A/B switch box

n. An enclosure that contains a two-position selector switch. When a user selects a switch setting, the signal passing through the box may be directed either from a single input to one of two outputs, or from the selected input to a single output. See also switch (definition 1).

Absolute URL

n. Short for absolute Uniform Resource Locator. The full Internet address of a page or other World Wide Web resource. The absolute URL includes a protocol, such as "http," the network server name and optional path, and the file name. For example, http://example.microsoft.com/ is an absolute URL. See also URL. Compare relative URL.

AC adapter

n. An external power supply that converts from a 110 VAC or 220 VAC domestic electric supply ("house current" or "main power") to low-voltage DC, which is required to operate solid-state electronic equipment (such as a laptop computer) that does not include an internal power supply.

accelerator card

n. A printed circuit board that replaces or augments the computer's main microprocessor, resulting in faster performance. Also called accelerator board. See also expansion board, graphics accelerator.

access¹

n. 1. The act of reading data from or writing data to memory. 2. Connection to the Internet or other network or system.

ACCESS.bus

n. A bidirectional bus for connecting peripherals to a PC. The ACCESS.bus can connect up to 125 low-speed peripherals, such as printers, modems, mice, and keyboards, to the system through a single, general-purpose port. Peripherals that support the ACCESS.bus provide a connector or port connection that is similar to a phone-jack connector and are daisy-chained together. However, the PC communicates directly with each peripheral and vice versa. Connecting an ACCESS.bus device (for example, a printer) to a system results in the system automatically identifying and configuring it for optimum performance. Peripherals can be connected while the computer is running (hot plugging) and are automatically assigned a unique address (auto-addressing). Developed by DEC, the ACCESS.bus competes with Intel's USB. See also bidirectional, bus, daisy chain, hot plugging, input/output port, peripheral. Compare USB.

access control

n. The mechanisms for limiting access to certain items of information or to certain controls based on users' identity and their membership in various predefined groups. Access control is typically used by system administrators for controlling user access to network resources, such as servers, directories, and files. See also access privileges, system administrator.

access control list

n. A list associated with a file that contains information about which users or groups have permission to access or modify the file. Acronym: ACL.

accessibility

n. The quality of a system incorporating hardware or software that makes it usable by people with one or more physical disabilities, such as restricted mobility, blindness, or deafness.

access number

n. The telephone number used by a subscriber to gain access to an online service.

access privileges

n. The type of operations permitted a given user for a certain system resource on a network or a file server. A variety of operations, such as the ability to access a server, view the contents of a directory, open or transfer files, and create, modify, or delete files or directories, can be allowed or disallowed by the system administrator. Assigning access privileges to users helps the system administrator to maintain security on the system, as well as the privacy of confidential information, and to allocate system resources, such as disk space. See also file protection, file server, permission, system administrator, write access.

access rights

n. The permission to view, enter, or modify a file, folder, or system.

access time

n. 1. The amount of time it takes for data to be delivered from memory to the processor after the address for the data has been selected. 2. The time needed for a read/write head in a disk drive to locate a track on a disk. Access time is usually measured in milliseconds and is used as a performance measure for hard disks and CD-ROM drives. See also read/write head, seek time, settling time, wait state. Compare cycle time.

account

n. 1. A record-keeping arrangement used by the vendor of an online service to identify a subscriber and to maintain a record of customer usage for billing purposes. 2. A record kept by local area networks and multi-user operating systems for each authorized user of the system for identification, administration, and security purposes.

account policy

n. 1. On local area networks and multiuser operating systems, a set of rules governing whether a new user is allowed access to the system and whether an existing user's rights are expanded to include additional system resources. An account policy also generally states the rules with which the user must comply while using the system in order to maintain access privileges. 2. In Windows NT, a set of rules controlling the use of passwords by the user accounts of a domain or of an individual computer. See also domain (definition 2).

ACK

n. Short for acknowledgment. A message sent by the receiving unit to the sending station or computer indicating either that the unit is ready to receive transmission or that a transmission was received without error. Compare NAK.

ACL

n. Short for Access Control List.

acronym

n. A word derived from the first letters or groups of letters in a multiword descriptive noun or other expression, often serving as a mnemonic, such as RAM (random access memory) and AUTOEXEC.BAT (automatically executed batch file).

active cell

n. The highlighted cell on a spreadsheet display that is the current focus of operation. Also called current cell, selected cell. See also range.

active content

n. Material on a Web page that changes on the screen with time or in response to user action. Active content is implemented through ActiveX controls. See also ActiveX controls.

Active Framework for Data Warehousing

n. A data warehousing solution developed by Microsoft and Texas Instruments that represents Microsoft's standard for managing meta data. See also ActiveX, meta data. Acronym: AFDW.

active hub

n. The central computer that regenerates and retransmits all signals in an active star network. See also active star.

active-matrix display

n. A liquid crystal display (LCD) made from a large array of liquid crystal cells using active-matrix technology. The active matrix is a method of addressing an array of simple LC cells--one cell per pixel. In its simplest form there is one thin-film transistor (TFT) for each cell. Active-matrix displays are used most frequently in laptop and notebook computers because of their thin width and are notable for their high-quality color displays, which are viewable from all angles, unlike passive-matrix displays. Also called TFT, TFT display, TFT LCD. See also liquid crystal display, TFT. Compare passive-matrix display.

