C

C

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, Inc. and Sun Micro systems, Inc. See also C, Objective-C, object-oriented programming.

C2 n. A security class of the U.S. Department of Defense Trusted Computer System Evaluation Criteria (DOD 4200.28.STD). C2 is 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).

CA n. See certificate authority.

.cab n. File extension for cabinet files, which are multiple files compressed into one and extractable with the extract.exe utility. Such files are frequently found on Microsoft software (for example, Windows 9x) distribution disks.

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.

cable1 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. See the illustration.

Cable.

cable2 adj. Pertaining to the cable television (CATV) distribution system. For example, a cable modem is a modem that sends and receives digital data through a connection to a cable TV system. Because cable TV is a broadband service, it can carry data (such as an Internet connection) at a very high speed. See also CATV.

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 matcher n. A device that allows the use of a cable that has slightly different wire connections from those required by the devices to which it is attached.

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. However, cable modems do not operate at the same rate upstream (when sending information) and downstream (when receiving information). Upstream rates vary from about 2 Mbps to 10 Mbps, downstream rates from about 10 Mbps to 36 Mbps. See also coaxial cable, modem.

cable telephony n. Telephone service provided over a cable TV connection rather than over traditional telephone lines. Although service is delivered over cable rather than telephone wire, the end user perceives no difference between cable telephony and normal telephone service. Proponents of cable telephony see it as part of the eventual integration of Internet, television, and telephone services into a single communication/entertainment unit.

cable television n. See CATV.

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.

cache card n. An expansion card that increases a system s cache memory. See also cache, expansion board.

Cache-Coherent Non-Uniform Memory Access n. See ccNUMA.

cache farm n. A group of servers that save copies of Web pages to caches to fulfill successive requests without calling the pages up repeatedly from the Web server. In essence, the servers are dedicated to caching. By saving Web pages where they can be accessed without increasing traffic on the Web site, the cache farm allows higher-performance Web access for the end user and a reduction in network congestion and volume. See also cache.

cache memory n. See cache.

cache poisoning n. Deliberate corruption of Internet Domain Name System (DNS) information through alteration of data that equates host names with their IP addresses. Misleading information of this type, when cached (saved) by one DNS server and later passed to another, exposes DNS servers to attacks in which data sent from one host to another can be accessed or corrupted. Cache poisoning has been used to redirect network requests from a legitimate server to an alternate Web site. See also DNS.

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.

CAD/CAM n. Acronym for computer-aided design/computer-aided manufacturing. The use of computers in both the design and manufacture of a product. With CAD/CAM, a product, such as a machine part, is designed with a CAD program and the finished design is translated into a set of instructions that can be transmitted to and used by the machines dedicated to fabrication, assembly, and process control. See also CAD, I-CASE.

CADD 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. Acronym: CADD. See also CAD.

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

CAE n. Acronym for computer-aided engineering. An application that enables the user to perform engineering tests and analyses on designs created with a computer. In some instances, capabilities such as logic testing that are generally attributed to CAE applications are also part of CAD programs, so the distinction between CAD and CAE is not a hard-and-fast one. See also CAD, I-CASE.

CAI n. Acronym for computer-aided (or computer-assisted) instruction. An educational program designed to serve as a teaching tool. CAI programs typically use tutorials, drills, and question-and-answer sessions to present a topic and to test the student s comprehension. CAI programs are excellent aids for presenting factual material and for allowing students to pace their learning speed. Subjects and complexity range from beginning arithmetic to advanced mathematics, science, history, computer studies, and specialized topics. Also called: CAL, CAT, computer-aided learning, computer-aided teaching, computer-assisted learning, computer-assisted teaching, computer-augmented learning. See also I-CASE. Compare CBT, CMI.

CAL n. 1. Acronym for computer-assisted (or computer-augmented) learning. See CAI. 2. Acronym for Common Application Language. An object-oriented communications language for controlling home-networking products. CAL, originally part of the CEBus (Consumer Electronic Bus) standard for home automation, can be implemented with various communication protocols, home-networking standards, and home electronic products. See also CEBus, home automation.

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 2003 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 or callback security n. A security feature used to authenticate users calling in to a network. During callback, the network validates the caller s username and password, hangs up, and then returns the call, usually to 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 remote access server. See also authentication, preset-to callback.

callback modem n. A modem that, instead of answering an incoming call, requires the caller to enter a touch-tone code and hang up so that the modem can return the call. When the modem receives the caller s code, it checks the code against a stored set of phone numbers. If the code matches an authorized number, the modem dials the number and then opens a connection for the original caller. Callback modems are used when communications lines must be available to outside users but data must be protected from unauthorized intruders.

calling sequence n. In a program when a subroutine call occurs, an agreement between the calling routine and the called routine on how arguments will be passed and in what order, how values will be returned, and which routine will handle any necessary housekeeping (such as cleaning up the stack). The calling sequence becomes important when the calling and called routines were created with different compilers or if either was written in assembly language. Two common calling sequences are the C calling sequence and the Pascal calling sequence. In the C calling sequence, the calling routine pushes any arguments included in the call on the stack in reverse order (right to left) and performs any stack cleanup; this permits a varying number of arguments to be passed to a given routine. In the Pascal calling sequence, the calling routine pushes any included arguments on the stack in the order in which they appear (left to right), and the called routine is expected to clean up the stack. See also argument, call1, stack.

CALL instruction n. A type of programming instruction that diverts program execution to a new area in memory (sequence of directives) and also allows eventual return to the original sequence of directives.

CALS n. Acronym for Computer-Aided Acquisition and Logistics Support. A U.S. Department of Defense standard for electronic exchange of data with commercial suppliers.

CAM n. 1. Acronym for computer-aided manufacturing. The use of computers in automating the fabrication, assembly, and control aspects of manufacturing. CAM applies to the manufacture of products ranging from small-scale production to the use of robotics in full-scale assembly lines. CAM relates more to the use of specialized programs and equipment than it does to the use of microcomputers in a manufacturing environment. See also CAD/CAM, I-CASE. 2. See Common Access Method.

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.

campuswide information system n. Information and services distributed on a college or university campus through computer networks. Campuswide information system services typically include student and faculty directories, calendars of campus events, and access to databases. Acronym: CWIS.

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.

cancelbot n. Short for cancel robot. A program that identifies articles in newsgroups based on a set of criteria and cancels the distribution of those articles. Although the criteria for cancellation is set by the owner of the cancelbot, most cancelbots exist to identify and eliminate spam messages posted to dozens or hundreds of newsgroups. See also spam.

cancel message n. A message sent to Usenet news servers indicating that a certain article is to be canceled, or deleted, from the server. See also article, news server, Usenet.

candidate key n. A unique identifier for a tuple (row) within a relation (database table). The candidate key may be either simple (a single attribute) or composite (two or more attributes). By definition, every relation must have at least one candidate key, but it is possible for a relation to have more than one candidate key. If there is only one candidate key, it automatically becomes the primary key for the relation. If there are multiple candidate keys, the designer must designate one as the primary key. Any candidate key that is not the designated primary key is an alternate key. See also key (definition 2), primary key.

canned program n. See canned software.

canned routine n. A previously written routine that is copied into a program and used as is, without modification. See also library routine.

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

canonical form n. In mathematics and programming, the standard or prototypical form of an expression or a statement.

canonical name n. An object s distinguished name presented with the root first and without the LDAP attribute tags (such as: CN=, DC=). The segments of the name are delimited with forward slashes (/). For example, CN=MyDocuments,OU=MyOU,DC=Microsoft,DC=Com is presented as microsoft.com/MyOU/MyDocuments in canonical form. See also Lightweight Directory Access Protocol.

capacitance n. The ability to store an electric charge. Capacitance is measured in farads. A capacitance of 1 farad will hold 1 coulomb of charge at a potential of 1 volt. In practical use, a farad is an extremely large amount of capacitance; typical capacitors have values of microfarads (10-6 ) or picofarads (10-12 ). See also capacitor.

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. Compare lowercase. Short for capital letters.

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. See the illustration.

Caps Lock key.

capstan n. On a tape recorder, a polished metal post against which a turning rubber wheel (called a pinch roller) presses to move a length of magnetic tape placed between the wheel and the post. The capstan controls the speed of the tape as it moves past the recording head. See also pinch roller.

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

capture board n. See video capture card.

capture card n. See video capture card.

Carbon n. Code name for the Application Program Interfaces (API) and shared libraries used to write applications for Macintosh OS X. Since Macintosh OS X is an entirely different system rather than an update of the previous Macintosh OS, Carbon bridges the gap between the systems, allowing developers to rewrite their programs to OS X without rewriting the code for the entire application. Carbon allows OS X native applications to run under earlier versions of the Macintosh OS without modification but with OS X advantages.

carbon copy n. See cc.

carbonize vb. To update a Macintosh application for OS X. Although older versions of Macintosh applications will run under OS X, only those that have been carbonized will be able to use OS X specific advantages.

carbon ribbon n. A ribbon used with impact printers, especially daisy-wheel printers, and with typewriters for highest-quality output. A carbon ribbon is made of a thin strip of Mylar coated on one side with a carbon film. Characters printed with a carbon ribbon are extremely crisp and free from the fuzziness that can be associated with an inked cloth ribbon. Also called: film ribbon, Mylar ribbon. See also daisy-wheel printer. Compare cloth ribbon.

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 cage n. An enclosure area for holding printed circuit boards (cards). Most computers have an area with protective metal and mounting brackets where cards are installed. The term originally came from an external box that held rack-mounted cards or peripherals and resembled a cage.

carder n. A person who engages in online credit card fraud. Specifically, a carder steals credit card numbers, either to purchase merchandise (often computer-related) from Web-based stores or to trade the stolen numbers with like-minded individuals again, over the Internet. Carders generally obtain credit card numbers through conventional means, such as trashing (searching through trash) or calling individuals and posing as bank officers. See also hacker (definition 2).

cardinal number n. A number that indicates how many items there are in a set for example, There are 27 names on that list. Compare ordinal number.

card punch n. See keypunch.

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 off line 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.

careware n. Software developed by an individual or a small group and distributed freely, with the proviso that users make a donation to a charity if they continue to use the software after trying it out. The charity is one usually designated by the software creator.

Carnivore n. Digital wiretap technology developed by the U.S. Federal Bureau of Investigation. Carnivore s purpose is to track and capture e-mail and other Internet-based communications sent from and received by a suspect. Carnivore copies all of an ISP s network traffic into a collection system where a filter sifts through all communications, disregarding all data but that related to the suspect.

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. Acronym: CTS. See also repetitive strain injury, wrist support.

carriage n. The assembly that holds the platen of a typewriter or a typewriterlike printer. On a standard typewriter, the platen and carriage move past a fixed position within the typewriter housing, where the keys strike the paper; the platen rotates to advance the paper held in the carriage. On most impact printers for computers, however, the print head moves back and forth across a platen, which rotates but does not move horizontally; in such machines, the assembly that carries the print head is often called the print-head carriage assembly. See also carriage return, platen.

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). See the illustration.

Carriage return.

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 Detect n. See CD (definition 2).

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 sense multiple access with collision detection n. See CSMA/CD.

carrier signal n. See carrier frequency.

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.

carry n. In arithmetic, the process of moving a digit to the next higher position when the sum of two numbers is greater than the largest digit in the number system being used. Computers, based on logic circuits, and often able to add all digits in two numbers simultaneously (do parallel addition), perform carries in several exotic ways. For example, they perform complete carries, in which one carry is allowed to propagate that is, to generate other carries in other digit positions. They can also perform partial carries, in which carries resulting from parallel addition are stored temporarily.

carry bit n. The bit, associated with an adder circuit, that indicates that an addition operation has produced a carry (as in 9 + 7). Also called: carry flag.

carry flag n. See carry bit.

Cartesian coordinates n. Points on a plane (two dimensions) or in space (three dimensions) that are located by their positions in relation to intersecting axes; named after the French mathematician Ren Descartes, who introduced the system in the seventeenth century. In two dimensions, points are described by their positions in relation to the two familiar axes, x (usually horizontal) and y (usually vertical). In three dimensions, a third axis, z, is added to the x- and y-axes. See the illustration. See also coordinate system. Compare polar coordinates.

Cartesian coordinates.

Cartesian product n. See product (definition 1).

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. See the illustration. 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.

Cascade.

cascade connection n. See pipe (definition 1).

cascaded star topology n. A star network in which nodes connect to hubs and hubs connect to other hubs in a hierarchical (cascaded) parent/child relationship. This topology is characteristic of 100Base-VG networks.

cascading hubs n. A network configuration in which hubs are connected to other hubs. See also hub.

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 Sheet mechanism n. See cascading style sheets.

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. Acronym: CSS. Also called: Cascading Style Sheet mechanism, CSS1. See also HTML, style sheet (definition 2).

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.

case sensitivity n. Discrimination between lowercase and uppercase characters in a program or a programming language. See also case.

case statement n. In programming languages such as Ada, Pascal, and C, a type of control statement that executes one of several sets of instructions based on some key value. Case statements are used in evaluating situations that can have a number of different results. Case in this sense refers to a refinement of a basic IF-THEN type of conditional statement (if A is true, then do B), but a case statement functions more like a series of nested IFs (if A, then do this; else if B, then do that; else . . .). In a case evaluation, a variable (such as a number or a string of characters) is compared against one after another of a series of constants assigned by the programmer. Each constant represents a different case and defines an action to be carried out. When the program finds a constant that matches the variable, it carries out whatever action is dictated by the case in which the match occurs. See also constant, control statement, variable.

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.

cast n. A programmer-specified data conversion from one type to another, such as a conversion from integer to floating point. Also called: coercion. See also data type.

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 or computer-aided teaching. See CAI. 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.

catch n. A keyword in the Java programming language used to declare a block of statements to be executed in the event that a Java exception or runtime error occurs in a preceding try block. See also block, exception, keyword, runtime, try.

Category 3 cable n. Network cable that supports frequencies up to 16 MHz and transmission speeds up to 10 Mbps (standard Ethernet). Category 3 cable has four unshielded twisted pairs (UTPs) of copper wire and RJ-45 connectors, and is used in voice and 10Base-T applications. Also called: Cat 3 cable.

Category 4 cable n. Network cable that supports frequencies up to 20 MHz and transmission speeds up to 16 Mbps. Category 4 cable has four unshielded twisted pairs (UTPs) of copper wire and RJ-45 connectors. Less popular than Category 3 and Category 5 cables, it is used primarily for token ring networks. Also called: Cat 4 cable.

Category 5 cable n. Network cable that supports frequencies up to 100 MHz and transmission speeds up to 100 Mbps (using two pairs) or 1000 Mbps (using four pairs and called gigabit over copper). Category 5 cable has four unshielded twisted pairs (UTPs) of copper wire and RJ-45 connectors, and is used for 10/100/1000 Base-T, ATM, and token ring networks. Also called: Cat 5 cable.

