mapper provides a 32-bit disk access interface to the DOS device driver chain. Acronym: RMM.

real number n. 1. A number that can be represented in a number system with a given base, such as the decimal system, by a finite or infinite sequence of digits and a radix point. For example, 1.1 is a real number, as is 0.33333.... See also irrational number. Compare complex number, imaginary number. 2. A data type, in a programming language such as Pascal, that is used for storing, to some limit of precision, values that include both integer and fractional parts. See also double-precision, single-precision. Compare floating-point number, integer.

RealPlayer n. An Internet media player and browser plug-in developed by RealNetworks, Inc., that supports playback of RealAudio and RealVideo, as well as certain other formats, after installation of appropriate plug-ins. The current version allows RealPlayer users to surf for media content directly from the player or through a Web browser. See also RealAudio, RealVideo.

Real Soon Now adv. Soon, but not really expected to be as soon as claimed. One might say, for example, that a commercial program will have some desired feature Real Soon Now if several versions ago the vendor knew of the need for the feature and has done nothing. Acronym: RSN.

real storage n. The amount of RAM memory in a system, as distinguished from virtual memory. Also called: physical memory, physical storage. See also virtual memory.

RealSystem G2 n. An open, standards-based platform for delivery of streaming audio and video over the Internet and other TCP/IP networks developed by RealNetworks, Inc. RealSystem G2 was introduced by RealNetworks in its audio and video players, servers, and development tools in 1998. Among other features, RealSystem G2 scales to different bandwidths, includes streaming that adjusts delivery to available bandwidth, and supports SMIL (Synchronized Multimedia Integration Language) for multimedia presentations. See also RealPlayer, RealVideo, SMIL, streaming.

RealSystem Producer n. A software application developed by RealNetworks that converts most types of video and sound files into RealMedia formats for use as streaming media over the Internet or within a corporate intranet.

RealSystem Server n. Software developed by RealNetworks to enable a server to broadcast streaming media. Several versions of RealSystem Server are available, designed to meet needs ranging from small intranet servers to large proxy servers.

real-time adj. Of, or relating to, a time frame imposed by external constraints. Real-time operations are those in which the machine s activities match the human perception of time or those in which computer operations proceed at the same rate as a physical or external process. Real-time operations are characteristic of aircraft guidance systems, transaction-processing systems, scientific applications, and other areas in which a computer must respond to situations as they occur (for example, animating a graphic in a flight simulator or making corrections based on measurements).

real-time animation n. Computer animation in which images are computed and updated on the screen at the same rate at which the objects simulated might move in the real world. Real-time animation allows dynamic involvement by the user because the computer can accept and incorporate keystrokes or controller movements as it is drawing the next image in the animation sequence. Arcade-style animation (such as in a flight simulator program) makes use of real-time animation in translating game plays into on-screen actions. In contrast, in animation done in virtual time, image frames are first calculated and stored and later replayed at a higher rate to achieve smoother movement. See also animation, bit block.

real-time clock n. In PCs, a circuit or other hardware element that provides the system with real-world time. Upon startup of the system, the real-time clock puts the date and time in memory, where it can then be systematically incremented by the BIOS. A real-time clock generally has a battery that is separate from the rest of the system, so it s not dependent upon the system s power source. This is not the same thing as a system clock, which synchronizes the processor. Acronym: RTC. See also clock (definition 2).

real-time conferencing n. See teleconferencing.

Real-Time Control Protocol n. A scalable transport control protocol that works with the Real-Time Protocol (RTP) to monitor real-time transmissions to multiple participants over a network for example, during videoconferencing. The Real-Time Control Protocol, or RTCP, transmits packets of control information at regular intervals and is used to determine how well information is being delivered to recipients. Acronym: RTCP. See also Real-Time Protocol, Real-Time Streaming Protocol, Resource Reservation Setup Protocol.

real-time operating system n. An operating system designed for the needs of a process-controlled environment. A real-time operating system recognizes that responses must be made and tasks handled instantly, with no lag time. Real-time operating systems are typically used as embedded systems in devices and applications requiring time-critical reaction, such as telecommunications, air traffic control, and robotic functions. Acronym: RTOS. See also real-time system.

Real-Time Protocol n. An Internet-standard network transport protocol used in delivering real-time data, including audio and video. The Real-Time Protocol, or RTP, works with both unicast (single sender, single recipient) and multicast (single sender, multiple recipients) services. RTP is often used in conjunction with the Real-Time Control Protocol (RTCP), which monitors delivery. Acronym: RTP. See also Real-Time Control Protocol, Real-Time Streaming Protocol, stream.

real-time streaming n. The process of delivering a streaming media file via a specialized streaming media server using real-time streaming protocol (RTSP). With real-time streaming, the file itself actually plays on the streaming media server, even though it is viewed on the computer that opened the file. Real-time streaming transmits at a higher bandwidth than HTTP streaming. It is often used to broadcast live events, such as concerts or keynote conference addresses. See also HTTP streaming.

Real-Time Streaming Protocol n. A control protocol for the delivery of streamed multimedia data over Internet Protocol (IP) networks. The Real-Time Streaming Protocol, or RTSP, was developed by Columbia University, Progressive Networks, and Netscape and has been submitted as a proposed standard to the IETF (Internet Engineering Task Force). RTSP is designed to deliver real-time, live, or stored audio and video efficiently over a network. It can be used either for groups of recipients or for on-demand delivery to a single recipient. Acronym: RTSP. See also Advanced Streaming Format, Real-Time Protocol, Resource Reservation Setup Protocol, stream.

real-time system n. A computer and/or a software system that reacts to events before the events become obsolete. For example, airline collision avoidance systems must process radar input, detect a possible collision, and warn air traffic controllers or pilots while they still have time to react.

RealVideo n. The streaming technology developed by RealNetworks, Inc., for distributing video over intranets and the Internet. RealVideo transmits video from a server in encoded (compressed) form. The video and accompanying sound are viewed on the client end with the help of a software player. RealVideo works with both IP and IP multicasting and, as with RealAudio, does not require transmission of complete files before playback can begin. See also RealAudio, RealPlayer, streaming.

reboot vb. To restart a computer by reloading the operating system. See also boot², cold boot, warm boot.

receipt notification n. An e-mail feature providing feedback to the sender that a message has been received by the recipient.

receive vb. To accept data from an external communications system, such as a local area network (LAN) or a telephone line, and store the data as a file.

Receive Data n. See RXD.

rec. newsgroups n. Usenet newsgroups that are part of the rec. hierarchy and whose names have the prefix rec. These newsgroups cover topics devoted to discussions of recreational activities, hobbies, and the arts. See also newsgroup, traditional newsgroup hierarchy, Usenet. Compare comp. newsgroups, misc. newsgroups, news. newsgroups, sci. newsgroups, soc. newsgroups, talk. newsgroups.

recompile vb. To compile a program again, usually because of changes that needed to be made in the source code in response to error messages generated by the compiler. See also compile.

record¹ n. A data structure that is a collection of fields (elements), each with its own name and type. Unlike an array, whose elements all represent the same type of information and are accessed using an index, the elements of a record represent different types of information and are accessed by name. A record can be accessed as a collective unit of elements, or the elements can be accessed individually. See also array, data structure, type¹ (definition 1).

record² vb. To retain information, usually in a file.

record format n. See record structure.

record head n. The device in a tape machine that places data on the tape. In some tape machines, the record head is combined with the read head.

record layout n. The organization of data fields within a record. See also record¹.

record length n. The amount of storage space required to contain a record, typically given in bytes. See also record¹.

record locking n. A strategy employed in distributed processing and other multiuser situations to prevent more than one user at a time from writing data to a record. See also record¹.

record number n. A unique number assigned to a record in a database in order to identify it. A record number can identify an existing record by its position (for example, the tenth record from the beginning of a database), or it can be assigned to the record to serve as a key (for example, the number 00742 assigned to the tenth record from the beginning of the database). See also record¹.

record structure n. An ordered list of the fields that compose a record, together with a definition of the domain (acceptable values) of each field. See also record¹.

recover vb. 1. To return to a stable condition after some error has occurred. A program recovers from an error by stabilizing itself and resuming execution of instructions without user intervention. 2. To put back into a stable condition. A computer user may be able to recover lost or damaged data by using a program to search for and salvage whatever information remains in storage. A database may be recovered by restoring its integrity after some problem has damaged it, such as abnormal termination of the database management program.

recoverable error n. An error that can be successfully managed by software. For example, when the user enters a number when a letter is required, the program can simply display an error message and prompt the user again.

recovery n. The restoration of lost data or the reconciliation of conflicting or erroneous data after a system failure. Recovery is often achieved using a disk or tape backup and system logs. See also backup.