ActiveMovie

n. Cross-platform digital video technology developed by Microsoft for online and desktop multimedia.

Active Server Page

n. A method for creating programs that run on a web server, first available on the Microsoft Internet Information Server (IIS) 3.0. ASP pages contain a mixture of HTML code and scripting code. ASP uses the ActiveX scripting engine to support both VBScript and JScript code. You can use only one type of script per page. The script is delineated either by inline server script tags, , or by the HTML tags. When a user requests data from a URL with an ASP file extension, the ActiveX server engine reads through the file from top to bottom, sending the HTML back to the browser and executing the script. See also IIS and ActiveX.

active window

n. In an environment capable of displaying multiple on-screen windows, the window containing the display or document that will be affected by current cursor movements, commands, and text entry. See also graphical user interface. Compare inactive window.

ActiveX

n. A set of technologies that enables software components to interact with one another in a networked environment, regardless of the language in which the components were created. ActiveX, which was developed as a proposed standard by Microsoft in the mid 1990s and is currently administered by the Open Group, is built on Microsoft's Component Object Model (COM). Currently, ActiveX is used primarily to develop interactive content for the World Wide Web, although it can be used in desktop applications and other programs. ActiveX controls can be embedded in Web pages to produce animation and other multimedia effects, interactive objects, and sophisticated applications. See also ActiveX controls, COM. Compare applet, plug-in (definition 2).

ActiveX controls

n. Reusable software components that incorporate ActiveX technology. These components can be used to add specialized functionality, such as animation or pop-up menus, to Web pages, desktop applications, and software development tools. ActiveX controls can be written in a variety of programming languages, including C, C++, Visual Basic, and Java. See also ActiveX. Compare helper program.

adapter

or adaptor n. A printed circuit board that enables a personal computer to use a peripheral device, such as a CD-ROM drive, modem, or joystick, for which it does not already have the necessary connections, ports, or circuit boards. Commonly, a single adapter card can have more than one adapter on it. Also called interface card. See also controller, expansion board, network adapter, port, video adapter.

adaptive system

n. A system that is capable of altering its behavior based on certain features of its experience or environment. See also expert system.

add-on

n. 1. A hardware device, such as an expansion board or chip, that can be added to a computer to expand its capabilities. Also called add-in. See also open architecture (definition 2). 2. A supplemental program that can extend the capabilities of an application program. See also utility program.

address¹

n. 1. A number specifying a location in memory where data is stored. See also absolute address, address space, physical address, virtual address. 2. A name or token specifying a particular site on the Internet or other network. 3. A code used to specify an e-mail destination.

address²

vb. To reference a particular storage location. See also absolute address, address space, physical address, virtual address.

address book

n. 1. In an e-mail program, a reference section listing e-mail addresses and individuals' names. 2. As a Web page, an informal e-mail or URL phone book.

address decoder

n. An electronic device that converts a numeric address so as to select a memory location on one or more RAM chips.

addressing

n. The process of assigning or referring to an address. In programming, the address is typically a value specifying a memory location. See also address¹.

address mapping table

n. A table used by routers or Domain Name System (DNS) servers to resolve Internet Protocol (IP) addresses from a text entry such as a name. See also DNS server, IP address, router. Acronym: AMT.

address resolution

n. The identification of a computer's hardware address by finding the corresponding match in an address mapping table. See also address mapping table.

address space

n. The total range of memory locations addressable by a computer.

address translation

n. The process of converting one kind of address to another, such as a virtual address to a physical address.

Adobe Type Manager

n. Software from Adobe Systems, Inc. that manages PostScript fonts on a system. See also PostScript. Acronym: ATM.

Advanced Digital Network

n. A dedicated line service capable of transmitting data, video, and other digital signals with exceptional reliability, offered as a premier service by communications companies. Usually Advanced Digital Network refers to speeds at or above 56 kilobits per second (Kbps). See also dedicated line.

Advanced Power Management

n. An application programming interface developed by Microsoft and Intel to monitor and conserve power on a PC-based system, particularly a battery-powered laptop computer, by enabling programs to communicate their power requirements so that the system can route power away from unused hardware components. See also application programming interface. Acronym: APM.

Advanced RISC

n. Short for Advanced reduced instruction set computing. A specification for a RISC microchip architecture and system environment designed by MIPS Computer Systems to provide binary compatibility among software applications. See also RISC.

Advanced RISC Computing Specification

n. The minimum hardware requirements enabling a RISC-based system to comply with the Advanced Computing Environment standard. See also Advanced RISC.

