C

n. A programming language developed by Dennis Ritchie at Bell Laboratories in 1972. It is so named because its immediate predecessor was the B programming language. Although C is considered by many to be more a machine-independent assembly language than a high-level language, its close association with the UNIX operating system, its enormous popularity, and its standardization by the American National Standards Institute (ANSI) have made it perhaps the closest thing to a standard programming language in the microcomputer/workstation marketplace. C is a compiled language that contains a small set of built-in functions that are machine dependent. The rest of the C functions are machine independent and are contained in libraries that can be accessed from C programs. C programs are composed of one or more functions defined by the programmer; thus C is a structured programming language. See also C++, compiled language, library, Objective-C, structured programming.

C++

n. An object-oriented version of the C programming language, developed by Bjarne Stroustrup in the early 1980s at Bell Laboratories and adopted by a number of vendors, including Apple Computer and Sun Microsystems. See also C, Objective-C, object-oriented programming.

C2

n. The lowest level of security in the U.S. National Computer Security Center's hierarchy of criteria for trusted computer systems, requiring user logon with password and a mechanism for auditing. The C2 level is outlined in the Orange Book. See also Orange Book (definition 1).

cabinet

n. The box in which the main components of a computer (CPU, the hard drive, floppy and CD-ROM drives, and expansion slots for peripheral devices, such as monitors) are located. See also CPU, expansion slot.

cable

n. A collection of wires shielded within a protective tube, used to connect peripheral devices to a computer. A mouse, a keyboard, and a printer might all be connected to a computer with cables. Printer cables typically implement a serial or a parallel path for data to travel along.

cable connector

n. The connector on either end of a cable. See also DB connector, DIN connector, RS-232-C standard, RS-422/423/449.

cable modem

n. A modem that sends and receives data through a coaxial cable television network instead of telephone lines, as with a conventional modem. Cable modems, which have speeds of 500 kilobits per second (Kbps), can generally transmit data faster than current conventional modems. See also coaxial cable, modem.

cabling diagram

n. A plan that shows the path of cables that attach computer system components or peripherals. Cabling diagrams are particularly important for explaining the connection of disk drives to a disk controller.

cache

n. A special memory subsystem in which frequently used data values are duplicated for quick access. A memory cache stores the contents of frequently accessed RAM locations and the addresses where these data items are stored. When the processor references an address in memory, the cache checks to see whether it holds that address. If it does hold the address, the data is returned to the processor; if it does not, a regular memory access occurs. A cache is useful when RAM accesses are slow compared with the microprocessor speed, because cache memory is always faster than main RAM memory. See also disk cache, wait state.

CAD

n. Acronym for computer-aided design. A system of programs and workstations used in designing engineering, architectural, and scientific models ranging from simple tools to buildings, aircraft, integrated circuits, and molecules. Various CAD applications create objects in two or three dimensions, presenting the results as wire-frame "skeletons," as more substantial models with shaded surfaces, or as solid objects. Some programs can also rotate or resize models, show interior views, generate lists of materials required for construction, and perform other allied functions. CAD programs rely on mathematics, often requiring the computing power of a high-performance workstation. See also CAD/CAM, I-CASE.

caddy

n. A plastic carrier that holds a CD-ROM and is inserted into a CD-ROM drive. Some personal computers, especially older models, have CD-ROM drives that require the use of a caddy. Most current CD-ROM drives do not require a caddy.

calculator

n. Broadly, any device that performs arithmetic operations on numbers. Sophisticated calculators can be programmed for certain functions and can store values in memory, but they differ from computers in several ways: they have a fixed set of commands, they do not recognize text, they cannot retrieve values stored in a data file, and they cannot find and use values generated by a program such as a spreadsheet.

calendar program

n. An application program in the form of an electronic calendar, commonly used for highlighting dates and scheduling appointments. Some calendar programs resemble wall calendars, displaying dates in blocks labeled with the days of the week; others display dates day by day and enable the user to enter appointments, notes, and other memoranda. A day-of-the-week type of calendar program could, for example, be used to find out that Christmas 1999 will be on a Saturday. Depending on its capabilities, such a program might cover only the current century, or it might cover hundreds of years and even allow for the change (in 1582) from the Julian to the Gregorian calendar. A calendar/scheduler program might show blocks of dates or, like an appointment book, single days divided into hours or half hours, with room for notes. Some programs allow the user to set an alarm to go off at an important point in the schedule. Other programs can coordinate the calendars of different people on the same network, so that a person entering an appointment into his or her calendar also enters the appointment into a colleague's calendar.

call¹

n. In a program, an instruction or statement that transfers program execution to some section of code, such as a subroutine, to perform a specific task. Once the task is performed, program execution resumes at the calling point in the program. See also calling sequence.

call²

vb. 1. To establish a connection through a telecommunications network. 2. To transfer program execution to some section of code (usually a subroutine) while saving the necessary information to allow execution to resume at the calling point when the called section has completed execution. Some languages (such as FORTRAN) have an explicit CALL statement; others (such as C and Pascal) perform a call when the name of a procedure or function appears. In assembly language, there are various names for a CALL instruction. When a subroutine call occurs in any language, one or more values (known as arguments or parameters) are often passed to the subroutine, which can then use and sometimes modify these values. See also argument, parameter.

callback

n. A user authentication scheme used by computers running dial-in services. A user dials in to a computer and types a logon ID and password. The computer breaks the connection and automatically calls the user back at a preauthorized number. This security measure usually prevents unauthorized access to an account even if an individual's logon ID and password have been stolen. See also authentication.

camera-ready

adj. In publishing, of or pertaining to the stage at which a document, with all typographic elements and graphics in place, is suitably prepared to be sent to a printing service. The printing service photographs the camera-ready copy and then uses the photograph to make plates for printing. Some applications are advertised as being able to bring documents to the camera-ready stage, eliminating the need for manual layout and pasteup of elements onto boards.

cancel

n. A control character used in communication with printers and other computers, commonly designated as CAN. It usually means that the line of text being sent should be canceled. In ASCII, which is the basis of character sets used by most microcomputers, this is represented internally as character code 24.

canned software

n. Off-the-shelf software, such as word processors and spreadsheet programs.

capacitor

n. A circuit component that provides a known amount of capacitance (ability to store an electric charge). A capacitor typically consists of two conductive plates separated by an insulating (dielectric) material. If other factors remain constant, capacitance increases as the plates are made larger or brought closer together. A capacitor blocks direct current but passes alternating current to an extent that depends on its capacitance and on the frequency of the current. See also capacitance.

capacity

n. The amount of information a computer or an attached device can process or store. See also computer.

caps

n. Short for capital letters. Compare lowercase.

Caps Lock key

n. A toggle key that, when on, shifts the alphabetic characters on the keyboard to uppercase. The Caps Lock key does not affect numbers, punctuation marks, or other symbols.

capture

vb. In communications, to transfer received data into a file for archiving or later analysis.

card

n. 1. A printed circuit board or adapter that can be plugged into a computer to provide added functionality or new capability. These cards provide specialized services, such as mouse support and modem capabilities, that are not built into the computer. See also adapter, board, printed circuit board. 2. In programs such as the HyperCard hypertext program, an on-screen representation of an index card on which information can be stored and "filed" (saved) for future reference. See also hypertext. 3. A manila card about 3 inches high by 7 inches long on which 80 columns of data could be entered in the form of holes punched with a keypunch machine. The punched holes corresponded to numbers, letters, and other characters and could be read by a computer that used a punched-card reader. Also called punched card. See also card reader (definition 2).

card reader

n. 1. An input device used chiefly for identification purposes that reads information that has been magnetically encoded, usually in two tracks, on a plastic card, such as a credit card or an employee badge. 2. A mechanical apparatus that reads computer data from punched cards. No longer in widespread use, card readers allow computer data to be created offline and then input to the computer for processing. This need for offline data creation was because of limited CPU resources. Reading batches of punched cards was a better use of CPU time than waiting for a human operator to key data directly into the computer's memory. Also called punched-card reader.

caret

n. The small, upward-pointing symbol (^) typically found over the 6 key on the top row of a microcomputer keyboard. In some programming languages, the caret is used as an exponentiation operator. For example, the expression 3 ^ 2 represents the number 3 raised to the second power. The caret is also used to represent the Control key on the keyboard. For example, ^Z means "hold the Control key down and press the Z key."

carpal tunnel syndrome

n. A form of repetitive strain injury to the wrist and hand. Making the same small motions over and over can cause swelling and scarring of the soft tissue of the wrist, which then compresses the main nerve leading to the hand. Symptoms of carpal tunnel syndrome include pain and tingling in the fingers, and in advanced cases, carpal tunnel syndrome can lead to loss of functionality of the hands. Typing at a computer keyboard without proper wrist support is a common cause of carpal tunnel syndrome. See also repetitive strain injury, wrist support. Acronym: CTS.

carriage return

n. A control character that tells a computer or printer to return to the beginning of the current line. A carriage return is similar to the return on a typewriter but does not automatically advance to the beginning of a new line. For example, a carriage-return character alone, received at the end of the words This is a sample line of text would cause the cursor or printer to return to the first letter of the word This. In the ASCII character set, the carriage-return character has the decimal value of 13 (hexadecimal 0D).

carrier

n. 1. In communications, a specified frequency that can be modulated to convey information. 2. A company that provides telephone and other communications services to consumers.

carrier frequency

n. A radio-frequency signal, such as those used with modems and on networks, used to transmit information. A carrier frequency is a signal that vibrates at a fixed number of cycles per second, or hertz (Hz), and is modulated (changed) in either frequency or amplitude to enable it to carry intelligible information.

carrier system

n. A communications method that uses different carrier frequencies to transfer information along multiple channels of a single path. Transmission involves modulating the signal on each frequency at the originating station and demodulating the signal at the receiving station.

cartridge

n. Any of various container devices that usually consist of some form of plastic housing. See also disk cartridge, ink cartridge, memory cartridge, ribbon cartridge, ROM cartridge, tape cartridge, toner cartridge.

cartridge font

n. A font contained in a plug-in cartridge and used to add fonts to laser, ink-jet, or high-end dot-matrix printers. Cartridge fonts are distinguished both from internal fonts, which are contained in ROM in the printer and are always available, and from downloadable (soft) fonts, which reside on disk and which can be sent to the printer as needed. See also font cartridge. Compare internal font.

cascade

n. 1. Additional elements displayed by a menu item or list box from which the user can choose in order to interact with other screen elements. 2. In newsgroup articles, the accumulation of quotation marks (often angle brackets) added by newsgroup readers each time an article is replied to. Most newsgroup readers will copy the original article in the body of the reply; after several replies, the original material will have several quotation marks. See also article, newsgroup, newsreader.

cascading menu

n. A hierarchical graphical menu system in which a side menu of subcategories is displayed when the pointer is placed on the main category.

cascading style sheets

n. A Hypertext Markup Language (HTML) specification developed by The World Wide Web Consortium (W3C) that allows authors of HTML documents and users to attach style sheets to HTML documents. The style sheets include typographical information on how the page should appear, such as the font of the text in the page. This specification also directs the way in which the style sheets of the HTML document and the user's style will blend. Cascading style sheets have been proposed for the HTML 3.2 standard. Also called Cascading Style Sheet mechanism, CSS1. See also HTML, style sheet.

cascading windows

n. A sequence of successive, overlapping windows in a graphical user interface, displayed so that the title bar of each is visible. Also called overlaid windows.

case

n. In text processing, an indication of whether one or more alphabetic characters are capitalized (uppercase) or not (lowercase). A case-sensitive program or routine distinguishes between uppercase and lowercase letters and treats the word cat as totally distinct from either Cat or CAT. A case-sensitive program that also separates capitalized and lowercased words would list Arkansas before aardvark or antimony, even though its alphabetic position follows both lowercased words.