Recreational Software Advisory Council n. An independent, nonprofit organization established in the fall of 1994 by a group of six trade organizations, led by the Software Publishers Association. The Council s goal was to create a new, objective content-labeling rating system for recreational software and other media such as the Internet. Acronym: RSAC.

rectangle ad n. An Internet ad format that is larger than a traditional banner ad and is generally inserted directly into page content for greater visibility.

rectifier n. A circuit component that passes current flowing in one direction but stops current flowing in the other direction. Rectifiers are used to convert alternating current to direct current.

recto n. The right-hand page of two facing pages. A recto is characteristically an odd-numbered page. Compare verso.

recursion n. The ability of a routine to call itself. Recursion enables certain algorithms to be implemented with small, simple routines, but it does not guarantee speed or efficiency. Erroneous use of recursion can cause a program to run out of stack space during execution, causing the program, and sometimes the entire system, to crash. See also call¹ (definition 2), routine.

Recycle Bin n. A folder in Windows 9x, Windows CE, Windows NT, Windows 2000, and Windows XP represented by an icon on the screen resembling a basket decorated with the recycling logo. To remove a file, the user drags its icon to the Recycle Bin. However, a file in the Recycle Bin is not actually deleted from the disk until the user opens the Recycle Bin, selects the file, and presses the Delete key; until then, the user can retrieve it. Compare Trash.

Red Book n. 1. The standards documents of the U.S. National Security Agency entitled Trusted Network Interpretation of the Trusted Computer System Evaluation Criteria (NCSC-TG-005) and Trusted Network Interpretation (NCS-TG-011). These documents define a system of ratings from A1 (most secure) to D (nonsecure), indicating the ability of a computer network to protect sensitive information. Compare Orange Book (definition 1). 2. A specifications book written by the Sony Corporation and Philips Corporation and endorsed by ISO, covering audio compact discs. Compare Green Book, Orange Book (definition 2). 3. Telecommunications standards published by the CCITT.

red-green-blue n. See RGB.

redirection n. The process of writing to or reading from a file or device different from the one that would normally be the target or the source. For example, the MS-DOS or OS/2 command dir >prn redirects a directory listing from the screen to the printer. Compare pipe.

redirector n. Software on a client computer that intercepts requests for information and, when appropriate, directs them to the network. Redirectors can either be built into the client operating system or be part of an added networking package.

redlining n. A feature of a word processing application that marks changes, additions, or deletions made to a document by a coauthor or editor. The purpose of redlining is to produce a record of the changes made to a document during the course of its development.

redraw n. See refresh (definition 1).

reduce vb. In a graphical user interface, to decrease the size of a window. A user can reduce a window either by clicking the appropriate button in the title bar or by clicking the mouse on the border of the window and dragging the border toward the middle of the window. See also maximize, minimize.

Reduced Instruction Set Computing n. See RISC.

redundancy n. Using one or more servers on a Web site to perform identical tasks. If one of the servers crashes, another server assumes its tasks. Redundancy ensures that the Web site will continue to function if one of the servers stops working.

redundancy check n. See CRC, LRC.

redundant code n. Code that duplicates a function performed elsewhere for example, code to sort a list that has already been sorted.

reengineer vb. To rethink and redefine processes and procedures. In the context of computer systems, to reengineer means to change the way work is done in order to maximize the benefits of new technology.

reengineering vb. 1. With regard to software, changing existing software to strengthen desirable characteristics and remove weaknesses. 2. With regard to corporate management, using information technology principles to address the challenges posed by a global economy and to consolidate management of a rapidly expanding work force.

reentrant code n. Code written so that it can be shared by several programs at the same time. When a program is executing reentrant code, another program can interrupt the execution and can then start or continue execution of that same code. Many operating-system routines are written to be reentrant so that only one copy needs to reside in memory to serve all executing applications. See also relocatable code.

refactoring n. An optimization process in object-oriented programming intended to improve the design or structure of a program without changing its functionality. The goal of refactoring is to make the program clearer and easier to work with in part by removing duplication, abstracting common behaviors, and refining class hierarchies and to improve the extensibility and reusability of existing code.

reference¹ n. A data type in the C++ programming language. A reference must be initialized with a variable name. The reference then becomes an alias for that variable but actually stores the address of the variable.

reference² vb. To access a variable, such as an element in an array or a field in a record.

reference parameter n. A parameter in which the address of a variable, rather than the explicit value, is passed to the called routine. See also parameter.

reference type n. A data type that is represented by a reference (similar to a pointer) to the type s actual value. If a reference type is assigned to a variable, that variable references (or points to ) the original value. No copy is made. Reference types comprise classes, interfaces, delegates, and boxed value types. See also data type, value type.

reflecting software n. See reflector.

reflective liquid-crystal display n. A liquid crystal display that is not equipped with edge light or backlight to enhance readability but rather depends on reflecting ambient light, making it difficult to read in brightly lit environments such as the outdoors. Also called: reflective LCD.

reflective routing n. In wide area networks, the process of using a reflector to distribute data, thereby reducing the load of the network server. See also reflector.

reflector n. A program that sends messages to a number of users upon receipt of a signal from a single user. A common type of reflector is an e-mail reflector, which forwards any e-mail sent to it to the multiple recipients currently on its list. See also multiple recipients. Compare mail reflector.

reformat vb. 1. In applications, to change the look of a document by altering stylistic details, such as font, layout, indention, and alignment. 2. In data storage, to prepare for reuse a disk that already contains programs or data, effectively destroying the existing contents.

refresh vb. 1. To retrace a video screen at frequent intervals, even if the image does not change, so as to keep the phosphors irradiated. 2. To recharge dynamic random access memory chips (DRAMs) so that they continue to retain the information stored in them. Circuitry on the memory board automatically performs this function. See also refresh cycle.

refreshable adj. In programming, referring to a program module capable of being replaced in memory without affecting processing of the program or the information being used by the program.

refresh cycle n. The process in which controller circuitry provides repeated electric pulses to dynamic random access memory chips in order to renew the stored electric charges in those locations that contain binary 1. Each pulse is one refresh cycle. Without constant refreshing, dynamic semiconductor RAM loses any information stored in it as it does when the computer is turned off or when the power fails. See also dynamic RAM, static RAM.

refresh rate n. In reference to video hardware, the frequency with which the entire screen is redrawn to maintain a constant, flicker-free image. On TV screens and raster-scan monitors, the electron beam that lights the phosphor coating on the inner surface of the screen typically refreshes the entire image area at a rate of about 60 hertz, or 60 times per second. Interlaced monitors, which redraw alternate lines during each sweep of the electron beam, actually refresh any particular line only 30 times per second. Because odd and even lines are refreshed on successive sweeps, however, the effective refresh rate is 60 times per second. See also refresh (definition 1).

REGEDIT n. See Registry Editor.

regenerate vb. See rewrite.

regeneration buffer n. See video buffer.

regenerator n. See repeater.

region n. 1. An area dedicated to or reserved for a particular purpose. 2. In video programming, a contiguous group of pixels that are treated as a unit. On the Apple Macintosh, for example, a region is an area in a grafPort that can be defined and manipulated as an entity. The visible working area within a window is an example of a region. See also grafPort.

region code n. Codes on DVD movie titles and DVD-ROM drives that prevent playback of certain DVDs in certain geographical regions. Region codes are part of the DVD specification. See also CSS, DeCSS.

region fill n. In computer graphics, the technique of filling a defined region on the screen with a selected color, pattern, or other attribute. See also region (definition 2).

register n. A set of bits of high-speed memory within a microprocessor or other electronic device, used to hold data for a particular purpose. Each register in a central processing unit is referred to in assembly language programs by a name such as AX (the register that contains the results of arithmetic operations in an Intel 80x86 processor) or SP (the register that contains the memory address of the top of the stack in various processors).

registered file type n. File types that are tracked by the system registry and are recognized by the programs you have installed on your computer. See also file type.

registration n. The process of precisely aligning elements or superimposing layers in a document or a graphic so that everything will print in the correct relative position. See also registration marks.

registration marks n. Marks placed on a page so that in printing, the elements or layers in a document can be arranged correctly with respect to each other. Each element to be assembled contains its own registration marks; when the marks are precisely superimposed, the elements are in the correct position. See the illustration.