Advanced SCSI Programming Interface

n. An interface specification developed by Adaptec, Inc. for sending commands to SCSI host adapters. The interface provides an abstraction layer that insulates the programmer from considerations of the particular host adapter used. See also adapter, SCSI. Acronym: ASPI.

agent

n. 1. A program that performs a background task for a user and reports to the user when the task is done or some expected event has taken place. 2. A program that searches through archives or other repositories of information on a topic specified by the user. Agents of this sort are used most often on the Internet and are generally dedicated to searching a single type of information repository, such as postings on Usenet groups. Spiders are a type of agent used on the Internet. Also called intelligent agent. See also spider. 3. In client/server applications, a process that mediates between the client and the server. 4. In SNMP (Simple Network Management Protocol), a program that monitors network traffic. See also SNMP.

AIFF

n. The sound format originally used on Apple and Silicon Graphics (SGI) computers. AIFF stores waveform files in an 8-bit monaural format. See also waveform.

AIX

n. Acronym for Advanced Interactive Executive. A version of the UNIX system provided by IBM for its UNIX workstations and its PCs.

alarm

n. A visual or auditory signal from a computer alerting the user to an error or hazardous situation.

alert

n. 1. On the Macintosh and in many graphical user interfaces, an audible or visual alarm that signals an error or represents a warning of some sort. See also alert box. 2. In programming, an asynchronous notification sent by one thread to another. The alert interrupts the recipient thread at defined points in its execution and causes it to execute an asynchronous procedure call. See also asynchronous procedure call, thread (definition 1).

alert box

n. An on-screen box, in a graphical user interface, that is used to deliver a message or warning. Compare dialog box.

algorithm

n. A finite sequence of steps for solving a logical or mathematical problem.

algorithmic language

n. A programming language, such as Ada, Basic, C, or Pascal, that uses algorithms for problem solving.

alias

n. 1. An alternative label for some object, such as a file or data collection. 2. A name used to direct e-mail messages to a person or group of people on a network. 3. A false signal that results from the digitization of an analog audio sample.

aliasing

n. In computer graphics, the jagged appearance of curves or diagonal lines on a display screen, which is caused by low screen resolution.

align

vb. 1. In an application such as a word processor, to position lines of type relative to some point, such as the page margin. The most common types of alignment are shown. k:\compdict\database\8301.doc 2. To adjust some device to position it within specified tolerances, such as the read/write head relative to a track on a disk. 3. In data handling, to store multiple-byte data units so that the respective bytes fall in corresponding locations of memory.

alignment

n. The arrangement of objects in fixed or predetermined positions, rows, or columns. For example, the Macintosh Finder can do automatic alignment of icons in a folder or on the desktop.

allocate

vb. To reserve a resource, such as sufficient memory, for use by a program. Compare deallocate.

allocation

n. In operating systems, the process of reserving memory for use by a program.

alpha²

n. A software product that has been completed and is ready for initial testing in a laboratory. Compare beta.

Alpha

n. Digital Equipment Corporation's (DEC's) internal name for its 64-bit RISC-based microprocessor product introduced in February 1992 as the DECchip 21064. For trademark reasons, DEC has expanded the name to Alpha AXP, used as an adjective to describe the DECchip technology. The term Alpha is sometimes used in literature to describe the DECchip product, in such phrases as "Alpha-based computer." See also DECchip 21064.

Alpha AXP

adj. Of, pertaining to, or characteristic of Digital Equipment Corporation's 64-bit RISC-based microprocessor technology implemented in its DECchip product. The designation AXP is used by DEC in its personal computer products to indicate that a product has a DECchip microprocessor. See also Alpha, DECchip 21064, RISC.

alphabet

n. 1. The set of characters composed of the letters used in a written language. 2. In communications and data processing, the subset of a complete character set, including letters, numerals, punctuation marks, and other common symbols as well as the codes used to represent them. See also ASCII, CCITT, character set, EBCDIC, ISO.

Alpha box

n. A computer built around the DECchip 21064 processor (called Alpha). See also DECchip 21064.

alpha channel

n. The high-order 8 bits of a 32-bit graphics pixel used to manipulate the remaining 24 bits for purposes of coloring or masking.

alphanumeric

adj. Consisting of letters or digits, or both, and sometimes including control characters, space characters, and other special characters. See also ASCII, character set, EBCDIC.

alpha test

n. The process of user testing that is carried out on a piece of alpha software.

AltaVista

n. A World Wide Web search site hosted by Digital Equipment Corporation. AltaVista may be found at URL http://www.altavista.digital.com/.

alternating current

n. Electric current that reverses its direction of flow (polarity) periodically according to a frequency measured in hertz, or cycles per second. Compare direct current. Acronym: AC.

Alt key

n. A key included on PC and other standard keyboards that is used in conjunction with another key to produce some special feature or function and is typically marked with the letters Alt.

alt. newsgroups

n. Internet newsgroups that are part of the alt. ("alternative") hierarchy and have the prefix alt. Unlike the seven Usenet newsgroup hierarchies (comp., misc., news., rec., sci., soc., and talk.) that require formal votes among users in the hierarchy before official newsgroups can be established, anybody can create an alt. newsgroup. Therefore, newsgroups devoted to discussions of obscure or bizarre topics are generally part of the alt. hierarchy.

