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.
n. An object-oriented version of the C programming language, developed by Bjarne Stroustrup in the early 1980s at Bell Laboratories and adopted by a number of vendors, including Apple Computer and Sun Microsystems. See also C, Objective-C, object-oriented programming.
n. The lowest level of security in the U.S. National Computer Security Center's hierarchy of criteria for trusted computer systems, requiring user logon with password and a mechanism for auditing. The C2 level is outlined in the Orange Book. See also Orange Book (definition 1).
n. On the Internet, the major geographic domain specifying that an address is located in Canada.
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 95) distribution disks.
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.
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.
n. The connector on either end of a cable. See also DB connector, DIN connector, RS-232-C standard, RS-422/423/449.
n. A device that allows the use of a cable that has slightly different wire connections from those required by the device(s) to which it is attached.
n. A modem that sends and receives data through a coaxial cable television network instead of telephone lines, as with a conventional modem. Cable modems, which have speeds of 500 kilobits per second (Kbps), can generally transmit data faster than current conventional modems. See also coaxial cable, modem.
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.
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.
n. An expansion card that increases a system's cache memory. See also cache, expansion board.
n. See cache.
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.
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.
See computer-aided design and drafting.
n. A plastic carrier that holds a CD-ROM and is inserted into a CD-ROM drive. Some personal computers, especially older models, have CD-ROM drives that require the use of a caddy. Most current CD-ROM drives do not require a caddy.
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.
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. See also I-CASE. Compare CBT, CMI.
n. Acronym for computer-assisted (or computer-augmented) learning. See CAI.
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.
n. An application program in the form of an electronic calendar, commonly used for highlighting dates and scheduling appointments. Some calendar programs resemble wall calendars, displaying dates in blocks labeled with the days of the week; others display dates day by day and enable the user to enter appointments, notes, and other memoranda. A day-of-the-week type of calendar program could, for example, be used to find out that Christmas 1999 will be on a Saturday. Depending on its capabilities, such a program might cover only the current century, or it might cover hundreds of years and even allow for the change (in 1582) from the Julian to the Gregorian calendar. A calendar/scheduler program might show blocks of dates or, like an appointment book, single days divided into hours or half hours, with room for notes. Some programs allow the user to set an alarm to go off at an important point in the schedule. Other programs can coordinate the calendars of different people on the same network, so that a person entering an appointment into his or her calendar also enters the appointment into a colleague's calendar.
n. On the Internet, the major geographic domain specifying that an address is located in Calgary, Alberta, Canada.
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.
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.
n. A user authentication scheme used by computers running dial-in services. A user dials in to a computer and types a logon ID and password. The computer breaks the connection and automatically calls the user back at a preauthorized number. This security measure usually prevents unauthorized access to an account even if an individual's logon ID and password have been stolen. See also authentication.
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.
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, call, stack.
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.
n. Acronym for Computer-Aided Acquisition and Logistics Support. A Department of Defense standard for electronic exchange of data with commercial suppliers.
n. 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. See Common Access Method.
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.
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.
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.
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.
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.
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.
n. See canned software.
n. A previously written routine that is copied into a program and used as is, without modification. See also library routine.
n. Off-the-shelf software, such as word processors and spreadsheet programs.
n. In mathematics and programming, the standard or prototypical form of an expression or statement.
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
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.
n. The amount of information a computer or an attached device can process or store. See also computer.
n. Short for capital letters. Compare lowercase.
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.
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.
vb. In communications, to transfer received data into a file for archiving or later analysis.
n. See video capture card.
n. See video capture card.
n. See cc.
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.
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).
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.
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.
n. See keypunch.
n. 1. An input device used chiefly for identification purposes that reads information that has been magnetically encoded, usually in two tracks, on a plastic card, such as a credit card or an employee badge. 2. A mechanical apparatus that reads computer data from punched cards. No longer in widespread use, card readers allow computer data to be created offline and then input to the computer for processing. This need for offline data creation was because of limited CPU resources. Reading batches of punched cards was a better use of CPU time than waiting for a human operator to key data directly into the computer's memory. Also called punched-card reader.
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."
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.
n. A form of repetitive strain injury to the wrist and hand. Making the same small motions over and over can cause swelling and scarring of the soft tissue of the wrist, which then compresses the main nerve leading to the hand. Symptoms of carpal tunnel syndrome include pain and tingling in the fingers, and in advanced cases, carpal tunnel syndrome can lead to loss of functionality of the hands. Typing at a computer keyboard without proper wrist support is a common cause of carpal tunnel syndrome. See also repetitive strain injury, wrist support. Acronym: CTS.
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.
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).
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.
n. See CD.
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.
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.
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.
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.
n. See carry bit.
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 René 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 also x-y-z coordinate system. Compare polar coordinates.
n. See product (definition 1).
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.
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.
n. 1. Additional elements displayed by a menu item or list box from which the user can choose in order to interact with other screen elements. 2. In newsgroup articles, the accumulation of quotation marks (often angle brackets) added by newsgroup readers each time an article is replied to. Most newsgroup readers will copy the original article in the body of the reply; after several replies, the original material will have several quotation marks. See also article, newsgroup, newsreader.
n. See pipe (definition 1).
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.
n. A Hypertext Markup Language (HTML) specification developed by The World Wide Web Consortium (W3C) that allows authors of HTML documents and users to attach style sheets to HTML documents. The style sheets include typographical information on how the page should appear, such as the font of the text in the page. This specification also directs the way in which the style sheets of the HTML document and the user's style will blend. Cascading style sheets have been proposed for the HTML 3.2 standard. Also called Cascading Style Sheet mechanism, CSS1. See also HTML, style sheet.
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.
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.
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.