Registration marks.

registry n. A central hierarchical database in Windows 9x, Windows CE, Windows NT, and Windows 2000 used to store information necessary to configure the system for one or more users, applications, and hardware devices. The Registry contains information that Windows continually references during operation, such as profiles for each user, the applications installed on the computer and the types of documents each can create, property sheet settings for folders and application icons, what hardware exists on the system, and which ports are being used. The Registry replaces most of the text-based .ini files used in Windows 3. x and MS-DOS configuration files, such as AUTOEXEC.BAT and CONFIG.SYS. Although the Registry is common to the several Windows platforms, there are some differences among them. Also called: system registry. See also hierarchical database, .ini, input/output port, property sheet, Registry Editor.

Registry Editor n. An application under Windows that allows the user to edit the entries in the registry. Acronym: REGEDIT. See also registry.

regression analysis n. In statistics, an analysis of the degree to which variations in an independent variable affect a dependent variable (a variable whose value depends on the value of another variable). See also multiple regression.

regression testing n. Complete retesting of a modified program, rather than a test of only the modified routines, to ensure that no errors have been introduced with the modifications.

relation n. A structure composed of attributes (individual characteristics, such as name or address, corresponding to the columns in a table) and tuples (sets of attribute values describing particular entities, such as customers, corresponding to the rows in a table). Within a relation, tuples cannot be repeated; each must be unique. Further, tuples are unordered within a relation; interchanging two tuples does not change the relation. Finally, if relational theory is to be applicable, the domain of each attribute must be atomic that is, a simple value, rather than a structure such as an array or a record. A relation in which the domains of all attributes are atomic is said to be normalized or in first normal form. See also normal form (definition 1).

relational algebra n. A collection of rules and operators that permits relations (tables) to be manipulated. Relational algebra is usually described as having the following operators: SELECT, PROJECT, PRODUCT, UNION, INTERSECT, DIFFERENCE, JOIN (or INNER JOIN), and DIVIDE. In a relational database, relational algebra is used to develop procedures to build new relations based on the existing relations.

relational calculus n. In database management, a nonprocedural method for manipulating relations (tables). There are two families of relational calculus: domain calculus and tuple calculus. The two families of relational calculus are mathematically equivalent to each other and to relational algebra. Using either family, one can formulate a description of a desired relation, based on the existing relations in the database.

relational database n. A database or database management system that stores information in tables rows and columns of data and conducts searches by using data in specified columns of one table to find additional data in another table. In a relational database, the rows of a table represent records (collections of information about separate items) and the columns represent fields (particular attributes of a record). In conducting searches, a relational database matches information from a field in one table with information in a corresponding field of another table to produce a third table that combines requested data from both tables. For example, if one table contains the fields EMPLOYEE-ID, LAST-NAME, FIRST-NAME, and HIRE-DATE, and another contains the fields DEPT, EMPLOYEE-ID, and SALARY, a relational database can match the EMPLOYEE-ID fields in the two tables to find such information as the names of all employees earning a certain salary or the departments of all employees hired after a certain date. In other words, a relational database uses matching values in two tables to relate information in one to information in the other. Microcomputer database products typically are relational databases. Compare flat-file database, inverted-list database.

relational database management system n. See relational database.

relational expression n. An expression that uses a relational operator such as less than or greater than to compare two or more expressions. A relational expression resolves to a Boolean (true/false) value. See also Boolean, relational operator.

relational model n. A data model in which the data is organized in relations (tables). This is the model implemented in most modern database management systems.

relational operator n. An operator that allows the programmer to compare two (or more) values or expressions. Typical relational operators are greater than (>), equal to (=), less than (<), not equal to (<>), greater than or equal to (>=), and less than or equal to (<=). See also relational expression.

relational structure n. The record organization used in the implementation of a relational model.

relative address n. A location, as in a computer s memory, that is specified in terms of its distance (displacement or offset) from a starting point (base address). A relative address is typically computed by adding an offset to the base. In everyday terms, this is similar to creating the address 2001 Main Street, in which the base is the 2000 block of Main Street and the offset is 1, which specifies the first house from the beginning of the block. Also called: indirect address.

relative coordinates n. Coordinates that are defined in terms of their distance from a given starting point, rather than from the origin (intersection of two axes). For example, from a starting point on the screen, a square defined by relative coordinates can be drawn as a series of lines, each representing a displacement in distance and direction from the end of the preceding point. The entire square can be redrawn at another location simply by changing the coordinates of the starting point rather than by recalculating the coordinates of each corner with reference to the origin. See the illustration. Compare absolute coordinates.

Relative coordinates.

relative movement n. 1. Motion whose distance and direction are relative to a starting point. For example, when a mouse pointer is moved on the screen, the coordinates of its new position are relative to the previous location of the pointer. See also relative coordinates, relative pointing device. 2. In computer graphics and cinematography, the movement of one object in relation to another, such as the movement of horse A from the perspective of horse B on a racetrack.

relative path n. A path that is implied by the current working directory. When a user enters a command that refers to a file, if the full pathname is not entered the current working directory becomes the relative path of the file referred to. Compare full path.

relative pointing device n. A cursor-control device, such as a mouse or a trackball, in which the movement of an on-screen cursor is linked to the movement of the device but not to the position of the device. For example, if a user picks up a mouse and puts it down in a different location on a desk, the position of the on-screen cursor does not change because no movement (rolling) is detected. When the user rolls the mouse again, the cursor moves to reflect the mouse movement against the surface of the desk. Relative pointing devices differ from absolute pointing devices, such as graphics tablets, in which the device s location within a defined area is always associated with a predefined on-screen position. See also relative coordinates, relative movement (definition 1). Compare absolute pointing device.

relative URL n. Short for relative uniform resource locator. A form of URL in which the domain and some or all directory names are omitted, leaving only the document name and extension (and perhaps a partial list of directory names). The indicated file is found in a location relative to the pathname of the current document. Acronym: RELURL. See also file extension, URL.

RELAX NG n. An XML schema language based on Tree Regular Expressions for XML (TREX) and Regular Language Description for XML (RELAX). RELAX NG supports XML namespaces, uses XML syntax, maintains the information set of the XML document, and provides unrestricted support for mixed or unordered content.

relay n. A switch activated by an electrical signal. A relay allows another signal to be controlled without the need for human action to route the other signal to the control point, and it also allows a relatively low-power signal to control a high-power signal.

release¹ n. 1. A particular version of a piece of software, most commonly associated with the most recent version (as in the latest release ). Some companies use the term release as an integral part of the product name (as in Lotus 1-2-3 Release 2.2 ). 2. A version of a product that is available in general distribution. Compare alpha¹, beta¹.

release² vb. 1. To relinquish control of a block of memory, a device, or another system resource to the operating system. 2. To formally make a product available to the marketplace.

reliability n. The likelihood of a computer system or device continuing to function over a given period of time and under specified conditions. Reliability is measured by different performance indexes. For example, the reliability of a hard disk is often given as mean time between failures (MTBF): the average length of time the disk can be expected to function without failing. See also MTBF, MTTR.

reliability, availability, serviceability n. Acronym: RAS. See high availability.

reload vb. 1. To load a program into memory from a storage device again in order to run it, because the system has crashed or the program s operation was otherwise interrupted. 2. To retrieve a new copy of the Web page currently visible in a Web browser.

relocatable address n. In programming, an address that is to be adjusted to reflect the actual place in memory into which a program is loaded for execution. In Get the byte located 12 bytes from this instruction, the address is relocatable; in Get the byte located at address 255, the address is not relocatable. This convention is comparable to describing the address of a parked car as level 2, row G on one day and level 5, row B on another.

relocatable code n. A program written in such a way that it can be loaded into any part of available memory rather than having to be placed in one specific location. In relocatable code, address references that depend on the program s physical location in memory are calculated at run time so that program instructions can be carried out correctly. See also reentrant code.

relocate n. To move programs and blocks of memory about within available space so as to use memory resources flexibly and efficiently. A relocatable program can be loaded by the operating system into any part of available memory rather than into only one specific area. A relocatable block of memory is a portion of memory that can be moved around by the operating system as required; for example, the system might collect several available, relocatable blocks of memory to form one larger block of the size requested for use by a program.

RELURL n. See relative URL.

remailer n. A service that will forward e-mail while concealing the e-mail address of the originator of the message. Remailers may be used by individuals who wish to retain their privacy or avoid unsolicited commercial e-mail (UCE). Remailers may also be used to hide the identities of individuals and businesses sending spam or malicious or fraudulent e-mail.

remark n. See comment, REM statement.

remote adj. Not in the immediate vicinity, as a computer or other device located in another place (room, building, or city) and accessible through some type of cable or communications link.

remote access n. The use of a remote computer.

remote access server n. A host on a LAN (local area network) that is equipped with modems to enable users to connect to the network over telephone lines. Acronym: RAS.