CASE

n. Acronym for computer-aided software engineering. A comprehensive label for software designed to use computers in all phases of computer program development, from planning and modeling through coding and documentation. CASE represents a working environment consisting of programs and other development tools that help managers, systems analysts, programmers, and others to automate the design and implementation of programs and procedures for business, engineering, and scientific computer systems.

case-sensitive search

n. A search in a database in which capitalization of key words must exactly match the capitalization of words in the database. A case-sensitive search for "north and south" would fail to find a database entry for "North and South."

cassette

n. The unit consisting of both the plastic case and the magnetic tape it contains. Cassette tapes are used for backing up large amounts of computer data.

cassette tape

n. 1. The tape within a cassette. 2. The unit consisting of both the plastic cassette case and the tape it contains.

CAT

n. 1. Acronym for computer-aided testing. A procedure used by engineers for checking or analyzing designs, especially those created with CAD programs. Computer-aided testing is also used by software developers for automated regression testing. 2. Acronym for computer-assisted teaching. 3. Acronym for computerized axial tomography. A medical procedure in which a computer is used to generate a three-dimensional image of a body part from a series of X rays taken as cross sections along a single axis. See CAI.

catalog

n. 1. In a computer, a list containing specific information, such as name, length, type, and location of files or of storage space. 2. In a database, the data dictionary. See also data dictionary.

CBT

n. Acronym for computer-based training. The use of computers and specially developed tutorial programs for teaching. CBT uses color, graphics, and other attention-getting aids to help maintain interest, and it has both simple and sophisticated applications. A software developer, for example, might include a series of CBT lessons with an application to give new users a hands-on feel for the program; a consultant might use a longer and more detailed CBT program as a tool in a management-training seminar.

cc

n. Acronym for courtesy copy. A directive to an e-mail program to send a complete copy of a given piece of mail to another individual. The use of cc mail addressing, as opposed to directly addressing the mail to a person, generally implies that the recipient is not required to take any action; the message is for informational purposes only. In a cc directive, the fact that this recipient received the mail is printed in the mail header and is thus known to all other recipients. Also called carbon copy. See also e-mail, header. Compare bcc.

CCITT

n. Acronym for Comité Consultatif International Télégraphique et Téléphonique. Also known as the International Telegraph and Telephone Consultative Committee. An organization based in Geneva, Switzerland, and established as part of the United Nations International Telecommunications Union (ITU). Its functions have been taken over by the ITU. The ITU recommends use of communications standards that are recognized throughout the world. Protocols established by the ITU are applied to modems, networks, and facsimile transmission. See also CCITT Groups 1-4, CCITT V series, CCITT X series.

CCITT Groups 1-4

n. A set of four standards recommended by the Comité Consultatif International Télégraphique et Téléphonique (International Telegraph and Telephone Consultative Committee) for the encoding and transmission of images over fax machines. Groups 1 and 2 relate to analog devices and are generally out of use. Groups 3 and 4, which deal with digital devices, are outlined below. Group 3 is a widespread standard that supports standard images of 203 horizontal dots per inch (dpi) by 98 vertical dpi and fine images of 203 horizontal dpi by 198 vertical dpi; supports two methods of data compression, one (based on the Huffman code) reducing an image to 10 to 20 percent of the original, the second (READ, for relative element address designate) compressing images to 6 to 12 percent of the original; and provides for password protection and for polling so that a receiving machine can request transmission as appropriate. Group 4, a newer standard, supports images of up to 400 dpi; data compression based on a beginning row of white pixels (dots), with each succeeding line encoded as a series of changes from the line before, compressing images to 3 to 10 percent of the original; does not include error-correction information in the transmission; and requires an Integrated Services Digital Network (ISDN) phone line rather than a dial-up line.

CCITT V series

n. A set of recommendations developed by the Comité Consultatif International Télégraphique et Téléphonique (International Telegraph and Telephone Consultative Committee) for standardizing modem design and operations. The complete series includes a number of recommendations covering signaling, coding, and circuit characteristics, as well as modems. Those most relevant to computer users are briefly described below in terms of the modems they standardize: k:\compdict\database\3764.doc

CCITT X series

n. A set of recommendations adopted by the International Telecommunications Union (ITU-T), formerly the CCITT, and ISO for standardizing equipment and protocols used in both public-access and private computer networks. Some of the recommendations in the X series include the following: k:\compdict\database\2468.doc

cd

n. Acronym for change directory. In MS-DOS, UNIX, and FTP client programs, the command that changes the current directory to the directory whose path follows cd in the command. See also directory, path.

CD

1. Acronym for Carrier Detect, a signal sent from a modem to the attached computer to indicate that the modem is on line. See also DCD. 2. Acronym for compact disc. See also CD-I, CD-ROM, compact disc.

CDF

n. Short for Channel Definition Format.

CDFS

n. 1. Acronym for CD-ROM File System. A 32-bit protected-mode file system that controls access to the contents of CD-ROM drives in Windows 95. See also protected mode. 2. A designation used with UNIX computers to indicate that a file system resides on a read-only removable medium (that is a CD-ROM). This usually implies that the compact disc is compliant with the ISO 9660 standard. CDFS is also used as a part of commands that mount media (hard drives, tape drives, remote networked drives, and CD-ROMs) for use on a computer. See also CD-ROM, ISO 9660.

CD Plus

n. A compact disc encoding format that allows mixing of audio recordings and computer data on the same CD, without the possibility of audio equipment becoming damaged by attempting to play the data sections.

CD recorder

n. A device used to write CD-ROMs. Because a disc can be written only once on these machines, they are used most commonly to create CD-ROMs for data archival or to produce CD-ROM masters that can be duplicated for mass distribution. Also called CD-R machine, CD-ROM burner. See also CD-ROM.

CD-ROM

n. 1. Acronym for compact disc read-only memory. A form of storage characterized by high capacity (roughly 650 megabytes) and the use of laser optics rather than magnetic means for reading data. Although CD-ROM drives are strictly read-only, they are similar to CD-R drives (write once, read many), optical WORM devices, and optical read-write drives. See also CD-I, CD-R, WORM. 2. An individual compact disc designed for use with a computer and capable of storing up to 650 megabytes of data. See also compact disc, disc.

CD-ROM drive

n. A disk storage device that uses compact disc technology. See also CD-ROM, compact disc.

CD-ROM jukebox

n. A CD-ROM player that can contain up to 200 CD-ROMs and is connected to a CD-ROM drive in a personal computer or workstation. A user can request data from any of the CD-ROMs in the jukebox, and the device will locate and play the disk that contains the data. While only one CD-ROM can be played at a time, if multiple CD-ROM jukeboxes are each connected to separate CD-ROM drives that are daisy-chained together to the computer, more than one CD-ROM can be used at a time. See also CD-ROM, CD-ROM drive, daisy chain.

CDV

n. 1. Acronym for compressed digital video. The compression of video images for high-speed transmission. 2. Acronym for compact disc video. A 5-inch videodisc. See also videodisc.

cell

n. 1. The intersection of a row and a column in a spreadsheet. Each row and column in a spreadsheet is unique, so each cell can be uniquely identified--for example, cell B17, at the intersection of column B and row 17. Each cell is displayed as a rectangular space that can hold text, a value, or a formula. 2. An addressable (named or numbered) storage unit for information. A binary cell, for example, is a storage unit that can hold 1 bit of information--that is, it can be either on or off.

Cellular Digital Packet Data

n. A wireless standard providing two-way, 19.2-Kbps packet data transmission over existing cellular telephone channels. See also packet, wireless. Acronym: CDPD.

censorship

n. The action of preventing material that a party considers objectionable from circulating within a system of communication over which that party has some power. The Internet as a whole is not censored, but some parts of it come under varying degrees of control. A news server, for example, often is set to exclude any or all of the alt. newsgroups, such as alt.sex.* or alt.music.white-power, which are unmoderated and tend to be controversial. A moderated newsgroup or mailing list may be considered to be "censored" because the moderator will usually delete highly controversial and obscene content or content that is on a different topic from that followed by the newsgroup. Online services have identifiable owners, who often take some share of responsibility for what reaches their users' computer screens. In some countries, censorship of certain political or cultural Web sites is a matter of national policy.

center

vb. To align characters around a point located in the middle of a line, page, or other defined area; in effect, to place text an equal distance from each margin or border. See also align.

centi-

prefix 1. One hundred. 2. One hundredth, as in centimeter--one hundredth of a meter.

centralized processing

n. The location of computer processing facilities and operations in a single (centralized) place. Compare decentralized processing, distributed processing.

central processing unit

n. The computational and control unit of a computer. The central processing unit is the device that interprets and executes instructions. Mainframes and early minicomputers contained circuit boards full of integrated circuits that implemented the central processing unit. Single-chip central processing units, called microprocessors, made possible personal computers and workstations. Examples of single-chip central processing units are the Motorola 68000, 68020, and 68030 chips and the Intel 8080, 8086, 80286, 80386, and i486 chips. The central processing unit--or microprocessor, in the case of a microcomputer--has the ability to fetch, decode, and execute instructions and to transfer information to and from other resources over the computer's main data-transfer path, the bus. By definition, the central processing unit is the chip that functions as the "brain" of a computer. In some instances, however, the term encompasses both the processor and the computer's memory or, even more broadly, the main computer console (as opposed to peripheral equipment). See also microprocessor. Acronym: CPU.

Centronics parallel interface

n. A de facto standard for parallel data exchange paths between computers and peripherals, originally developed by the printer manufacturer Centronics, inc. The Centronics parallel interface provides eight parallel data lines plus additional lines for control and status information. See also parallel interface.

CERN

n. Acronym for Conseil Européen pour la Recherche Nucléaire (the European Laboratory for Particle Physics). CERN, a physics research center located in Geneva, Switzerland, is where the original development of the World Wide Web took place by Tim Berners-Lee in 1989 as a method to facilitate communication among members of the scientific community. See also NCSA (definition 1).

CERN server

n. One of the first Hypertext Transfer Protocol (HTTP) servers, developed at CERN by Tim Berners-Lee. The CERN server is still in wide use and is free of charge. See also CERN, HTTP server.

CERT

n. Acronym for Computer Emergency Response Team. An organization that provides a round-the-clock security consultation service for Internet users and provides advisories whenever new virus programs and other computer security threats are discovered.

certificate

n. A certificate is a statement guaranteeing the identity of a person or the security of a Web site. Microsoft Internet Explorer uses two different types of certificates: personal certificate and Web site certificates. See digital ID, personal certificate, Web site certificate.

certificate authority

n. A trusted third-party organization that issues digital certificates. See also digital ID, certificate.

certification

n. 1. The act of awarding a document to demonstrate a computer professional's competence in a particular field. Some hardware and software suppliers, such as Microsoft and Novell, offer certification in the use of their products; other organizations, such as the Institute for Certification of Computer Professionals (ICCP) and the Computing Technology Industry Association (CompTIA), offer more general certification. 2. The act of awarding a document to demonstrate that a hardware or software product meets some specification, such as being able to work with a certain other hardware or software product. 3. The issuance of a notice that a user or site is trusted for the purpose of security and computer authentication. Often certification is used with Web sites.