Category 5e cable n. Network cable that supports frequencies up to 100 MHz and transmission speeds up to 1000 Mbps (half-duplex mode) or 2000 Mbps (full-duplex mode). Category 5e cable has four unshielded twisted pairs (UTPs) of copper wire, RJ-45 connectors, and enhanced shielding to prevent signal degradation. Category 5e cable can be used for 10/100/1000 Base-T, ATM, and token ring networks. Also called: Cat 5e cable. See also duplex2 (definition 1), half-duplex transmission.

catena n. A series of items in a chained list that is, a list in which one item points to the next in sequence. See also linked list.

cathode n. 1. The terminal or electrode that is negatively charged and from which electrons flow. 2. The electron-emitting electrode in a vacuum tube. 3. The negative terminal of a battery. Compare anode.

cathode-ray oscilloscope n. See oscilloscope.

cathode-ray tube n. See CRT.

CATV n. Acronym for community antenna television or cable television. A television broadcasting system that uses coaxial or fiber-optic cable to distribute a broadband signal containing many separate television program channels. CATV systems are also increasingly being used to carry digital data for example, Internet connections to and from subscribers.

CatXML n. Acronym for Catalogue XML. An open standard for using XML in catalogue information exchanges over the Internet. CatXML uses a flexible XML schema with multiple profiles that can be adapted to meet the needs of individual businesses. CatXML supports existing information structures and provides distributed query information grid models and dynamic output formats.

cavity virus n. A type of virus that overwrites and hides within a section of the file it has infected. A cavity virus overwrites only a part of the host file filled with a constant, allowing the file to continue to function.

CBEMA n. Acronym for Computer and Business Equipment Manufacturers Association. An organization of hardware vendors and manufacturers in the United States involved in standardizing information processing and related equipment.

CBL n. Acronym for computer-based learning. Applies to either computer-aided instruction (CAI), which focuses primarily on education, or computer-based training (CBT), which is application-specific or job-oriented teaching. See also CAI, CBT.

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-mail1 (definition 1), header. Compare bcc.

CCC n. Acronym for Computer Controlled Character. CCC is generally used in role-playing computer games like MUD. It refers to a character that is not played by a human player but is actually a computer-generated character built into the game itself. See also computer game, MUD, role-playing game.

CCD n. See charge-coupled device.

CCI n. See Common Client Interface.

CCITT n. Acronym for Comit Consultatif International T l graphique et T l phonique, now called the International Telecommunication Union-Telecommunication Standardization Sector (ITU-TSS, often abbreviated as ITU-T). CCITT was the organization that performed the standardization functions for the International Telecommunication Union (ITU). Following a reorganization of the ITU in 1992, CCITT ceased to exist as a separate body, although several standards are still known by the CCITT prefix. See also ITU.

CCITT Groups 1 4 n. A set of four standards recommended by the Comit Consultatif International T l graphique et T l phonique (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; supports 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. See V series.

CCITT X series n. See X series.

cc:Mail n. An e-mail program originally introduced by cc:mail, Inc., and currently produced by the Lotus Development Corporation. Lotus cc:Mail runs on multiple networking platforms and the Internet and is closely integrated with Lotus Notes collaborative software.

ccNUMA n. Acronym for Cache-Coherent Non-Uniform Memory Access. A technology that enables many symmetric multiprocessing systems to be connected by high-speed/wide-bandwidth interconnect hardware so that they function as one machine. See also symmetric multiprocessing.

CCP n. Acronym for Certificate in Computer Programming. A senior-level programming credential awarded by the Institute for Certification of Computer Professionals to individuals who pass an extensive set of programming examinations.

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 (definition 5).

CD n. 1. An individual compact disc, such as a CD-ROM. See also CD-ROM, compact disc (definition 2). 2. 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.

CD burner n. See CD recorder.

CD drive n. See CD-ROM drive.

CD-E n. Acronym for compact disc-erasable. A technological improvement in CDs (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.

cdev n. Short for control panel device. A Macintosh utility that allows basic system settings to be customized. In Macintosh computers running System 6, a cdev is a utility program placed in the system folder. Keyboard and mouse cdevs are preinstalled. Other cdevs are provided with software packages and utilities. In System 7, cdevs are called control panels. See also control panel, system folder. Compare INIT.

CDF n. See 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 9x. 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-I n. Acronym for compact disc-interactive. A hardware and software standard for a form of optical disc technology that can combine audio, video, and text on high-capacity compact discs. CD-I includes such features as image display and resolution, animation, special effects, and audio. The standard covers methods of encoding, compressing, decompressing, and displaying stored information. See also CD-ROM.

CDMA n. See Code Division Multiple Access.

CDN n. Acronym for content delivery network. A service that caches the pages of a Web site on geographically dispersed servers to enable faster delivery of Web pages. When a page is requested at a URL that is content delivery enabled, the content delivery network routes the user s request to a cache server close to the user. See also content delivery.

CDP n. Acronym for Certificate in Data Processing. A certificate awarded by the Institute for Certification of Computer Professionals to individuals who pass a set of examinations on computers and related areas, including programming, software, and systems analysis.

CDPD n. See Cellular Digital Packet Data.

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

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-R n. Acronym for compact disc-recordable. A type of CD-ROM that can be written on a CD recorder and read on a CD-ROM drive. See also CD recorder, CD-ROM.

CD-R/E adj. Acronym for compact disc-recordable and erasable. Of or pertaining to hardware and software for interfacing computers with both CD-R (compact disc-recordable) and CD-E (compact disc-erasable) devices. See also CD-R.

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 archives 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-R machine n. See CD recorder.

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 CD (compact disc) designed for use with a computer and capable of storing up to 650 megabytes of data. See also CD, disc.

CD-ROM burner n. See CD recorder.

CD-ROM drive n. An electromechancial device that reads data on CD-ROMs. Most CD-ROM drives have a SCSI interface, although some are connected to a PC via a controller for a disk drive. Data is read through a small laser that is focused on the surface of the CD-ROM through optical mirrors in the read/write head. A spindle and drive motor revolve the CD-ROM, so all data, which is stored in spirals from the center, can be read. CD-ROM drives vary in the access time to locate a track on the CD-ROM and the seek time to move the read/write head. See the illustration. Also called: CD drive. See also CD-ROM, compact disc.

CD-ROM drive.

CD-ROM Extended Architecture n. See CD-ROM/XA.

CD-ROM File System n. See CDFS (definition 1).

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. Although 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.

CD-ROM/XA n. Short for CD-ROM Extended Architecture. An extended CD-ROM format developed by Philips, Sony, and Microsoft. CD-ROM/XA is consistent with the ISO 9660 (High Sierra) standard, with further specification of ADPCM (adaptive differential pulse code modulation) audio, images, and interleaved data. See also adaptive differential pulse code modulation, CD-ROM, High Sierra specification.

CD-RW n. Acronym for compact disc-rewritable. The technology, equipment, software, and media used in the production of multiple-write CDs (compact discs).

CDS n. See Circuit Data Services.

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.

CD Video n. See CDV (definition 2).

CeBIT n. One of the world s leading tradeshows for the information technology, telecommunications, and office automation industries. Held annually in Hannover, Germany, CeBIT attracts hundreds of thousands of visitors and exhibitors from more than 60 countries.

CEBus n. Short for Consumer Electronic Bus. CEBus is an open architecture set of specification documents that define protocols for how to make products communicate through power line wires, low voltage twisted pairs, coax, infrared, RF, and fiber optics. Anyone, anywhere can get a copy of the plans and develop products that work with the CEBus standard.

Celeron n. Intel s family of budget-priced microprocessors introduced in 1998. Celeron chips are based on the same P6 microarchitecture as the Pentium II processor. They include an integrated 128-KB L2 cache and support Intel s MMX technology. Celeron chips have speeds of up to 1.3 GHz in early 2002. See also Pentium.

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. 3. A fixed-length packet, the basic transmission unit on high-speed networks, such as ATM. See also ATM. 4. Coverage area for wireless phones served by a single base station (cell tower), usually surrounded by six other cells. As a wireless phone moves across the boundary between cells, the conversation is handed from one cell to the next. Cells may be less than a half mile or more than 15 miles in radius, depending on the volume of wireless calls or the presence of large buildings or terrain that might interfere with signals.

cell animation or cel animation n. A process performed by software that emulates traditional cell animation, which uses transparent celluloid sheets ( cells or cels for short) to overlay active elements in an animation frame onto a static background. Computer cell animation is quite efficient because images can be quickly reproduced and manipulated.

cell padding n. The space between the contents and the inside edges of a table cell.

cell reference n. The set of coordinates that a cell occupies on a worksheet. For example, the reference of the cell that appears at the intersection of column B and row 3 is B3.

cell relay n. A form of packet switching in which information is multiplexed onto a carrier and transferred in fixed-length packets (cells).

cellular automata n. 1. In computer science, theoretical models of parallel computers. They enable the investigation of parallel computers without the need to actually build them. The cellular automaton is composed of a network of multiple cells, each representing a processor in the parallel computer. The cells must be identical, and they must have a finite amount of available memory. Each cell outputs a value calculated from the input values it receives from its neighboring cells, and all cells output their values simultaneously. 2. Systems in which rules are applied to multiple cells and their neighbors in a regular spatial lattice or grid that advances through time. Usually, each cell in a cellular automaton has any one state out of a finite number of states. The state changes discretely in time according to rules that depend on the condition of the individual cell and its neighbors. Thus, an individual cell in a cellular automaton takes a neighbor cell s state as input before outputting its own state. Additionally, all the cells in the lattice are updated simultaneously, while the state of the entire lattice also advances discretely in time. Many computer simulations of cellular automata are demonstrated on Web sites; the best known Web example is J.H. Conway s Game of Life.

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

Cellular Telecommunications and Internet Association n. Association based in Washington, D.C. that represents the wireless telecommunications industry and its equipment manufacturers. Acronym: CTIA.

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 might 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.

censorware n. Software that imposes restrictions on what Internet sites, newsgroups, or files may be accessed by the user.

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 (definition 1).

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

centralized network n. A network in which nodes connect to and use resources on a single central computer, typically a mainframe.

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

central office n. In communications, the switching center where interconnections between customers communications lines are made.

central office exchange service n. See Centrex.

central processing unit n. See CPU.

Centrex n. An option offered by some phone companies in which up-to-date phone facilities are available to business customers, giving the customer access to a complete range of phone services without having to purchase or maintain the necessary equipment. Customers can purchase just the lines and services they will use. The name central office exchange refers to the fact that the phone facilities for Centrex services, particularly switching services, are generally maintained at the offices of the local or central phone company. Since Centrex offers a wider range of services, it is replacing PBX for businesses. See also switching. Compare PBX.

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 Europ en pour la Recherche Nucl aire (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 (definition 1).

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 sent when a message is digitally signed. The certificate proves the sender s identity and supplies the recipient with a public key with which to decrypt the sender s encrypted messages. Also called: digital certificate.

certificate authority n. An issuer of digital certificates, the cyberspace equivalent of identity cards. A certificate authority may be an external issuing company (such as VeriSign) or an internal company authority that has installed its own server (such as the Microsoft Certificate Server) for issuing and verifying certificates. A certificate authority is responsible for providing and assigning the unique strings of numbers that make up the keys used in digital certificates for authentication and to encrypt and decrypt sensitive or confidential incoming and outgoing online information. Acronym: CA. See also digital certificate, encryption.

Certificate in Computer Programming n. See CCP.

Certificate in Data Processing n. See CDP.

certificate revocation list n. A document maintained and published by a certification authority that lists certificates that have been revoked. Acronym: CRL. See also certificate, certification authority.

certificate trust list n. A signed list of root certification authority certificates that an administrator considers reputable for designated purposes, such as client authentication or secure e-mail. Acronym: CTL. See also certificate, certificate authority, root 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.

certification authority n. An organization that assigns encryption keys. See also certificate authority.

CFML n. Acronym for Cold Fusion Markup Language. A programming environment and proprietary, tag-based markup language for server-side processing.

CGA n. Acronym for Color/Graphics Adapter. A video adapter board introduced by IBM in 1981. The CGA is capable of several character and graphics modes, including character modes of 40 or 80 horizontal characters (columns) by 25 vertical lines with 16 colors, and graphics modes of 640 horizontal pixels by 200 vertical pixels with 2 colors, or 320 horizontal pixels by 200 vertical pixels with 4 colors. See also graphics adapter, video adapter.

CGI n. 1. Acronym for Common Gateway Interface. 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 (definition 1). 2. See Computer Graphics Interface.

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 program n. See CGI script.

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 on 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 control, Java applet.

CGM n. See Computer Graphics Metafile.

chad n. The paper removed when a hole is punched in a card, in a tape, or at the perforated edge of continuous-form paper the computer equivalent of a doughnut hole.

chaining n. 1. In computers, the linking of two or more entities so that they are dependent upon one another for operation. 2. In programming, the linking of two or more programs so that the first program causes the second program to begin executing. 3. In programming, linking program statements so that each statement, except for the first, relies on the previous statement for input. 4. With batch files, linking two or more batch files so that the completion of the first batch file causes the second batch file to begin executing. 5. With data storage, linking two or more individual units of storage. 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. 6. See daisy chaining.

chain printer n. See line printer.

chalkware n. See vaporware.

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. Acronym: CHAP. See also authentication, PPP.

change directory n. See cd.

change file n. A file that records transactional changes occurring in a database, providing a basis for updating a master file and establishing an audit trail. Also called: transaction log. See also addition record.

change management n. 1. The process of tracking and controlling updates, revisions, and other changes to a hardware or software product or project. 2. The process of managing change during a company s restructuring or reengineering.

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. 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, electromagnetic spectrum, frequency. 3. A single color within a digital color space. For example, the RGB color space contains three channels red, green, and blue and all colors within the RGB color space are created with a combination of one or more of those three color channels. In CMYK there are four channels cyan, magenta, yellow, and black. Color management and graphics applications rely on control and manipulation of individual color channels. See also color space.

channel access n. 1. A method used in networked systems to gain access to the data communication channel that links two or more computers. Common methods of channel access are contention, polling, and the token ring network. See also channel, contention, polling, token ring network. 2. In wireless technology, an access method such as CDMA (Code Division Multiple Access). See also Code Division Multiple Access.

channel adapter n. A device that enables hardware using two different types of communications channels to communicate.

channel aggregator n. See content aggregator.

channel capacity n. The speed at which a communications channel can transfer information, measured in bits per second (bps) or in baud.

Channel Definition Format n. A file format based on XML that describes a channel a collection of Web pages on a server. The Channel Definition Format is used with the Active Channel feature in Microsoft Internet Explorer to deliver selected, often personalized, information to individuals on a subscription basis. See also Active Channel, webcasting.

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.

channel operator n. See channel op.

Channel Service Unit n. See DDS.