Remote Access Service n. Windows software that allows a user to gain remote access to the network server via a modem. Acronym: RAS. See also remote access.

remote administration n. The performance of system administration related tasks via access from another machine in a network.

Remote Application Programming Interface n. A Remote Procedure Call (RPC) mechanism that enables an application running on a desktop computer to make function calls on a Windows CE based device. The desktop computer is known as the Remote Application Programming Interface (RAPI) client, and the Windows CE device is known as the RAPI server. RAPI runs over Winsock and TCP/IP. Acronym: RAPI. See also remote procedure call.

Remote Authentication Dial-In User Service n. See RADIUS.

remote communications n. Interaction with a remote computer through a telephone connection or another communications line.

remote computer system n. See remote system.

Remote Data Objects n. An object-oriented data access tool featured in Visual Basic 4 and later. Remote Data Objects have no native file format of their own; they can be used only with databases complying with the most recent ODBC standards. This feature is popular for its speed and minimal coding requirements. Acronym: RDO. See also ODBC, Visual Basic.

Remote Installation Services n. Software services that allow an administrator to set up new client computers remotely, without having to visit each client. The target clients must support remote booting. Acronym: RIS.

remote login n. The action of logging in to a computer at a distant location by means of a data communications connection with the computer that one is presently using. After remote login, the user s own computer behaves like a terminal connected to the remote system. On the Internet, remote login is done primarily by rlogin and telnet. See also rlogin¹ (definition 1), telnet¹.

remote monitoring n. See RMON.

remote network monitoring n. See RMON.

Remote PC n. See remote system.

remote procedure call n. In programming, a call by one program to a second program on a remote system. The second program generally performs a task and returns the results of that task to the first program. Acronym: RPC.

remote system n. The computer or network that a remote user is accessing via a modem. See also remote access. Compare remote terminal.

remote terminal n. A terminal that is located at a site removed from the computer to which it is attached. Remote terminals rely on modems and telephone lines to communicate with the host computer. See also remote access. Compare remote system.

removable disk n. A disk that can be removed from a disk drive. Floppy disks are removable; hard disks usually are not. Also called: exchangeable disk.

REM statement n. Short for remark statement. A statement in the Basic programming language and the MS-DOS and OS/2 batch file languages that is used to add comments to a program or batch file. Any statement beginning with the word REM is ignored by the interpreter or compiler or the command processor. See also comment.

rename n. A command in most file transfer protocol (FTP) clients and in many other systems that allows the user to assign a new name to a file or files.

render vb. To produce a graphic image from a data file on an output device such as a video display or printer.

rendering n. The creation of an image containing geometric models, using color and shading to give the image a realistic look. Usually part of a geometric modeling package such as a CAD program, rendering uses mathematics to describe the location of a light source in relation to the object and to calculate the way in which the light would create highlights, shading, and variations in color. The degree of realism can range from opaque, shaded polygons to images approximating photographs in their complexity. See also ray tracing.

RenderMan Shading Language n. A C-like graphics and rendering language developed by Pixar.

repaginate vb. To recalculate the page breaks in a document.

Repeat n. A command in Microsoft Word that causes all information contained in either the last command dialog box or the last uninterrupted editing session to be repeated.

repeat counter n. A loop counter; typically, a register that holds a number representing how many times a repetitive process has been or is to be executed.

Repeat delay n. A delay for the amount of time that elapses before a character begins repeating when you hold down a key.

repeater n. A device used on communications circuits that decreases distortion by amplifying or regenerating a signal so that it can be transmitted onward in its original strength and form. On a network, a repeater connects two networks or two network segments at the physical layer of the ISO/OSI reference model and regenerates the signal.

repeating Ethernet n. See repeater.

repeat key n. On some keyboards, a key that must be held down at the same time as a character key to cause the character key s key code to be sent repeatedly. On most computer keyboards, however, a repeat key is not needed because a key automatically repeats if held down for longer than a brief delay. Compare typematic.

RepeatKeys n. A feature of Windows 9x and Windows NT that allows a user to adjust or disable the typematic keyboard feature so as to accommodate users with restricted mobility, who may activate typematic by accident because they have trouble lifting their fingers from the keys. See also typematic. Compare BounceKeys, FilterKeys, MouseKeys, ShowSounds, SoundSentry, StickyKeys, ToggleKeys.

repetitive strain injury n. An occupational disorder of the tendons, ligaments, and nerves caused by the cumulative effects of prolonged repetitious movements. Repetitive strain injuries are appearing with increasing frequency among office workers who spend long hours typing at computerized workstations that are not equipped with safeguards such as wrist supports. Acronym: RSI. See also carpal tunnel syndrome, ergonomic keyboard, wrist support.

replace vb. To put new data in the place of other data, usually after conducting a search for the data to be replaced. Text-based applications such as word processors typically include search-and-replace commands. In such operations, both old and new data must be specified, and search-and-replace procedures may or may not be sensitive to uppercase and lowercase, depending on the application program. See also search¹, search and replace.

replay attack n. An attack in which a valid message is intercepted and then repeatedly retransmitted, either for fraudulent purposes or as part of a larger attack scheme.

replication n. In a distributed database management system, the process of copying the database (or parts of it) to the other parts of the network. Replication allows distributed database systems to remain synchronized. See also distributed database, distributed database management system.

report n. The presentation of information about a given topic, typically in printed form. Reports prepared with computers and appropriate software can include text, graphics, and charts. Database programs can include special software for creating report forms and generating reports. Desktop publishing software and laser printers or typesetting equipment can be used to produce publication-quality output.

report generator n. An application, commonly part of a database management program, that uses a report form created by the user to lay out and print the contents of a database. A report generator is used to select specific record fields or ranges of records, to make the output attractive by including such features as headings, running heads, page numbers, and fonts.

Report Program Generator n. See RPG (definition 2).

report writer n. See report generator.

repository n. 1. A collection of information about a computing system. 2. A superset of a data dictionary. See also data dictionary.

reprogrammable PROM n. See EPROM.

reprogrammable read-only memory n. See EPROM.

requested permissions n. Optionally specified permissions in an assembly that represent the minimum required, optionally desired, and always refused permissions for all code in the assembly. If there is no request, the code is granted the maximum that policy allows.

Request for Comments n. See RFC.

Request for Discussion n. A formal proposal for a discussion concerning the addition of a newsgroup to the Usenet hierarchy, the first step in a process that ends with a call for votes. Acronym: RFD. See also traditional newsgroup hierarchy, Usenet.

Request to Send n. See RTS.

required hyphen n. See hyphen.

Research Libraries Information Network n. The combined online catalog of the Research Libraries Group, which includes many of the major research libraries in the United States. Acronym: RLIN.

reserve n. A command that allocates contiguous disk space for the device instance s workspace. Digital video devices recognize this command.

reserve accumulator n. An auxiliary storage register generally used to store the intermediate results of an extended calculation.

reserved character n. A keyboard character that has a special meaning to a program and, as a result, normally cannot be used in assigning names to files, documents, and other user-generated tools, such as macros. Characters commonly reserved for special uses include the asterisk (*), forward slash (/), backslash (\), question mark (?), and vertical bar ( ).

reserved date n. A date with a special meaning, rather than the date on the calendar. For example, some programs use 9999 to indicate an account or a database listing that does not expire. See also magic dates.

reserved memory n. See UMA.

reserved word n. A word that has special meaning to a program or in a programming language. Reserved words usually include those used for control statements (IF, FOR, END), data declarations, and the like. A reserved word can be used only in certain predefined circumstances; it cannot be used in naming documents, files, labels, variables, or user-generated tools such as macros.

reset button n. A device that restarts a computer without turning off its power. Compare big red switch.

resident font n. See internal font.

resident program n. See TSR.

resistance n. The ability to impede (resist) the flow of electric current. With the exception of superconductors, all substances have a greater or lesser degree of resistance. Substances with very low resistance, such as metals, conduct electricity well and are called conductors. Substances with very high resistance, such as glass and rubber, conduct electricity poorly and are called nonconductors or insulators.

resistor n. A circuit component designed to provide a specific amount of resistance to current flow.

resize vb. To make an object or space larger or smaller. Also called: scale.

resolution n. 1. The fineness of detail attained by a printer or a monitor in producing an image. For printers that form characters from small, closely spaced dots, resolution is measured in dots per inch, or dpi, and ranges from about 125 dpi for low-quality dot-matrix printers to about 600 dpi for some laser and ink-jet printers (typesetting equipment can print at resolutions of over 1000 dpi). For a video display, the number of pixels is determined by the graphics mode and video adapter, but the size of the display depends on the size and adjustment of the monitor; hence the resolution of a video display is taken as the total number of pixels displayed horizontally and vertically. See also high resolution, low resolution. 2. The process of translation between a domain name address and an IP address. See also DNS, IP address.

resolve vb. 1. To match one piece of information to another in a database or lookup table. 2. To find a setting in which no hardware conflicts occur. 3. To convert a logical address to a physical address or vice versa. 4. To convert an Internet domain name to its corresponding IP address. See also DNS, IP address.

resource n. 1. Any part of a computer system or a network, such as a disk drive, printer, or memory, that can be allotted to a program or a process while it is running. 2. An item of data or code that can be used by more than one program or in more than one place in a program, such as a dialog box, a sound effect, or a font in a windowing environment. Many features in a program can be altered by adding or replacing resources without the necessity of recompiling the program from source code. Resources can also be copied and pasted from one program into another, typically by a specialized utility program called a resource editor. 3. Any nonexecutable data that is logically deployed with an application. A resource might be displayed in an application as error messages or as part of the user interface. Resources can contain data in a number of forms, including strings, images, and persisted objects.

resource allocation n. The process of distributing a computer system s facilities to different components of a job in order to perform the job.

resource data n. The data structures, templates, definition procedures, management routines, icon maps, and so forth associated with a particular resource, such as a menu, window, or dialog box. See also resource (definition 2), resource fork.