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."
n. Discrimination between lowercase and uppercase characters in a program or a programming language. See also case.
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.
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.
n. 1. The tape within a cassette. 2. The unit consisting of both the plastic cassette case and the tape it contains.
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.
n. 1. Acronym for computer-aided testing. A procedure used by engineers for checking or analyzing designs, especially those created with CAD programs. Computer-aided testing is also used by software developers for automated regression testing. 2. Acronym for computer-assisted teaching. 3. Acronym for computerized axial tomography. A medical procedure in which a computer is used to generate a three-dimensional image of a body part from a series of X rays taken as cross sections along a single axis. See CAI.
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.
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.
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.
n. See oscilloscope.
n. See CRT.
n. On the Internet, the major geographic domain specifying that an address is located in California, United States.
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.
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.
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.
n. Acronym for courtesy copy. A directive to an e-mail program to send a complete copy of a given piece of mail to another individual. The use of cc mail addressing, as opposed to directly addressing the mail to a person, generally implies that the recipient is not required to take any action; the message is for informational purposes only. In a cc directive, the fact that this recipient received the mail is printed in the mail header and is thus known to all other recipients. Also called carbon copy. See also e-mail, header. Compare bcc.
n. On the Internet, the major geographic domain specifying that an address is located in the Cocos Islands.
n. See charge-coupled device.
n. See Common Client Interface.
n. Acronym for Comité Consultatif International Télégraphique et Téléphonique. Also known as the International Telegraph and Telephone Consultative Committee. An organization based in Geneva, Switzerland, and established as part of the United Nations International Telecommunications Union (ITU). Its functions have been taken over by the ITU. The ITU recommends use of communications standards that are recognized throughout the world. Protocols established by the ITU are applied to modems, networks, and facsimile transmission. See also CCITT Groups 1
n. A set of four standards recommended by the Comité Consultatif International Télégraphique et Téléphonique (International Telegraph and Telephone Consultative Committee) for the encoding and transmission of images over fax machines. Groups 1 and 2 relate to analog devices and are generally out of use. Groups 3 and 4, which deal with digital devices, are outlined below. Group 3 is a widespread standard that supports standard images of 203 horizontal dots per inch (dpi) by 98 vertical dpi and fine images of 203 horizontal dpi by 198 vertical dpi; supports two methods of data compression, one (based on the Huffman code) reducing an image to 10 to 20 percent of the original, the second (READ, for relative element address designate) compressing images to 6 to 12 percent of the original; and provides for password protection and for polling so that a receiving machine can request transmission as appropriate. Group 4, a newer standard, supports images of up to 400 dpi; data compression based on a beginning row of white pixels (dots), with each succeeding line encoded as a series of changes from the line before, compressing images to 3 to 10 percent of the original; does not include error-correction information in the transmission; and requires an Integrated Services Digital Network (ISDN) phone line rather than a dial-up line.
n. A set of recommendations developed by the Comité Consultatif International Télégraphique et Téléphonique (International Telegraph and Telephone Consultative Committee) for standardizing modem design and operations. The complete series includes a number of recommendations covering signaling, coding, and circuit characteristics, as well as modems. Those most relevant to computer users are briefly described below in terms of the modems they standardize:
n. A set of recommendations adopted by the International Telecommunications Union (ITU-T), formerly the CCITT, and ISO for standardizing equipment and protocols used in both public-access and private computer networks. Some of the recommendations in the X series include the following:
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.
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.
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.
1. Acronym for Carrier Detect, a signal sent from a modem to the attached computer to indicate that the modem is on line. See also DCD. 2. Acronym for compact disc. See also CD-I, CD-ROM, compact disc.
n. See CD recorder.
See compact disc
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.
n. 1. Acronym for CD-ROM File System. A 32-bit protected-mode file system that controls access to the contents of CD-ROM drives in Windows 95. See also protected mode. 2. A designation used with UNIX computers to indicate that a file system resides on a read-only removable medium (that is a CD-ROM). This usually implies that the compact disc is compliant with the ISO 9660 standard. CDFS is also used as a part of commands that mount media (hard drives, tape drives, remote networked drives, and CD-ROMs) for use on a computer. See also CD-ROM, ISO 9660.
n. Acronym for compact disc
n. See Code Division Multiple Access.
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.
n. See Cellular Digital Packet Data.
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.
n. Acronym for compact disc
n. See compact disc
n. A device used to write CD-ROMs. Because a disc can be written only once on these machines, they are used most commonly to create CD-ROMs for data archival or to produce CD-ROM masters that can be duplicated for mass distribution. Also called CD-R machine, CD-ROM burner. See also CD-ROM.
n. See CD recorder.
n. 1. Acronym for compact disc read-only memory. A form of storage characterized by high capacity (roughly 650 megabytes) and the use of laser optics rather than magnetic means for reading data. Although CD-ROM drives are strictly read-only, they are similar to CD-R drives (write once, read many), optical WORM devices, and optical read-write drives. See also CD-I, CD-R, WORM. 2. An individual compact disc designed for use with a computer and capable of storing up to 650 megabytes of data. See also compact disc, disc.
n. See CD recorder.
n. A disk storage device that uses compact disc technology. See also CD-ROM, compact disc.
n. See CD-ROM/XA.
n. See CDFS (definition 1).
n. A CD-ROM player that can contain up to 200 CD-ROMs and is connected to a CD-ROM drive in a personal computer or workstation. A user can request data from any of the CD-ROMs in the jukebox, and the device will locate and play the disk that contains the data. While only one CD-ROM can be played at a time, if multiple CD-ROM jukeboxes are each connected to separate CD-ROM drives that are daisy-chained together to the computer, more than one CD-ROM can be used at a time. See also CD-ROM, CD-ROM drive, daisy chain.