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.

character cell n. A rectangular block of pixels that represents the space in which a given character is drawn on the screen. Computer displays use different numbers of pixels as character cells. Character cells are not always the same size for a given font, however; for proportionally spaced fonts, such as those commonly displayed on the Apple Macintosh, the height within a given font remains the same, but the width varies with each character.

character code n. A specific code that represents a particular character in a set, such as the ASCII character set. The character code for a given key depends on whether another key, such as Shift, is pressed at the same time. For example, pressing the A key alone normally generates the character code for a lowercase a. Pressing Shift plus the A key normally generates the character code for an uppercase A. Compare key code.

character definition table n. A table of patterns that a computer can hold in memory and use as a reference for determining the arrangement of dots used to create and display bitmapped characters on the screen. See also bitmapped font.

character density n. In printing or screen display, a measure of the number of characters per unit of area or of linear distance. See also pitch (definition 1).

character device n. 1. A computer device, such as a keyboard or printer, that receives or transmits information as a stream of characters, one character at a time. The characters can be transferred either bit by bit (serial transmission) or byte by byte (parallel transmission) but are not moved from place to place in blocks (groups of bytes). Compare block device. 2. In reference to video displays, a device that handles text but not graphics. See also text mode.

character entity n. In HTML and SGML, the notation for a special character. A character entity begins with an & (ampersand), followed by either a string of letters or of numbers, and ends with a semicolon. The special characters represented by character entities include acute and grave accents, the tilde, and Greek letters, among others. Also called: named entity.

character generator n. A program or a hardware device that translates a given character code, such as an ASCII code, into a matching pixel pattern for display on the screen. Such devices are typically limited in the number and range of styles of fonts they support, as compared to machines that support bitmapped characters. Compare bitmapped font.

character image n. A set of bits arranged in the shape of a character. Each character image exists within a rectangular grid, or character rectangle, that defines its height and width. See also bitmapped font.

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 mode n. See text mode.

character-oriented protocol n. See byte-oriented protocol.

character printer n. 1. A printer that operates by printing one character at a time, such as a standard dot-matrix printer or a daisy-wheel printer. Compare line printer, page printer. 2. A printer that cannot print graphics, such as a daisy-wheel printer or even a dot-matrix or laser printer that lacks a graphics mode. Such a printer simply receives character codes from the controlling system and prints the appropriate characters. Compare graphics printer.

character recognition n. The process of applying pattern-matching methods to character shapes that have been read into a computer to determine which alphanumeric characters or punctuation marks the shapes represent. Because different typefaces and text treatments, such as bold and italic, can make big differences in the way characters are shaped, character recognition can be prone to error. Some systems work only with known typefaces and sizes, with no text treatments. These systems achieve very high accuracy levels, but they can work only with text specifically printed for them. Other systems use extremely sophisticated pattern-matching techniques to learn new typefaces and sizes, achieving fairly good accuracy. See also magnetic-ink character recognition, optical character recognition, pattern recognition (definition 1).

character rectangle n. The space taken up by the graphical representation (bit map) of a character. See the illustration. See also bit map.

Character rectangle.

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.

characters per inch n. A measurement for the number of characters of a particular size and font that can fit into a line one inch long. This number is affected by two attributes of the type: its point size and the width of the letters in the particular font being measured. In monospace fonts, characters have a constant width; in proportional fonts, characters have varying widths. Thus, measurements of the number of characters per inch must be averaged. Acronym: cpi. See also monospace font, pitch (definition 1), proportional font.

characters per second n. 1. A measure of the speed of a nonlaser printer, such as a dot-matrix or an ink-jet printer. 2. A measure of the rate at which a device, such as a disk drive, can transfer data. In serial communications, the speed of a modem in bits per second can generally be divided by 10 for a rough determination of the number of characters per second transmitted. Acronym: CPS.

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.

character user interface n. A user interface that displays only text characters. Acronym: CUI. See also user interface. Compare graphical user interface.

charge n. A property of subatomic particles, which can have either a negative charge or a positive charge. In electronics, a charge consists of either an excess of electrons (a negative charge) or a deficiency of electrons (a positive charge). The unit of charge is the coulomb, which corresponds to 6.26 x 1018 electrons.

charge-coupled device n. A device in which individual semiconductor components are connected so that the electrical charge at the output of one device provides the input to the next. The light-detecting component of digital cameras and many video cameras is a charge-coupled device. Acronym: CCD.

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. See the illustration.

Chassis.

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.

chat room n. The informal term for a data communication channel that links computers and permits users to converse by sending text messages to one another in real time. Similar to the channels provided by IRC (Internet Relay Chat), chat rooms are available through online services and some electronic bulletin board systems (BBSs). Chat rooms are often devoted to a particular subject or are conducted on a certain schedule. See also BBS, chat, IRC, room.

Cheapernet n. See 10Base2.

cheat code n. In computer games, a secret keyboard sequence or code that gives a player an advantage in the game. For example, cheat codes often confer more ammunition, lives, or the ability to fly or walk through obstacles. See also adventure games, computer games.

check bit n. One of a set of bits that are added to a data message at its origin and scrutinized by the receiving process to determine whether an error has occurred during transmission. The simplest example is a parity bit. See also data integrity, parity bit.

check box n. An interactive control often found in graphical user interfaces. Check boxes are used to enable or disable one or more features or options from a set. When an option is selected, an x or a check mark appears in the box. See also control (definition 2). Compare radio button.

check digit n. A digit added to an account number or other identifying key value and then recomputed when the number is used. This process determines whether an error occurred when the number was entered. See also checksum.

checkpoint n. 1. A processing juncture at which the normal operation of a program or system is momentarily suspended in order to determine its environmental status. 2. A file containing information that describes the state of the system (the environment) at a particular time.

checksum n. A calculated value that is used to test data for the presence of errors that can occur when data is transmitted or when it is written to disk. The checksum is calculated for a given chunk of data by sequentially combining all the bytes of data with a series of arithmetic or logical operations. After the data is transmitted or stored, a new checksum is calculated in the same way using the (possibly faulty) transmitted or stored data. If the two checksums do not match, an error has occurred and the data should be transmitted or stored again. Checksums cannot detect all errors, and they cannot be used to correct erroneous data. See also error-correction coding.

Cheese worm n. An Internet worm that patches security holes created by the Lion worm. The Cheese worm searches out and infects Linux-based systems that were previously compromised by the Lion worm, repairing vulnerabilities and closing a back door left by the earlier infection. It then uses the healed computer to scan for other vulnerable computers connected to the Internet and sends itself to them.

Chernobyl packet n. A form of network attack in which a data packet sent by a hacker activates every available option for the protocol in use on the receiving system. The Chernobyl packet will cause a packet storm that will eventually overload and crash the network. Also called: kamikaze packet.

Chernobyl virus n. See CIH virus.

chiclet keyboard n. A microcomputer keyboard used on the first version of the IBM PCjr home computer. Chiclet keys are small and square, resembling the chewing gum pieces, and they act like pushbuttons, without the resistance and clear feedback of traditional keys. They are also much smaller and typically are spread out, so touch typing is more difficult than on a conventional keyboard.

child n. 1. A process initiated by another process (the parent). This initiating action is frequently called a fork. The parent process often sleeps (is suspended) until the child process stops executing. 2. In a tree structure, the relationship of a node to its immediate predecessor. See also generation (definition 2), tree structure.

child directory n. See subdirectory.

child menu n. See submenu.

child process n. See child (definition 1).

Children s Online Privacy Protection Act n. See COPPA.

chimes of doom n. In Macintosh computers, a series of chimes that sound as a result of serious system failure.

chip n. See integrated circuit.

chip card n. See smart card.

chip set or chipset 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 CPU, integrated circuit, programmable interrupt controller.

choke n. See inductor.

choose vb. To pick a command or an 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).

chroma n. The quality of a color that combines hue and saturation. See also hue, saturation.

CHRP n. See Common Hardware Reference Platform.

churn rate n. The rate of customer subscription turnover. In beeper, cell phone, and online businesses, it is common for customers to drop their monthly subscriptions, creating a churn rate as high as 2 or 3 percent per month. High churn rates are costly to companies because attracting new subscribers through advertising and promotion is expensive.

CIDR n. See classless interdomain routing.

CIFS n. See Common Internet File System.

CIH virus n. A highly destructive virus that first appeared in early 1998. When activated, the CIH virus code will attempt to overwrite the flash BIOS of infected machines, rendering the computer unbootable. The CIH virus is also known as the Chernobyl virus because in its original form it was set to activate on the anniversary of the Chernobyl nuclear accident. Although the CIH virus lacks stealth or sophisticated replication capabilities and is easily detected by current virus security programs, it continues to appear regularly. Also called: Chernobyl virus. See also virus.

CIM n. 1. Acronym for Common Information Model. A conceptual specification supported by the Desktop Management Task Force (DMTF) for applying an object-oriented, Web-based model to describing management data in an enterprise network. Part of the DMTF s Web-Based Enterprise Management initiative, CIM is a system-independent and application-independent common framework for describing and sharing management information. It is based on a three-tiered model based on schemas sets of classes: the Core Schema covers all areas of management; Common Schemas cover specific management areas, such as networks, applications, and devices; and Extension Schemas cover specific technologies, such as operating systems and applications. CIM is supported by a number of industry vendors, including Sun, IBM, Microsoft, and Cisco. See also DMTF, WBEM. 2. Acronym for computer-integrated manufacturing. The use of computers, communication lines, and specialized software to automate both the managerial functions and the operational activities involved in the manufacturing process. A common database is used in all aspects of the process, from design through assembly, accounting, and resource management. Advanced CIM systems integrate computer-aided design and engineering (CAD/CAE), material requirements planning (MRP), and robotic assembly control to provide paperless management of the entire manufacturing process. 3. Acronym for computer-input microfilm. A process in which information stored on microfilm is scanned and the data (both text and graphics) converted into codes that can be used and manipulated by a computer. Computer-input microfilm is similar to processes such as optical character recognition, in which images on paper are scanned and converted to text or graphics. Compare COM (definition 4).

CIP n. 1. Short for Commerce Interchange Pipeline. A Microsoft technology that provides for secure routing of business data between applications over a public network such as the Internet. CIP is independent of data format and supports encryption and digital signatures, as well as various transport protocols including SMTP, HTTP, DCOM, and EDI value-added networks. Typically, data such as invoices and purchase orders travel over a network through a transmit pipeline and are read from the network by a receive pipeline that decodes and prepares the data for the receiving application. 2. Short for Common Indexing Protocol. A protocol defined by the Internet Engineering Task Force (IETF) for enabling servers to share indexing information. CIP was developed to provide servers with a standard means of sharing information about the contents of their databases. With such sharing, a server unable to resolve a particular query would be able to route the query to other servers that might contain the desired information for example, to find the e-mail address of a particular user on the Web.

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

ciphertext n. The scrambled or otherwise encoded text of an encrypted message. See also encryption.

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 the illustration. See also board, printed circuit board.

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.

circuit card n. See circuit board.

Circuit Data Services n. A GTE service that uses circuit switching technology to provide fast data transfer using a laptop computer and cellular telephone. Acronym: CDS. See also circuit switching.

circuit-switched data n. An ISDN option that can be specified for B (bearer) channels that enables an ISDN user to transmit digital data over the channel at 64 Kbps along a point-to-point, dedicated connection for the duration of a call. Acronym: CSD. See also alternate circuit-switched voice/circuit-switched data, B channel, ISDN. Compare circuit-switched voice.

circuit-switched voice n. An ISDN option that can be specified for B (bearer) channels that uses the channel to set up a point-to-point, dedicated connection for the digital transmission of voice communications for the duration of a call. Acronym: CSV. See also alternate circuit-switched voice/circuit-switched data, B channel, ISDN. Compare circuit-switched data.

circuit switching n. A method of opening communications lines, as through the telephone system, by creating a physical link between the initiating and receiving parties. In circuit switching, the connection is made at a switching center, which physically connects the two parties and maintains an open line between them for as long as needed. Circuit switching is typically used on the dial-up telephone network, and it is also used on a smaller scale in privately maintained communications networks. Unlike other methods of transmission, such as packet switching, it requires the link to be established before any communication can take place. Compare message switching, packet switching.

circular list n. A linked or chained list in which processing continues through all items, as in a ring, and returns to the starting point, no matter where that point is located in the list. See also linked list.

CIS n. 1. Acronym for CompuServe Information Service See CompuServe. 2. Short for contact image sensor. A light-sensitive mechanism used in scanners and fax machines. A CIS scanner reflects light from a row of light-emitting diodes (LEDs) onto a document or other object and converts the reflected light to digital images. CIS sensors are smaller and lighter than the charge-coupled devices (CCDs) traditionally used in scanners, but the image quality they produce is not as good as the image quality produced by CCDs. See also light-emitting diode, scanner. Compare charge-coupled device.

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.

CIX n. See Commercial Internet Exchange.

CKO n. Acronym for Chief Knowledge Officer. A corporate executive in charge of management and distribution of all the business and technical knowledge of a company. The CKO maximizes the value of stored knowledge by ensuring that employees have access, and by avoiding knowledge loss caused by technology-based changes and upgrades in databases and other storage.

ClariNet n. A commercial service that distributes news articles from United Press International (UPI) and other news agencies in newsgroups that are part of the clari. hierarchy. Unlike most other newsgroups, access to the clari. newsgroups is restricted to Internet service providers who pay a subscription fee to ClariNet.

clari. newsgroups n. Internet newsgroups maintained by ClariNet Communications, Inc. ClariNet newsgroups contain news articles obtained from the Reuters and United Press International wire services, SportsTicker, Commerce Business Daily, and other sources. Unlike most other newsgroups, ClariNet groups are only accessible through Internet service providers who purchase the service. See also ClariNet, ISP, newsgroup.

ClarisWorks n. See AppleWorks.

class n. 1. 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. 2. For hardware, the method for grouping particular types of devices and buses according to the basic ways that they can be installed and managed by the operating system. The hardware tree is organized by device class, and Windows uses class installers to install drivers for all hardware classes.

Class A IP address n. A unicast IP address that ranges from 1.0.0.1 through 126.255.255.254. The first octet indicates the network, and the last three octets indicate the host on the network. See also Class B IP address, Class C IP address, IP address classes.

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.

Class B IP address n. A unicast IP address that ranges from 128.0.0.1 through 191.255.255.254. The first two octets indicate the network, and the last two octets indicate the host on the network. See also Class A IP address, Class C IP address, IP address classes.

Class C IP address n. A unicast IP address that ranges from 192.0.0.1 to 223.255.255.254. The first three octets indicate the network, and the last octet indicates the host on the network. See also Class A IP address, Class B IP address, IP address classes.

classful IP addressing n. An IP addressing scheme where IP addresses are organized into classes: Class A, Class B, and Class C. See also IP address classes.