Resource Description Framework n. A specification developed by the World Wide Web Consortium (W3C) to define a flexible infrastructure for organizing and managing metadata (data about data) across the Web and the Internet. The Resource Description Framework is intended to provide a framework based on XML (eXtensible Markup Language) that can standardize the way applications exchange metadata (or metacontent). Possible uses include search engines, content rating systems, and other areas in which exchange of information about data is valuable. Acronym: RDF. See also XML.

resource file n. A file that consists of resource data and the resource map that indexes it. See also resource (definition 2), resource fork.

resource fork n. One of the two forks of an Apple Macintosh file (the other being the data fork ). The resource fork of a program file contains reusable items of information that the program can use during the course of execution, such as fonts, icons, windows, dialog boxes, menus, and the program code itself. A user-created document typically stores its data in the data fork, but it can also use its resource fork for storing items that might be used more than once in the document. For example, in a HyperCard stack, the data that constitutes each card, or record, in the stack is stored in the data fork; digitized sounds and icons that might be used more than once are stored in the resource fork. The use of such resources makes program development easier because resources can be developed and altered independently of the program code. See also HyperCard, resource (definition 2). Compare data fork.

resource ID n. A number that identifies a particular resource within a given resource type on the Apple Macintosh for example, a particular menu among many resources of type MENU that a program might use. See also resource (definition 2).

Resource Reservation Setup Protocol n. A communications protocol designed to allow for bandwidth on demand. A remote receiver requests that a certain amount of bandwidth be reserved by the server for a data stream; the server sends back a message (similar to the RSVP sent in reply to an invitation) indicating whether or not the request has been granted. Acronym: RSVP (Resourceeeration Setuprotocol).

resource sharing n. The act of making files, printers, and other network resources available for use by others.

resource type n. One of numerous classes of structural and procedural resources in the Macintosh operating system, such as code, fonts, windows, dialog boxes, templates, icons, patterns, strings, drivers, cursors, color tables, and menus. Resource types have characteristic identifying labels, such as CODE for blocks of program instructions, FONT for fonts, and CURS for mouse cursors. See also resource (definition 2), resource fork.

response time n. 1. The time, often an average, that elapses between the issuance of a request and the provision of the data requested (or notification of inability to provide it). 2. The time required for a memory circuit or storage device to furnish data requested by the central processing unit (CPU).

restart vb. See reboot.

restore¹ n. The act of restoring a file or files. See also backup, recovery.

restore² vb. To copy files from a backup storage device to their normal location, especially if the files are being copied to replace files that were accidentally lost or deleted.

restricted function n. A function or an operation that can be executed only under certain circumstances, especially when the central processing unit (CPU) is in privileged mode. See also privileged mode.

Restructured Extended Executor n. See REXX.

retrace n. The path followed by the electron beam in a raster-scan computer monitor as it returns either from the right to the left edge of the screen or from the bottom to the top of the screen. The retrace positions the electron beam for its next sweep across or down the screen; during this interval, the beam is briefly turned off to avoid drawing an unwanted line on the screen. Retracing occurs many times each second and uses tightly synchronized signals to ensure that the electron beam is turned off and on during the retrace. See also blanking, horizontal retrace, raster display, vertical retrace.

retrieve vb. To obtain a specific requested item or set of data by locating it and returning it to a program or to the user. Computers can retrieve information from any source of storage disks, tapes, or memory.

retro virus n. A type of virus that avoids detection by attacking or disabling antivirus programs. Also called: anti-anti-virus.

return vb. 1. To transfer control of the system from a called routine or program back to the calling routine or program. Some languages support an explicit return or exit statement; others allow return only at the end (last statement) of the called routine or program. See also call(definition 2). 2. To report the outcome of a called routine to the calling routine or program.

return code n. In programming, a code that is used to report the outcome of a procedure or to influence subsequent events when a routine or process terminates (returns) and passes control of the system to another routine. Return codes can, for example, indicate whether an operation was successful or not and can thus be used to determine what is to be done next.

return from the dead vb. To regain access to the Internet after having been disconnected.

Return key n. A key on a keyboard that is used to terminate input of a field or record or to execute the default action of a dialog box. On IBM PCs and compatibles, this key is called ENTER. The corresponding key on a typewriter causes the carriage holding the paper to return to the starting position to begin a new line; hence the name. See also Enter key.

return to zero n. A method of recording on magnetic media in which the reference condition, or neutral state, is the absence of magnetization. Abbreviation: RZ. Compare nonreturn to zero.

reusability n. The ability of code or a design to be usable again in another application or system.

Reverse Address Resolution Protocol n. See RARP.

Reverse ARP n. See RARP.

reverse byte ordering n. See little endian.

reverse engineering n. A method of analyzing a product in which the finished item is studied to determine its makeup or component parts for example, studying a completed ROM chip to determine its programming or studying a new computer system to learn about its design. For computer software, reverse engineering typically involves decompilation of a substantial portion of the object code and studying the resulting decompiled code.

reverse path forwarding n. A technique that makes routing decisions through a TCP/IP network by using the source address of a datagram rather than the destination address. Reverse path forwarding is used in broadcast and multicast applications because it reduces redundant transmissions to multiple recipients. Acronym: RPF. See also datagram, TCP/IP.

reverse Polish notation n. See postfix notation.

reverse video n. The reversal of light and dark in the display of selected characters on a video screen. For example, if text is normally displayed as white characters on a black background, reverse video presents text as black letters on a white background. Programmers commonly use reverse video as a means of highlighting text or special items (such as menu choices or the cursor) on the screen.

revert vb. To return to the last saved version of a document. Choosing this command tells the application to abandon all changes made in a document since the last time it was saved.

Revisable-Form-Text DCA n. A standard within Document Content Architecture (DCA) for storing documents in such a way that the formatting can be changed by the receiver. A related standard is Final-Form-Text DCA. Acronym: RFTDCA. See also DCA. Compare Final-Form-Text DCA.

revision mark n. A mark that shows where a deletion, insertion, or other editing change has been made in a document.

rewind vb. To wind a magnetic tape spool or cassette to its beginning.

rewritable digital video disc n. Technology for recording data on disks that have the same storage capacity as digital video discs (DVDs) but can be rewritten like the compact disc rewritable (CD-RW) devices. See also digital video disc, PD-CD drive.

rewrite vb. To write again, especially in situations where information is not permanently recorded, such as RAM or a video display. Also called: refresh, regenerate. See also dynamic RAM.

REXX n. Acronym for Restructured Extended Executor. A structured programming language used on IBM mainframes and with OS/2 Version 2.0. REXX programs invoke application programs and operating system commands.

RF n. See radio frequency.

RFC n. Acronym for Request for Comments. A document in which a standard, a protocol, or other information pertaining to the operation of the Internet is published. The RFC is actually issued, under the control of the IAB, after discussion and serves as the standard. RFCs can be obtained from sources such as InterNIC.

RFD n. See Request for Discussion.

RFI n. Acronym for radio frequency interference. Noise introduced into an electronic circuit, such as a radio or television, by electromagnetic radiation produced by another circuit, such as a computer.