CGI

n. 1. Acronym for Common Gateway Interface. 2. Acronym for Computer Graphics Interface.

CGM

n. Acronym for Computer Graphics Metafile.

cgi-bin

n. Short for Common Gateway Interface-binaries. A file directory that holds external applications to be executed by HTTP servers via CGI. See also CGI (definition 1).

CGI script

n. Short for Common Gateway Interface script. An external application that is executed by an HTTP server machine in response to a request by a client, such as a Web browser. Generally, the CGI script is invoked when the user clicks on some element in a Web page, such as a link or an image. Communication between the CGI script and the server is carried out via the CGI specification. CGI scripts can be written in many programming languages, including C, C++, and Visual Basic. However, the most commonly used language for CGI scripts is Perl, because it is a small but robust language and it is common on UNIX, which is the platform on which the majority of Web sites run. CGI scripts don't necessarily need to be scripts; they can also be batch programs or compiled programs. CGI scripts are used to provide interactivity in a Web page, including such features as providing a form that users can fill out, image maps that contain links to other Web pages or resources, and links that users can click on to send e-mail to a specified address. ActiveX controls and Java applets can provide much the same functionality as CGI scripts, through different means. See also CGI (definition 1), cgi-bin, image map, Perl. Compare ActiveX controls, Java applet.

chaining

n. In computers, the linking of two or more entities so that they are dependent upon one another for operation. In programming, two or more programs are said to be chained if the first program causes the second program to begin executing. In addition, program statements are said to be chained if each statement, except for the first, relies on the previous statement for input. With batch files, two or more batch files are said to be chained if the completion of the first batch file causes the second batch file to begin executing. With data storage, the term chained applies to two or more individual units of storage that are linked together. For example, a single file on a disk may actually be stored on several different sectors of the disk, each of which points to the next sector containing a piece of that file. These sectors are said to be chained together, or, more literally, to be a chain of clusters.

Challenge Handshake Authentication Protocol

n. An authentication scheme used by PPP servers to validate the identity of the originator of a connection, upon connection or any time later. See also authentication, PPP. Acronym: CHAP.

channel

n. 1. A path or link through which information passes between two devices. A channel can be either internal or external to a microcomputer. See also bus. 2. In communications, a medium for transferring information. Depending on its type, a communications channel can carry information (data, sound, and/or video) in either analog or digital form. A communications channel can be a physical link, such as the cable connecting two stations in a network, or it can consist of some electromagnetic transmission on one or more frequencies within a bandwidth in the electromagnetic spectrum, as in radio and television, or in optical, microwave, or voice-grade communication. Also called circuit, line. See also analog, band, bandwidth, digital (definition 2), electromagnetic spectrum, frequency. 3. A push technology that allows users to subscribe to a Web site to browse offline, automatically display updated pages on their screen savers, and download or receive notifications when pages in the Web site are modified. Channels are available only in browsers that support channel definitions, such as Microsoft Internet Explorer version 4.0. See also Channel Definition Format.

Channel Definition Format

n. A specification developed by Microsoft that allows Web publishers to deliver content from the Internet to your computer, similar to subscribing to a favorite Web site.

channel hop

vb. To switch repeatedly from one IRC channel to another. See also IRC.

channel op

n. Short for channel operator. A user on an IRC channel who has the privilege of expelling undesirable participants. See also IRC.

CHAP

n. See Challenge Handshake Authentication Protocol.

character

n. A letter, number, punctuation mark, or other symbol or control code that is represented to a computer by one unit--1 byte--of information. A character is not necessarily visible, either on the screen or on paper; a space, for example, is as much a character as is the letter a or any of the digits 0 through 9. Because computers must manage not only so-called printable characters but also the look (formatting) and transfer of electronically stored information, a character can additionally indicate a carriage return or a paragraph mark in a word-processed document. It can be a signal to sound a beep, begin a new page, or mark the end of a file. See also ASCII, control character, EBCDIC.

characteristic

n. In mathematics, the exponent of a floating-point number (the portion following the E that indicates the position of the decimal point) or the integer portion of a logarithm. See also floating-point notation, logarithm.

character map

n. In text-based computer graphics, a block of memory addresses that correspond to character spaces on a display screen. The memory allocated to each character space is used to hold the description of the character to be displayed in that space. See also alphageometric.

character set

n. A grouping of alphabetic, numeric, and other characters that have some relationship in common. For example, the standard ASCII character set includes letters, numbers, symbols, and control codes that make up the ASCII coding scheme.

character string

n. A set of characters treated as a unit and interpreted by a computer as text rather than numbers. A character string can contain any sequence of elements from a given character set, such as letters, numbers, control characters, and extended ASCII characters. Also called string. See also ASCII, control character, extended ASCII.

character style

n. Any attribute, such as boldface, italic, underline, or small caps, applied to a character. Depending on the operating system or program considered, the range of character styles of text might or might not include the font, which refers to the design of a group of characters in a given size. See also font family.

chart

n. A graphic or diagram that displays data or the relationships between sets of data in pictorial rather than numeric form.

chassis

n. A metal frame on which electronic components, such as printed circuit boards, fans, and power supplies, are mounted.

chat¹

n. 1. Real-time conversation via computer. When a participant types a line of text and then presses the Enter key, that participant's words appear on the screens of the other participants, who can then respond in kind. Most online services support chat; on the Internet, IRC is the usual system. See also IRC. 2. An Internet utility program that supports chat. IRC has largely superseded it.

chat²

vb. To carry on a real-time conversation with other users by computer. See also IRC.

chip set

n. A collection of chips designed to function as a unit in the performance of some common task. The term is most commonly used to refer to the set of integrated circuits, such as the programmable interrupt controller, that support a CPU together with the CPU itself. Often a chip set will fit on one chip. See also central processing unit, chip, integrated circuit, programmable interrupt controller.

choose

vb. To pick a command or option from within a graphical user interface, as by clicking a button in a dialog box or pulling down a menu and then releasing the mouse button on one of its options. Although select is often used instead of choose to describe the same action, choose is the preferred term because select has specific connotations within computing. See also select.

Chooser

n. On the Apple Macintosh, a desk accessory that allows the user to select a printer or a device on a network, such as a file server or a printer.

Chooser extension

n. A program that adds items to the Macintosh Chooser desk accessory. At system startup, Chooser adds to its menu of options from the extensions available in the system extensions folder. For example, if you want to use a particular printer with your Mac OS, you must have the right Chooser extension for that printer in the extensions folder when the computer is turned on. See also Chooser, extension (definition 4).

cipher

n. 1. A code. 2. An encoded character. 3. A zero.

circuit

n. 1. Any path that can carry electrical current. 2. A combination of electrical components interconnected to perform a particular task. At one level, a computer consists of a single circuit; at another, it consists of hundreds of interconnected circuits.

circuit analyzer

n. Any device for measuring one or more characteristics of an electrical circuit. Voltage, current, and resistance are the characteristics most commonly measured. Oscilloscopes are circuit analyzers.

circuit board

n. A flat piece of insulating material, such as epoxy or phenolic resin, on which electrical components are mounted and interconnected to form a circuit. Most modern circuit boards use patterns of copper foil to interconnect the components. The foil layers may be on one or both sides of the board and, in more advanced designs, in several layers within the board. A printed circuit board is one in which the pattern of copper foil is laid down by a printing process such as photolithography. See also board, printed circuit board.

circuit breaker

n. A switch that opens and cuts off the flow of current when the current exceeds a certain level. Circuit breakers are placed at critical points in circuits to protect against damage that could result from excessive current flow, which is typically caused by component failure. Circuit breakers are often used in place of fuses because they need only to be reset rather than replaced. Compare surge protector.

CISC

n. Acronym for complex instruction set computing. The implementation of complex instructions in a microprocessor design so that they can be invoked at the assembly language level. The instructions can be very powerful, allowing for complicated and flexible ways of calculating such elements as memory addresses. All this complexity, however, usually requires many clock cycles to execute each instruction. Compare RISC.

class

n. In object-oriented programming, a generalized category that describes a group of more specific items, called objects, that can exist within it. A class is a descriptive tool used in a program to define a set of attributes or a set of services (actions available to other parts of the program) that characterize any member (object) of the class. Program classes are comparable in concept to the categories that people use to organize information about their world, such as animal, vegetable, and mineral, that define the types of entities they include and the ways those entities behave. The definition of classes in object-oriented programming is comparable to the definition of types in languages such as C and Pascal. See also object-oriented programming.

Class A network

n. An Internet network that can define a maximum of 16,777,215 hosts. Class A networks use the first byte of an IP address to designate the network, with the first (high-order) bit set to 0. The host is designated by the last 3 bytes. Class A addressing currently allows for a maximum of 128 networks. Class A networks are best suited for sites with few networks but numerous hosts and are usually designated for use by large government or educational institutions. See also host, IP address.

classless interdomain routing

n. An address scheme that uses aggregation strategies to minimize the size of top-level Internet routing tables. Routes are grouped with the objective of minimizing the quantity of information carried by core routers. The main requirement for this scheme is the use of routing protocols that support it, such as Border Gateway Protocol (BGP) Version 4 and RIP Version 2. See also Border Gateway Protocol, communications protocol, RIP, router. Acronym: CIDR.

clean boot

n. Booting or starting a computer using the minimum system files in the operating system. The clean boot is used as a troubleshooting method for isolating problems associated with software that may be calling on the same system resources at the same time, causing conflicts that lower the performance of the system, make some programs inoperable, or crash the computer. See also boot¹, crash² (definition 1), operating system.

clean install

n. Reinstallation of software in a manner that ensures that no application or system files from a previous installation will remain. The procedure prevents "smart" installer programs from skipping file installations where a file already exists, which could potentially keep a problem from being removed.