Classic n. An environment within Mac OS X that allows a user to run legacy software. Classic emulates the earlier Macintosh operating system chosen by the user and provides support for programs that aren t compatible with Mac OS X architecture. See also Carbon, Cocoa, Mac OS X.

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. Acronym: CIDR. See also Border Gateway Protocol, communications protocol, RIP, router, supernetting.

class library n. A collection of standard routines and sub-programs that a programmer can use in object-oriented programs. A typical class library for a graphical user interface might include routines for buttons and scroll bars; or a class library for a communications program might include a routine for dialing a telephone line through a modem. See also class, object-oriented programming.

classpath n. In Java programming, a classpath is an environmental variable that tells the Java Virtual Machine (JVM) and Java programs where to find class libraries, including user-defined class libraries. See also class, class library, Java Virtual Machine.

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, crash1 (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.

clean interface n. A user interface with simple features and intuitive commands. See also user interface.

clean room n. A room in which dust and other small particles are filtered from the air and in which protective clothing is worn to avoid contaminating electronic components and other delicate, sensitive equipment.

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. See the illustration.

Clear key.

clear memory vb. A process that erases all data stored in RAM.

Clear To Send n. See CTS.

ClearType n. A Microsoft font technology that improves the resolution of text on LCD displays, such as those used on laptop computers. ClearType technology uses proprietary signal processing and the properties of LCD displays to produce clearer, more detailed characters and spacing, and thus significantly increase readability.

CLEC n. Acronym for Competitive Local Exchange Carrier. A company that sells access to the public switched telephone network, or other last mile network connections, in competition with a traditional telephone company. See also ILEC, last mile.

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.

clickable maps n. See image map.

click rate n. See clickthrough rate.

clicks and mortar n. A business that combines an online presence with traditional bricks and mortar outlets.

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.

clickstream n. The path a user takes while browsing a Web site. Each distinct selection made on a Web page adds one click to the stream. The further down the clickstream the user goes without finding the sought item, the more likely he or she is to depart to another Web site. Analysis of usage patterns helps Web site designers create user-friendly site structures, links, and search facilities. See also Web site.

clickthrough n. The number of times that visitors to a Web site click on an advertising banner within a specified period of time. Clickthrough is one of the elements that Web site producers use to decide how much to charge advertisers. See also clickthrough rate.

clickthrough rate n. The proportion of visitors to a Web site who click on a banner advertisement there, expressed as a percentage of total visitors to the Web site. Also called: click rate. See also clickthrough.

clickwrap agreement n. A contract or license in software or on a Web site that sets forth conditions for use of the software or for goods and services distributed through the Web site. Users must agree to the terms in a clickwrap agreement typically by clicking on a button that states I Agree or Agree before they can install the software or utilize goods or services. A clickwrap agreement is an electronic version of an End-User License Agreement. Also called: clickwrap license. See also End-User License Agreement. Compare shrinkwrap agreement.

clickwrap license n. See clickwrap agreement.

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 LANs (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. Compare peer-to-peer network.

client/server network n. See client/server architecture.

client-side image maps n. An image map that performs the processing completely within the client program (i.e., Web browser) itself. Early Web implementations of image maps (circa 1993) transmitted user mouse click coordinates to the Web server for processing. Generally client-side image maps improve 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.

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 illustration 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.

clipboard computer n. A portable computer whose overall appearance and operation resembles that of a traditional clipboard. A clipboard computer has an LCD or similar flat display and has a pen for user input instead of a keyboard, mouse, or other input device; the user operates the computer by touching the pen to the display. Data entered in a clipboard computer is generally transferred to another computer via a cable or a modem. A clipboard computer is used as a traditional clipboard is used, as in field work, data collection, or meetings. See also pen computer, portable 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 Chip 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.

clip source tag n. Computer coding tag that locates a streaming digital media image for use on a Web page. The clip source tag includes the pathway to the image, which may be stored on a Web server, a Web site, or on the computer where the Web page is displayed.

clobber vb. To destroy data, generally by inadvertently writing other data over it.

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.

clocking n. See synchronization (definition 3).

clockless chip n. See asynchronous chip.

clock pulse n. An electronic pulse generated periodically by a crystal oscillator to synchronize the actions of a digital device.

clock rate n. The speed at which the internal clock in an electronic device oscillates. In computers, each tick (oscillation) of the clock is called a cycle, and the clock rate is measured in megahertz, or millions of cycles per second. Also called clock speed, the clock rate determines how quickly the CPU can execute basic instructions, such as adding two numbers, and it is used to synchronize the activities of various components in the system. Between 1981, when the IBM PC was released, and early 2002, typical clock rates for personal computers increased about 1000-fold, from 4.77 MHz to 2 GHz and faster. Also called: clock speed, hertz time. See also clock (definition 1).

clock speed n. See clock rate.

clock tick n. See CPU cycle (definition 2).

clone1 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.

clone2 vb. To copy or replicate the entire contents of a hard disk drive, including the operating system, configuration settings, and programs, by creating an image of the hard disk drive. Hard disk drives are often cloned for batch installation on other computers, particularly those on a network, or for use as backups.

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 9x, 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 x 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).

closed file n. A file not being used by an application. An application must open such a file before reading or writing to it and must close it afterward. Compare open file.

closed shop n. A computer environment in which access to the computer is restricted to programmers and other specialists. Compare open shop.

closed system n. See closed architecture (definition 2).

cloth ribbon n. An inked ribbon generally used with impact printers and typewriters. The print element strikes the ribbon and drives it against the paper so as to transfer ink; then the ribbon advances slightly to make fresh ink available. A cloth ribbon is wrapped onto a spool or loaded into a cartridge that is made to fit the printer used. Cloth ribbon, although adequate for most tasks, is sometimes replaced by film ribbon when the crispest possible output is called for. However, a cloth ribbon, which re-inks itself by capillary action, is usable for multiple impressions, unlike a film ribbon. Compare carbon ribbon.

CLS n. Acronym for Common Language Specification. A subset of language features supported by the .NET common language runtime, comprised of features common to several object-oriented programming languages. CLS-compliant components and tools are guaranteed to interoperate with other CLS-compliant components and tools.

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). 4. A group of independent network servers that operate and appear to clients as if they were a single unit. A cluster network is designed to improve network capacity by, among other things, enabling the servers within a cluster to shift work in order to balance the load. By enabling one server to take over for another, a cluster network also enhances stability and minimizes or eliminates downtime caused by application or system failure. See also client/server architecture.

cluster analysis n. A technique used in data mining and knowledge discovery to group observations by identifying and extracting like or similar group conditions. Cluster analysis aims to describe the structure of a complex data set. See also ART, data mining.

cluster controller n. An intermediary device that is situated between a computer and a group (cluster) of subsidiary devices, such as terminals on a network, and is used to control the cluster.

clustering n. The grouping of multiple servers in a way that allows them to appear to be a single unit to client computers on a network. Clustering is a means of increasing network capacity, providing live backup in case one of the servers fails, and improving data security. See also cluster (definition 4), server.

cluster network n. See cluster (definition 4).

cluster virus n. A type of virus that infects once but gives the appearance of infecting every application launched. A cluster virus modifies the file system so that it is loaded before any application that the user attempts to open. Because the virus is also run when running any program, it appears that every program on the disk is infected.

CLUT n. Acronym for Color Look Up Table. In digital graphics applications, a specific set of colors used in the creation of graphics. When a graphic is created or edited, the user may specify a CLUT that corresponds with the needs of print, Web, or other destination media. In Web design, a specific CLUT of browser-safe colors is used to be certain graphics and designs will display consistently across different platforms and with different browsers. See also browser CLUT, websafe palette.

CMI n. Acronym for computer-managed instruction. Any type of teaching that uses computers as educational tools. See also CAI, CBT.

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 one 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 used to store parameter values needed to boot PCs, such as the type of disks and the amount of memory, as well as the clock/calendar time.

CMOS RAM n. Short for 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).

CMS n. See color management system.

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 round, flexible, two-conductor cable consisting of from the center outwards a copper wire, a layer of protective insulation, a braided metal mesh sleeve, and an outer shield, or jacket of PVC or fire-resistant material. 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. Coaxial cable is widely used in networks. It is the same type of wiring as that used for cable television. See the illustration. Compare fiberoptic cable, twisted-pair wiring.

Coaxial cable.

COBOL n. Acronym for Common Business-Oriented Language. A verbose, English-like compiled programming language developed between 1959 and 1961 and still in widespread use today, especially in business applications typically run on mainframes. A COBOL program consists of an Identification Division, which specifies the name of the program and contains any other documentation the programmer wants to add; an Environment Division, which specifies the computers being used and the files used in the program for input and output; a Data Division, which describes the format of the data structures used in the program; and a Procedure Division, which contains the procedures that dictate the actions of the program. See also compiled language.

cobweb site n. A Web site that is far out of date. See also Web site.

Cocoa n. A set of object-oriented development tools and interfaces available on Mac OS X. Cocoa contains a set of frameworks, software components, and development tools used to construct applications for Mac OS X and provides programming interfaces in Java and Objective-C. Cocoa is based on NeXT s OpenStep and is integrated with Apple technologies.

CODASYL n. Acronym for Conference on Data Systems Languages. An organization founded by the U.S. Department of Defense. CODASYL is dedicated to the development of data-management systems and languages, among them the widely used COBOL.

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.

code access security n. A mechanism provided by the runtime whereby managed code is granted permissions by security policy and these permissions are enforced, limiting what operations the code will be allowed to perform. To prevent unintended code paths from exposing a security vulnerability, all callers on the call stack must be granted the necessary permissions (possibly subject to override by assertion or denial).

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.

code conversion n. 1. The process of translating program instructions from one form into another. Code may be converted at the source-language level (for example, from C to Pascal), at the hardware-platform level (for example, from working on the IBM PC to working on the Apple Macintosh), or at the language level (for example, from source code in C to machine code). See also code1 (definition 1). 2. The process of transforming data from one representation to another, such as from ASCII to EBCDIC or from two s complement to binary-coded decimal.

Code Division Multiple Access n. A form of multiplexing in which the transmitter encodes the signal, using a pseudo-random sequence that the receiver also knows and can use to decode the received signal. Each different random sequence corresponds to a different communication channel. Motorola uses Code Division Multiple Access for digital cellular phones. Acronym: CDMA. Also called: spread spectrum. See also multiplexing, transmitter.

code page n. In MS-DOS versions 3.3 and later, a table that relates the binary character codes used by a program to keys on the keyboard or to the appearance of characters on the display. Code pages are a means of providing support for character sets and keyboard layouts used in different countries. Devices such as the display and the keyboard can be configured to use a specific code page and to switch from one code page (such as United States) to another (such as Portugal) at the user s request.

code profiler n. A tool designed to aid developers in identifying and eliminating the code inefficiencies that cause bottlenecks and degrade performance in their applications. Code profilers analyze an executing application to determine both how long functions take to execute and how often they are called. Using a code profiler is a repetitive process in that the tool must be reused after each section of inefficient code has been found and corrected.

coder n. See programmer.

Code Red worm n. A fast-spreading and pernicious Internet worm first discovered in mid-2001. The Code Red worm propagates quickly, and any machine that was infected once is potentially vulnerable to re-infection. The Code Red worm is time sensitive, spreading in propagation mode from the 1st to the 19th of each month, attacking in flood mode from the 20th to the 27th, and finally hiding in hibernation mode until the 1st of the next month when the cycle begins again. The worm maintains a list of all computers previously infected, and all these computers will be attacked each month by every newly infected machine. This makes total eradication of the worm difficult because a single machine remaining infected from earlier propagation/attack cycles can potentially re-infect every machine on the list, and each computer might be subject to multiple attacks. At least three versions of the Code Red worm are known to exist. The Code Red worm was named for a caffeinated soft drink by the security team that first tracked the worm.

code segment n. 1. A memory segment containing program instructions. 2. A named and segregated portion of a program s code typically performing a specific class of operations. Code segments in this sense are often loaded into memory as memory segments. The main program segment is kept in memory, and auxiliary segments are loaded only when they are required.

code signing n. The process of adding a digital signature to additions and updates made to source code and applications published on the Internet. Code signing is intended to provide a level of security and trust to Internet software distribution. See also digital signature.

code snippet n. 1. In a graphical user interface, programming instructions embedded in a menu option or button defined by the user. The snippet consisting of one or more lines of source code determines what the option or button does when chosen or clicked. 2. A small piece of programming code that is part of a larger program. Usually the code snippet performs a specific function or task.

coding form n. A sheet of paper ruled with horizontal and vertical lines to aid in writing source code for older languages that have position-dependent syntax (such as FORTRAN). Most programmers now use graph paper if they use paper at all.

coercion n. See cast.

Coffee Pot Control Protocol n. See HTCPCP.

coherence n. 1. In raster-scan technology, the assignment of the value of one pixel to the pixel next to it. 2. In optics, the property of some electromagnetic waves of being in phase with one another, as in light from a laser.

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.

cold fault n. A fatal error that occurs immediately upon or shortly after startup as a result of the misalignment of components in the system. The process of running and shutting down any computer induces a series of thermal expansions and contractions in its internal components. Over time, these changes in the dimensions of components can create a microscopic crack in a chip or loosen a pin in a socket; thus, the system crashes when cold, but the problem seems to disappear after the machine is warm. For this reason, some users leave the system unit (but not the monitor) of a computer running from day to day, rather than turn the machine on only when needed.

cold link n. A link established upon a request for data. Once the request is filled, the link is broken. The next time data is required, a link from the client to the server must be reestablished. In a client/server architecture, cold links are useful when the linked item consists of a large amount of data. Dynamic Data Exchange (DDE), used in applications such as Microsoft Excel, uses cold links for data exchange. See also client/server architecture, DDE. Compare hot link.

cold start n. See cold boot.

collaboration data object n. Microsoft Exchange Server technology for creating messaging and collaboration applications. A collaboration data object consists of a scripting interface added to Microsoft Messaging Application Programming Interface (MAPI). Acronym: CDO.

collaborative filtering n. A means of deriving information from the experiences and opinions of a number of people. The term was coined by Doug Terry at Xerox PARC, who first used the technique by allowing users to annotate documents as they read them and to choose which documents to read next based not only on their content but also on what others wrote about them. A common use of collaborative filtering is the creation of lists of World Wide Web pages of interest to particular people; by documenting the experiences of several people, a list of interesting Web sites can be filtered. Collaborative filtering is also used as a marketing research tool; by keeping a database of opinions and ratings regarding several products, researchers can predict which new products the people contributing to the database will like.

collapsed backbone n. See backbone (definition 3).

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.

collating sort n. A sort that proceeds by continuous merging of two or more files to produce a certain sequence of records or data items.

collation sequence n. The ordering relationship (sequence) among objects that is to be established by a collating sort. See also collating sort.

collector n. The region of a bipolar transistor into which charge carriers flow under normal operating conditions. The output of the transistor is usually taken from the collector. With respect to the base and emitter, the collector is positive in an NPN transistor and negative in a PNP transistor. See also NPN transistor, PNP transistor. Compare base (definition 3), emitter.