RF shielding n. A structure, generally sheet metal or metallic foil, designed to prevent the passage of radio frequency (RF) electromagnetic radiation. RF shielding is intended to keep RF radiation either inside a device or out of a device. Without proper RF shielding, devices that use or emit RF radiation can interfere with each other; for example, running an electric mixer might cause interference on a television. Computers generate RF radiation and, to meet Federal Communications Commission (FCC) standards, must be properly shielded to prevent this RF radiation from leaking out. The metal case of a PC provides most of the needed RF shielding. Devices meeting FCC type A standards are suitable for business use. Devices meeting the more stringent FCC type B standards are suitable for home use. See also radio frequency, RFI.

RFTDCA n. See Revisable-Form-Text DCA.

RGB n. Acronym for red-green-blue. A model for describing colors that are produced by emitting light, as on a video monitor, rather than by absorbing it, as with ink on paper. The three kinds of cone cells in the eye respond to red, green, and blue light, respectively, so percentages of these additive primary colors can be mixed to get the appearance of any desired color. Adding no color produces black; adding 100 percent of all three colors results in white. See also CMYK, RGB monitor. Compare CMY.

RGB display n. See RGB monitor.

RGB monitor n. A color monitor that receives its signals for red, green, and blue levels over separate lines. An RGB monitor generally produces sharper and cleaner images than those produced by a composite monitor, which receives levels for all three colors over a single line. See also RGB. Compare composite video display.

ribbon cable n. A flat cable containing up to 100 parallel wires for data and control lines. For example, ribbon cables are used inside a computer s case to connect the disk drives to their controllers.

ribbon cartridge n. A disposable module containing an inked fabric ribbon or a carbon-coated plastic film ribbon. Many impact printers use ribbon cartridges to make ribbon changing easier and cleaner.

Rich Text Format n. An adaptation of DCA (Document Content Architecture) that is used for transferring formatted text documents between applications, even those applications running on different platforms, such as between IBM and compatibles and Macintoshes. Acronym: RTF. See also DCA.

RIFF n. Acronym for Resource Interchange File Format. Developed jointly by IBM and Microsoft, RIFF is a broad-based specification designed to be used in defining standard formats for different types of multimedia files. A tagged-file specification, RIFF relies on headers that tag individual data elements in a file, identifying them by type and length. Because tags identify data elements, the RIFF specification can be extended to cover new types of elements while continuing to support older applications, which can simply ignore new, unrecognized elements they encounter in a file. See also AVI, MCI.

right click vb. To make a selection using the button on the right side of a mouse or other pointing device. Doing so in Windows 9x and Windows NT 4.0 and later typically brings up a pop-up menu with options applicable to the object over which the cursor is positioned. See also mouse, pointing device.

right click disabler n. A program or script that prevents a user from employing any functions controlled by clicking the right mouse button. A right click disabler script may be run when a user visits a Web site to control the user s actions and options.

right justification n. In typesetting, word processing, and desktop publishing, the process of aligning text evenly along the right margins of a column or page. The left edge of the text is ragged. See also justify (definition 1), rag. Compare full justification, left justification.

right-justify vb. To align lines of text and other display elements so that the right edges form a smooth line. See also align (definition 1), rag. Compare left-justify.

rigid disk n. See hard disk.

RIMM n. A plug-in module jointly developed by Rambus and Intel for the high-bandwidth computer memory known as Direct RDRAM. A RIMM is comparable to a DIMM in size and shape, but the two are not pin-compatible. See also DIMM, RDRAM.

ring network n. A LAN (local area network) in which devices (nodes) are connected in a closed loop, or ring. Messages in a ring network pass around the ring from node to node in one direction. When a node receives a message, it examines the destination address attached to the message. If the address is the same as the node s, the node accepts the message; otherwise, it regenerates the signal and passes the message along to the next node in the ring. Such regeneration allows a ring network to cover larger distances than star and bus networks. The ring can also be designed to bypass any malfunctioning or failed node. Because of the closed loop, however, adding new nodes can be difficult. See the illustration. Also called: ring topology. See also token passing, token ring network. Compare bus network, star network.

Ring network.

ring topology n. See ring network.

rip vb. To convert audio data from a compact disc into a WAV file or other digital format, typically in preparation for further encoding as an MP3 file. See also MP3.

RIP n. 1. Acronym for Routing Information Protocol. An Internet protocol, defined in RFC 1058, that defines the exchange of routing table information. Through RIP, each router on a network sends its routing table to its nearest neighbor every 30 seconds. Under RIP, routing is determined by the number of hops between source and destination. RIP is an interior gateway protocol (a protocol used by gateways for exchanging routing information). Because it is not the most efficient of routing protocols, it is being replaced by the more efficient Open Shortest Path First (OSPF) protocol. See also Bellman-Ford distance-vector routing algorithm, communications protocol, interior gateway protocol, OSPF. 2. See raster image processor.

RIPE n. Acronym for Reseaux IP Europ ens. A voluntary organization of ISPs (Internet service providers) dedicated to the goal of a smoothly functioning, pan-European Internet network. Most of the work performed by RIPE is handled by discrete working groups that deal with issues such as management of the RIPE database and technical networking questions. RIPE also provides services that include registering domain names within top-level Internet domains and assigning IP (Internet Protocol) addresses. Member organizations of RIPE are supported by the RIPE NCC (Network Coordination Centre), based in Amsterdam, The Netherlands. See also American Registry for Internet Numbers.

ripper n. Digital audio technology that converts audio data from a compact disc into a WAV file or other digital format. An encoder then converts this file into a file (typically an MP3 file) that can be played back by software known as a player. See also encoder, MP3.

RIPX n. A protocol used by routers to exchange information between routers on an IPX network and by hosts to determine the best routers to use when forwarding IPX traffic to a remote IPX network. Also called: RIP for IPX. See also communications protocol, IPX, NWLink, router.

RIS n. See Remote Installation Services.

RISC n. Acronym for Reduced Instruction Set Computing. A microprocessor design that focuses on rapid and efficient processing of a relatively small set of simple instructions that comprises most of the instructions a computer decodes and executes. RISC architecture optimizes each of these instructions so that it can be carried out very rapidly usually within a single clock cycle. RISC chips thus execute simple instructions more quickly than general-purpose CISC (Complex Instruction Set Computing) microprocessors, which are designed to handle a much wider array of instructions. They are, however, slower than CISC chips at executing complex instructions, which must be broken down into many machine instructions that RISC microprocessors can perform. Families of RISC chips include Sun Microsystems SPARC, Motorola s 88000, Intel s i860, and the PowerPC developed by Apple, IBM, and Motorola. See also architecture, SPARC. Compare CISC.

RISC86 n. A hybrid microprocessor technology in which CISC (Complex Instruction Set Computing) instructions are translated into RISC (Reduced Instruction Set Computing) instructions for processing. RISC86 is designed to support the 80x86 CISC architecture while providing the speed gains characteristic of RISC technology. RISC86 was developed by NexGen and is implemented in AMD s K6 microprocessor.

Rivest-Shamir-Adleman encryption n. See RSA encryption.

RJ-11 connector n. See phone connector.

RJ-11 jack n. See phone connector.

RJ-45 connector n. Short for Registered Jack-45 connector. An eight-wire connector used to attach devices to cables. The eight wires are encased in a plastic sheath and color-coded to match corresponding slots in jacks. RJ-45 jacks are used to connect computers to LANs (local area networks) and to link ISDN (Integrated Services Digital Network) devices to NT-1 (Network Terminator 1) devices. Also called: RJ-45 jack. See also ISDN.

RJ-45 jack n. See RJ-45 connector.

RLE n. Short for Run Length Encoding. A data compression format in which only the first of a series of consecutive identical pixels is saved, along with the total number of pixels in the run. When the file is decompressed, each representative pixel is copied the correct number of times to replace those not saved. RLE compression works best with simple black and white or flat color graphics.

RLIN n. See Research Libraries Information Network.

RLL encoding n. See run-length limited encoding.

rlogin¹ n. 1. A protocol used to log in to a networked computer in which the local system automatically supplies the user s login name. See also communications protocol, logon. Compare telnet. 2. A UNIX command in BSD UNIX that enables a user to log in to a remote computer on a network using the rlogin protocol. See also BSD UNIX.

rlogin² vb. To connect to a networked computer using the rlogin protocol.

RLSD n. Acronym for Received Line Signal Detect. See DCD.

RMI-IIOP n. Acronym for Remote Method Invocation over Internet Inter-ORB Protocol. A subsystem of the Java 2 Platform, Enterprise Edition (J2EE). It provides the ability to write CORBA applications for the Java platform without learning the CORBA Interface Definition Language (IDL). RMI-IIOP includes the full functionality of a CORBA Object Request Broker and allows the programming of CORBA servers and applications via the RMI application programming interface (API). RMI-IIOP is useful for developers using Enterprise Java Beans (EJBs), since the remote object model for an EJB is RMI-based. Also called: RMI over IIOP. See also CORBA, Enterprise JavaBeans, J2EE.