Clear key

n. A key in the upper left corner of the numeric keypad on some keyboards. In many applications, it clears the currently selected menu choice or deletes the current selection.

click

vb. To press and release a mouse button once without moving the mouse. Clicking is usually performed to select or deselect an item or to activate a program or program feature. See also right click. Compare double-click, drag.

click speed

n. The maximum interval between the first and second time a user presses a button on a mouse or other pointing device that will still identify these actions as a double-click to the computer as opposed to two single-clicks. See also double-click, mouse, pointing device.

client

n. 1. In object-oriented programming, a member of a class (group) that uses the services of another class to which it is not related. See also inheritance (definition 1). 2. A process, such as a program or task, that requests a service provided by another program--for example, a word processor that calls on a sort routine built into another program. The client process uses the requested service without having to "know" any working details about the other program or the service itself. Compare child (definition 1), descendant (definition 2). 3. On a local area network or the Internet, a computer that accesses shared network resources provided by another computer (called a server). See also client/server architecture, server.

client error

n. A problem reported by the Hypertext Transfer Protocol (HTTP) client module as the result of difficulty in interpreting a command or the inability to connect properly to a remote host.

client/server architecture

n. An arrangement used on local area networks that makes use of distributed intelligence to treat both the server and the individual workstations as intelligent, programmable devices, thus exploiting the full computing power of each. This is done by splitting the processing of an application between two distinct components: a "front-end" client and a "back-end" server. The client component is a complete, stand-alone personal computer (not a "dumb" terminal), and it offers the user its full range of power and features for running applications. The server component can be a personal computer, a minicomputer, or a mainframe that provides the traditional strengths offered by minicomputers and mainframes in a time-sharing environment: data management, information sharing between clients, and sophisticated network administration and security features. The client and server machines work together to accomplish the processing of the application being used. Not only does this increase the processing power available over older architectures but it also uses that power more efficiently. The client portion of the application is typically optimized for user interaction, whereas the server portion provides the centralized, multiuser functionality. See also distributed intelligence.

client-side image maps

n. A Web page user selection device whereby regions of an image can be clicked with the mouse to indicate user selections from a presented collection of options, comparable to clicking an icon of the desired item on a menu. Unlike the earliest Web implementation of image maps (circa 1993), client-side image maps do not transmit the mouse click coordinates to the Web server for processing but perform the processing completely within the client program (i.e., Web browser) itself, generally improving the speed of response to the user. See also image map.

client-side program

n. On the Internet, a program that is run on a client computer rather than on a server computer. Client-side programs do not communicate over the Internet.

clip

vb. 1. To cut off the portion of a displayed image that lies beyond a certain boundary, such as the edge of a window. Certain graphics programs also support clipping as a means of masking everything but a certain object so that painting tools, for example, can be applied to the object alone. 2. To cut a photograph, drawing, or other illustrations from a clip art collection--either in a book or on a disk. See also clip art. 3. To cut off the peaks of a signal in an electronic circuit.

clip art

n. A collection--either in a book or on a disk--of proprietary or public-domain photographs, diagrams, maps, drawings, and other such graphics that can be "clipped" from the collection and incorporated into other documents.

clipboard

n. 1. A special memory resource maintained by windowing operating systems. The clipboard stores a copy of the last information that was "copied" or "cut." A "paste" operation passes data from the clipboard to the current program. A clipboard allows information to be transferred from one program to another, provided the second program can read data generated by the first. Data copied using the clipboard is static and will not reflect later changes. See also cut and paste, DDE. Compare scrap. 2. A computer that uses a pen as the primary input device. See also clipboard computer, pen computer.

Clipper Chip

n. An integrated circuit that implements the SkipJack algorithm, an encryption algorithm created by the National Security Agency that encrypts 64-bit blocks of data with an 80-bit key. The Clipper is manufactured by the U.S. government to encrypt telephone data. It has the added feature that it can be decrypted by the U.S. government, which has tried unsuccessfully to make the chip compulsory in the United States. See also encryption.

clipping path

n. A polygon or curve that is used to mask an area in a document. Only what is inside the clipping path appears when the document is printed. See also PostScript.

clock

n. 1. The electronic circuit in a computer that generates a steady stream of timing pulses--the digital signals that synchronize every operation. The system clock signal is precisely set by a quartz crystal, typically at a specific frequency between 1 and 50 megahertz. The clock rate of a computer is one of the prime determinants of its overall processing speed, and it can go as high as the other components of the computer allow. Also called system clock. 2. The battery-backed circuit that keeps track of the time and date in a computer--not the same as the system clock. Also called clock/calendar.

clock/calendar

n. An independent timekeeping circuit used within a microcomputer to maintain the correct time and calendar date. A clock/calendar circuit is battery powered, so it continues running even when the computer is turned off. The time and date kept by the clock/calendar can be used by the operating system (for example, to "stamp" files with the date and time of creation or revision) and by application programs (for example, to insert the date or time in a document). Also called clock, internal clock.

clock doubling

n. A technology employed by some Intel microprocessors that enables the chip to process data and instructions at twice the speed of the rest of the system. See also i486DX2.

clock rate

n. The rate at which the clock in an electronic device, such as a computer, oscillates. The clock rate is normally given in hertz (Hz, one cycle per second), kilohertz (kHz, one thousand cycles per second), or megahertz (MHz, one million cycles per second). Clock rates in personal computers increased from about 5 MHz to about 50 MHz between 1981 and 1995. Also called clock speed, hertz time. See also clock (definition 1).

clone

n. A copy; in microcomputer terminology, a look-alike, act-alike computer that contains the same microprocessor and runs the same programs as a better-known, more prestigious, and often more expensive machine.

close¹

n. An FTP command that instructs the client to close the current connection with a server. See also FTP¹ (definition 1), Web site.

close²

vb. 1. To end an application's relationship with an open file so that the application will no longer be able to access the file without opening it again. 2. To end a computer's connection with another computer on a network.

close box

n. In the Macintosh graphical user interface, a small box in the left corner of a window's title bar. Clicking on the box closes the window. Compare close button.

close button

n. In the graphical user interface for Windows 95, Windows NT, and the X Window System, a square button in the right corner (left corner in X Windows) of a window's title bar with an × mark on it. Clicking on the button closes the window. Also called X button. Compare close box.

closed architecture

n. 1. Any computer design whose specifications are not freely available. Such proprietary specifications make it difficult or impossible for third-party vendors to create ancillary devices that work correctly with a closed-architecture machine; usually only its original maker can build peripherals and add-ons for such a machine. Compare open architecture (definition 1). 2. A computer system that provides no expansion slots for adding new types of circuit boards within the system unit. The original Apple Macintosh was an example of a closed architecture. Compare open architecture (definition 2).

cluster

n. 1. An aggregation, such as a group of data points on a graph. 2. A communications computer and its associated terminals. 3. In data storage, a disk-storage unit consisting of a fixed number of sectors (storage segments on the disk) that the operating system uses to read or write information; typically, a cluster consists of two to eight sectors, each of which holds a certain number of bytes (characters).

CMOS

n. 1. Acronym for complementary metal-oxide semiconductor. A semiconductor technology in which pairs of metal-oxide semiconductor field effect transistors (MOSFETs), one N-type and the other P-type, are integrated on a single silicon chip. Generally used for RAM and switching applications, these devices have very high speed and extremely low power consumption. They are, however, easily damaged by static electricity. See also MOSFET, N-type semiconductor, P-type semiconductor. 2. The battery-backed memory (presumably made with complementary metal-oxide semiconductor technology) used to store parameter values needed to boot IBM Personal Computers and compatibles, such as the type of disks and the amount of memory, as well as the clock/calendar time.

CMOS RAM

n. Random access memory made using complementary metal-oxide semiconductor technology. CMOS chips consume extremely little power and have high tolerance for noise from the power supply. These characteristics make CMOS chips, including CMOS RAM chips, very useful in hardware components that are powered by batteries, such as most microcomputer clocks and certain types of scratchpad RAM that are maintained by the operating system. See also CMOS (definition 1), parameter RAM, RAM.

CMOS setup

n. A system configuration utility, accessible at boot time, for setting up certain system options, such as the date and time, the kind of drives installed, and port configuration. See also CMOS (definition 2).

CMY

n. Acronym for cyan-magenta-yellow. A model for describing colors that are produced by absorbing light, as by ink on paper, rather than by emitting light, as on a video monitor. The three kinds of cone cells in the eye respond to red, green, and blue light, which are absorbed (removed from white light) by cyan, magenta, and yellow pigments, respectively. Percentages of pigments in these subtractive primary colors can therefore be mixed to get the appearance of any desired color. Absence of any pigment leaves white unchanged; adding 100 percent of all three pigments turns white to black. Compare CMYK, RGB.

CMYK

n. Acronym for cyan-magenta-yellow-black. A color model that is similar to the CMY color model but produces black with a separate black component rather than by adding 100 percent of cyan, magenta, and yellow. See also CMY.

coaxial cable

n. A two-conductor cable consisting of a center wire inside a grounded cylindrical shield, typically made of braided wire, that is insulated from the center wire. The shield prevents signals transmitted on the center wire from affecting nearby components and prevents external interference from affecting the signal carried on the center wire.

code¹

n. 1. Program instructions. Source code consists of human-readable statements written by a programmer in a programming language. Machine code consists of numerical instructions that the computer can recognize and execute and that were converted from source code. See also data, program. 2. A system of symbols used to convert information from one form to another. A code for converting information in order to conceal it is often called a cipher. 3. One of a set of symbols used to represent information.

code²

vb. To write program instructions in a programming language. See also program.

codec

n. 1. Short for coder/decoder. Hardware that can convert audio or video signals between analog and digital forms. 2. Short for compressor/decompressor. Hardware or software that can compress and uncompress audio or video data. See also compress², uncompress. 3. Hardware that combines the functions of definitions 1 and 2.

cold boot

n. A startup process that begins with turning on the computer's power. Typically, a cold boot involves some basic hardware checking by the system, after which the operating system is loaded from disk into memory. See also boot¹. Compare warm boot.

collate

vb. In data handling, to merge items from two or more similar sets to create a combined set that maintains the order or sequence of items in the original sets.

collision

n. The result of two devices or network workstations trying to transmit signals at the exact same time on the same channel. The typical outcome is a garbled transmission.

collision detection

n. 1. The process by which a node on a local area network monitors the communications line to determine when a collision has occurred; that is, when two nodes have attempted to transmit at the same time. Although network stations usually avoid collisions by monitoring the line and waiting for it to clear before transmitting, the method is not foolproof. When a collision does occur, the two nodes involved usually wait a random amount of time before attempting to retransmit. See also contention, CSMA/CD. 2. The process by which a game or simulation program determines whether two objects on the screen are touching each other. This is a time-consuming, often complicated procedure; some computers optimized for graphics and games, such as the Amiga, have special hardware built in specifically to detect collisions.

color

n. In physics, the component of the human perception of light that depends on frequency. For light of a single frequency, color ranges from violet at the high-frequency end of the visible-light band (a small portion of the total electromagnetic spectrum) to red at the low-frequency end. In computer video, color is produced by a combination of hardware and software. Software manipulates combinations of bits that represent the distinct shades of color that are destined for particular positions on the screen (characters or individual dots, called pixels). The video adapter hardware translates these bits into electrical signals, which in turn control the brightnesses of different-colored phosphors at the corresponding positions on the screen of the monitor CRT. The user's eye unites the light from the phosphors to perceive a single color. See also color model, color monitor, CRT, HSB, monitor, RGB, video, video adapter.

color bits

n. A predetermined number of bits assigned to each displayable pixel that determine its color when it is displayed on a monitor. For example, two color bits are required for four colors; eight color bits are required for 256 colors. See also pixel image. Compare bit plane.

color box

n. In the Microsoft NT and Windows 95 Paint accessory, a graphic screen element in the form of a paint box that is used to select foreground and background colors.

color management

n. In printing, the process of producing accurate, consistent color using any of a variety of output devices. Color management includes accurate conversion of RGB input from a scanner, camera, or monitor to CMYK output for a printer; application of a device profile for the printer or other output device on which the image will be reproduced; and allowance for environmental variations such as humidity and barometric pressure. See also CMYK, RGB.

color management system

n. A technology developed by Kodak and licensed to many other software vendors that is designed to calibrate and match colors that appear on video monitors and computer monitors and those that appear in any printed form. Acronym: CMS.

color printer

n. A computer printer that can print full-color output. Most color printers can also produce black-and-white output.

color saturation

n. The amount of a hue contained in a color; the more saturation, the more intense the color. See also color model, HSB.

color scanner

n. A scanner that converts images to a digitized format and is able to interpret color. Depth of color depends on the scanner's bit depth--its ability to transform color into 8, 16, 24, or 32 bits. High-end color scanners, commonly used when output is to be printed, are able to encode information at a high resolution or number of dots per inch (dpi). Low-end color scanners encode information at a resolution of 72 dpi and are commonly used for computer screen images not intended for printing. See also resolution (definition 1), scanner.

column

n. 1. A series of items arranged vertically within some type of framework--for example, a continuous series of cells running from top to bottom in a spreadsheet, a set of lines of specified width on a printed page, a vertical line of pixels on a video screen, or a set of values aligned vertically in a table or matrix. Compare row. 2. In a relational database management system, the name for an attribute. The collection of column values that form the description of a particular entity is called a tuple or row. A column is equivalent to a field in a record in a nonrelational file system. See also entity, field (definition 1), row, table (definition 2).

column chart

n. A bar chart in which values are displayed and printed as vertical bars. See also bar chart.