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.
n. See compact disc
n. See Circuit Data Services.
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.
n. See CDV (definition 2).
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.
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.
n. 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.
n. A wireless standard providing two-way, 19.2-Kbps packet data transmission over existing cellular telephone channels. See also packet, wireless. Acronym: CDPD.
n. The action of preventing material that a party considers objectionable from circulating within a system of communication over which that party has some power. The Internet as a whole is not censored, but some parts of it come under varying degrees of control. A news server, for example, often is set to exclude any or all of the alt. newsgroups, such as alt.sex.* or alt.music.white-power, which are unmoderated and tend to be controversial. A moderated newsgroup or mailing list may be considered to be "censored" because the moderator will usually delete highly controversial and obscene content or content that is on a different topic from that followed by the newsgroup. Online services have identifiable owners, who often take some share of responsibility for what reaches their users' computer screens. In some countries, censorship of certain political or cultural Web sites is a matter of national policy.
n. Software that imposes restrictions on what Internet sites, newsgroups, or files may be accessed by the user.
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.
prefix 1. One hundred. 2. One hundredth, as in centimeter--one hundredth of a meter.
n. The location of computer processing facilities and operations in a single (centralized) place. Compare decentralized processing, distributed processing.
n. In communications, the switching center where interconnections between customers' communications lines are made.
n. The computational and control unit of a computer. The central processing unit is the device that interprets and executes instructions. Mainframes and early minicomputers contained circuit boards full of integrated circuits that implemented the central processing unit. Single-chip central processing units, called microprocessors, made possible personal computers and workstations. Examples of single-chip central processing units are the Motorola 68000, 68020, and 68030 chips and the Intel 8080, 8086, 80286, 80386, and i486 chips. The central processing unit--or microprocessor, in the case of a microcomputer--has the ability to fetch, decode, and execute instructions and to transfer information to and from other resources over the computer's main data-transfer path, the bus. By definition, the central processing unit is the chip that functions as the "brain" of a computer. In some instances, however, the term encompasses both the processor and the computer's memory or, even more broadly, the main computer console (as opposed to peripheral equipment). See also microprocessor. Acronym: CPU.
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.
n. Acronym for Conseil Européen pour la Recherche Nucléaire (the European Laboratory for Particle Physics). CERN, a physics research center located in Geneva, Switzerland, is where the original development of the World Wide Web took place by Tim Berners-Lee in 1989 as a method to facilitate communication among members of the scientific community. See also NCSA (definition 1).
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.
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.
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.
n. On the Internet, the major geographic domain specifying that an address is located in the Central African Republic.
n. On the Internet, the major geographic domain specifying that an address is located in the Congo.
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.
n. 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. See Computer Graphics Interface.
n. Short for Common Gateway Interface
n. Short for Common Gateway Interface script. An external application that is executed by an HTTP server machine in response to a request by a client, such as a Web browser. Generally, the CGI script is invoked when the user clicks on some element in a Web page, such as a link or an image. Communication between the CGI script and the server is carried out via the CGI specification. CGI scripts can be written in many programming languages, including C, C++, and Visual Basic. However, the most commonly used language for CGI scripts is Perl, because it is a small but robust language and it is common on UNIX, which is the platform on which the majority of Web sites run. CGI scripts don't necessarily need to be scripts; they can also be batch programs or compiled programs. CGI scripts are used to provide interactivity in a Web page, including such features as providing a form that users can fill out, image maps that contain links to other Web pages or resources, and links that users can click on to send e-mail to a specified address. ActiveX controls and Java applets can provide much the same functionality as CGI scripts, through different means. See also CGI (definition 1), cgi-bin, image map, Perl. Compare ActiveX controls, Java applet.
n. See Computer Graphics Metafile.
n. On the Internet, the major geographic domain specifying that an address is located in Switzerland.
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.
n. In computers, the linking of two or more entities so that they are dependent upon one another for operation. In programming, two or more programs are said to be chained if the first program causes the second program to begin executing. In addition, program statements are said to be chained if each statement, except for the first, relies on the previous statement for input. With batch files, two or more batch files are said to be chained if the completion of the first batch file causes the second batch file to begin executing. With data storage, the term chained applies to two or more individual units of storage that are linked together. For example, a single file on a disk may actually be stored on several different sectors of the disk, each of which points to the next sector containing a piece of that file. These sectors are said to be chained together, or, more literally, to be a chain of clusters.
n. See line printer.
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. See also authentication, PPP. Acronym: CHAP.
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.
n. 1. A path or link through which information passes between two devices. A channel can be either internal or external to a microcomputer. See also bus. 2. In communications, a medium for transferring information. Depending on its type, a communications channel can carry information (data, sound, and/or video) in either analog or digital form. A communications channel can be a physical link, such as the cable connecting two stations in a network, or it can consist of some electromagnetic transmission on one or more frequencies within a bandwidth in the electromagnetic spectrum, as in radio and television, or in optical, microwave, or voice-grade communication. Also called circuit, line. See also analog, band, bandwidth, digital (definition 2), electromagnetic spectrum, frequency.
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.
n. A device that enables hardware using two different types of communications channels to communicate.
n. The speed at which a communications channel can transfer information, measured in bits per second (bps) or in baud.
vb. To switch repeatedly from one IRC channel to another. See also IRC.
n. Short for channel operator. A user on an IRC channel who has the privilege of expelling undesirable participants. See also IRC.
n. See Challenge Handshake Authentication Protocol.
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.
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.
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.
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.
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).
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.
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.
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.
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.
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.
n. See text mode.
n. See byte-oriented protocol.
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.
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).
n. The space taken up by the graphical representation (bit map) of a character. See also bit map.