RMM n. See real-mode mapper.

RMON n. Acronym for remote monitoring or remote network monitoring. A protocol that enables network information to be monitored and analyzed at a central site. The nine management information bases (MIBs) defined by RMON provide statistics about network traffic. See also MIB. Compare SNMP.

roaming user profile n. A server-based user profile that is downloaded to the local computer when a user logs on; it is updated both locally and on the server when the user logs off. A roaming user profile is available from the server when logging on to a workstation or server computer. When logging on, the user can use the local user profile if it is more current than the copy on the server. See also local user profile, mandatory user profile, user profile.

robopost vb. To post articles to newsgroups automatically, usually by means of a bot. See also bot (definition 3), newsgroup, post.

robot n. 1. A machine that can sense and react to input and cause changes in its surroundings with some degree of intelligence, ideally without human supervision. Although robots are often designed to mimic human movements in carrying out their work, they are seldom humanlike in appearance. Robots are commonly used in manufacturing products such as automobiles and computers. See also robotics. 2. See bot, spider.

robotics n. The branch of engineering devoted to the creation and training of robots. Roboticists work within a wide range of fields, such as mechanical and electronic engineering, cybernetics, bionics, and artificial intelligence, all toward the end of endowing their creations with as much sensory awareness, physical dexterity, independence, and flexibility as possible. See also artificial intelligence, bionics, cybernetics.

robust adj. Able to function or to continue functioning well in unexpected situations.

ROFL n. Acronym for rolling on the floor, laughing. An expression, used mostly in newsgroups and online conferences, to indicate one s appreciation of a joke or other humorous circumstance. Also called: ROTFL.

role-playing game n. A game that is played on line, such as MUD, in which participants take on the identities of characters who interact with each other. These games often have a fantasy or science fiction setting and a set of rules that all players need to follow. Role-playing games may be similar to adventure games in terms of story line, but also feature management and decision making for the character assumed during the course of the game. Acronym: RPG. See also MUD. Compare adventure game.

rollback n. 1. A return to a previous stable condition, as when the contents of a hard disk are restored from a backup after a destructive hard disk error. 2. The point in an online transaction when all updates to any databases involved in the transaction are reversed.

rollover n. See Year 2000 rollover.

ROM n. 1. Acronym for read-only memory. A semiconductor circuit into which code or data is permanently installed by the manufacturing process. The use of this technology is economically viable only if the chips are produced in large quantities; experimental designs or small volumes are best handled using PROM or EPROM. 2. Acronym for read-only memory. Any semiconductor circuit serving as a memory that contains instructions or data that can be read but not modified (whether placed there by manufacturing or by a programming process, as in PROM and EPROM). See also EEPROM, EPROM, PROM.

roman adj. Having upright rather than slanted characters in a typeface. See also font family. Compare italic.

ROM Basic n. Short for Read-Only Memory Beginner s All-purpose Symbolic Instruction Code. A Basic interpreter stored in ROM (read-only memory) so that the user can start programming after simply turning on the machine, without having to load Basic from a disk or tape. ROM Basic was a feature of many early home computers.

ROM BIOS n. Acronym for read-only memory basic input/output system. See BIOS.

ROM card n. Short for read-only memory card. A plug-in module that contains one or more printer fonts, programs, or games or other information stored in ROM (read-only memory). A typical ROM card is about the size of a credit card and several times thicker. It stores information directly in integrated circuit boards. Also called: font card, game card. See also ROM (definition 1), ROM cartridge.

ROM cartridge n. Short for read-only memory cartridge. A plug-in module that contains one or more printer fonts, programs, games, or other information stored in ROM (read-only memory) chips on a board enclosed in a plastic case with a connector exposed at one end so that it can easily plug into a printer, computer, game system, or other device. For example, a cartridge that plugs into a game system is a ROM cartridge. Also called: game cartridge. See also ROM (definition 1), ROM card.

ROM emulator n. Short for read-only memory emulator. A special circuit containing RAM memory that is connected to a target computer in place of the target computer s ROM chips. A separate computer writes the contents into the RAM, and then the target computer reads the RAM as if it were ROM. ROM emulators are used to debug ROM-resident software without the high cost and delay of manufacturing chips. Even though the use of a ROM emulator is more expensive than programming an EPROM, it is often preferred today because its contents can be changed much more quickly than those of an EPROM. Also called: ROM simulator. See also EEPROM, EPROM, ROM (definition 1).

ROM simulator n. See ROM emulator.

root n. The main or uppermost level in a hierarchically organized set of information. The root is the point from which subsets branch in a logical sequence that moves from a broad focus to narrower perspectives. See also leaf, tree.

root account n. On UNIX systems, the account having control over the operation of a computer. The system administrator uses this account for system maintenance. Also called: superuser. See also system administrator.

root directory n. The point of entry into the directory tree in a disk-based hierarchical directory structure. Branching from this root are various directories and subdirectories, each of which can contain one or more files and subdirectories of its own. For example, in the MS-DOS operating system the root directory is identified by a name consisting of a single backslash character (\). Beneath the root are other directories, which may contain further directories, and so on. See the illustration.

Root directory.

root folder n. The folder on a drive from which all other folders branch. The root folder s name consists of a single backslash character (\). For example, on drive C, this folder would be represented in the file system as C:\.

rootless n. A mode in which an application belonging to a different user interface can run on top of a computer s underlying operating system without affecting that desktop or applications it may be running. For example, programs belonging to a rootless version of the X Window System can be run on a Mac OS X computer without disturbing the Aqua desktop. See also Mac OS X, X Window System.

root name n. In MS-DOS and Windows, the first part of a filename. In MS-DOS and earlier versions of Windows, the maximum length of the root name was eight characters; in Windows NT and later versions of Windows, the root name may be as long as 255 characters. See also 8.3, extension (definition 1), filename, long filenames.

root name server n. See root server.

root server n. A computer with the ability to locate DNS servers containing information about top-level Internet domains, such as com, org, uk, it, jp, and other country domains, in the Internet s Domain Name System (DNS) hierarchy. Beginning with the root server and continuing through referrals to name servers at lower levels of the hierarchy, the DNS is able to match a friendly Internet address, such as microsoft.com, with its numerical counterpart, the IP address. Root servers thus contain the data needed for referrals to name servers at the highest level of the hierarchy. There are 13 root servers in the world, located in the United States, the United Kingdom, Sweden, and Japan. Also called: root name server. See also DNS (definition 1), DNS server, top-level domain.

root web n. The default, top-level web provided by a Web server. To access the root web, you supply the URL of the server without specifying a page name or subweb.

ROT13 encryption n. A simple encryption method in which each letter is replaced with the letter of the alphabet 13 letters after the original letter, so that A is replaced by N, and so forth; N, in turn, is replaced by A, and Z is replaced by M. ROT13 encryption is not used to protect messages against unauthorized readers; rather, it is used in newsgroups to encode messages that a user may not want to read, such as sexual jokes or spoilers. Some newsreaders can automatically perform ROT13 encryption and decryption at the touch of a key.

rotary dialing n. The signaling system used in telephones with rotary dials, in which each digit is associated with a set number of pulses. During dialing, these pulses, which are audible as series of clicks, momentarily turn the current in the telephone wires on and off. Also called: pulse dialing. Compare touch tone dialing.

rotate vb. 1. To turn a model or other graphical image so that it is viewed at a different angle. 2. To move bits in a register to the left or to the right. The bit that moves out of the end position rotates to the newly vacated position at the opposite end of the register. Compare shift.

rotational delay n. The time required for a desired disk sector to rotate to the read/write head. Also called: rotational latency.

rotational latency n. See rotational delay.

RO terminal n. Short for read-only terminal. A terminal that can receive data but cannot send data. Nearly all printers can be classified as RO terminals.