America Online

n. An online information service, based in Vienna, Virginia, that provides e-mail, news, educational and entertainment services, and computer support by means of a graphical user interface. America Online is one of the largest American Internet access providers. Acronym: AOL.

AMI BIOS

n. A ROM BIOS developed and marketed by American Megatrends, Inc. (AMI), for use in IBM-compatible computers. A popular feature is that its configuration software is stored in the ROM chip along with the BIOS routines, so that the user does not need a separate configuration disk to modify system settings, such as amount of memory installed and number and types of disk drives. See also BIOS, Phoenix BIOS, ROM BIOS.

amplitude

n. A measure of the strength of a signal, such as sound or voltage, determined by the distance from the baseline to the peak of the waveform. See also waveform.

amplitude modulation

n. A method of encoding information in a transmission, such as radio, using a carrier wave of constant frequency but of varying amplitude. Acronym: AM.

AMPS

n. Acronym for Advanced Mobile Phone Service. One of the original cellular phone services, relying on frequency-division multiplexing.

analog

adj. Pertaining to or being a device or signal having the property of continuously varying in strength or quantity, such as voltage or audio. Compare digital (definition 2).

analog channel

n. A communications channel, such as a voice-grade telephone line, carrying signals that vary continuously and can assume any value within a specified range.

analog data

n. Data that is represented by continuous variations in some physical property, such as voltage, frequency, or pressure. Compare digital data transmission.

analog line

n. A communications line, such as a standard telephone line, that carries continuously varying signals.

analog-to-digital converter

n. A device that converts a continuously varying (analog) signal, such as sound or voltage, from a monitoring instrument to binary code for use by a computer. Also called A-D converter. See also modem. Compare digital-to-analog converter. Acronym: ADC.

anchor

n. 1. A format code in a desktop publishing or word processing document that keeps an element in the document, such as a figure or a caption or label associated with the figure, in a certain position in the document. The anchored object is generally attached to another element in the document such as a piece of text (often a paragraph), a graphic, or a particular place in the document. As text and other objects are added to the document, the anchored object moves relative to the object to which it is anchored or remains stationary. 2. A tag in an HTML document that defines a section of text, an icon, or other element as a link to another element in the document or to another document or file. See hyperlink.

angstrom

n. Abbreviated , a unit of measure equal to one 10-billionth (10^-10) of a meter or one 250-millionth of an inch. Light wavelength, for example, is commonly measured in angstroms.

animated cursors

n. A Windows 95 and Windows NT feature that allows a series of frames, one after another, to appear at the mouse pointer location instead of a single image, thus producing a short loop of animation. The animated cursors feature is designated by the .ani suffix.

animated GIF

n. A series of GIF (Graphics Interchange Format) images that are displayed in rapid sequence by some Web browsers, giving an animated effect. See also GIF.

animation

n. The illusion of movement created by using a succession of static images. In computer graphics, the images can all be drawn separately, or starting and ending points can be drawn with the intervening images provided by software. See also 3-D graphic, surface modeling, tween, wire-frame model.

annotation

n. A note or comment attached to some part of a document to provide related information. Some applications support voice annotations or annotations accessible by icons. See also comment.

annoybot

n. A bot on an Internet Relay Chat (IRC) channel or multi-user dungeon (MUD) that interacts with the user in an obnoxious manner. See also bot, IRC, MUD.

anonymous

n. On the Internet, the standard login name used to obtain access to a public FTP file archive. See also anonymous FTP.

anonymous FTP

n. The ability to access a remote computer system on which one does not have an account, via the Internet's File Transfer Protocol (FTP). Users have restricted access rights with anonymous FTP and usually can only copy files to or from a public directory, often named /pub, on the remote system. Users can also typically use FTP commands, such as listing files and directories. When using anonymous FTP, the user accesses the remote computer system with an FTP program and generally uses anonymous or ftp as a logon name. The password is usually the user's e-mail address, although a user can often skip giving a password or give a false e-mail address. In other cases, the password can be the word anonymous. Many FTP sites do not permit anonymous FTP access in order to maintain security. Those that do permit anonymous FTP sometimes restrict users to only downloading files for the same reason. See also FTP¹ (definition 1), logon, /pub.

anonymous post

n. A message in a newsgroup or mailing list that cannot be traced to its originator. Generally this is accomplished by using an anonymous server for newsgroup posts or an anonymous remailer for e-mail. See also anonymous remailer.

anonymous remailer

n. An e-mail server that receives incoming messages, replaces the headers that identify the original sources of the messages, and sends the messages to their ultimate destinations. The purpose of an anonymous remailer is to hide the identities of the senders of the e-mail messages.

anonymous server

n. 1. The software used by an anonymous remailer. See also anonymous remailer. 2. Software that provides anonymous FTP service. See also anonymous FTP. See anonymous remailer.

ANSI

n. Acronym for American National Standards Institute. A voluntary, nonprofit organization of U.S. business and industry groups formed in 1918 for the development of trade and communication standards. ANSI is the American representative of the International Standards Organization and has developed recommendations for the use of programming languages including FORTRAN, C, and COBOL. See also ANSI C, ANSI.SYS, SCSI.