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.
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. See also monospace font, pitch (definition 1), proportional font. Acronym: cpi.
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.
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.
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.
n. A user interface that displays only text characters. See also user interface. Compare graphical user interface. Acronym: CUI.
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 6.28
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.
n. A graphic or diagram that displays data or the relationships between sets of data in pictorial rather than numeric form.
n. A metal frame on which electronic components, such as printed circuit boards, fans, and power supplies, are mounted.
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.
vb. To carry on a real-time conversation with other users by computer. See also IRC.
n. See 10Base2.
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.
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 × or a check mark appears in the box. See also control (definition 2). Compare radio button.
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.
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.
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.
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.
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.
n. See subdirectory.
n. See submenu.
n. See child (definition 1).
n. In Macintosh computers, a series of chimes that sound as a result of serious system failure.
n. See integrated circuit.
n. A collection of chips designed to function as a unit in the performance of some common task. The term is most commonly used to refer to the set of integrated circuits, such as the programmable interrupt controller, that support a CPU together with the CPU itself. Often a chip set will fit on one chip. See also central processing unit, chip, integrated circuit, programmable interrupt controller.
n. See inductor.
vb. To pick a command or option from within a graphical user interface, as by clicking a button in a dialog box or pulling down a menu and then releasing the mouse button on one of its options. Although select is often used instead of choose to describe the same action, choose is the preferred term because select has specific connotations within computing. See also select.
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.
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).
n. The quality of a color that combines hue and saturation. See also hue, saturation.
n. See Common Hardware Reference Platform.
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.
n. On the Internet, the major geographic domain specifying that an address is located in the Ivory Coast.
n. See classless interdomain routing.
n. See Common Internet File System.
n. 1. 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. 2. 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).
n. On the Internet, the major geographic domain specifying that an address is located in Cincinnati, Ohio, United States.
n. 1. A code. 2. An encoded character. 3. A zero.
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.
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.
n. A flat piece of insulating material, such as epoxy or phenolic resin, on which electrical components are mounted and interconnected to form a circuit. Most modern circuit boards use patterns of copper foil to interconnect the components. The foil layers may be on one or both sides of the board and, in more advanced designs, in several layers within the board. A printed circuit board is one in which the pattern of copper foil is laid down by a printing process such as photolithography. See also board, printed circuit board.
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.
n. See circuit board.
n. A GTE service that uses circuit switching technology to provide fast data transfer using a laptop computer and cellular telephone. See also circuit switching. Acronym: CDS.
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. Compare message switching, packet switching.
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.
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.
n. See Commercial Internet Exchange.
n. On the Internet, the major geographic domain specifying that an address is located in the Cook Islands.
n. On the Internet, the major geographic domain specifying that an address is located in Chile.
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.
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, Internet service provider, newsgroup.
n. In object-oriented programming, a generalized category that describes a group of more specific items, called objects, that can exist within it. A class is a descriptive tool used in a program to define a set of attributes or a set of services (actions available to other parts of the program) that characterize any member (object) of the class. Program classes are comparable in concept to the categories that people use to organize information about their world, such as animal, vegetable, and mineral, that define the types of entities they include and the ways those entities behave. The definition of classes in object-oriented programming is comparable to the definition of types in languages such as C and Pascal. See also object-oriented programming.
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.
n. An address scheme that uses aggregation strategies to minimize the size of top-level Internet routing tables. Routes are grouped with the objective of minimizing the quantity of information carried by core routers. The main requirement for this scheme is the use of routing protocols that support it, such as Border Gateway Protocol (BGP) Version 4 and RIP Version 2. See also Border Gateway Protocol, communications protocol, RIP, router. Acronym: CIDR.
n. Booting or starting a computer using the minimum system files in the operating system. The clean boot is used as a troubleshooting method for isolating problems associated with software that may be calling on the same system resources at the same time, causing conflicts that lower the performance of the system, make some programs inoperable, or crash the computer. See also boot1, crash2 (definition 1), operating system.
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.
n. A user interface with simple features and intuitive commands. See also user interface.
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.
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.
n. See CTS.
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.
n. See image map.
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.
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.
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.
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.
n. An arrangement used on local area networks that makes use of distributed intelligence to treat both the server and the individual workstations as intelligent, programmable devices, thus exploiting the full computing power of each. This is done by splitting the processing of an application between two distinct components: a "front-end" client and a "back-end" server. The client component is a complete, stand-alone personal computer (not a "dumb" terminal), and it offers the user its full range of power and features for running applications. The server component can be a personal computer, a minicomputer, or a mainframe that provides the traditional strengths offered by minicomputers and mainframes in a time-sharing environment: data management, information sharing between clients, and sophisticated network administration and security features. The client and server machines work together to accomplish the processing of the application being used. Not only does this increase the processing power available over older architectures but it also uses that power more efficiently. The client portion of the application is typically optimized for user interaction, whereas the server portion provides the centralized, multiuser functionality. See also distributed intelligence.
n. A Web page user selection device whereby regions of an image can be clicked with the mouse to indicate user selections from a presented collection of options, comparable to clicking an icon of the desired item on a menu. Unlike the earliest Web implementation of image maps (circa 1993), client-side image maps do not transmit the mouse click coordinates to the Web server for processing but perform the processing completely within the client program (i.e., Web browser) itself, generally improving the speed of response to the user. See also image map.
vb. 1. To cut off the portion of a displayed image that lies beyond a certain boundary, such as the edge of a window. Certain graphics programs also support clipping as a means of masking everything but a certain object so that painting tools, for example, can be applied to the object alone. 2. To cut a photograph, drawing, or other illustrations from a clip art collection--either in a book or on a disk. See also clip art. 3. To cut off the peaks of a signal in an electronic circuit.