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.

colocation or co-location n. The operation of a server, router, or other device in a facility that provides a dedicated Internet connection, physical space in a secured cage, and regulated power. Colocation services often include fire detection and extinguishing, backup power, technical support, and additional security measures to ensure high availability.

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 the pixel s 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 Windows NT and Windows 9x Paint accessory, a graphic screen element in the form of a paint box that is used to select foreground and background colors.

color burst n. A technique used to encode color in a composite video signal, originally developed so that black-and-white television monitors could display programs broadcast in color. The color burst consists of a combination of the red, green, and blue intensities (used by black-and-white displays) and two color-difference signals that determine separate red, green, and blue intensities (used by color displays). See also color look-up table.

color cycling n. A technique used in computer graphics for changing the color of one or more pixels on the screen by changing the color palette used by the video adapter rather than by changing the color bits for each pixel. For example, to cause a red circle to fade away to a black background color, the program need only change the set of signal values corresponding to red in the video adapter s color look-up table, periodically making it darker until it matches the black background. At each step, the apparent color of the whole circle changes instantly; it appears to fade rather than to be painted over and over. The speed at which and the degree to which the circle fades are entirely up to the programmer.

color depth n. The number of color values that can be assigned to a single pixel in an image. Also known as bit depth, color depth can range from 1 bit (black and white) to 32 bits (over 16.7 million colors). See also bit depth.

color gamut n. The particular range of colors that a device is able to produce. A device such as a scanner, monitor, or printer can produce a unique range of colors, which is determined by the characteristics of the device itself. See also rendering intent.

Color/Graphics Adapter n. See CGA.

colorimeter n. A device that evaluates and identifies colors in terms of a standard set of synthesized colors.

color look-up table n. A table stored in a computer s video adapter, containing the color signal values that correspond to the different colors that can be displayed on the computer s monitor. When color is displayed indirectly, a small number of color bits are stored for each pixel and are used to select a set of signal values from the color look-up table. Also called: color map, color table, video look-up table. See also color bits, palette (definition 2), pixel.

Color Look Up Table n. See CLUT.

color management n. The process of producing or reproducing accurate, consistent color across any of a variety of color input, output, and display devices. Color management includes, but is not limited to, accurate conversion of RGB input from input devices such as a scanner or a camera or from display devices such as a monitor to CMYK output for an output device such as a printer. Color management also encompasses application of a device profile, which contains information on color behavior for the printer or other device on which the image will be reproduced, and allowance for environmental variations such as humidity and lighting. See also CMYK, RGB.

color management system n. A technology designed to calibrate, characterize, and process color production and reproduction across a variety of color input, output, and display devices. See also color management.

color map n. See color look-up table.

color model n. Any method or convention for representing color in desktop publishing and graphic arts. In the graphic arts and printing fields, colors are often specified with the Pantone system. In computer graphics, colors can be described using any of several different color systems: HSB (hue, saturation, and brightness), CMY (cyan, magenta, and yellow), and RGB (red, green, and blue). See also CMY, HSB, Pantone Matching System, process color, RGB, spot color.

color monitor n. A video display device designed to work with a video card or an adapter to produce text or graphics images in color. A color monitor, unlike a monochrome display, has a screen coated internally with patterns of three phosphors that glow red, green, and blue when struck by an electron beam. To create colors such as yellow, pink, and orange, the three phosphors are lighted together in varying degrees. A video card that uses large groups of bits (6 or more) to describe colors and that generates analog (continuously variable) signals is capable of generating an enormous potential range of colors on a color monitor. See also color, color model, Cycolor.

color palette n. See palette (definition 1).

color plane n. See bit plane.

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.

color separation n. 1. The process of printing the colors in a document as separate output files, each of which is to be printed using a different-colored ink. There are two types of color separation: spot color separation and process color separation. See also color model, process color, spot color. 2. One of the output files produced by a color document, to be printed in its own color of ink.

color space n. A means of describing color in digital environments. RGB is the most common color space on the Web, and with other color, the most common color space viewed on computer displays, while CMYK is the main color space for desktop publishing and other digital print media.

color supertwist nematic display n. See supertwist display.

color table n. See color look-up table.

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 the illustration. See also bar chart.

Column chart.

.com n. 1. In the Internet s Domain Name System, the top-level domain that identifies addresses operated by commercial organizations. The domain name .com appears as a suffix at the end of the address. See also DNS (definition 1), domain (definition 3). Compare .edu, .gov, .mil, .net, .org. 2. In MS-DOS, the file extension that identifies a command file. See also COM (definition 3).

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 runtime 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 (Windows running on an Intel chip) 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, port, Wintel.

combinatorial explosion n. A condition inherent in certain types of mathematical problems in which small increases in the problem s size (number of data items or parameters of the operation) lead to enormous increases in the time required to obtain a solution. See also combinatorics.

combinatorics n. A branch of mathematics related to probability and statistics, involving the study of counting, grouping, and arrangement of finite sets of elements. Combinatorics involves the two concepts of combinations and permutations. A combination is the grouping of elements taken from a larger set without regard to the order of the elements in each group; for example, taking two elements at a time from a set of four objects (A, B, C, and D) creates six combinations of objects: AB, AC, AD, BC, BD, and CD. A permutation is a grouping of elements taken from a larger set with regard to the order of the elements. For example, in making permutations of two objects from the same set of four objects, there would be four candidates to choose from for the first selection (A), and three left over to choose from for the second selection (B), or 12 permutations in all: AB, AC, AD, BA, BC, BD, CA, CB, CD, DA, DB, DC. See also combinatorial explosion.

COM callable wrapper n. A proxy object generated by the runtime so that existing COM applications can use managed classes, including .NET Framework classes, transparently. Acronym: CCW.

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.

Comit Consultatif International T l graphique et T l phonique n. 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 buffer n. An area in memory in which commands entered by the user are kept. A command buffer can enable the user to repeat commands without retyping them completely, edit past commands to change some argument or correct a mistake, undo commands, or obtain a list of past commands. See also history, template (definition 4).

command button n. A control shaped like a pushbutton in a dialog box in a graphical user interface. By clicking a command button, the user causes the computer to perform some action, such as opening a file that has just been selected using the other controls in the dialog box.

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-driven system n. A system in which the user initiates operations by a command entered from the console. Compare graphical user interface.

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 language n. The set of keywords and expressions that are accepted as valid by the command interpreter. See also command interpreter.

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

command-line interface n. A form of interface between the operating system and the user in which the user types commands, using a special command language. Although systems with command-line interfaces are usually considered more difficult to learn and use than those with graphical interfaces, command-based systems are usually programmable; this gives them flexibility unavailable in graphics-based systems that do not have a programming interface. Compare graphical user interface.

command mode n. A mode of operation in which a program waits for a command to be issued. Compare edit mode, insert mode.

command processing n. See command-driven system.

command processor n. See command interpreter.

command prompt window n. A window displayed on the desktop used to interface with the MS-DOS operating system. MS-DOS commands are typed at an entry point identified by a blinking cursor. See also MS-DOS.

command shell n. See shell1.

command state n. The state in which a modem accepts commands, such as a command to dial a telephone number. Compare online state.

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 Interchange Pipeline n. See CIP.

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 access provider n. See ISP.

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

commercial off-the-shelf board n. A hardware board or platform that is readily available in the industry for purchase and can be used for development or test purposes. Also called: COTS board.

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 Application Language n. See CAL.

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

Common Client Interface n. A control interface begun with the X Windows version of NCSA Mosaic whereby other programs can control the local copy of a Web browser. The X Windows and Windows versions of NCSA Mosaic can communicate with other programs via TCP/IP. The Windows version is also capable of OLE communication. Acronym: CCI. See also Mosaic, OLE, TCP/IP, X Window System.

Common Gateway Interface n. See CGI (definition 1), CGI script.

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. Acronym: CHRP. See also PowerPC.

Common Indexing Protocol n. See CIP.

Common Information Model n. See CIM (definition 1).

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.

common language runtime n. The engine at the core of managed code execution. The runtime supplies managed code with services such as cross-language integration, code access security, object lifetime management, and debugging and profiling support.

common language runtime host n. An unmanaged application that uses a set of APIs, called the hosting interfaces, to integrate managed code into the application. Common language runtime hosts often require a high degree of customization over the runtime that is loaded into the process. The hosting interfaces allow common language runtime hosts to specify settings that configure the garbage collector, select the appropriate build for their environment (server versus workstation), and so on. Common language runtime hosts often support an extensibility model that allows the end user to dynamically add new pieces of functionality, such as a new control or a user-written function. These extensions are typically isolated from each other in the process using application domains and custom security settings. Examples of common language runtime hosts include ASP.NET, Microsoft Internet Explorer, and a host to run executables launched from the Windows Shell.

Common Language Specification n. See CLS.

Common LISP n. Short for Common List Processing. A formalized and standardized version of the LISP programming language. Because LISP is in the public domain, a number of different versions of the language have evolved, and Common LISP was made a standard to give programmers a definitive source for LISP. See also LISP, programming language, standard (definition 1).

Common Object Request Broker Architecture n. See CORBA.

common type system n. The specification that determines how the runtime defines, uses, and manages types.

Common User Access n. A set of standards for management of user interfaces as part of IBM s Systems Application Architecture (SAA). Common User Access is designed to facilitate development of applications that are compatible and consistent across different platforms. Acronym: CUA. See also standard (definition 1), user interface.

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 Act of 1934 n. See FCC.

Communication Satellite Corporation n. Corporation created by the U.S. government to provide international satellite services for telecommunications. Acronym: COMSAT.

communications channel n. See channel (definition 2).

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 network n. See network.

communications parameter n. Any of several settings required in order to enable computers to communicate. In asynchronous communications, for example, modem speed, number of data bits and stop bits, and type of parity are parameters that must be set correctly to establish communication between two modems.

communications port n. See COM.

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.

Communications Terminal Protocol n. A terminal protocol that enables a user at a remote location to access a computer as if the remote computer were directly connected (hardwired) to the computer. Acronym: CTERM.

community antenna television n. See CATV.

COMNET Conference & Expo n. Conference and exposition for the communications networking industry. The conference features educational sessions and exhibitions on technical and business issues affecting communications networks.

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 (definition 2). 3. See CD.

compact disc-erasable n. See CD-E.

compact disc-interactive n. See CD-I.

compact disc player n. See CD player.

compact disc-recordable n. See CD-R.

compact disc-recordable and erasable adj. See CD-R/E.

compact disc-rewritable n. See CD-RW.

CompactFlash n. Plug-in memory devices designed by the CompactFlash Association for use in digital cameras and, eventually, other devices for storing and transporting digital data, sound, images, and video. CompactFlash devices are small cards 1.7 x 1.4 x 0.13 inches (43 x 36 x 3.3 mm) in size. They are based on nonvolatile flash technology, so they do not rely on batteries or other power to retain information. See also digital camera.

CompactFlash Association n. A nonprofit association that developed and promotes the CompactFlash specification. Founded in October 1995, it has a membership that includes 3COM, Eastman Kodak Company, Hewlett-Packard, IBM, and NEC, among other corporations. See also CompactFlash.

compaction n. The process of gathering and packing the currently allocated regions of memory or auxiliary storage into as small a space as possible, so as to create as much continuous free space as possible. Compare dispersion, file fragmentation (definition 1).

compact model n. A memory model of the Intel 80x86 processor family. The compact model allows only 64 kilobytes (KB) for the code of a program but up to 1 megabyte (MB) for the program s data. See also memory model.

CompactPCI n. An open bus specification for industrial computing needs developed by the PCI Industrial Computer Manufacturers Group (PICMG). CompactPCI is based on the desktop-computing PCI bus but differs in a number of respects, including a pin-and-socket connector and a design that allows for front loading and removal of cards. CompactPCI is intended for applications such as industrial automation, military systems, and real-time data acquisition. It is suitable for high-speed communications devices, such as routers, and allows for hot-plugging. See also hot plugging, PCI local bus.

comparator n. A device for comparing two items to determine whether they are equal. In electronics, for example, a comparator is a circuit that compares two input voltages and indicates which is higher.

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.

comparison criteria n. A set of search conditions that is used to find data. Comparison criteria can be a series of characters that you want to match, such as Northwind Traders , or an expression, such as >300 .

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 box n. See DOS box (definition 1).

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.

Competitive Local Exchange Carrier n. See CLEC.

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 (definition 2), compile time, high-level language, machine code, source code. Compare interpret.

compile-and-go adj. Of, pertaining to, or characteristic of a development environment that automatically runs a program after compiling it. See also compile, execute.

compiled Basic n. Any version of Basic that is translated into machine code prior to execution by a compiler. Basic has traditionally been an interpreted language (translated and executed statement by statement); because compiled Basic generally produces faster-executing programs, it is the technology of choice for professional Basic programmers. See also Basic, compiled language, interpreted language.

compiled language n. A language that is translated into machine code prior to any execution, as opposed to an interpreted language, which is translated and executed statement by statement. See also compiler (definition 2). Compare interpreted language.

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.

compile time n. 1. The amount of time required to perform a compilation of a program. Compile time can range from a fraction of a second to many hours, depending on the size and complexity of the program, the speed of the compiler, and the performance of the hardware. See also compiler (definition 2). 2. The point at which a program is being compiled (i.e., most languages evaluate constant expressions at compile time but evaluate variable expressions at run time). See also link time, run time.

compile-time binding n. Assignment of a meaning to an identifier (such as a function name or a constant) in a program at the time the program is compiled rather than at the time it is run. Compare run-time binding.

complement n. Loosely, a number that can be thought of as the mirror image of another number written to the same base, such as base 10 or base 2. Complements are commonly used to represent negative numbers. Two types of complements are encountered in computer-related contexts: radix-minus-1 complements and true complements. A radix-minus-1 complement is known in the decimal system as a nine s complement and in the binary system as a one s complement. True complements are known in the decimal system as ten s complement and in binary as two s complement a form commonly used to represent negative numbers in processing. See also complementary operation, nine s complement, one s complement, ten s complement, two s complement.

complementary metal-oxide semiconductor n. See CMOS.

complementary operation n. In Boolean logic, an operation that produces the opposite result from that of another operation performed on the same data. For example, if A is true, NOT A (its complement) is false. See also Boolean algebra.

completeness check n. A survey to determine that all data required in a record is present. Compare consistency check.

complex instruction set computing n. See CISC.

complex number n. A number of the form a + bi, where a and b are real numbers and i is the square root of -1, called the imaginary unit. Complex numbers can be plotted as points on a two-dimensional plane called the complex plane. The a number is plotted along the plane s horizontal axis (the real axis), and the b number is plotted along the vertical axis (the imaginary axis). Compare real number.