ANSI.SYS

n. An installable device driver for MS-DOS computers that uses ANSI commands (escape sequences) to enhance the user's control of the console. See also ANSI, driver, escape sequence, install.

answer mode

n. A setting that allows a modem to answer an incoming call automatically. It is used in all fax machines. Also called auto answer.

answer-only modem

n. A modem that can receive but not originate calls.

anti-aliasing

n. A software technique for smoothing the jagged appearance of curved or diagonal lines caused by poor resolution on a display screen. Methods of anti-aliasing include surrounding pixels with intermediate shades, and manipulating the size and horizontal alignment of pixels. See also dithering. Compare aliasing.

anti-glare

adj. Pertaining to any measure taken to reduce reflections of external light on a monitor screen. The screen may be coated with a chemical (which may reduce its brightness), covered with a polarizing filter, or simply rotated so that external light is not reflected into the user's eye.

antistatic device

n. A device designed to minimize shocks caused by the buildup of static electricity, which can disrupt computer equipment or cause data loss. An antistatic device may take the form of a floor mat, a wristband with a wire attached to the workstation, a spray, a lotion, or other special-purpose device. See also static, static electricity.

antivirus program

n. A computer program that scans a computer's memory and mass storage to identify, isolate, and eliminate viruses, and that examines incoming files for viruses as the computer receives them.

any key

n. Any random key on a computer keyboard. Some programs prompt the user to "press any key" to continue. It does not matter which key the user presses. There is no key on the keyboard called Any.

append

vb. To place or insert as an attachment by adding data to the end of a file or database or extending a character string. See also file, string. Compare truncate.

Apple Desktop Bus

n. A serial communications pathway built into Apple Macintosh and Apple IIGS computers. Typically a flexible cord, it enables low-speed input devices, such as a keyboard or mouse, to communicate with the computer. The bus functions like a simple local area network that can connect up to 16 devices, including light pens, trackballs, and graphics tablets, to the computer. Although there are only two external ports, more than two devices can be linked in a series called a daisy chain. See also bus, daisy chain, device driver, input/output port, serial communication. Acronym: ADB.

Apple Events

n. A feature added to Mac OS System 7 that enables one application to send a command, such as save or open, to another application. See also Mac OS.

Apple key

n. A key on Apple keyboards labeled with an outline of the Apple logo. On the Apple Extended Keyboard, this key is the same as the Command key, which functions similarly to the Control key on IBM and compatible keyboards. It is generally used in conjunction with a character key as a shortcut to making menu selections or starting a macro.

AppleScript

n. A script language used with Macintosh computers running under the System 7 operating system to execute commands and automate functions. See also script.

AppleShare

n. File server software that works with the Mac OS and allows one Macintosh computer to share files with another on the same network. See also file server, Mac OS.

applet

n. A small piece of code that can be transported over the Internet and executed on the recipient's machine. The term is especially used to refer to such programs as they are embedded in line as objects in HTML documents on the World Wide Web.

AppleTalk

n. An inexpensive local area network developed by Apple that can be used by Apple and non-Apple computers to communicate and share resources such as printers and file servers. Non-Apple computers must be equipped with AppleTalk hardware and suitable software. The network uses a layered set of protocols similar to the ISO/OSI model and transfers information in the form of packets called frames. AppleTalk supports connections to other AppleTalk networks through devices known as bridges, and it supports connections to dissimilar networks through devices called gateways. See also bridge, frame (definition 2), gateway.

application

n. A program designed to assist in the performance of a specific task, such as word processing, accounting, or inventory management. Compare utility.

application-centric

adj. Of, pertaining to, or characteristic of an operating system in which a user invokes an application to open or create documents (such as word processing files or spreadsheets). Command-line interfaces and some graphical user interfaces such as the Windows 3.x Program Manager are application-centric. Compare document-centric.

application developer

n. An individual who designs and analyzes the appearance and operation of an application program.

application development environment

n. An integrated suite of programs for use by software developers. Typical components of application development environments include a compiler, file browsing system, debugger, and text editor for use in creating programs.

application gateway

n. Software running on a machine that is intended to maintain security on a secluded network yet allow certain traffic to go between the private network and the outside world. See also firewall.

application layer

n. The highest layer of standards in the Open Systems Interconnection (OSI) model. The application layer contains signals that perform useful work for the user, such as file transfer or remote access to a computer, as opposed to lower levels, which control the exchange of data between transmitter and receiver. See also ISO/OSI model.

application programming interface

or application program interface n. A set of routines used by an application program to direct the performance of procedures by the computer's operating system. Acronym: API.

application shortcut key

n. A key or combination of keys that when pressed will quickly perform an action within an application that would normally require several user actions, such as menu selections. Also called keyboard shortcut.

Archie

n. An Internet utility for finding files in public archives obtainable by anonymous FTP. The master Archie server at McGill University in Montreal downloads FTP indexes from participating FTP servers and merges them into a master list and sends updated copies of the master list to other Archie servers each day. Archie is a shortened form of archive. See also anonymous FTP, FTP¹ (definition 1). Compare Jughead, Veronica.