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.
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.
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 it 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.
n. An integrated circuit that implements the SkipJack algorithm, an encryption algorithm created by the National Security Agency that encrypts 64-bit blocks of data with an 80-bit key. The Clipper is manufactured by the U.S. government to encrypt telephone data. It has the added feature that it can be decrypted by the U.S. government, which has tried unsuccessfully to make the chip compulsory in the United States. See also encryption.
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.
vb. To destroy data, generally by inadvertently writing other data over it.
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.
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.
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.
n. See synchronization (definition 3).
n. An electronic pulse generated periodically by a crystal oscillator to synchronize the actions of a digital device.
n. The rate at which the clock in an electronic device, such as a computer, oscillates. The clock rate is normally given in hertz (Hz, one cycle per second), kilohertz (kHz, one thousand cycles per second), or megahertz (MHz, one million cycles per second). Clock rates in personal computers increased from about 5 MHz to about 50 MHz between 1981 and 1995. Also called clock speed, hertz time. See also clock (definition 1).
n. See clock rate.
n. See CPU cycle (definition 2).
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.
n. An FTP command that instructs the client to close the current connection with a server. See also FTP1 (definition 1), Web site.
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.
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.
n. In the graphical user interface for Windows 95, Windows NT, and the X Window System, a square button in the right corner (left corner in X Windows) of a window's title bar with an × mark on it. Clicking on the button closes the window. Also called X button. Compare close box.
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).
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.
n. A computer environment in which access to the computer is restricted to programmers and other specialists. Compare open shop.
n. See closed architecture (definition 2).
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.
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).
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.
n. On the Internet, the major geographic domain specifying that an address is located in Cameroon.
n. Acronym for computer-managed instruction. Any type of teaching that uses computers as educational tools. See also CAI, CBT.
n. 1. Acronym for complementary metal-oxide semiconductor. A semiconductor technology in which pairs of metal-oxide semiconductor field effect transistors (MOSFETs), one N-type and the other P-type, are integrated on a single silicon chip. Generally used for RAM and switching applications, these devices have very high speed and extremely low power consumption. They are, however, easily damaged by static electricity. See also MOSFET, N-type semiconductor, P-type semiconductor. 2. The battery-backed memory (presumably made with complementary metal-oxide semiconductor technology) used to store parameter values needed to boot IBM Personal Computers and compatibles, such as the type of disks and the amount of memory, as well as the clock/calendar time.
n. Random access memory made using complementary metal-oxide semiconductor technology. CMOS chips consume extremely little power and have high tolerance for noise from the power supply. These characteristics make CMOS chips, including CMOS RAM chips, very useful in hardware components that are powered by batteries, such as most microcomputer clocks and certain types of scratchpad RAM that are maintained by the operating system. See also CMOS (definition 1), parameter RAM, RAM.
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).
n. See color management system.
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.
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.
n. On the Internet, the major geographic domain specifying that an address is located in China.
n. On the Internet, the major geographic domain specifying that an address is located in Colombia.
n. A two-conductor cable consisting of a center wire inside a grounded cylindrical shield, typically made of braided wire, that is insulated from the center wire. The shield prevents signals transmitted on the center wire from affecting nearby components and prevents external interference from affecting the signal carried on the center wire.
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 computer(s) 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.
n. A Web site that is far out of date. See also Web site.
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 business language.
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.
vb. To write program instructions in a programming language. See also program.
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.
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.
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. Also called spread spectrum. See also multiplexing, transmitter. Acronym: CDMA.
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.
n. See programmer.
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.
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 on. 2. A small piece of programming code that is part of a larger program. Usually the code snippet performs a specific function or task.
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.
n. See cast.
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.
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.
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 turning the machine on only when needed.
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.
n. See cold boot.
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.
n. See backbone (definition 3).
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.
n. A sort that proceeds by continuous merging of two or more files to produce a certain sequence of records or data items.
n. The ordering relationship (sequence) among objects that is to be established by a collating sort. See also collating sort.
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.
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.
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.
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.
n. A predetermined number of bits assigned to each displayable pixel that determine its color when it is displayed on a monitor. For example, two color bits are required for four colors; eight color bits are required for 256 colors. See also pixel image. Compare bit plane.
n. In the Microsoft NT and Windows 95 Paint accessory, a graphic screen element in the form of a paint box that is used to select foreground and background colors.
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.
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.
n. See CGA.
n. A device that evaluates and identifies colors in terms of a standard set of synthesized colors.
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.
n. In printing, the process of producing accurate, consistent color using any of a variety of output devices. Color management includes accurate conversion of RGB input from a scanner, camera, or monitor to CMYK output for a printer; application of a device profile for the printer or other output device on which the image will be reproduced; and allowance for environmental variations such as humidity and barometric pressure. See also CMYK, RGB.
n. A technology developed by Kodak and licensed to many other software vendors that is designed to calibrate and match colors that appear on video monitors and computer monitors and those that appear in any printed form. Acronym: CMS.
n. See color look-up table.
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.
n. A video display device designed to work with a video card or 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.
n. See palette (definition 1).
n. See bit plane.
n. A computer printer that can print full-color output. Most color printers can also produce black-and-white output.
n. The amount of a hue contained in a color; the more saturation, the more intense the color. See also color model, HSB.
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.
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.
n. See color look-up table.
n. On the Internet, the major geographic domain specifying that an address is located in Columbus, Ohio, United States.
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).
n. A bar chart in which values are displayed and printed as vertical bars. See also bar chart.