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. 3. In Sun Microsystem s J2EE network platform, an application-level software unit supported by a container. Components are configurable at deployment time. The J2EE platform defines four types of components: enterprise java beans, Web components, applets, and application clients. See also applet, container (definition 3), Enterprise JavaBeans, J2EE.

Component Object Model n. See COM (definition 2).

Component Pascal n. A Pascal derivative designed for programming software components for .NET and JVM platforms. See also Oberon, Pascal.

component software n. Modular software routines, or components, that can be combined with other components to form an overall program. A programmer can use and reuse an existing component and not have to understand its inner workings, just how to have another program or component call it and pass data to and from it. Also called: componentware. See also component, program, routine.

componentware n. See component software.

COM port or comm port n. Short for communications port , the logical address assigned by MS-DOS (versions 3.3 and later) and Microsoft Windows (including Windows 9x 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 the illustration. See also COM (definition 1), input/output port, serial port.

COM port.

composite display n. A display, characteristic of television monitors and some computer monitors, that is capable of extracting an image from a composite signal (also called an NTSC signal). A composite display signal carries on one wire not only the coded information required to form an image on the screen but also the pulses needed to synchronize horizontal and vertical scanning as the electron beam sweeps back and forth across the screen. Composite displays can be either monochrome or color. A composite color signal combines the three primary video colors (red, green, and blue) in a color burst component that determines the shade of color displayed on the screen. Composite color monitors are less readable than either monochrome monitors or the RGB color monitors that use separate signals (and wires) for the red, green, and blue components of the image. See also color burst, color monitor, monochrome display, NTSC, RGB monitor.

composite key n. A key whose definition consists of two or more fields in a file, columns in a table, or attributes in a relation.

composite video display n. A display that receives all encoded video information (including color, horizontal synchronization, and vertical synchronization) in one signal. A composite video signal under NTSC (National Television System Committee) standards is generally required for television sets and videotape recorders. See also NTSC. Compare RGB monitor.

compound document n. A document that contains different types of information, each type created with a different application; for example, a report containing both charts (created with a spreadsheet) and text (created with a word processor) is a compound document. Although a compound document is visually a single, seamless unit, it is actually formed of discrete objects (blocks of information) that are created in their own applications. These objects can either be physically embedded in the destination document, or they can be linked to it while remaining in the originating file. Both embedded and linked objects can be edited. Linked objects, however, can be updated to reflect changes made to the source file. See also ActiveX, OLE, OpenDoc.

compound statement n. A single instruction composed of two or more individual instructions.

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 digital video n. See CDV (definition 1).

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.

Compressed Read-Only File System n. See cramfs.

Compressed SLIP n. Short for Compressed Serial Line Internet Protocol. A version of SLIP using compressed Internet address information, thereby making the protocol faster than SLIP. Acronym: CSLIP. See also SLIP.

compression n. See data compression.

compressor n. A device that limits some aspect of a transmitted signal, such as volume, in order to increase efficiency.

CompuServe n. An online information service that is a subsidiary of America Online. CompuServe 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 commercial online services. CompuServe also operates various private network services.

computational intelligence n. The study of the design of intelligent agents whose reasoning is based on computational methods. The central scientific goal of computational intelligence is to understand the principles that make intelligent behavior possible, in natural or artificial systems. An intelligent agent is flexible to changing environments and changing goals it learns from experience, and it makes appropriate choices given perceptual limitations and finite computation. The central engineering goal of computational intelligence is to specify methods for the design of useful, intelligent artifacts. See also agents (definition 2), artificial intelligence, autonomous agent.

computation-bound adj. Of, pertaining to, or characteristic of a situation in which the performance of a computer is limited by the number of arithmetic operations the microprocessor must perform. When a system is computation-bound, the microprocessor is overloaded with calculations. Also called: CPU-bound.

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

computer n. Any device capable of processing information to produce a desired result. No matter how large or small they are, computers typically perform their work in three well-defined steps: (1) accepting input, (2) processing the input according to predefined rules (programs), and (3) producing output. There are several ways to categorize computers, including class (ranging from microcomputers to supercomputers), generation (first through fifth generation), and mode of processing (analog versus digital). See the table. See also analog, digital (definition 2), integrated circuit, large-scale integration, very-large-scale integration.

Table C.1 Ways to Categorize Computers
Class Computers can be classified as supercomputers, mainframes, superminicomputers, minicomputers, workstations, microcomputers, or PDAs. All other things (for example, the age of the machine) being equal, such a categorization provides some indication of the computer s speed, size, cost, and abilities.
Generation First-generation computers of historic significance, such as UNIVAC, introduced in the early 1950s, were based on vacuum tubes. Second-generation computers, appearing in the early 1960s, were those in which transistors replaced vacuum tubes. Third-generation computers, dating from the 1960s, were those in which integrated circuits replaced transistors. Fourth-generation computers, appearing in the mid-1970s, are those, such as microcomputers, in which large-scale integration (LSI) enabled thousands of circuits to be incorporated on one chip. Fifth-generation computers are expected to combine very-large-scale integration (VLSI) with sophisticated approaches to computing, including artificial intelligence and true distributed processing.
Mode of processing Computers are either analog or digital. Analog computers, generally used in scientific pursuits, represent values by continuously variable signals that can have any of an infinite number of values within a limited range at any particular time. Digital computers, the type most people think of as computers, represent values by discrete signals the bits representing the binary digits 0 and 1.

computer-aided design n. See CAD.

computer-aided design and drafting n. See CADD.

computer-aided design/computer-aided manufacturing n. See CAD/CAM.

computer-aided engineering n. See CAE.

computer-aided instruction n. See CAI.

computer-aided learning n. See CAL.

computer-aided manufacturing n. See CAM (definition 1).

computer-aided testing n. See CAT (definition 1).

Computer and Business Equipment Manufacturers Association n. See CBEMA.

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 diagnosis n. The use of computers by physicians in diagnosing patient conditions. Medical application programs can help to determine the cause, symptoms, and treatment of a problem as well as to maintain a record of a patient s medical history and test results. See also expert system.

computer-assisted instruction n. See CAI.

computer-assisted learning n. See CAL.

computer-assisted teaching n. See CAI.

computer-augmented learning n. See CAL.

computer-based learning n. See CBL.

computer-based training n. See CBT.

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 conferencing n. Person-to-person interaction through the use of computers located in different places but connected through communications facilities.

computer control console n. See system console.

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-dependent adj. See hardware-dependent.

Computer Emergency Response Team n. See CERT.

computer engineering n. The discipline that involves the design and underlying philosophies involved in the development of computer hardware.

computer family n. A term commonly used to indicate a group of computers that are built around the same microprocessor or around a series of related microprocessors and that share significant design features. For example, the Apple Macintosh computers, from the original Macintosh (introduced in 1984) to the Quadra, represent a family designed by Apple around the Motorola 68000, 68020, 68030, and 68040 microprocessors. Computer families tend to parallel microprocessor families, but this is not always the case. For instance, Macintoshes are no longer made with 680x0 processors, and the Macintosh family has extended to another generation: the Power Macs, based on the PowerPC microprocessor.

computer game n. A class of computer program in which one or more users interacts 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, on the Internet, 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. Acronym: CGI. See also Graphical Kernel System.

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. Acronym: CGM. See also Graphical Kernel System.

computer-independent language n. A computer language designed to be independent of any given hardware platform. Most high-level languages are intended to be computer-independent; actual implementations of the languages (in the form of compilers and interpreters) tend to have some hardware-specific features and aspects. See also computer language.

computer-input microfilm n. See CIM (definition 2).

computer instruction n. 1. An instruction that a computer can recognize and act on. See also machine instruction. 2. The use of a computer in teaching. See also CAI.

computer-integrated manufacturing n. See CIM (definition 1).

computer interface unit n. See interface (definition 3).

computerized axial tomography n. See CAT (definition 3).

computerized mail n. See e-mail1.

computer language n. An artificial language that specifies instructions to be executed on a computer. The term covers a wide spectrum, from binary-coded machine language to high-level languages. See also assembly language, high-level language, machine code.

computer letter n. See form letter.

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-managed instruction n. See CMI.

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.

computer network n. See network.

computer-output microfilm n. See COM (definition 4).

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

computer power n. The ability of a computer to perform work. If defined as the number of instructions the machine can carry out in a given time, computer power is measured in millions of instructions per second (MIPS) or millions of floating-point operations per second (MFLOPS). Power is measured in other ways too, depending on the needs or objectives of the person evaluating the machine. By users or purchasers of computers, power is often considered in terms of the machine s amount of random access memory (RAM), the speed at which the processor works, or the number of bits (8, 16, 32, and so on) handled by the computer at one time. Other factors enter into such an evaluation, however; two of the most important are how well the components of the computer work together and how well they are matched to the tasks required of them. For example, no matter how fast or powerful the computer, its speed will be hampered during operations involving the hard disk if the hard disk is slow (for example, with an access time of 65 milliseconds or higher). See also access time (definition 2), benchmark1, MFLOPS, MIPS.

Computer Press Association n. A trade organization of journalists, broadcasters, and authors who write or report about computer technology and the computer industry.

Computer Professionals for Social Responsibility n. See CPSR.

computer program n. A set of instructions in some computer language intended to be executed on a computer so as to perform some task. The term usually implies a self-contained entity, as opposed to a routine or a library. See also computer language. Compare library (definition 1), routine.

computer-readable adj. Of, pertaining to, or characteristic of information that can be interpreted and acted on by a computer. Two types of information are referred to as computer-readable: bar codes, magnetic tape, magnetic-ink characters, and other formats that can be scanned in some way and read as data by a computer; and machine code, the form in which instructions and data reach the computer s microprocessor.

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 that many people have access to, 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.

computer simulation n. See simulation.

computer system n. The configuration that includes all functional components of a computer and its associated hardware. A basic microcomputer system includes a console, or system unit, with one or more disk drives, a monitor, and a keyboard. Additional hardware, called peripherals, can include such devices as a printer, a modem, and a mouse. Software is usually not considered part of a computer system, although the operating system that runs the hardware is known as system software.

computer telephone integration n. A process allowing computer applications to answer incoming calls, provide database information on-screen at the same time the call comes in, automatically route and reroute calls by drag-and-drop, automatically dial and speed-dial outgoing calls from a computer-resident database, and identify incoming customer calls and transfer them to predetermined destinations. See also drag-and-drop.

Computer Telephony Expo n. See CT Expo.

computer typesetting n. Typesetting operations that are partially or totally controlled by computers. Partial control can involve the transmittal of text directly from the source to the typesetter, without a paste-up stage. Full computerization can include the digitization of all graphics, which would then also be transmitted directly to the typesetter and regenerated without paste-up.

computer users group n. See user group.

computer utility n. See utility.

computer virus n. See virus.

computer vision n. The processing of visual information by a computer. Computer vision is a form of artificial intelligence that creates a symbolic description of images that are generally input from a video camera or sensor in order to convert the images to digital form. Computer vision is often associated with robotics. Acronym: CV. See also artificial intelligence, robotics.

Computer Vision Syndrome n. A change in a user s vision caused by prolonged exposure to computer monitors. Symptoms of Computer Vision Syndrome (CVS) can include blurred vision, dry, burning eyes, focusing problems, and headaches. CVS may be controlled with regular breaks from the computer, use of monitor filters or color adjustments, or adjustments to eyeglass prescriptions. Acronym: CVS.

COM recorder n. Short for computer output microfilm recorder. A device that records computer information on microfilm.

COMSAT n. See Communication Satellite Corporation.

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.

concatenate vb. To join sequentially (for example, to combine the two strings hello and there into the single string hello there ). See also character string.

concatenated data set n. A group of separate sets of related data treated as a single unit for processing.

concentrator n. A communications device that combines signals from multiple sources, such as terminals on a network, into one or more signals before sending them to their destination. Compare multiplexer (definition 2).

conceptual schema n. In a database model that supports a three-schema architecture (such as that described by ANSI/X3/SPARC), a description of the information contents and structure of a database. A conceptual schema (also known as a logical schema) provides a model of the total database, thus acting as an intermediary between the two other types of schemas (internal and external) that deal with storing information and presenting it to the user. Schemas are generally defined using commands from a DDL (data definition language) supported by the database system. See also internal schema, schema.

concordance n. A list of words that appear in a document, along with the contexts of the appearances.

concrete class n. In object-oriented programming, a class in which objects can be created. See also class (definition 1). Compare abstract class.

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.

concurrent operation n. See concurrent.

concurrent processing n. See concurrent.

concurrent program execution n. See concurrent.

Concurrent Versions System n. See CVS (definition 2).

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.

condition n. The state of an expression or a variable (for example, when a result can be either true or false, or equal or not equal).

conditional adj. Of, pertaining to, or characteristic of an action or operation that takes place based on whether or not a certain condition is true. See also Boolean expression, conditional statement.

conditional branch n. In a program, a branch instruction that occurs when a particular condition code is true or false. The term is normally used in relation to low-level languages. See also branch instruction, condition code.

conditional compilation n. Selective compilation or translation of source code of a program based on certain conditions or flags; for example, sections of a program specified by the programmer might be compiled only if a DEBUG flag has been defined at compilation time. See also comment out.

conditional expression n. See Boolean expression.

conditional jump n. In a program, a jump instruction that occurs when a particular condition code is true or false. The term is normally used in relation to low-level languages. See also condition code, jump instruction.

conditional statement n. A programming-language statement that selects an execution path based on whether some condition is true or false (for example, the IF statement). See also case statement, conditional, IF statement, statement.

conditional transfer n. A transfer of the flow of execution to a given location in a program based on whether a particular condition is true. The term is usually used in relation to high-level languages. See also conditional statement.

condition code n. One of a set of bits that are set on (1, or true) or off (0, or false) as the result of previous machine instructions. The term is used primarily in assembly or machine language situations. Condition codes are hardware-specific but usually include carry, overflow, zero result, and negative result codes. See also conditional branch.

conditioning n. The use of special equipment to improve the ability of a communications line to transmit data. Conditioning controls or compensates for signal attenuation, noise, and distortion. It can be used only on leased lines, where the path from sending to receiving computer is known in advance.

conductor n. A substance that conducts electricity well. Metals are good conductors, with silver and gold being among the best. The most commonly used conductor is copper. Compare insulator, semiconductor.

Conference on Data Systems Languages n. See CODASYL.

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.

congestion n. The condition of a network when the current load approaches or exceeds the available resources and bandwidth designed to handle that load at a particular location in the network. Packet loss and delays are associated with congestion.

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, fiberoptic cable, or other medium between two or more communications devices.

connection-based session n. A communications session that requires a connection to be established between hosts prior to an exchange of data.

connectionism n. A model in artificial intelligence that advocates using highly parallel, specialized processes that compute simultaneously and are massively connected. Thus, the connectionist approach would not use a single high-speed processor to compute an algorithm, but would break out many simple specialized processing elements that are highly connected. Neural networks are classic examples of connectionism in that each neuron in the network may be assigned to a single processor. See also algorithm, artificial intelligence, neural network.