Archie server

n. On the Internet, a server that contains Archie indexes to the names and addresses of files in public FTP archives. See also Archie, FTP¹ (definition 1), server (definition 2).

architecture

n. 1. The physical construction or design of a computer system and its components. See also cache, CISC, closed architecture, network architecture, open architecture, pipelining, RISC. 2. The data-handling capacity of a microprocessor. 3. The design of application software incorporating protocols and the means for expansion and interfacing with other programs.

archive¹

n. 1. A tape or disk containing files copied from another storage device and used as backup storage. 2. A compressed file. 3. A file directory on the Internet that is available by File Transfer Protocol (FTP) or an Internet directory established for dissemination of stored files.

archive²

vb. 1. To copy files onto a tape or disk for long-term storage. 2. To compress a file.

archive bit

n. A bit that is associated with a file and is used to indicate whether or not the file has been backed up. See also back up, bit.

archive site

n. A site on the Internet that stores files. The files are usually accessed through one of the following ways: downloaded through anonymous FTP, retrieved through Gopher, or viewed on the World Wide Web. See also anonymous FTP, Gopher.

area chart

n. A graphical presentation, such as of quarterly sales figures, that uses shading or coloring to emphasize the difference between the line representing one set of data points and the line representing a separate but related set of data points.

arithmetic operation

n. Any of the standard calculations performed in arithmetic--addition, subtraction, multiplication, or division. The term is also used in reference to negative numbers and absolute values.

ARP

n. Acronym for Address Resolution Protocol. A TCP/IP protocol for determining the hardware address (or physical address) of a node on a local area network connected to the Internet, when only the IP address (or logical address) is known. An ARP request is sent to the network, and the node that has the IP address responds with its hardware address. Although ARP technically refers only to finding the hardware address, and RARP (for Reversed ARP) refers to the reverse procedure, ARP is commonly used for both senses. See also IP address, TCP/IP.

ARPANET

n. A large wide area network created in the 1960s by the U.S. Department of Defense Advanced Research Projects Agency (ARPA, renamed DARPA in the 1970s) for the free exchange of information between universities and research organizations, although the military also used this network for communications. In the 1980s MILNET, a separate network, was spun off from ARPANET for use by the military. ARPANET was the network from which the Internet evolved. See also Internet, MILNET.

ARP request

n. Short for Address Resolution Protocol request. An ARP packet containing the Internet address of a host computer. The receiving computer responds with or passes along the corresponding Ethernet address. See also ARP, Ethernet, IP address, packet.

arrow key

n. Any of four keys labeled with arrows pointing up, down, left, and right, used to move the cursor vertically or horizontally on the display screen or, in some programs, to extend the highlight.

artificial intelligence

n. The branch of computer science concerned with enabling computers to simulate such aspects of human intelligence as speech recognition, deduction, inference, creative response, the ability to learn from experience, and the ability to make inferences given incomplete information. Two common areas of artificial-intelligence research are expert systems and natural-language processing. See also expert system, natural-language processing. Acronym: AI.

artificial life

n. The study of computer systems that simulate some aspects of the behavior of living organisms. Artificial life includes systems in which programs intended to perform some particular task compete for survival and reproduction based on their performance; the offspring can combine pieces of code and undergo random variations, and the programs so modified compete in turn, until an optimal solution is found.

ascender

n. The portion of a lowercase letter that extends above the main body (x-height) of the letter. See also baseline, x-height. Compare descender.

ascending order

n. The arrangement of a sequence of items from lowest to highest, such as from 1 to 10 or from A to Z. The rules for determining ascending order in a particular application can sometimes be very complicated: capital letters before lowercase letters, extended ASCII characters in ASCII order, and so on.

ascending sort

n. A sort that results in the arrangement of items in ascending order. See also alphanumeric sort, ascending order. Compare descending sort.

ascii

n. In an FTP client program, the command that instructs the FTP server to send or receive files as ASCII text. See also ASCII, FTP client. Compare binary².

ASCII

n. Acronym for American Standard Code for Information Interchange. A coding scheme using 7 or 8 bits that assigns numeric values to up to 256 characters, including letters, numerals, punctuation marks, control characters, and other symbols. ASCII was developed in 1968 to standardize data transmission among disparate hardware and software systems and is built into most minicomputers and all personal computers. See also ASCII file, character, character code, control character, extended ASCII. Compare EBCDIC.

ASCII file

n. A document file in ASCII format, containing characters, spaces, punctuation, carriage returns, and sometimes tabs and an end-of-file marker, but no formatting information. Also called ASCII file, text file, text-only file. See also ASCII, text file. Compare binary file.