COM

n. 1. A name reserved by the MS-DOS operating system for serial communications ports. For example, if a modem is connected to one serial port and a serial printer to another, the devices are identified as COM1 and COM2 by the operating system. 2. Acronym for Component Object Model. A specification developed by Microsoft for building software components that can be assembled into programs or add functionality to existing programs running on Microsoft Windows platforms. COM components can be written in a variety of languages, although most are written in C++, and can be unplugged from a program at run time without having to recompile the program. COM is the foundation of the OLE (object linking and embedding), ActiveX, and DirectX specifications. See also ActiveX, component (definition 2), DirectX, OLE. 3. The extension reserved by MS-DOS for a type of executable binary (program) file limited to a single 64-kilobyte (KB) segment. COM files are often used for utility programs and short routines. They are not supported in OS/2. 4. Acronym for computer-output microfilm. Microfilm that can record data from a computer.

COM1

n. A serial communications port in Wintel systems. COM1 is usually specified by the I/O range 03F8H, is usually associated with interrupt request line IRQ4, and in many systems is used to connect an RS232 serial mouse. See also IRQ.

COM2

n. A serial communications port in Wintel systems. COM2 is usually specified by the I/O range 02F8H, is usually associated with interrupt request line IRQ3, and in many systems is used to connect a modem. See also IRQ.

COM3

n. A serial communications port in Wintel systems. COM3 is usually specified by the I/O range 03E8H, is usually associated with interrupt request line IRQ4, and in many systems is used as an alternative to COM1 or COM2 if the latter is being used by some other peripheral. See also IRQ.

COMDEX

n. Any of a series of annual computer trade shows operated by Softbank COMDEX,Inc. One of these shows takes place in Las Vegas each November and is the largest computer trade show in the United States.

Comité Consultatif International Télégraphique et Téléphonique

n. Also called International Telegraph and Telephone Consultative. See CCITT.

comma-delimited file

n. A data file consisting of fields and records, stored as text, in which the fields are separated from each other by commas. Use of comma-delimited files allows communication between database systems that use different formats. If the data in a field contains a comma, the field is further surrounded with quotation marks.

command

n. An instruction to a computer program that, when issued by the user, causes an action to be carried out. Commands are usually either typed at the keyboard or chosen from a menu.

COMMAND.COM

n. The command interpreter for MS-DOS. See also command interpreter.

command-driven

adj. Accepting commands in the form of code words or letters, which the user must learn. Compare menu-driven.

command interpreter

n. A program, usually part of the operating system, that accepts typed commands from the keyboard and performs tasks as directed. The command interpreter is responsible for loading applications and directing the flow of information between applications. In OS/2 and MS-DOS, the command interpreter also handles simple functions, such as moving and copying files and displaying disk directory information. See also shell¹.

Command key

n. On the original Macintosh keyboard, a key labeled with the special symbol, sometimes called the propeller or puppy foot. This key is found on one or both sides of the Spacebar, depending on the version of the Apple keyboard. The key serves some of the same functions as the Control key on IBM keyboards. See also Control key.

command line

n. A string of text written in the command language and passed to the command interpreter for execution. See also command language.

comment

n. Text embedded in a program for documentation purposes. Comments usually describe what the program does, who wrote it, why it was changed, and so on. Most programming languages have a syntax for creating comments so that they can be recognized and ignored by the compiler or assembler. Also called remark. See also comment out.

comment out

vb. To disable one or more lines of code from a program temporarily by enclosing them within a comment statement. See also comment, conditional compilation, nest.

commerce server

n. An HTTP server designed for conducting online business transactions. Data is transferred between the server and Web browser in an encrypted form to keep information such as credit card numbers reasonably secure. Commerce servers are typically used by online stores and companies that are set up for mail order business. The wares or services offered by the store or company are described and displayed in photographs on the store or company Web site, and users can order directly from the site, using their Web browser. A number of companies market commerce servers, including Netscape, Microsoft, and Quarterdeck. See also HTTP server (definition 1), Secure Sockets Layer, Web browser.

Commercial Internet Exchange

n. A non-profit trade organization of public Internet service providers. In addition to the usual representational and social activities, CIX also operates an Internet backbone router that is accessible to its members. See also backbone (definition 1), ISP, router. Acronym: CIX.

Common Access Method

n. A standard developed by Future Domain and other SCSI vendors allowing SCSI adapters to communicate with SCSI peripherals regardless of the particular hardware used. See also SCSI.

common carrier

n. A communications company (e.g., a telephone company) that provides service to the public and is regulated by governmental organizations.

Common Gateway Interface

n. The specification that defines communications between information servers (such as HTTP servers) and resources on the server's host computer, such as databases and other programs. For example, when a user submits a form through a Web browser, the HTTP server executes a program (often called a CGI script) and passes the user's input information to that program via CGI. The program then returns information to the server via CGI. Use of CGI can make a Web page much more dynamic and add interactivity for the user. See also CGI script, HTTP server.

Computer Graphics Interface

n. Acronym CGI. A software standard applied to computer graphics devices, such as printers and plotters. Computer Graphics Interface is an offshoot of a widely recognized graphics standard called GKS (Graphical Kernel System), which provides applications programmers with standard methods of creating, manipulating, and displaying or printing computer graphics. See also Graphical Kernel System.

Common Hardware Reference Platform

n. A specification describing a family of machines, based on the PowerPC processor, that are capable of booting multiple operating systems, including Mac OS, Windows NT, AIX, and Solaris. See also PowerPC. Acronym: CHRP.

Common Internet File System

n. A standard proposed by Microsoft that would compete directly with Sun Microsystems' Web Network File System. A system of file sharing of Internet or intranet files. Acronym: CIFS.

communications

n. The vast discipline encompassing the methods, mechanisms, and media involved in information transfer. In computer-related areas, communications involves data transfer from one computer to another through a communications medium, such as a telephone, microwave relay, satellite link, or physical cable. Two primary methods of computer communications exist: temporary connection of two computers through a switched network, such as the public telephone system, and permanent or semipermanent linking of multiple workstations or computers in a network. The line between the two is indistinct, however, because microcomputers equipped with modems are often used to access both privately owned and public-access network computers. See also asynchronous transmission, CCITT, channel (definition 2), communications protocol, IEEE, ISDN, ISO/OSI model, LAN, modem, network, synchronous transmission. Compare data transmission, telecommunications, teleprocess.

communications controller

n. A device used as an intermediary in transferring communications to and from the host computer to which it is connected. By relieving the host computer of the actual tasks of sending, receiving, deciphering, and checking transmissions for errors, a communications controller helps to make efficient use of the host computer's processing time--time that might be better used for noncommunications tasks. A communications controller can be either a programmable machine in its own right or a nonprogrammable device designed to follow certain communications protocols. See also front-end processor (definition 2).

communications link

n. The connection between computers that enables data transfer.

communications program

n. A software program that enables a computer to connect with another computer and to exchange information. For initiating communications, communications programs perform such tasks as maintaining communications parameters, storing and dialing phone numbers automatically, recording and executing logon procedures, and repeatedly dialing busy lines. Once a connection is made, communications programs can also be instructed to save incoming messages on disk or to find and transmit disk files. During communication, these types of programs perform the major, and usually invisible, tasks of encoding data, coordinating transmissions to and from the distant computer, and checking incoming data for transmission errors.

communications protocol

n. A set of rules or standards designed to enable computers to connect with one another and to exchange information with as little error as possible. The protocol generally accepted for standardizing overall computer communications is a seven-layer set of hardware and software guidelines known as the OSI (Open Systems Interconnection) model. A somewhat different standard, widely used before the OSI model was developed, is IBM's SNA (Systems Network Architecture). The word protocol is often used, sometimes confusingly, in reference to a multitude of standards affecting different aspects of communication, such as file transfer (for example, XMODEM and ZMODEM), handshaking (for example, XON/XOFF), and network transmissions (for example, CSMA/CD). See also ISO/OSI model, SNA.

communications satellite

n. A satellite stationed in geosynchronous orbit that acts as a microwave relay station, receiving signals sent from a ground-based station (earth station), amplifying them, and retransmitting them on a different frequency to another ground-based station. Initially used for telephone and television signals, communications satellites can also be used for high-speed transmission of computer data. Two factors affecting the use of satellites with computers, however, are propagation delay (the time lag caused by the distance traveled by the signal) and security concerns. See also downlink, uplink.

communications server

n. A gateway that translates packets on a local area network (LAN) into asynchronous signals, such as those used on telephone lines or in RS-232-C serial communications, and allows all nodes on the LAN access to its modems or RS-232-C connections. See also gateway, RS-232-C standard.

communications slot

n. On many models of the Apple Macintosh, a dedicated expansion slot for network interface cards. Acronym: CS.

communications software

n. The software that controls the modem in response to user commands. Generally such software includes terminal emulation as well as file transfer facilities. See also modem, terminal emulation.

communications system

n. The combination of hardware, software, and data transfer links that make up a communications facility.

compact disc

n. 1. An optical storage medium for digital data, usually audio. A compact disc is a nonmagnetic, polished metal disc with a protective plastic coating that can hold up to 74 minutes of high-fidelity recorded sound. The disk is read by an optical scanning mechanism that uses a high-intensity light source, such as a laser, and mirrors. Also called optical disc. 2. A technology that forms the basis of media such as CD-ROM, CD-ROM/XA, CD-I, CD-R, DVI, and PhotoCD. These media are all compact disc-based but store various types of digital information and have different read/write capabilities. Documentation for compact disc formats can be found in books designated by the color of their covers. For example, documentation for audio compact discs is found in the Red Book. See also CD-I, CD-R, CD-ROM, CD-ROM/XA, DVI, Green Book (definition 2), Orange Book (definition 2), PhotoCD, Red Book. Acronym: CD.

compact disc-erasable

n. A technological improvement in compact discs whereby information can be repeatedly changed on the CD. Contemporary CDs are "write once, read many," in that the information originally written cannot be changed, but can only be appended to. Acronym: CD-E.

compact disc player

n. A device that reads the information stored on a compact disc. A compact disc player contains the optical equipment necessary for reading a disc's contents and the electronic circuitry for interpreting the data as it is read.

compare

vb. To check two items, such as words, files, or numeric values, so as to determine whether they are the same or different. In a program, the outcome of a compare operation often determines which of two or more actions is taken next.

compatibility

n. 1. The degree to which a computer, an attached device, a data file, or a program can work with or understand the same commands, formats, or language as another. True compatibility means that any operational differences are invisible to people and programs alike. 2. The extent to which two machines can work in harmony. Compatibility (or the lack thereof) between two machines indicates whether, and to what degree, the computers can communicate, share data, or run the same programs. For example, an Apple Macintosh and an IBM PC are generally incompatible because they cannot communicate freely or share data without the aid of hardware and/or software that functions as an intermediary or a converter. 3. The extent to which a piece of hardware conforms to an accepted standard (for example, IBM-compatible or Hayes-compatible). In this sense, compatibility means that the hardware ideally operates in all respects like the standard on which it is based. 4. In reference to software, harmony on a task-oriented level among computers and computer programs. Computers deemed software-compatible are those that can run programs originally designed for other makes or models. Software compatibility also refers to the extent to which programs can work together and share data. In another area, totally different programs, such as a word processor and a drawing program, are compatible with one another if each can incorporate images or files created using the other. All types of software compatibility become increasingly important as computer communications, networks, and program-to-program file transfers become near-essential aspects of microcomputer operation. See also downward compatibility, upward-compatible.