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.

connectionless session n. A communications session that does not require a connection to be established between hosts prior to an exchange of data.

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.

connection pooling n. A resource optimization feature of ODBC (Open Database Connectivity) 3 that results in more efficient sharing of database connections and objects. Connection pooling maintains open collections (pools) of database connections that can be used and reused by applications without the need to open and close a connection for each request. This is particularly important for Web-based applications. Connection pooling enables sharing among different components, maximizes performance, and minimizes the number of idle connections. See also ODBC.

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 9x and Windows NT, an icon representing a dial-up networking connection that will also execute 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 sockets or jacks 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.

consistency check n. A survey to verify that items of data conform to certain formats, bounds, and other parameters and are not internally contradictory. Compare completeness check.

console n. 1. 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 device (screen), as evidenced by the device name CON. See also CON, system console. 2. See game console.

console game n. A special-purpose computer system designed specifically for the home user to play video games. A game console typically includes a CPU, one or more game controllers, audio output, and a video output that connects to a television set. Individual games and memory cards are supplied on plug-in cartridges or compact discs. Many recent versions are 128-bit systems and also include a modem for online gaming over the Internet. Well-known console games include Microsoft Xbox, Sony PlayStation 2, Nintendo GameCube, and Sega Dreamcast. Also called: game console. See also computer game, Dreamcast, GameCube, PlayStation, Xbox. Compare arcade game.

constant n. A named item that retains a consistent value throughout the execution of a program, as opposed to a variable, which can have its value changed during execution. Compare variable.

constant expression n. An expression that is composed only of constants and, hence, whose value does not change during program execution. Compare variable expression.

constellation n. In communications, a pattern representing the possible states of a carrier wave, each of which is associated with a particular bit combination. A constellation shows the number of states that can be recognized as unique changes in a communications signal and thus the maximum number of bits that can be encoded in a single change (equivalent to 1 baud, or one event). See the illustration.

Constellation.

constraint n. In programming, a restriction on the solutions that are acceptable for a problem.

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.

Consumer Electronics Show n. Annual tradeshow of the consumer electronics industry, held in Las Vegas, Nevada. CES features exhibits of the latest consumer electronics products and conference events that focus on consumer trends and business strategies. Acronym: CES.

contact manager n. A type of specialized database that allows a user to maintain a record of personal communication with others. Contact managers are widely used by salespeople and others who want to keep track of conversations, e-mail, and other forms of communication with a large number of current and prospective customers or clients. See also database.

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, SGML, tag. 3. In Sun Microsystem s J2EE network platform, an entity that provides life cycle management, security, deployment, and runtime services to components such as beans, Web components, applets, and application clients. Each type of container created (for example, EJB, Web, JSP, servlet, applet, and application client) also provides component-specific services. See also applet, component (definition 3), enterprise java bean, JSP, servlet.

container object n. An object that can logically contain other objects. For example, a folder is a container object. See also noncontainer object, object.

content n. 1. The data that appears between the starting and ending tags of an element in an SGML, XML, 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. 3. The meat of a document, as opposed to its format or appearance.

content-addressed storage n. See associative storage.

content aggregator n. 1. Broadly, an organization or business that groups Internet-based information by topic or area of interest for example, sports scores, business news, or online shopping to provide users with a means of accessing that content from a single location. 2. In terms of push technology and multicasting, a service business that mediates between subscribers ( customers ) and content providers by gathering and organizing information for broadcast over the Internet. Content aggregators supply subscribers with client software through which content providers broadcast (push) information via channels that allow users both to choose the kind of information they receive and to decide when they want it updated. Also called: channel aggregator. See also push, webcasting. Compare content provider.

content caching n. See content delivery.

content delivery n. The process of caching the pages of a Web site on geographically dispersed servers to enable faster delivery of Web pages. When a page is requested at a URL that is content-delivery enabled, the content-delivery network routes the user s request to a cache server closer to the user. Content delivery frequently is used for high-traffic Web sites or for specific high-traffic events. Also called: content distribution, content caching.

content distribution n. See content delivery.

contention n. On a network, competition among nodes 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.

Content Management Server n. Automated software application developed by Microsoft Corporation to assist nontechnical users in creating, tracking, and publishing content for Web sites. A workflow system delineates the tasks each user can perform, assigns content to individuals or groups, and allows users to monitor the status of content with which they are associated.

Content Protection for Recordable Media n. See CPRM.

content provider n. 1. Broadly, an individual, group, or business that provides information for viewing or distribution on the Internet or on private or semiprivate intranets or extranets. Content in this sense includes not only information but also video, audio, software, listings of Web sites, and product-specific materials such as online catalogs. 2. A service business that makes Internet information resources available to users. Content providers include online services such as America Online and CompuServe, Internet service providers (ISPs), and an increasing number of media companies representing television, long-distance telephone, and publishing industries. See also ISP, online information service. Compare content aggregator.

Content Scrambling System n. See CSS.

contents directory n. A series of queues that contain the descriptors and addresses of routines located within a region of memory.

context-dependent adj. Of, pertaining to, or characteristic of a process or a set of data characters whose meaning depends on the surrounding environment.

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-form paper n. Paper in which each sheet is connected to the sheets before and after it, for use with most impact and ink-jet printers and some other printing devices designed with an appropriate paper-feed mechanism. The paper usually has holes punched along each side so that it can be pulled by a tractor-feed device. See the illustration. See also pin feed, sprocket feed, tractor feed.

Continuous-form paper.

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

continuous speech recognition n. A type of automatic speech recognition (ASR) technology that responds to strings of words. Continuous speech recognition allows a user to speak in a natural voice without the need to slow down and enunciate each word separately. Continuous speech recognition software takes advantage of context in recognizing words, and thus will not operate at full efficiency if each word is spoken with distinct separation. See also ASR (definition 2).

continuous-tone image n. An image, such as a photograph, in which color or varying shades of gray are reproduced as gradients rather than as clustered or variably sized dots, as in traditional book or newspaper printing. Continuous-tone images can be viewed on an analog monitor (such as a television monitor), which accepts input as a continuously variable signal. They cannot be viewed on a digital monitor, which requires input broken into discrete units, nor can they be printed in books or newspapers, which represent illustrations as groups of dots. See also scan (definition 2), video digitizer. Compare halftone.

continuous-tone printer n. A printer that produces an image using smoothly blended levels of continuous ink for gradations of gray or color. Compare dithering.

contouring n. 1. In computer graphics, such as CAD models, the representation of the surface of an object its bumps and crannies. See the illustration. 2. In image processing, the loss of detail that occurs in a shaded image when too few gradations of gray are used to reproduce a graphic, such as a photograph. In photography and graphic arts, this phenomenon is sometimes called posterization.

Contouring.

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 break n. A transition in control of the computer that typically gives control of the CPU (central processing unit) to the user console or to some other program.

Control-Break n. See Break key.

control bus n. The set of lines (conductors) within a computer that carry control signals between the CPU (central processing unit) 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 console n. See console.

control data n. Data that consists of information about timing and switching, used to synchronize and route other data or to manage the operation of a device such as a bus or a port.

control flow n. The tracing of all possible execution paths in a program, often represented in the form of a diagram. See the illustration.

Control flow.

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 the illustration. See also control character (definition 2).

Control key.

controller n. A device that other devices rely on 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 logic n. The electronic circuitry that generates, interprets, and uses control data.

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 panel device n. See cdev.

control sequence n. See control code.

control signal n. An electronic signal used to control internal or external devices or processes.

control statement n. A statement that affects the flow of execution through a program. Control statements include conditional statements (CASE, IF-THEN-ELSE), iterative statements (DO, FOR, REPEAT, WHILE), and transfer statements (GOTO). See also conditional statement, iterative statement, statement, transfer statement.

control strip n. 1. An equipment calibration tool used to determine the corrections needed to restore accuracy by comparing recorded data against known values. 2. A utility that groups shortcuts to commonly used items or information, such as time, battery power level, desktop items, and programs, in an easily accessible place. See also shortcut.

control structure n. A portion of a program defined by the relationship between the statements, used in structured programming. There are three basic control structures: sequence, where one statement simply follows another; selection, where program flow depends on which criteria are met; and iteration, where an action is repeated until some condition occurs.

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.

control variable n. In programming, the variable in a control statement that dictates the flow of execution. For example, the index variable in a FOR loop controls the number of times a group of statements are executed. See also control statement.

convenience adapter n. See port replicator.

convention n. Any standard that is used more or less universally in a given situation. Many conventions are applied to microcomputers. In programming, for example, a language such as C relies on formally accepted symbols and abbreviations that must be used in programs. Less formally, programmers usually adopt the convention of indenting subordinate instructions in a routine so that the structure of the program is more easily visualized. National and international committees often discuss and arbitrate conventions for programming languages, data structures, communication standards, and device characteristics. See also CCITT, ISO, NTSC, standard (definition 1).

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.

convergence n. A coming together. Convergence can occur between different disciplines and technologies, as when telephone communications and computing converge in the field of telecommunications. It can also occur within a program, such as a spreadsheet, when a circular set of formulas are repeatedly recalculated (iterated), with the results of each iteration coming closer to a true solution.

conversational adj. Of, pertaining to, or characteristic of the mode of operation, typical of microcomputers, in which the computer user and the system engage in a dialogue of commands and system responses. See also interactive.

conversational interaction n. Interaction in which two or more parties alternately transmit and receive messages from each other. See also interactive processing.

conversational language n. Any programming language that allows the programmer to instruct the computer in a conversational mode, as opposed to more formal, structured languages. For example, in a COBOL program, in order to execute a procedure called CHECK 10 times, a program would use the following statement: PERFORM CHECK 10 TIMES.

conversational mode n. See conversational.

conversion n. The process of changing from one form or format to another; where information is concerned, a changeover that affects form but not substance. Types of conversion include data (changing the way information is represented), file (changing a file from one format to another), hardware (changing all or part of a computer system), media (transferring data from one storage media to another), software (changing a program designed for one platform so that it runs on another), and system (changing from one operating system to another).

conversion table n. A table listing a set of characters or numbers and their equivalents in another coding scheme. Common examples of conversion tables include ASCII tables, which list characters and their ASCII values, and decimal-to-hexadecimal tables. Several conversion tables are in Appendixes A-E.

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.

converter box n. See converter.

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.

cooked mode n. One of two forms (the other being raw mode) in which an operating system such as UNIX or MS-DOS sees the handle, or identifier, for a character-based device. If the handle is in cooked mode, the operating system stores each character in a buffer and gives special treatment to carriage returns, end-of-file markers, and linefeed and tab characters, sending a line of data to a device, such as the screen, only after it reads a carriage-return or end-of-file character. In cooked mode, characters read from standard input are often automatically echoed (displayed) on the screen. Compare raw mode.

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).

cookies policy n. A statement that describes a Web site s policy regarding cookies. The policy usually defines a cookie, explains the types of cookies used by the Web site, and describes how the Web site uses the information stored in the cookies.

.coop n. One of seven new top-level domain names approved in 2000 by the Internet Corporation for Assigned Names and Numbers (ICANN), .coop is meant for use with the Web sites of nonprofit cooperatives. The seven new domain names became available for use in the spring of 2001.

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, foreground1, 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.

coordinate n. Any element in a group of references to a particular location, such as the intersection of a certain row and column. In computer graphics and displays, coordinates specify such elements as points on a line, the corners of a square, or the location of a pixel on the screen. In other computer applications, coordinates specify cells on a spreadsheet, data points on a graph, locations in memory, and so on. See also Cartesian coordinates, polar coordinates.

coordinate dimensioning n. A form of spatial positioning in which a point is described, relative to a fixed reference, in terms of its distance and direction along predefined axes. See also Cartesian coordinates, three-dimensional model, two-dimensional model.

coordinated universal time format n. See Universal Time Coordinate.

coordinate pair n. A pair of values representing the x-coordinate and y-coordinate of a point that are stored in a two-dimensional array that can contain coordinates for many points.

COPPA n. Acronym for Children s Online Privacy Protection Act. A U.S. federal law enacted in April 2000 and designed to protect the online privacy of children under the age of 13. COPPA requires Web sites that collect personal information from children under 13 to receive permission from parents or guardians first, and to monitor and supervise children s experiences with interactive Web elements such as chat rooms and e-mail.

copper chip n. A microprocessor that uses copper (rather than the more common aluminum) to connect transistors in a computer chip. Copper chip technology, which was developed by IBM and introduced in 1997, can be expected to boost the speed of a microprocessor by as much as 33 percent.

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 from 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 Windows or 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 disk n. An MS-DOS command to duplicate the contents of a floppy disk on a second disk. See also floppy disk, MS-DOS.

copy holder n. An inclined clipboard or other such device designed to hold printed material so that it can be easily viewed by someone working at a computer keyboard.

copyleft n. See General Public License.

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.

copy protection n. A software lock placed on a computer program by its developer to prevent the product from being copied and distributed without approval or authorization.

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 which the object comes. CORBA is designed to work in object-oriented environments. See also IIOP, 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 class n. In the Java programming language, a public class or interface that is a standard member of the language. Core classes, at minimum, are available on all operating systems where the Java platform runs. A program written entirely in the Java programming language relies only on core classes. See also class (definition 1), object, object-oriented programming.

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

coresident adj. Of or pertaining to a condition in which two or more programs are loaded in memory at the same time.

corona wire n. In laser printers, a wire though which high voltage is passed to ionize the air and transfer a uniform electrostatic charge to the photosensitive medium in preparation for the laser.

coroutine n. A routine that is in memory at the same time as, and frequently executed concurrently with, another.

corrective maintenance n. The process of diagnosing and correcting computer problems after they occur. Compare preventive maintenance.

correspondence quality n. See print quality.

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.

coulomb n. A unit of electrical charge equivalent to roughly 6.26 x 1018 electrons, with a negative charge being an excess of electrons and a positive charge being a deficiency of electrons.

counter n. 1. In programming, a variable used to keep count of something. 2. In electronics, a circuit that counts a specified number of pulses before generating an output. 3. A device that keeps track of the number of visitors to a World Wide Web site.

counting loop n. In a program, a group of statements that are repeated, thereby incrementing a variable used as a counter (for example, a program might repeat a counting loop that adds 1 to its counter until the counter equals 10). See also loop1 (definition 1).

country code n. See major geographic domain.

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.

courtesy copy n. See cc.

CPA n. See Computer Press Association.

CPCP n. See HTCPCP.

cpi n. See characters per inch.

CP/M n. Acronym for Control Program/Monitor. A line of operating systems from Digital Research, Inc. (DRI), 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.

CPM n. See critical path method.