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 2). See COM (definition 3).
n. 1. A name reserved by the MS-DOS operating system for serial communications ports. For example, if a modem is connected to one serial port and a serial printer to another, the devices are identified as COM1 and COM2 by the operating system. 2. Acronym for Component Object Model. A specification developed by Microsoft for building software components that can be assembled into programs or add functionality to existing programs running on Microsoft Windows platforms. COM components can be written in a variety of languages, although most are written in C++, and can be unplugged from a program at run time without having to recompile the program. COM is the foundation of the OLE (object linking and embedding), ActiveX, and DirectX specifications. See also ActiveX, component (definition 2), DirectX, OLE. 3. The extension reserved by MS-DOS for a type of executable binary (program) file limited to a single 64-kilobyte (KB) segment. COM files are often used for utility programs and short routines. They are not supported in OS/2. 4. Acronym for computer-output microfilm. Microfilm that can record data from a computer.
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.
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.
n. A serial communications port in Wintel systems. COM3 is usually specified by the I/O range 03E8H, is usually associated with interrupt request line IRQ4, and in many systems is used as an alternative to COM1 or COM2 if the latter is being used by some other peripheral. See also IRQ.
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.
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 twelve permutations in all: AB, AC, AD, BA, BC, BD, CA, CB, CD, DA, DB, DC. See also combinatorial explosion.
n. Any of a series of annual computer trade shows operated by Softbank COMDEX,Inc. One of these shows takes place in Las Vegas each November and is the largest computer trade show in the United States.
Comité Consultatif International Télégraphique et Téléphonique
n. Also called International Telegraph and Telephone Consultative. See CCITT.
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.
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.
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).
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.
n. The command interpreter for MS-DOS. See also command interpreter.
adj. Accepting commands in the form of code words or letters, which the user must learn. Compare menu-driven.
n. A system in which the user initiates operations by a command entered from the console. Compare graphical user interface.
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.
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.
n. The set of keywords and expressions that are accepted as valid by the command interpreter. See also command interpreter.
n. A string of text written in the command language and passed to the command interpreter for execution. See also command language.
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.
n. A mode of operation in which a program waits for a command to be issued. Compare edit mode, insert mode.
n. See command-driven system.
n. See command interpreter.
n. See shell1.
n. The state in which a modem accepts commands, such as a command to dial a telephone number. Compare online state.
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.
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.
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.
n. See ISP.
n. A non-profit trade organization of public Internet service providers. In addition to the usual representational and social activities, CIX also operates an Internet backbone router that is accessible to its members. See also backbone (definition 1), ISP, router. Acronym: CIX.
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.
n. A communications company (e.g., a telephone company) that provides service to the public and is regulated by governmental organizations.
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. See also Mosaic, OLE, TCP/IP, X Window System. Acronym: CCI.
n. See CGI (definition 1).
Common Hardware Reference Platform
n. A specification describing a family of machines, based on the PowerPC processor, that are capable of booting multiple operating systems, including Mac OS, Windows NT, AIX, and Solaris. See also PowerPC. Acronym: CHRP.
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.
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.
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. See also standard (definition 1), user interface. Acronym: CUA.
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.
n. See FCC.
n. See channel (definition 2).
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).
n. The connection between computers that enables data transfer.
n. See network.
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.
n. See COM (definition 1).
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.
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.
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.
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.
n. On many models of the Apple Macintosh, a dedicated expansion slot for network interface cards. Acronym: CS.
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.
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.
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
n. A technological improvement in compact discs whereby information can be repeatedly changed on the CD. Contemporary CDs are "write once, read many," in that the information originally written cannot be changed, but can only be appended to. Acronym: CD-E.
n. See CD-I.
n. A device that reads the information stored on a compact disc. A compact disc player contains the optical equipment necessary for reading a disc's contents and the electronic circuitry for interpreting the data as it is read.
compact disc
adj. Of or pertaining to hardware and software for interfacing computers with both compact disc
n. The technology, equipment, software, and media used in the production of multiple-write compact discs. Acronym: CD-RW.
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).
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.
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.
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.
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.
n. See DOS box (definition 1).
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.
vb. To translate all the source code of a program from a high-level language into object code prior to execution of the program. Object code is executable machine code or a variation of machine code. More generally, compiling is sometimes used to describe translating any high-level symbolic description into a lower-level symbolic or machine-readable format. A program that performs this task is known as a compiler. See also compiler, compile time, high-level language, machine code, source code. Compare interpret.
adj. Of, pertaining to, or characteristic of a development environment that automatically runs a program after compiling it. See also compile, execute.
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.
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.
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.
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.
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.
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.
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.
n. A survey to determine that all data required in a record is present. Compare consistency check.
complex instruction set computing
n. See CISC.
n. A number of the form a + bi, where a and b are real numbers and i is the square root of
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.
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.
n. See COM (definition 2).
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.
n. See component software.
or comm port n. Short for communications port, the logical address assigned by MS-DOS (versions 3.3 and higher) and Microsoft Windows (including Windows 95 and Windows NT) to each of the four serial ports on an IBM Personal Computer or a PC compatible. COM ports also have come to be known as the actual serial ports on a PC's CPU where peripherals, such as printers, scanners, and external modems, are plugged in. See also COM (definition 1), input/output port, serial port.
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.
n. A key whose definition consists of two or more fields in a file, columns in a table, or attributes in a relation.
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.
n. A single instruction composed of two or more individual instructions.
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.
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.
n. See CDV (definition 1).
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.
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.
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.
n. Short for Compressed Serial Line Internet Protocol. A version of SLIP using compressed Internet address information, thereby making the protocol faster than SLIP. See also SLIP. Acronym: CSLIP.
n. See data compression.
n. A device that limits some aspect of a transmitted signal, such as volume, in order to increase efficiency.
n. An online information service that provides information and communications capabilities, including Internet access. It is primarily known for its technical support forums for commercial hardware and software products and for being one of the first large commericial online services. CompuServe also operates various private network services.