compatibility mode

n. A mode in which hardware or software in one system supports operations of software from another system. The term often refers to the ability of advanced operating systems designed for Intel microprocessors (for example, OS/2 and Windows NT) to run MS-DOS software or to the ability of some UNIX workstations and of some Apple Macintosh systems to run MS-DOS software.

compile

vb. To translate all the source code of a program from a high-level language into object code prior to execution of the program. Object code is executable machine code or a variation of machine code. More generally, compiling is sometimes used to describe translating any high-level symbolic description into a lower-level symbolic or machine-readable format. A program that performs this task is known as a compiler. See also compiler, compile time, high-level language, machine code, source code. Compare interpret.

compiler

n. 1. Any program that transforms one set of symbols into another by following a set of syntactic and semantic rules. 2. A program that translates all the source code of a program written in a high-level language into object code prior to execution of the program. See also assembler, compile, high-level language, interpreted language, language processor, object code.

comp. newsgroups

n. Usenet newsgroups that are part of the comp. hierarchy and have the prefix comp. These newsgroups are devoted to discussions of computer hardware, software, and other aspects of computer science. Comp. newsgroups are one of the seven original Usenet newsgroup hierarchies. The other six are misc., news., rec., sci., soc., and talk. See also newsgroup, traditional newsgroup hierarchy, Usenet.

component

n. 1. A discrete part of a larger system or structure. 2. An individual modular software routine that has been compiled and dynamically linked, and is ready to use with other components or programs. See also compile, component software, link (definition 1), program, routine.

COM port

or comm port n. Short for communications port, the logical address assigned by MS-DOS (versions 3.3 and higher) and Microsoft Windows (including Windows 95 and Windows NT) to each of the four serial ports on an IBM Personal Computer or a PC compatible. COM ports also have come to be known as the actual serial ports on a PC's CPU where peripherals, such as printers, scanners, and external modems, are plugged in. See also COM (definition 1), input/output port, serial port.

compress¹

n. A proprietary UNIX utility for reducing the size of data files. Files compressed with this utility have the extension .Z added to their names.

compress²

vb. To reduce the size of a set of data, such as a file or a communications message, so that it can be stored in less space or transmitted with less bandwidth. Data can be compressed by removing repeated patterns of bits and replacing them with some form of summary that takes up less space; restoring the repeated patterns decompresses the data. Lossless compression methods must be used for text, code, and numeric data files; lossy compression may be used for video and sound files. See also lossless compression, lossy compression.

compressed disk

n. A hard disk or floppy disk whose apparent capacity to hold data has been increased through the use of a compression utility, such as Stacker or Double Space. See also data compression.

compressed drive

n. A hard disk whose apparent capacity has been increased through the use of a compression utility, such as Stacker or Double Space. See also compressed disk, data compression.

compressed file

n. A file whose contents have been compressed by a special utility program so that it occupies less space on a disk or other storage device than in its uncompressed (normal) state. See also installation program, LHARC, PKUNZIP, PKZIP, utility program.

CompuServe

n. An online information service that provides information and communications capabilities, including Internet access. It is primarily known for its technical support forums for commercial hardware and software products and for being one of the first large commericial online services. CompuServe also operates various private network services.

compute

vb. 1. To perform calculations. 2. To use a computer or cause it to do work.

computer

n. Any machine that does three things: accepts structured input, processes it according to prescribed rules, and produces the results as output. Ways to categorize computers are described in the table. See also analog, digital, integrated circuit, large-scale integration, very-large-scale integration. k:\compdict\database\4128.doc

computer-aided design and drafting

n. A system of hardware and software similar to CAD but with additional features related to engineering conventions, including the ability to display dimension specifications and other notes. See also CAD. Acronym: CADD.

computer art

n. A broad term that can refer either to art created on a computer or to art generated by a computer, the difference being whether the artist is human or electronic. When created by human beings, computer art is done with painting programs that offer a range of line-drawing tools, brushes, shapes, patterns, and colors. Some programs also offer predrawn figures and animation capabilities.

computer-assisted learning

n. The use of computers and their multimedia abilities to present information for educational purposes.

computer center

n. A centralized location that contains computers, such as mainframes or minicomputers, along with associated equipment for providing data processing services to a group of people.

computer crime

n. The illegal use of a computer by an unauthorized individual, either for pleasure (as by a computer hacker) or for profit (as by a thief). See also hacker (definition 2).

computer game

n. A class of computer program in which one or more users interact with the computer as a form of entertainment. Computer games run the gamut from simple alphabet games for toddlers to chess, treasure hunts, war games, and simulations of world events. The games are controlled from a keyboard or with a joystick or other device and are supplied on disks, on CD-ROMs, as game cartridges, or as arcade devices.

computer graphics

n. The display of "pictures," as opposed to only alphabetic and numeric characters, on a computer screen. Computer graphics encompasses different methods of generating, displaying, and storing information. Thus, computer graphics can refer to the creation of business charts and diagrams; the display of drawings, italic characters, and mouse pointers on the screen; or the way images are generated and displayed on the screen. See also graphics mode, presentation graphics, raster graphics, vector graphics.

Computer Graphics Interface

n. A software standard applied to computer graphics devices, such as printers and plotters. Computer Graphics Interface is an offshoot of a widely recognized graphics standard called GKS (Graphical Kernel System), which provides applications programmers with standard methods of creating, manipulating, and displaying or printing computer graphics. See also Graphical Kernel System. Acronym: CGI.

Computer Graphics Metafile

n. A software standard related to the widely recognized GKS (Graphical Kernel System) that provides applications programmers with a standard means of describing a graphic as a set of instructions for re-creating it. A graphics metafile can be stored on disk or sent to an output device; Computer Graphics Metafile provides a common language for describing such files in relation to the GKS standard. See also Graphical Kernel System. Acronym: CGM.

computer literacy

n. Knowledge and an understanding of computers combined with the ability to use them effectively. On the least specialized level, computer literacy involves knowing how to turn on a computer, start and stop simple application programs, and save and print information. At higher levels, computer literacy becomes more detailed, involving the ability of power users to manipulate complex applications and, possibly, to program in languages such as Basic or C. At the highest levels, computer literacy leads to specialized technical knowledge of electronics and assembly language. See also power user.

computer name

n. In computer networking, a name that uniquely identifies a computer to the network. A computer's name cannot be the same as any other computer or domain name on the network. It differs from a user name in that the computer name is used to identify a particular computer and all its shared resources to the rest of the system so that they can be accessed. Compare alias (definition 2), user name.

computerphile

n. A person who is immersed in the world of computing, who collects computers, or whose hobby involves computing.

computer revolution

n. The societal and technological phenomenon involving the swift development and widespread use and acceptance of computers--specifically single-user personal computers. The impact of these machines is considered revolutionary for two reasons. First, their appearance and success were rapid. Second, and more important, their speed and accuracy produced a change in the ways in which information can be processed, stored, and transferred.

computer science

n. The study of computers, including their design, operation, and use in processing information. Computer science combines both theoretical and practical aspects of engineering, electronics, information theory, mathematics, logic, and human behavior. Aspects of computer science range from programming and computer architecture to artificial intelligence and robotics.

computer security

n. The steps taken to protect a computer and the information it contains. On large systems or those handling financial or confidential data, computer security requires professional supervision that combines legal and technical expertise. On a microcomputer, data protection can be achieved by backing up and storing copies of files in a separate location, and the integrity of data on the computer can be maintained by assigning passwords to files, marking files "read-only" to avoid changes to them, physically locking a hard disk, storing sensitive information on floppy disks kept in locked cabinets, and installing special programs to protect against viruses. On a computer to which many people have access, security can be maintained by requiring personnel to use passwords and by granting only approved users access to sensitive information. See also bacterium, encryption, virus.

CON

n. The logical device name for console; reserved by the MS-DOS operating system for the keyboard and the screen. The input-only keyboard and the output-only screen together make up the console and represent the primary sources of input and output in an MS-DOS computer system.

concurrent

adj. Of, pertaining to, or characteristic of a computer operation in which two or more processes (programs) have access to the microprocessor's time and are therefore carried out nearly simultaneously. Because a microprocessor can work with much smaller units of time than people can perceive, concurrent processes appear to be occurring simultaneously but in reality are not.

concurrent execution

n. The apparently simultaneous execution of two or more routines or programs. Concurrent execution can be accomplished on a single process or by using time-sharing techniques, such as dividing programs into different tasks or threads of execution, or by using multiple processors. Also called parallel execution. See also parallel algorithm, processor, sequential execution, task, thread (definition 1), time-sharing.

condensed

adj. Of, pertaining to, or characteristic of a font style, supported in some applications, that reduces the width of each character and then sets the characters closer together than their normal spacing. Many dot-matrix printers have a feature that causes the printer to reduce the width of each character and print them closer together, resulting in more characters fitting on a single line. Compare expanded.

CONFIG.SYS

n. A special text file that controls certain aspects of operating-system behavior in MS-DOS and OS/2. Commands in the CONFIG.SYS file enable or disable system features, set limits on resources (for example, the maximum number of open files), and extend the operating system by loading device drivers that control hardware specific to an individual computer system.

configuration

n. 1. In reference to a single microcomputer, the sum of a system's internal and external components, including memory, disk drives, keyboard, video, and generally less critical add-on hardware, such as a mouse, modem, or printer. Software (the operating system and various device drivers), the user's choices established through configuration files such as the AUTOEXEC.BAT and CONFIG.SYS files on IBM PCs and compatibles, and sometimes hardware (switches and jumpers) are needed to "configure the configuration" to work correctly. Although system configuration can be changed, as by adding more memory or disk capacity, the basic structure of the system--its architecture--remains the same. See also AUTOEXEC.BAT, CONFIG.SYS. 2. In relation to networks, the entire interconnected set of hardware, or the way in which a network is laid out--the manner in which elements are connected.

configuration file

n. A file that contains machine-readable operating specifications for a piece of hardware or software or that contains information on another file or on a specific user, such as the user's logon ID.

connect charge

n. The amount of money a user must pay for connecting to a commercial communications system or service. Some services calculate the connect charge as a flat rate per billing period. Others charge a varying rate based on the type of service or the amount of information being accessed. Still others base their charges on the number of time units used, the time or distance involved per connection, the bandwidth of each connected session, or some combination of the preceding criteria. See also connect time.

connection

n. A physical link via wire, radio, fiber-optic cable, or other medium between two or more communications devices.

connectionless

adj. In communications, of, pertaining to, or characteristic of a method of data transmission that does not require a direct connection between two nodes on one or more networks. Connectionless communication is achieved by passing, or routing, data packets, each of which contains a source and destination address, through the nodes until the destination is reached. See also node (definition 2), packet (definition 2). Compare connection-oriented.

connection-oriented

adj. In communications, of, pertaining to, or characteristic of a method of data transmission that requires a direct connection between two nodes on one or more networks. Compare connectionless.