ASP

n. Short for Active Server Page.

aspect ratio

n. In computer displays and graphics, the ratio of the width of an image or image area to its height. An aspect ratio of 2:1, for example, indicates that the image is twice as wide as it is high. The aspect ratio is an important factor in maintaining correct proportions when an image is printed, rescaled, or incorporated into another document.

assembler

n. A program that converts assembly language programs, which are understandable by humans, into executable machine language. See also assemble, assembly language, assembly listing, compiler (definition 2), machine code.

assembly language

n. A low-level programming language using abbreviations or mnemonic codes in which each statement corresponds to a single machine instruction. An assembly language is translated to machine language by the assembler and is specific to a given processor. Advantages of using an assembly language include increased execution speed and direct programmer interaction with system hardware. See also assembler, compiler, high-level language, low-level language, machine code.

associate

vb. To inform the operating system that a particular filename extension is linked to a specific application. When a file is opened that has an extension associated with a given application, the operating system automatically starts the application and loads the file.

asterisk

n. 1. The character (*) used in applications and programming languages to signify multiplication. 2. In Windows, MS-DOS, OS/2, and other operating systems, a wildcard character that can be used in place of other characters, as in *.*, which represents any combination of filename and extension. See also question mark, star-dot-star, wildcard character. 3. In the C and C++ programming languages, the character used to dereference a pointer to a class or structure. See also dereference, pointer (definition 1).

asynchronous device

n. A device whose internal operations are not synchronized with the timing of any other part of the system.

asynchronous operation

n. An operation that proceeds independently of any timing mechanism, such as a clock. For example, two modems communicating asynchronously rely upon each sending the other start and stop signals in order to pace the exchange of information. Compare synchronous operation.

asynchronous procedure call

n. A function call that executes separately from an executing program when a set of enabling conditions exist. After the conditions have been met, the operating system's kernel issues a software interrupt and directs the executing program to execute the call. See also function call. Acronym: APC.

asynchronous transmission

n. In modem communication, a form of data transmission in which data is sent intermittently, one character at a time, rather than in a steady stream with characters separated by fixed time intervals. Asynchronous transmission relies on the use of a start bit and stop bit(s), in addition to the bits representing the character (and an optional parity bit), to distinguish separate characters.

ATA

n. Acronym for Advanced Technology Attachment. ANSI group X3T10's official name for the disk drive interface standard commonly known as Integrated Drive Electronics (IDE). Also called AT Attachment.

ATA/IDE hard disk drive

n. IDE (Integrated Drive Electronics--or numerous other interpretations) and ATA (AT Attachment) are one and the same thing: a disk drive implementation designed to integrate the controller onto the drive itself, thereby reducing interface costs and making firmware implementations easier.

ATAPI

n. The interface used by the IBM PC AT system for accessing CD-ROM devices.

AT bus

n. The electric pathway used by IBM AT and compatible computers to connect the motherboard and peripheral devices. The AT bus supports 16 bits of data, whereas the original PC bus supports only 8 bits. Also called expansion bus. See also EISA, ISA, Micro Channel Architecture.

ATDP

n. Acronym for Attention Dial Pulse, a command that initiates pulse (as opposed to touch-tone) dialing in Hayes and Hayes-compatible modems. Compare ATDT.

ATDT

n. Acronym for Attention Dial Tone, a command that initiates touch-tone (as opposed to pulse) dialing in Hayes and Hayes-compatible modems. Compare ATDP.

ATM

n. Acronym for Asynchronous Transfer Mode. A network technology capable of transmitting data, voice, video, and frame relay traffic in real time. Data, including frame relay data, is broken into packets containing 53 bytes each, which are switched between any two nodes in the system at rates ranging from 1.5 Mbps to 622 Mbps. ATM is defined in the broadband ISDN protocol at the levels corresponding to levels 1 and 2 of the ISO/OSI model. It is currently used in local area networks involving workstations and personal computers, but it is expected to be adopted by the telephone companies, which will be able to charge customers for the data they transmit rather than for their connect time. See also broadband, ISDN, ISO/OSI model. See Adobe Type Manager.

ATM Forum

n. Forum created in 1991 and including more than 750 companies related to communications and computing, as well as government agencies and research groups. The forum aims to promote Asynchronous Transfer Mode for data communication. See also ATM (definition 1).

attach

vb. To include an external document as part of an e-mail message, using MIME or some other encoding application. Most modern e-mail clients have the ability to attach documents, as well as to decode attached documents that are received.

attached document

n. An ASCII text file or a binary file, such as a document created in a word processing system, that is included with an e-mail message as an attachment. The file is not part of the actual e-mail message, and it is generally encoded using uuencoding, MIME, or BinHex. Most e-mail programs automatically encode an attached document for transmission with a message. The recipient of the message must have an e-mail program capable of decoding the attached document or use a separate utility to decode it in order to read the document. See also ASCII, binary file, BinHex, MIME, uuencode.

attached processor

n. A secondary processor attached to a computer system, such as a keyboard or video subsystem processor.

attenuation

n. The weakening of a transmitted signal, such as the distortion of a digital signal or the reduction in amplitude of an electrical signal, as it travels farther from its source. Attenuation is usually measured in decibels and is sometimes desirable, as when signal strength is reduced electronically, for example, by a radio volume control, to prevent overloading.