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.
vb. 1. To perform calculations. 2. To use a computer or cause it to do work.
n. Any machine that does three things: accepts structured input, processes it according to prescribed rules, and produces the results as output. Ways to categorize computers are described in the table. See also analog, digital, integrated circuit, large-scale integration, very-large-scale integration.
n. See CAD.
computer-aided design and drafting
n. A system of hardware and software similar to CAD but with additional features related to engineering conventions, including the ability to display dimension specifications and other notes. See also CAD. Acronym: CADD.
computer-aided design/computer-aided manufacturing
n. See CAD/CAM.
n. See CAE.
n. See CAI.
n. See CAM (definition 1).
n. See CAT (definition 1).
Computer and Business Equipment Manufacturers Association
n. See CBEMA.
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.
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.
n. See CAI.
n. The use of computers and their multimedia abilities to present information for educational purposes.
n. See CAI.
n. See CBL.
n. See CBT.
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.
n. Person-to-person interaction through the use of computers located in different places but connected through communications facilities.
n. See system console.
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).
adj. See hardware-dependent.
Computer Emergency Response Team
n. See CERT.
n. The discipline that involves the design and underlying philosophies involved in the development of computer hardware.
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.
n. A class of computer program in which one or more users interact with the computer as a form of entertainment. Computer games run the gamut from simple alphabet games for toddlers to chess, treasure hunts, war games, and simulations of world events. The games are controlled from a keyboard or with a joystick or other device and are supplied on disks, on CD-ROMs, as game cartridges, or as arcade devices.
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.
n. A software standard applied to computer graphics devices, such as printers and plotters. Computer Graphics Interface is an offshoot of a widely recognized graphics standard called GKS (Graphical Kernel System), which provides applications programmers with standard methods of creating, manipulating, and displaying or printing computer graphics. See also Graphical Kernel System. Acronym: CGI.
n. A software standard related to the widely recognized GKS (Graphical Kernel System) that provides applications programmers with a standard means of describing a graphic as a set of instructions for re-creating it. A graphics metafile can be stored on disk or sent to an output device; Computer Graphics Metafile provides a common language for describing such files in relation to the GKS standard. See also Graphical Kernel System. Acronym: CGM.
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.
n. See CIM (definition 2).
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).
n. See interface.
n. See CAT (definition 3).
n. See e-mail.
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.
n. See form letter.
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.
n. See CMI.
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.
n. See network.
n. See COM (definition 4).
n. A person who is immersed in the world of computing, who collects computers, or whose hobby involves computing.
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.
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.
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.
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.
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.
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.
n. The steps taken to protect a computer and the information it contains. On large systems or those handling financial or confidential data, computer security requires professional supervision that combines legal and technical expertise. On a microcomputer, data protection can be achieved by backing up and storing copies of files in a separate location, and the integrity of data on the computer can be maintained by assigning passwords to files, marking files "read-only" to avoid changes to them, physically locking a hard disk, storing sensitive information on floppy disks kept in locked cabinets, and installing special programs to protect against viruses. On a computer to which many people have access, security can be maintained by requiring personnel to use passwords and by granting only approved users access to sensitive information. See also bacterium, encryption, virus.
n. See simulation.
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.
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.
n. See user group.
n. See utility.
n. See virus.
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. See also artificial intelligence, robotics. Acronym: CV.
n. Short for computer output microfilm recorder. A device that records computer information on microfilm.
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.
vb. To join sequentially (for example, to combine the two strings "hello" and "there" into the single string "hello there"). See also character string.
n. A group of separate sets of related data treated as a single unit for processing.
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.
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.
n. A list of words that appear in a document, along with the contexts of the appearances.
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.
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.
n. See concurrent.
n. See concurrent.
n. See concurrent.
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.
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).
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.
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.
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.
n. See Boolean expression.
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.
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.
n. A transfer of the flow of execution to a given location in a program based on whether or not a particular condition is true. The term is usually used in relation to high-level languages. See also conditional statement.
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.
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.
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.
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.
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.
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.
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.
n. A physical link via wire, radio, fiber-optic cable, or other medium between two or more communications devices.
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.
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.
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.
n. In Windows 95 and Windows NT, an icon representing a dial-up networking connection that will also execute a script for logging onto the network dialed.
n. 1. In hardware, a coupler used to join cables or to join a cable to a device (for example, an RS-232-C connector used to join a modem cable to a computer). Most connector types are available in one of two genders--male or female. A male connector is characterized by one or more exposed pins; a female connector is characterized by one or more receptacles designed to accept the pins on the male connector. See also DB connector, DIN connector. 2. In programming, a circular symbol used in a flowchart to indicate a break, as to another page.
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.
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.
n. A control unit, such as a terminal, through which a user communicates with a computer. In microcomputers, the console is the cabinet that houses the main components and controls of the system, sometimes including the screen, the keyboard, or both. With the MS-DOS operating system, the console is the primary input (keyboard) and primary output (screen) device, as evidenced by the device name CON. See also CON, system console.
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.
n. An expression that is composed only of constants and, hence, whose value does not change during program execution. Compare variable expression.
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).
n. In programming, a restriction on the solutions that are acceptable for a problem.
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.