CPRM n. Acronym for Content Protection for Recordable Media. Technology developed to control the use of copyrighted digital music and video material by blocking the transfer of protected files to portable media such as zip disks and smart cards. CPRM would be added to storage devices and provide data scrambling and identification codes to block the copying of copyrighted files.

cps n. See characters per second.

CPSR n. Acronym for Computer Professionals for Social Responsibility. A public advocacy organization of computer professionals. CPSR was originally formed out of concern over the use of computer technology for military purposes but has extended its interest to such issues as civil liberties and the effect of computers on workers.

CPU n. Acronym for central processing unit. The computational and control unit of a computer. The CPU is the device that interprets and executes instructions. Mainframes and early minicomputers contained circuit boards full of integrated circuits that implemented the CPU. Single-chip central processing units, called microprocessors, made possible personal computers and workstations. Examples of single-chip CPUs are the Motorola 68000, 68020, and 68030 chips and the Intel 8080, 8086, 80286, 80386, and i486 chips. The CPU 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 CPU 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 the illustration. See also microprocessor.

CPU.

CPU-bound adj. See computation-bound.

CPU cache n. A section of fast memory linking the CPU (central processing unit) 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, CPU, VCACHE.

CPU cycle n. 1. The smallest unit of time recognized by the CPU (central processing unit) 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 CPU (central processing unit) or on the CPU s heat sink to help dissipate heat from the chip by circulating air around it. See also CPU, heat sink.

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

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

CR n. See carriage return.

crack vb. 1. To gain unauthorized access to a network by breaching its security. 2. To decipher encrypted information.

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 only to break into the system. See also hacker (definition 2).

cradle n. A receptacle used to recharge the batteries in some handheld or palm-size PCs or PDAs (personal digital assistants). Some cradles also serve as a means to connect these smaller devices with a desktop PC. Not all of these devices require a cradle to recharge or connect to a desktop system. Also called: dock, docking station.

cramfs n. Short for Compressed Read-Only File System and cram a File System onto a small ROM. A filesystem feature available with Linux version 2.4 systems. Cramfs are used in handheld Linux devices to compress and write applications to ROM or Flash memory.

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.

crawl vb. To compile and organize entries for a search engine by reading Web pages and related information. Crawling is typically performed by programs called spiders.

crawler n. See spider, Web browser.

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 includes it in the packet that it sends 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.

create method n. In Java programming, a method defined in the home interface and invoked by a client to create an enterprise java bean. See also enterprise java bean, method.

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.

credentials n. A set of information that includes identification and proof of identification that is used to gain access to local and network resources. Examples of credentials are user names and passwords, smart cards, and certificates.

creeping featurism n. The process by which features are added to a new version of a program by software developers until the program becomes unduly cumbersome and difficult to use. Generally, creeping featurism occurs as developers attempt to enhance the competitiveness of the program with each new release by adding new features.

crippled version n. A scaled-down or functionally reduced version of hardware or software, distributed for demonstration purposes. See also demo.

critical error n. An error that suspends processing until the condition can be corrected either by software or by user intervention (for example, an attempt to read to a nonexistent disk, an out-of-paper condition on the printer, or a checksum fault in a data message).

critical-error handler n. A software routine that attempts to correct or achieve a graceful exit from a critical or threatening error. See also critical error, graceful exit.

critical path method n. A means of evaluating and managing a large project by isolating tasks, milestone events, and schedules and by showing interrelationships among them. The critical path for which this method is named is a line connecting crucial events, any of which, if delayed, affects subsequent events and, ultimately, completion of the project. Acronym: CPM.

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 the illustration. See also registration marks. 2. Lines drawn on photographs or illustrations to indicate where they will be cropped, or cut. See also crop.

Crop marks.

cross-assembler n. An assembler that executes on one hardware platform but generates machine code for another. See also assembler, compiler, cross-compiler, cross development.

cross-check vb. To check the accuracy of a calculation by using another method to verify the result. Compare cross-foot.

cross-compiler n. A compiler that executes on one hardware platform but generates object code for another. See also assembler, compiler (definition 2), cross-assembler, cross development.

cross development n. The use of one system to develop programs for a different type of system, often because the software development tools of the development system are superior to those of the target system.

cross-foot vb. To check the accuracy of a total, as on a ledger sheet, by adding across columns and down rows, all figures contributing to the total.

cross hairs n. Intersecting lines used by some computer input devices to locate a particular x-y-coordinate.

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. See the illustration.

Cross-hatching.

cross-linked files n. In Windows 9x, 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.

crossover cable n. A cable used to connect two computers together for file sharing and personal networking. Crossover cables may be connected to Ethernet or FireWire ports.

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.

cross-site scripting n. A security vulnerability of dynamic Web pages generated from a database in response to user input. With cross-site scripting, a malicious user introduces unwanted executable script or code into another user s Web session. Once running, this script could allow others to monitor the user s Web session, change what is displayed on the screen, or shut down the Web browser. Web sites that allow visitors to add comments or make other additions or changes to the pages are the most vulnerable to this flaw. Cross-site scripting is not restricted to the products of a particular vendor or a particular operating system. See also script.

crosstab query n. A query that calculates a sum, an average, a count, or other type of total on records, and then groups the result by two types of information one down the left side of the datasheet and the other across the top.

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 the illustration. See also pixel, raster, resolution (definition 1).

CRT. Cutaway view of a CRT.

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.

cruise vb. See surf.

crunch vb. To process information. See also number crunching.

cryoelectronic adj. Involving the use of superconducting electronics kept in a cryogenic environment at very low temperatures.

crypto n. See cryptography.

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

CryptoAPI n. An application programming interface (API) that is provided as part of Microsoft Windows. CryptoAPI provides a set of functions that allows applications to encrypt or digitally sign data in a flexible manner while providing protection for the user s sensitive private key data. Actual cryptographic operations are performed by independent modules known as cryptographic service providers (CSPs). See also application programming interface (API), cryptographic service provider, private key.

cryptographic service provider n. An independent module that performs cryptographic operations, such as creating and destroying keys. A cryptographic service provider consists of, at a minimum, a DLL and a signature file. Acronym: CSP.

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. Also called: crypto. See also code1 (definition 2), encryption, PGP, private key, public key.

CSD n. See circuit-switched data.

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.

CSLIP n. See Compressed SLIP.

CSMA/CA n. Acronym for Carrier Sense Multiple Access with Collision Avoidance, a protocol for controlling network access similar to CSMA/CD, in that nodes (stations) listen to the network and transmit only when it is free. But in CSMA/CA, nodes avoid data collisions by signaling their intention with a brief Request to Send (RTS) signal and then waiting for acknowledgment before actually transmitting.

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.

CSO n. Acronym for Computing Services Office. An Internet directory service that matches users own names with e-mail addresses, generally at colleges and universities. The CSO service, which can be reached through Gopher, was originally developed at the Computing Services Office at the University of Illinois.

CSO name server n. A facility that provides e-mail directory information through the CSO system. See also CSO.

CSR n. See continuous speech recognition.

CSS n. 1. See cascading style sheets. 2. Acronym for Content Scrambling System. An encryption feature added to DVDs distributed with approval of the MPAA. CSS looks for a matching region code on the DVD and the playback device. If the codes do not match (such as for a DVD purchased in Japan and a DVD player purchased in the United States), CSS will not allow the DVD to play. CSS also will not allow a DVD to be played on playback equipment not approved by the MPAA. See also deCSS, region code.

CSS1 n. See cascading style sheets.

CSTN display n. See supertwist display.

CSU n. See DDS.

.csv n. The file extension for a comma-delimited text file.

CSV n. 1. See circuit-switched voice. 2. See alternate circuit-switched voice/circuit-switched data. 3. Acronym for comma separated values. Filename extension assigned to text files containing tabular data of the sort stored in database fields. As the name indicates, individual data entries are separated by commas. Compare TSV.

CTERM n. See Communications Terminal Protocol.

CT Expo n. Acronym for Computer Telephony Expo. Annual exposition on data and communications issues involving the computer, telecommunications, and Internet industries. Held in Los Angeles, California, CT Expo features exhibits by hundreds of companies displaying their latest products and services, as well as conferences on a range of subjects affecting computer telephony.

CTI n. Acronym for computer-telephony integration. The practice of using a computer to control one or more telephone and communications functions.

CTIA n. See Cellular Telecommunications and Internet Association.

CTIA Wireless n. Annual conference of the wireless data, mobile Internet, and handheld computing industries. Sponsored by the Cellular Telecommunications and Internet Association, CTIA Wireless showcases products and technical developments in the field of wireless communications and data.

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

CTO n. Acronym for Chief Technology Officer. A corporate executive in charge of managing a company s information technology (IT) architecture and other technological assets. The CTO s responsibilities may include oversight of IT centers, networks and intranet, applications, databases, Web presence, and other technological resources.

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

Ctrl+Alt+Delete n. A three-key combination used with IBM and compatible computers to restart (reboot) the machine. Pressing Ctrl+Alt+Delete (Control+Alternate+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 9x and Windows NT, Ctrl+Alt+Delete 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.

CTS n. Acronym for Clear To Send. In serial communications, a signal sent, as from a modem to its computer, to indicate that transmission can proceed. CTS is a hardware signal sent over line 5 in RS-232-C connections. Compare RTS.

CUA n. See Common User Access.

cube n. An OLAP data structure. A cube contains dimensions (like Country/Region/City) and data fields (like Sales Amount). Dimensions organize types of data into hierarchies with levels of detail, and data fields measure quantities.

Cube n. A personal computer design introduced by Apple in 2000. The Cube featured a unique 8-by-8-by-8-inch transparent curved cube shape with the power supply outside the chassis to create a small and extremely quiet computer. The Cube offered the same G4 processor and features available on other Macintosh computers, but with fewer expansion options. Although the unique design drew notice for innovation, Apple discontinued manufacture of the Cube in 2001 after only one year of production.

CUI n. See character user interface.

CUL8R n. A fanciful shorthand notation meaning See you later, sometimes seen in Internet discussion groups as a farewell by a participant temporarily leaving the group.

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 cell n. See active cell.

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).

current drain n. 1. The current taken from a voltage source by its load (the object receiving the current). Also called: drain. 2. The load itself. For example, a flashlight bulb takes current from the battery; this current is the drain on the battery, and the bulb itself may also be called the drain.

current location counter n. See program counter.

current-mode logic n. A type of circuit design in which the transistors operate in unsaturated (amplifying) mode.

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 a screen flashes on and off. See also cursor (definition 1).

cursor control n. The ability of a computer user to move the cursor to a specified location on the screen. Keys dedicated to cursor control include the left, right, up, and down arrow keys and certain others, such as Backspace, Home, and End. Pointing devices such as the mouse can also control cursor movements, often helping the user move the cursor long distances from place to place in a document.

cursor key n. See arrow key.

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

custom control n. A control authored by a user or a third-party software vendor that does not belong to the .NET Framework class library. This is a generic term that includes user controls. A custom server control is used in Web Forms (ASP.NET pages). A custom client control is used in Windows Forms applications.

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 queuing n. A form of queuing on Cisco routers where the wide area network (WAN) link is divided into micropipes based on a percentage of the total bandwidth available on the pipe. See also bandwidth reservation.

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.

cut-through switch n. A network switch that routes packets immediately to the port associated with the packet s recipient. See also packet.

CV n. See computer vision.

CVS n. 1. See Computer Vision Syndrome. 2. Acronym for Concurrent Versions System. An open-source network-transparent version control system which allows multiple developers to view and edit code simultaneously. Popular because the client-server function allows operation over the Internet. CVS maintains a single copy of the source code with a record of who initiated changes and when the changes were made. CVS was developed for the UNIX operating system and is commonly used by programmers working with Linux, Mac OS X, and other UNIX-based environments.

CWIS n. See campuswide information system.

cXML n. Acronym for commerce XML. A set of document definitions for Extensible Markup Language (XML) developed for use in business-to-business e-commerce. cXML defines standards for product listings, allows for electronic requests and responses between procurement applications and suppliers, and provides for secure financial transactions via the Internet.

cyber- prefix A prefix attached to everyday words in order to give them a computer-based or online meaning, as in cyberlaw (the practice of law either in relation to or through the use of the Internet) and cyberspace (the virtual online world). The prefix is derived from the word cybernetics, which refers to the study of mechanisms used to control and regulate complex systems, either human or machine.

cyberart n. The artwork of artists who use computers to create or distribute their efforts.

cybercafe or cyber caf 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 caf 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.

cybercash n. See e-money.

cyberchat n. See IRC.

cybercop n. A person who investigates criminal acts committed on line, especially fraud and harassment.

cyberculture n. The behavior, beliefs, customs, and etiquette that characterize groups of individuals who communicate or socialize over computer networks, such as the Internet. The cyberculture of one group can be vastly different from the cyberculture of another.

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

cyberlawyer n. 1. An attorney whose practice involves the law related to computers and online communication, including elements of communications law, intellectual property rights, privacy and security issues, and other specialties. 2. An attorney who advertises or distributes information over the Internet and the World Wide Web.

cyberlife n. In the gaming world, a technology that mimics biological DNA. See also digital DNA.

cybernaut n. One who spends copious time on line, 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 living or nonliving systems 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.

cyberspeak n. Terminology and language (often jargon, slang, and acronyms) relating to the Internet (computer-connected) environment, that is, cyberspace. See also cyberspace.

cybersquatter n. A person who registers company names and other trademarks as Internet domain names in order to force the named companies or owners of the trademarks to buy them at an inflated price.

cyberwidow n. The spouse of a person who spends inordinate amounts of time on the Internet.

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 n. The amount of time between a random access memory (RAM) access and the earliest time a new access can occur. See also access time (definition 1).

cyclical redundancy check n. See CRC.

cyclic binary code n. A binary representation of numbers in which each number differs from the one that precedes it by one unit (bit), in one position. Cyclic binary numbers differ from plain binary numbers, even though both are based on two digits, 0 and 1. The numbers in the cyclic binary system represent a code, much like Morse code, whereas plain binary numbers represent actual values in the binary number system. Because sequential numbers differ by only 1 bit, cyclic binary is used to minimize errors in representing unit measurements. See the table.

Table C.2 Cyclic Binary Code Compared to Other Numeral Systems
Cyclic binary Plain binary Decimal
0000 0000 0
0001 0001 1
0011 0010 2
0010 0011 3
0110 0100 4
0111 0101 5
0101 0110 6
0100 0111 7
1100 1000 8
1101 1001 9

Cycolor n. A color printing process that uses a special film embedded with millions of capsules filled with cyan, magenta, and yellow dyes. When exposed to red, green, or blue light, the respective capsules become hard and unbreakable. The film is then pressed against specially treated paper, and the capsules that have not hardened in the previous process break, releasing their colors onto the paper. See also CMY.



Microsoft Computer Dictionary
MicrosoftВ® Computer Dictionary, Fifth Edition
ISBN: 0735614954
EAN: 2147483647
Year: 2002
Pages: 36

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