ROTFL n. See ROFL.

round vb. To shorten the fractional part of a number, increasing the last remaining (rightmost) digit or not, according to whether the deleted portion was over or under five. For example, 0.3333 rounded to two decimal places is 0.33, and 0.6666 is 0.67. Computer programs often round numbers, sometimes causing confusion when the resulting values do not add up correctly. Percentages in a spreadsheet can thus total 99 percent or 101 percent because of rounding.

round robin n. A sequential, cyclical allocation of resources to more than one process or device.

roundtripping n. The process of converting files from one format to another for viewing or editing and then converting the files back to the original format again. In some cases, roundtripping can involve repeated conversions of the file from one format to another and back. Frequent roundtripping may be a concern because each conversion has the potential to introduce unwanted changes to the file.

routable protocol n. A communications protocol that is used to route data from one network to another by means of a network address and a device address. TCP/IP is an example of a routable protocol.

router n. An intermediary device on a communications network that expedites message delivery. On a single network linking many computers through a mesh of possible connections, a router receives transmitted messages and forwards them to their correct destinations over the most efficient available route. On an interconnected set of LANs (local area networks) including those based on differing architectures and protocols using the same communications protocols, a router serves the somewhat different function of acting as a link between LANs, enabling messages to be sent from one to another. See also bridge, gateway.

routine n. Any section of code that can be invoked (executed) within a program. A routine usually has a name (identifier) associated with it and is executed by referencing that name. Related terms (which may or may not be exact synonyms, depending on the context) are function, procedure, and subroutine. See also function (definition 3), procedure, subroutine.

routing n. The process of forwarding packets between networks from source to destination. See also dynamic routing, static routing.

Routing Information Protocol n. See RIP (definition 1).

routing table n. In data communications, a table of information that provides network hardware (bridges and routers) with the directions needed to forward packets of data to locations on other networks. The information contained in a routing table differs according to whether it is used by a bridge or a router. A bridge relies on both the source (originating) and destination addresses to determine where and how to forward a packet. A router relies on the destination address and on information in the table that gives the possible routes in hops or in number of jumps between itself, intervening routers, and the destination. Routing tables are updated frequently as new or more current information becomes available. See also bridge, hop, internetwork, router.

row n. A series of items arranged horizontally within some type of framework for example, a continuous series of cells running from left to right in a spreadsheet; a horizontal line of pixels on a video screen; or a set of data values aligned horizontally in a table. Compare column.

royalty-free n. The absence of a requirement to pay the original owner of music, images, software, or other content for the right to use, edit, or distribute their content.

RPC n. See remote procedure call.

RPF n. See reverse path forwarding.

RPG n. 1. See role-playing game. 2. Acronym for Report Program Generator. An IBM programming platform introduced in 1964. The earliest version of RPG was not a language but a program generator intended to aid in producing business reports. Versions of RPG have been developed for various platforms, including IBM s AS/400 server, UNIX, MS-DOS, and Windows.

RPN n. Acronym for reverse Polish notation. See postfix notation.

RPROM n. Short for reprogrammable PROM. See EPROM.

RS-232-C standard n. An accepted industry standard for serial communications connections. Adopted by the Electrical Industries Association, this Recommended Standard (RS) defines the specific lines and signal characteristics used by serial communications controllers to standardize the transmission of serial data between devices. The letter C denotes that the current version of the standard is the third in a series. See also CTS, DSR, DTR, RTS, RXD, TXD.

RS-422/423/449 n. Standards for serial communications with transmission distances over 50 feet. RS-449 incorporates RS-422 and RS-423. Macintosh serial ports are RS-422 ports. See also RS-232-C standard.

RSA n. A widely used public/private key algorithm. It is the default cryptographic service provider (CSP) for Microsoft Windows. It was patented by RSA Data Security, Inc., in 1977. See also cryptographic service provider.

RSAC n. See Recreational Software Advisory Council.

RSA encryption n. Short for Rivest-Shamir-Adleman encryption. The public key encryption algorithm, introduced by Ronald Rivest, Adi Shamir, and Leonard Adleman in 1978, on which the PGP (Pretty Good Privacy) encryption program is based. See also PGP, public key encryption.

RSI n. See repetitive strain injury.

RSN adv. See Real Soon Now.

R-squared value n. An indicator from 0 to 1 that reveals how closely the estimated values for the trendline correspond to your actual data. A trendline is most reliable when its R-squared value is at or near 1. Also called: the coefficient of determination.

RSVP n. See Resource Reservation Setup Protocol.

RTC n. See clock (definition 2).

RTCP n. See Real-Time Control Protocol.

RTF n. See Rich Text Format.

RTFM n. Acronym for read the flaming (or friendly) manual. A common answer to a question in an Internet newsgroup or product support conference that is adequately explained in the instruction manual. (The F in this acronym is not necessarily assumed to represent polite language.) Also called: RTM.

RTM n. Acronym for read the manual. See RTFM.

RTOS n. See real-time operating system.

RTP n. See Real-Time Protocol.

RTS n. Acronym for Request to Send. A signal sent, as from a computer to its modem, to request permission to transmit; the signal is often used in serial communications. RTS is a hardware signal sent over pin 4 in RS-232-C connections. See also RS-232-C standard. Compare CTS.

RTSP n. See Real-Time Streaming Protocol.

rubber banding n. In computer graphics, changing the shape of an object made up of connected lines by grabbing a point on an anchored line and pulling it to the new location.

Ruby n. An interpreted open source scripting language for object-oriented programming. Its simple syntax is partially based on the syntax of Eiffel and Ada. Considered to be similar to Perl, it has many features to process text files and perform system management tasks.

rudder control n. A device, consisting of a pair of pedals, that enables a user to input rudder movements in a flight simulation program. The rudder control is used along with a joystick (which controls the simulated ailerons and elevators) and possibly a throttle control.

rule n. 1. A line printed above, below, or to the side of some element, either to set that item off from the remainder of the page or to improve the look of the page. Footnotes, for example, often appear below a short rule that sets them off from the main text on the page. The thickness of a rule is typically measured in points. (A point is approximately ¹/₇₂ inch.) See also point¹ (definition 1). 2. In expert systems, a statement that can be used to verify premises and to enable a conclusion to be drawn. See also expert system.

rule-based system n. See expert system, production system.

ruler n. In some application programs, such as word processors, an on-screen scale marked off in inches or other units of measure and used to show line widths, tab settings, paragraph indents, and so on. In programs in which the ruler is live, the on-screen ruler can be used with the mouse or with the keyboard to set, adjust, or remove tab stops and other settings.

run vb. To execute a program.

run around vb. In page composition, to position text so that it flows around an illustration or other display.

run-length encoding n. A simple compression method that replaces a contiguous series (run) of identical values in a data stream with a pair of values that represent the length of the series and the value itself. For example, a data stream that contains 57 consecutive entries with the value 10 could replace them all with the much shorter pair of values 57, 10. Acronym: RLE.

Run Length Encoding n. See RLE.

run-length limited encoding n. A fast and highly efficient method of storing data on a disk (usually a hard disk) in which patterns in the bits representing information are translated into codes rather than being stored literally bit by bit and character by character. In RLL encoding, changes in magnetic flux are based on the number of zeros that occur in sequence. This scheme allows data to be stored with fewer changes in magnetic flux than would otherwise be needed for the number of data bits involved and results in considerably higher storage capacity than is possible with older technologies, such as frequency modulation (FM) and modified frequency modulation (MFM) encoding. Abbreviation: RLL encoding. Compare frequency modulation encoding, modified frequency modulation encoding.

running foot n. One or more lines of text in the bottom margin area of a page, composed of one or more elements such as the page number, the name of the chapter, and the date. Also called: footer.

running head n. One or more lines of text in the top margin area of a page, composed of one or more elements such as the page number, the name of the chapter, and the date. Also called: header.

RUNOFF n. A very early text editor/text formatting program, developed by J. E. Saltzer at M.I.T. for the CTSS (Compatible Time-Sharing System) operating system in the mid-1960s, in order to format his Ph.D. thesis. RUNOFF was the ancestor of many other text processors, including TeX, and the UNIX programs roff, nroff, and troff.

run-time adj. Occurring after a program has begun to be executed, such as evaluation of variable expressions and dynamic allocation of memory.

run time n. 1. The time period during which a program is running. See also compile time, dynamic allocation, dynamic binding, link time. 2. The amount of time needed to execute a given program.

runtime n. See common language runtime.

run-time binding n. Assignment of a meaning to an identifier (such as a variable) in a program at the time the program is executed rather than at the time the program is compiled. Compare compile-time binding, link-time binding.

run-time error n. A software error that occurs while a program is being executed, as detected by a compiler or other supervisory program.

run-time library n. A file containing one or more prewritten routines to perform specific, commonly used functions. A run-time library, used primarily in high-level languages such as C, saves the programmer from having to rewrite those routines.

run-time version n. 1. Program code that is ready to be executed. Generally, this code has been compiled and can operate without error under most user command sequences and over most ranges of data sets. 2. A special release that provides the computer user with some, but not all, of the capabilities available in the full-fledged software package.

R/W adj. See read/write.

RXD n. Short for Receive (rx) Data. A line used to carry received serial data from one device to another, such as from a modem to a computer. Pin 3 is the RXD line in RS-232-C connections. See also RS-232-C standard. Compare TXD.

RZ n. See return to zero.