connectivity

n. 1. The nature of the connection between a user's computer and another computer, such as a server or a host computer on the Internet or a network. This may describe the quality of the circuit or telephone line, the degree of freedom from noise, or the bandwidth of the communications devices. 2. The ability of hardware devices or software packages to transmit data between other devices or packages. 3. The ability of hardware devices, software packages, or a computer itself to work with network devices or with other hardware devices, software packages, or a computer over a network connection.

connectoid

n. In Windows 95/98 and Windows NT, an icon representing a dial-up networking connection that also executes a script for logging onto the network dialed.

connector

n. 1. In hardware, a coupler used to join cables or to join a cable to a device (for example, an RS-232-C connector used to join a modem cable to a computer). Most connector types are available in one of two genders--male or female. A male connector is characterized by one or more exposed pins; a female connector is characterized by one or more receptacles designed to accept the pins on the male connector. See also DB connector, DIN connector. 2. In programming, a circular symbol used in a flowchart to indicate a break, as to another page.

connect time

n. The amount of time during which a user is actively connected to a remote computer. On commercial systems, the connect time is one means of calculating how much money the user must pay for using the system. See also connect charge.

console

n. A control unit, such as a terminal, through which a user communicates with a computer. In microcomputers, the console is the cabinet that houses the main components and controls of the system, sometimes including the screen, the keyboard, or both. With the MS-DOS operating system, the console is the primary input (keyboard) and primary output (screen) device, as evidenced by the device name CON. See also CON, system console.

consultant

n. A computer professional who deals with client firms as an independent contractor rather than as an employee. Consultants are often engaged to analyze user needs and develop system specifications.

container

n. 1. In OLE terminology, a file containing linked or embedded objects. See also OLE. 2. In SGML, an element that has content as opposed to one consisting solely of the tag name and attributes. See also element (definition 2), SGML, tag (definition 3).

content

n. 1. The data that appears between the starting and ending tags of an element in an SGML or HTML document. The content of an element may consist of plain text or other elements. See also element (definition 2), HTML, SGML, tag (definition 3). 2. The message body of a newsgroup article or e-mail message.

contention

n. On a network, competition among stations for the opportunity to use a communications line or network resource. In one sense, contention applies to a situation in which two or more devices attempt to transmit at the same time, thus causing a collision on the line. In a somewhat different sense, contention also applies to a free-for-all method of controlling access to a communications line, in which the right to transmit is awarded to the station that wins control of the line. See also CSMA/CD. Compare token passing.

context-sensitive help

n. A form of assistance in which a program that provides on-screen help shows information to the user concerning the current command or operation being attempted.

context-sensitive menu

n. A menu that highlights options as available or unavailable depending on the context in which the option is called. The menus on Windows' menu bar, for example, are context sensitive; options such as "copy" are grayed out if nothing is selected.

context switching

n. A type of multitasking; the act of turning the central processor's "attention" from one task to another, rather than allocating increments of time to each task in turn. See also multitasking, time slice.

contextual search

n. A search operation in which the user can direct a program to search specified files for a particular set of text characters.

contiguous

adj. Having a shared boundary; being immediately adjacent. For example, contiguous sectors on a disk are data-storage segments physically located next to one another.

contiguous data structure

n. A data structure, such as an array, that is stored in a consecutive set of memory locations. See also data structure. Compare noncontiguous data structure.

continuous carrier

n. In communications, a carrier signal that remains on throughout the transmission, whether or not it is carrying information.

continuous processing

n. The processing of transactions as they are input to the system. Compare batch processing (definition 3).

contrast

n. 1. The degree of difference between light and dark extremes of color on a monitor or on printed output. 2. The control knob by which the contrast of a monitor is changed.

control

n. 1. Management of a computer and its processing abilities so as to maintain order as tasks and activities are carried out. Control applies to measures designed to ensure error-free actions carried out at the right time and in the right order relative to other data-handling or hardware-based activities. In reference to hardware, control of system operations can reside in a data pathway called a control bus. In reference to software, control refers to program instructions that manage data-handling tasks. 2. In a graphical user interface, an object on the screen that can be manipulated by the user to perform an action. The most common controls are buttons, which allow the user to select options, and scroll bars, which allow the user to move through a document or position text in a window.

control bus

n. The set of lines (conductors) within a computer that carry control signals between the central processing unit (CPU) and other devices. For example, a control bus line is used to indicate whether the CPU is attempting to read from memory or to write to it; another control bus line is used by memory to request an interrupt in case of a memory error.

control character

n. 1. Any of the first 32 characters in the ASCII character set (0 through 31 in decimal representation), each of which is defined as having a standard control function, such as carriage return, linefeed, or backspace. 2. Any of the 26 characters Control-A through Control-Z (1 through 26 in decimal representation) that can be typed at the keyboard by holding the Control key down and typing the appropriate letter. The six remaining characters with control functions, such as Escape (ASCII 27), cannot be typed using the Control key. Compare control code.

control code

n. One or more nonprinting characters used by a computer program to control the actions of a device, used in printing, communications, and management of display screens. Control codes are mainly employed by programmers or by users to control a printer when an application program does not support the printer or one of its specialized features. In video, control codes are sent from a computer to a display unit to manipulate the appearance of text or a cursor on the screen. Popular video control code sets are ANSI and VT-100. Also called escape sequence, setup string. See also control character.

Control key

n. A key that, when pressed in combination with another key, gives the other key an alternative meaning. In many application programs, Control (labeled CTRL or Ctrl on a PC keyboard) plus another key is used as a command for special functions. See also control character (definition 2).

controller

n. A device on which other devices rely for access to a computer subsystem. A disk controller, for example, controls access to one or more disk drives, managing physical and logical access to the drive or drives.

control panel

n. In Windows and Macintosh systems, a utility that allows the user to control aspects of the operating system or hardware, such as system time and date, keyboard characteristics, and networking parameters.

control unit

n. A device or circuit that performs an arbitrating or regulating function. For example, a memory controller chip controls access to a computer's memory and is the control unit for that memory.

conventional memory

n. The amount of RAM addressable by an IBM PC or compatible machine operating in real mode. This is typically 640 kilobytes (KB). Without the use of special techniques, conventional memory is the only kind of RAM accessible to MS-DOS programs. See also protected mode, real mode. Compare expanded memory, extended memory.

converter

n. Any device that changes electrical signals or computer data from one form to another. For example, an analog-to-digital converter translates analog signals to digital signals.

cookbook¹

adj. Of, pertaining to, or characteristic of a book or manual that presents information using a step-by-step approach. For example, a cookbook approach to programming might present a series of sample programs that the reader could analyze and adapt to his or her own needs.

cookbook²

n. A computer book or manual that presents information using a step-by-step approach. Most often, cookbook refers to a programming guide, but it can refer to a book that shows how to accomplish specialized tasks in an application.

cookie

n. 1. A block of data that a server returns to a client in response to a request from the client. 2. On the World Wide Web, a block of data that a Web server stores on a client system. When a user returns to the same Web site, the browser sends a copy of the cookie back to the server. Cookies are used to identify users, to instruct the server to send a customized version of the requested Web page, to submit account information for the user, and for other administrative purposes. 3. Originally an allusion to "fortune cookie," a UNIX program that outputs a different message, or "fortune," each time it is used. On some systems, the cookie program is run during user logon.

cookie filtering tool

n. A utility that prevents a cookie on a Web browser from relaying information about the user requesting access to a Web site. See also cookie (definition 2).

cooperative multitasking

n. A type of multitasking in which one or more background tasks are given processing time during idle times in the foreground task only if the foreground task allows it. This is the primary mode of multitasking in the Macintosh operating system. See also background¹, context switching, foreground ¹, multitasking, time slice. Compare preemptive multitasking.

cooperative processing

n. A mode of operation characteristic of distributed systems in which two or more computers, such as a mainframe and a microcomputer, can simultaneously carry out portions of the same program or work on the same data. Compare distributed processing.

coprocessor

n. A processor, distinct from the main microprocessor, that performs additional functions or assists the main microprocessor. The most common type of coprocessor is the floating-point coprocessor, also called a numeric or math coprocessor, which is designed to perform numeric calculations faster and better than the general-purpose microprocessors used in personal computers. See also floating-point processor.

copy

vb. To duplicate information and reproduce it in another part of a document, in a different file or memory location, or in a different medium. A copy operation can affect data ranging from a single character to large segments of text, a graphics image, or one to many data files. Text and graphics, for example, can be copied to another part of a document, to the computer's memory (by means of a temporary storage facility such as the Microsoft Windows or Apple Macintosh Clipboard), or to a different file. Similarly, files can be copied from one disk or directory to another, and data can be copied from the screen to a printer or to a data file. In most cases, a copy procedure leaves the original information in place. Compare cut and paste, move.

copy program

n. 1. A program designed to duplicate one or more files to another disk or directory. 2. A program that disables or circumvents the copy-protection device on a computer program so that the software can be copied, often illegally, to another disk. See also copy protection.

copyright

n. A method of protecting the rights of an originator of a creative work, such as a text, a piece of music, a painting, or a computer program, through law. In many countries the originator of a work has copyright in the work as soon as it is fixed in a tangible medium (such as a piece of paper or a disk file); that rule applies in the United States for works created after 1977. Registration of a copyright, or the use of a copyright symbol, is not needed to create the copyright but does strengthen the originator's legal powers. Unauthorized copying and distribution of copyrighted material can lead to severe penalties, whether done for profit or not. Copyrights affect the computer community in three ways: the copyright protection of software, the copyright status of material (such as song lyrics) distributed over a network such as the Internet, and the copyright status of original material distributed over a network (such as a newsgroup post). The latter two involve electronic media that are arguably not tangible, and legislation protecting the information disseminated through electronic media is still evolving. See also fair use, General Public License.

CORBA

n. Acronym for Common Object Request Broker Architecture. A specification developed by the Object Management Group in 1992 in which pieces of programs (objects) communicate with other objects in other programs, even if the two programs are written in different programming languages and are running on different platforms. A program makes its request for objects through an object request broker, or ORB, and thus does not need to know the structure of the program from where the object comes. CORBA is designed to work in object-oriented environments. See also object (definition 2), Object Management Group, object-oriented.

core

n. One of the types of memory built into computers before random access memory (RAM) was available or affordable. Some people still use the term to refer to the main memory of any computer system, as in the phrase core dump--a listing of the raw contents of main memory at the moment of a system crash. Compare RAM.

core program

n. A program or program segment that is resident in random access memory (RAM).

corruption

n. A process wherein data in memory or on disk is unintentionally changed, with its meaning thereby altered or obliterated.

cost-benefit analysis

n. The comparison of benefits to costs for a particular item or action. Cost-benefit analysis is often used in MIS or IS departments to determine such things as whether purchasing a new computer system is a good investment or whether hiring more staff is necessary. See also IS, MIS.

country-specific

adj. Of, pertaining to, or characteristic of hardware or software that uses characters or conventions unique to a particular country or group of countries. Country-specific does not necessarily refer to spoken languages, although it does allow for special characters (such as accent marks) that are language-specific. Generally, the features considered country-specific include keyboard layout (including special-character keys), time and date conventions, financial and monetary symbols, decimal notation (decimal point or comma), and alphabetic sorting order. Such features are handled either by a computer's operating system (for example, by the Keyboard and Country commands in MS-DOS) or by application programs that offer options for tailoring documents to a particular set of national or international conventions.

courseware

n. Software dedicated to education or training.