attribute

n. 1. In a database record, the name or structure of a field. For example, the files LASTNAME, FIRSTNAME, and PHONE would be attributes of each record in a PHONELIST database. The size of a field or the type of information it contains would also be attributes of a database record. 2. In screen displays, an element of additional information stored with each character in the video buffer of a video adapter running in character mode. Such attributes control the background and foreground colors of the character, underlining, and blinking. 3. In markup languages such as SGML and HTML, a name-value pair within a tagged element that modifies certain features of that element. See also HTML, SGML.

audio

adj. Relating to frequencies within the range of perception by the human ear--from about 15 to 20,000 hertz (cycles per second). See also audio response, synthesizer.

audio card

n. An expansion card that converts analog audio signals from a microphone, audio tape, or other source to digital form that can be stored as a computer audio file, and converts computer audio files to electrical signals that can be played through a speaker. Output sounds can be routed through speakers or headphones. Input can be entered through a microphone connected to the computer. Most audio cards support MIDI. Audio cards enable sounds to be heard from CD-ROMs and other storage media or over the Internet. Also called audio board, sound board, sound card. See also MIDI.

audiocast

n. The transmission of an audio signal using IP protocols. See also IP.

audio compression

n. A method of reducing the overall loudness of an audio signal. This is accomplished by limiting the amount of apparent distortion when the signal is played back through a speaker or transmitted through a communications link.

audiovisual

adj. Relating to or being any material that uses a combination of sight and sound to present information.

audit trail

n. In reference to computing, a means of tracing all activities affecting a piece of information, such as a data record, from the time it is entered into a system to the time it is removed. An audit trail makes it possible to document, for example, who made changes to a particular record and when.

authentication

n. In a multiuser or network operating system, the process by which the system validates a user's logon information. A user's name and password are compared against an authorized list, and if the system detects a match, access is granted to the extent specified in the permission list for that user. See also logon, password, permission, user account, user name.

authorization

n. In reference to computing, especially remote computers on a network, the right granted an individual to use the system and the data stored on it. Authorization is typically set up by a system administrator and verified by the computer based on some form of user identification, such as a code number or password. Also called access privileges, permission. See also network, system administrator.

AutoCorrect

n. A function in Microsoft Word for Windows that automatically corrects errors and makes other substitutions as soon as a user types text. For example, AutoCorrect can be set up to fix misspellings, such as teh for the, or to change "straight" quotation marks to "smart" quotation marks. The user can select which AutoCorrect features to enable. See also smart quotes.

auto dial

n. A feature enabling a modem to open a telephone line and initiate a call by transmitting a stored telephone number as a series of pulses or tones.

AUTOEXEC.BAT

n. A special-purpose batch file (set of commands) that is automatically carried out by the MS-DOS operating system when the computer is started or restarted. Created by the user or (in later versions of MS-DOS) by the operating system at system installation, the file contains basic startup commands that help configure the system to installed devices and to the user's preferences.

AutoPlay

n. A feature in Windows 95 that allows it to automatically operate a CD-ROM. When a CD is inserted into a CD-ROM drive, Windows 95 looks for a file called AUTORUN.INF on the CD. If the file is found, Windows 95 will open it and carry out its instructions, which are usually to set up an application from the CD-ROM on the computer's hard disk or to start the application once it has been installed. If an audio CD is inserted into the drive, Windows 95 will automatically launch the CD Player application and play it.

autopolling

n. The process of periodically determining the status of each device in a set so that the active program can process the events generated by each device, such as whether a mouse button was pressed or whether new data is available at a serial port. This can be contrasted with event-driven processing, in which the operating system alerts a program or routine to the occurrence of an event by means of an interrupt or message rather than having to check each device in turn. Also called polling. Compare event-driven processing, interrupt-driven processing.

autorestart

n. A process or system feature that can automatically restart the system after the occurrence of certain types of errors or a power system failure.

autosave

n. A program feature that automatically saves an open file to a disk or other medium at defined intervals or after a certain number of keystrokes to ensure that changes to a document are periodically saved.

autosizing

n. The ability of a monitor to accept signals at one resolution and display the image at a different resolution. A monitor capable of autosizing maintains the aspect ratio of an image but enlarges or reduces the image to fit in the space available. See also monitor, resolution.

AUX

n. The logical device name for auxiliary device; a name reserved by the MS-DOS operating system for the standard auxiliary device. AUX usually refers to a system's first serial port, also known as COM1.

A/UX

n. A version of the multi-user, multitasking UNIX operating system provided by Apple Computer for various Macintosh computers and based on the AT&T System V, release 2.2 of UNIX with some enhancements. A/UX incorporates a number of Apple features, including support for the Macintosh Toolbox, so that applications can provide users with the graphics-based interface characteristic of that computer. See also System V.

availability

n. In processing, the accessibility of a computer system or resource, such as a printer, in terms of usage or of the percentage of the total amount of time the device is needed.

avatar

n. In virtual-reality environments such as certain types of Internet chat rooms, a graphical representation of a user. An avatar typically is a generic picture or animation of a human of either gender, a photograph or caricature of the user, a picture or animation of an animal, or an object chosen by the user to depict his or her virtual-reality "identity." See superuser.

AVI