CP/M

n. Acronym for Control Program/Monitor. A line of operating systems from Digital Research, Inc., for microcomputers based on Intel microprocessors. The first system, CP/M-80, was the most popular operating system for 8080- and Z80-based microcomputers. Digital Research also developed CP/M-86 for 8086/8088-based computers, CP/M-Z8000 for Zilog Z8000-based computers, and CP/M-68K for Motorola 68000-based computers. When the IBM PC and MS-DOS were introduced, common use of CP/M by end users dwindled. DRI continues to enhance the CP/M line, supporting multitasking with the concurrent CP/M and MP/M products. See also MP/M.

CPU

n. Short for central processing unit.

CPU cache

n. A section of fast memory linking the central processing unit (CPU) and main memory that temporarily stores data and instructions the CPU needs to execute upcoming commands and programs. Considerably faster than main memory, the CPU cache contains data that is transferred in blocks, thereby speeding execution. The system anticipates the data it will need through algorithms. Also called cache memory, memory cache. See also cache, central processing unit, VCACHE.

CPU cycle

n. 1. The smallest unit of time recognized by the central processing unit (CPU)--typically a few hundred-millionths of a second. 2. The time required for the CPU to perform the simplest instruction, such as fetching the contents of a register or performing a no-operation instruction (NOP). Also called clock tick.

CPU fan

n. An electric fan usually placed directly on a central processing unit (CPU) or on the CPU's heat sink to help dissipate heat from the chip by circulating air around it. See also central processing unit, heat sink.

CPU speed

n. A relative measure of the data-processing capacity of a particular central processing unit (CPU), usually measured in megahertz. See also central processing unit.

CPU time

n. In multiprocessing, the amount of time during which a particular process has active control of the central processing unit (CPU). See also central processing unit, multiprocessing.

cracker

n. A person who overcomes the security measures of a computer system and gains unauthorized access. The goal of some crackers is to obtain information illegally from a computer system or use computer resources. However, the goal of the majority is to merely break into the system. See also hacker.

crash¹

n. The failure of either a program or a disk drive. A program crash results in the loss of all unsaved data and can leave the operating system unstable enough to require restarting the computer. A disk drive crash, sometimes called a disk crash, leaves the drive inoperable and can cause loss of data. See also abend, head crash.

crash²

vb. 1. For a system or program, to fail to function correctly, resulting in the suspension of operation. See also abend. 2. For a magnetic head, to hit a recording medium, with possible damage to one or both.

crash recovery

n. The ability of a computer to resume operation after a disastrous failure, such as the failure of a hard drive. Ideally, recovery can occur without any loss of data, although usually some, if not all, data is lost. See also crash¹.

Cray-1

n. An early supercomputer developed in 1976 by Seymour Cray. Extremely powerful in its day, the 64-bit Cray-1 ran at 75 MHz and was capable of executing 160 million floating-point operations per second. See also supercomputer.

CRC

n. Acronym for cyclical (or cyclic) redundancy check. A procedure used in checking for errors in data transmission. CRC error checking uses a complex calculation to generate a number based on the data transmitted. The sending device performs the calculation before transmission and sends its result to the receiving device. The receiving device repeats the same calculation after transmission. If both devices obtain the same result, it is assumed that the transmission was error-free. The procedure is known as a redundancy check because each transmission includes not only data but extra (redundant) error-checking values. Communications protocols such as XMODEM and Kermit use cyclical redundancy checking.

creator

n. On the Apple Macintosh, the program that creates a file. Files are linked to their creators by creator codes; this link enables the operating system to open the creator application when a document file is opened.

crop

vb. In computer graphics, to cut off part of an image, such as unneeded sections of a graphic or extra white space around the borders. As in preparing photographs or illustrations for traditional printing, cropping is used to refine or clean up a graphic for placement in a document.

crop marks

n. 1. Lines drawn at the edges of pages to mark where the paper will be cut to form pages in the final document. See also registration marks. 2. Lines drawn on photographs or illustrations to indicate where they will be cropped, or cut. See also crop.

cross-hatching

n. Shading made up of regularly spaced, intersecting lines. Cross-hatching is one of several methods for filling in areas of a graphic.

cross-linked files

n. In Windows 95, Windows 3.x, and MS-DOS, a file-storage error occurring when one or more sections, or clusters, of the hard drive or a floppy disk have been erroneously allocated to more than one file in the file allocation table. Like lost clusters, cross-linked files can result from the ungraceful exit (messy or abrupt termination) of an application program. See also file allocation table, lost cluster.

cross-platform

adj. Of, pertaining to, or characteristic of a software application or hardware device that can be run or operated on more than one system platform.

cross-post

vb. To copy a message or news article from one newsgroup, conference topic, e-mail system, or other communications channel to another--for example, from a Usenet newsgroup to a CompuServe forum or from e-mail to a newsgroup.

crosstalk

n. Interference caused by a signal transferring from one circuit to another, as on a telephone line.

CRT

n. Acronym for cathode-ray tube. The basis of the television screen and the standard microcomputer display screen. A CRT display is built around a vacuum tube containing one or more electron guns whose electron beams rapidly sweep horizontally across the inside of the front surface of the tube, which is coated with a material that glows when irradiated. Each electron beam moves from left to right, top to bottom, one horizontal scan line at a time. To keep the screen image from flickering, the electron beam refreshes the screen 30 times or more per second. The clarity of the image is determined by the number of pixels on the screen. See also pixel, raster, resolution (definition 1).

CRT controller

n. The part of a video adapter board that generates the video signal, including the horizontal and vertical synchronization signals. See also video adapter.

cryptoanalysis

n. The decoding of electronically encrypted information for the purpose of understanding encryption techniques. See also cryptography, encryption.

cryptography

n. The use of codes to convert data so that only a specific recipient will be able to read it, using a key. The persistent problem of cryptography is that the key must be transmitted to the intended recipient and may be intercepted. Public key cryptography is a recent significant advance. See also code¹ (definition 2), encryption, PGP, private key, public key.

C shell

n. One of the command line interfaces available under UNIX. The C shell is very usable but is not on every system. Compare Bourne shell, Korn shell.

CSMA/CD

n. Acronym for Carrier Sense Multiple Access with Collision Detection. A network protocol for handling situations in which two or more nodes (stations) transmit at the same time, thus causing a collision. With CSMA/CD, each node on the network monitors the line and transmits when it senses that the line is not busy. If a collision occurs because another node is using the same opportunity to transmit, both nodes stop transmitting. To avoid another collision, both then wait for differing random amounts of time before attempting to transmit again. Compare token passing.

CTL

n. Short for control. See control character (definition 2), Control key.

CTRL

or Ctrl Short for control. A designation used to label the Control key on computer keyboards. See also control character (definition 2), Control key.

Ctrl-Alt-Del

n. A three-key combination used with IBM and compatible computers to restart (reboot) the machine. Pressing Ctrl-Alt-Del (Control-Alt-Delete) causes a warm boot in MS-DOS--the computer restarts but does not go through all of the internal checks involved when power to the system is switched on (cold boot). In Windows 95 and Windows NT, Ctrl-Alt-Del provides a dialog box from which the user may choose to shut down the computer or end any current tasks.

Ctrl-C

n. 1. In UNIX, the key combination used to break out of a running process. 2. The keyboard shortcut recognized by many programs (as in Windows) as an instruction to copy the currently selected item.

Ctrl-S

n. 1. On systems in which a software handshake is used between terminals and a central computer, the key combination used to suspend output. Ctrl-Q will resume output after a Ctrl-S suspension. See also software handshake, XON/XOFF. 2. A keyboard shortcut recognized by many programs as an instruction to save the current document or file.

curly quotes

n. See smart quotes.

current

n. The flow of electric charge through a conductor, or the amount of such flow. Current is measured in amperes. See also ampere, coulomb. Compare volt.

current directory

n. The disk directory at the end of the active directory path--the directory that is searched first for a requested file, and the one in which a new file is stored unless another directory is specified. See also path (definition 2).

cursor

n. 1. A special on-screen indicator, such as a blinking underline or rectangle, that marks the place at which a keystroke will appear when typed. 2. In reference to digitizing tablets, the stylus (pointer or "pen"). 3. In applications and operating systems that use a mouse, the arrow or other on-screen icon that moves with movements of the mouse.

cursor blink speed

n. The rate at which a cursor on screen flashes on and off. See also cursor (definition 1).

CUSeeMe

n. A videoconferencing program developed at Cornell University. It was the first program to give Windows and Mac OS users the ability to engage in real-time videoconferencing over the Internet, but it requires a lot of bandwidth (at least 128 Kbps speed) to function properly.

customize

vb. To modify or assemble hardware or software to suit the needs or preferences of the user. Traditionally, hardware customizing ranges from designing an electronic circuit for a particular customer to putting together a computer facility tailored to a customer's special need. Software customizing usually means modifying or designing software for a specific customer.

custom software

n. Any type of program developed for a particular client or to address a special need. Certain products, such as dBASE and Lotus 1-2-3, are designed to provide the flexibility and tools required for producing tailor-made applications. See also CASE.

cut

vb. To remove part of a document, usually placing it temporarily in memory so that the cut portion can be inserted (pasted) elsewhere. Compare delete.

cut and paste

n. A procedure in which the computer acts as an electronic combination of scissors and glue for reorganizing a document or for compiling a document from different sources. In cut and paste, the portion of a document to be moved is selected, removed to storage in memory or on disk, and then reinserted into the same or a different document.

cybercafe

or cyber café n. 1. A coffee shop or restaurant that offers access to PCs or other terminals that are connected to the Internet, usually for a per-hour or per-minute fee. Users are encouraged to buy beverages or food to drink or eat while accessing the Internet. 2. A virtual café on the Internet, generally used for social purposes. Users interact with each other by means of a chat program or by posting messages to one another through a bulletin board system, such as in a newsgroup or on a Web site.

cybercop

n. A person who investigates criminal acts committed online, especially fraud and harassment.

Cyberdog

n. Apple's Internet suite for HTML browsing and e-mail, based on OpenDoc for easy integration with other applications. See also OpenDoc.

cybernaut

n. One who spends copious time online, exploring the Internet. Also called Internaut. See also cyberspace.

cybernetics

n. The study of control systems, such as the nervous system, in living organisms and the development of equivalent systems in electronic and mechanical devices. Cybernetics compares similarities and differences between living and nonliving systems (whether those systems comprise individuals, groups, or societies) and is based on theories of communication and control that can be applied to either or both. See also bionics.

cyberpunk

n. 1. A genre of near-future science fiction in which conflict and action take place in virtual-reality environments maintained on global computer networks in a worldwide culture of dystopian alienation. The prototypical cyberpunk novel is William Gibson's Neuromancer (1982). 2. A category of popular culture that resembles the ethos of cyberpunk fiction. 3. A person or fictional character who resembles the heroes of cyberpunk fiction.

cybersex

n. Communication via electronic means, such as e-mail, chat, or newsgroups, for the purpose of sexual stimulation or gratification. See also chat¹ (definition 1), newsgroup.

cyberspace

n. 1. The advanced shared virtual-reality network imagined by William Gibson in his novel Neuromancer (1982). 2. The universe of environments, such as the Internet, in which persons interact by means of connected computers. A defining characteristic of cyberspace is that communication is independent of physical distance.

cybrarian

n. Software used at some libraries that allows one to query a database through the use of an interactive search engine.

cycle power

vb. To turn the power to a machine off and back on in order to clear something out of memory or to reboot after a hung or crashed state.

cycle time