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.
n. 1. In OLE terminology, a file containing linked or embedded objects. See also OLE. 2. In SGML, an element that has content as opposed to one consisting solely of the tag name and attributes. See also element (definition 2), SGML, tag (definition 3).
n. 1. The data that appears between the starting and ending tags of an element in an SGML or HTML document. The content of an element may consist of plain text or other elements. See also element (definition 2), HTML, SGML, tag (definition 3). 2. The message body of a newsgroup article or e-mail message.
n. See associative storage.
n. On a network, competition among stations for the opportunity to use a communications line or network resource. In one sense, contention applies to a situation in which two or more devices attempt to transmit at the same time, thus causing a collision on the line. In a somewhat different sense, contention also applies to a free-for-all method of controlling access to a communications line, in which the right to transmit is awarded to the station that wins control of the line. See also CSMA/CD. Compare token passing.
n. A series of queues that contain the descriptors and addresses of routines located within a region of memory.
adj. Of, pertaining to, or characteristic of a process or a set of data characters whose meaning depends on the surrounding environment.
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.
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.
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.
n. A search operation in which the user can direct a program to search specified files for a particular set of text characters.
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.
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.
n. In communications, a carrier signal that remains on throughout the transmission, whether or not it is carrying information.
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 also pin feed, sprocket feed, tractor feed.
n. The processing of transactions as they are input to the system. Compare batch processing (definition 3).
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.
n. A printer that produces an image using smoothly blended levels of continuous ink for gradations of gray or color. Compare dithering.
n. 1. In computer graphics, such as CAD models, the representation of the surface of an object--its bumps and crannies. 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.
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.
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.
n. A transition in control of the computer that typically gives control of the central processing unit (CPU) to the user console or to some other program.
n. See Break key.
n. The set of lines (conductors) within a computer that carry control signals between the central processing unit (CPU) and other devices. For example, a control bus line is used to indicate whether the CPU is attempting to read from memory or to write to it; another control bus line is used by memory to request an interrupt in case of a memory error.
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.
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.
n. See console.
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.
n. The tracing of all possible execution paths in a program, often represented in the form of a diagram.
n. A key that, when pressed in combination with another key, gives the other key an alternative meaning. In many application programs, Control (labeled CTRL or Ctrl on a PC keyboard) plus another key is used as a command for special functions. See also control character (definition 2).
n. A device on which other devices rely for access to a computer subsystem. A disk controller, for example, controls access to one or more disk drives, managing physical and logical access to the drive or drives.
n. The electronic circuitry that generates, interprets, and uses control data.
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.
n. See control code.
n. An electronic signal used to control internal or external devices or processes.
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.
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.
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.
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.
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.
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).
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.
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.
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.
n. Interaction in which two or more parties alternately transmit and receive messages from each other. See also interactive processing.
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.
n. See conversational.
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:
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
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.
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.
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.
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.
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.
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).
n. A type of multitasking in which one or more background tasks are given processing time during idle times in the foreground task only if the foreground task allows it. This is the primary mode of multitasking in the Macintosh operating system. See also background1, context switching, foreground 1, multitasking, time slice. Compare preemptive multitasking.
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.
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.
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.
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.
vb. To duplicate information and reproduce it in another part of a document, in a different file or memory location, or in a different medium. A copy operation can affect data ranging from a single character to large segments of text, a graphics image, or one to many data files. Text and graphics, for example, can be copied to another part of a document, to the computer's memory (by means of a temporary storage facility such as the Microsoft Windows or Apple Macintosh Clipboard), or to a different file. Similarly, files can be copied from one disk or directory to another, and data can be copied from the screen to a printer or to a data file. In most cases, a copy procedure leaves the original information in place. Compare cut and paste, move.
n. An MS-DOS command to duplicate the contents of a floppy disk on a second disk. See also floppy disk, MS-DOS.
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.
n. See General Public License.
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.
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.
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.
n. Acronym for Common Object Request Broker Architecture. A specification developed by the Object Management Group in 1992 in which pieces of programs (objects) communicate with other objects in other programs, even if the two programs are written in different programming languages and are running on different platforms. A program makes its request for objects through an object request broker, or ORB, and thus does not need to know the structure of the program from where the object comes. CORBA is designed to work in object-oriented environments. See also object (definition 2), Object Management Group, object-oriented.
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.
n. A program or program segment that is resident in random access memory (RAM).
adj. Of or pertaining to a condition in which two or more programs are loaded in memory at the same time.
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.
n. A routine that is in memory at the same time as, and frequently executed concurrently with, another.
n. The process of diagnosing and correcting computer problems after they occur. Compare preventive maintenance.
n. See print quality.
n. A process wherein data in memory or on disk is unintentionally changed, with its meaning thereby altered or obliterated.
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.
n. A unit of electrical charge equivalent to roughly 6.26 × 1018 electrons, with a negative charge being an excess of electrons and a positive charge being a deficiency of electrons.
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.
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).
n. See major geographic domain.
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.
n. Software dedicated to education or training.
n. See cc.
n. See Computer Press Association.
n. See characters per inch.
n. Acronym for Control Program/Monitor. A line of operating systems from Digital Research, Inc., for microcomputers based on Intel microprocessors. The first system, CP/M-80, was the most popular operating system for 8080- and Z80-based microcomputers. Digital Research also developed CP/M-86 for 8086/8088-based computers, CP/M-Z8000 for Zilog Z8000-based computers, and CP/M-68K for Motorola 68000-based computers. When the IBM PC and MS-DOS were introduced, common use of CP/M by end users dwindled. DRI continues to enhance the CP/M line, supporting multitasking with the concurrent CP/M and MP/M products. See also MP/M.
n. See critical path method.
n. See characters per second.
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.
n. See central processing unit.
adj. See computation-bound.
n. A section of fast memory linking the central processing unit (CPU) and main memory that temporarily stores data and instructions the CPU needs to execute upcoming commands and programs. Considerably faster than main memory, the CPU cache contains data that is transferred in blocks, thereby speeding execution. The system anticipates the data it will need through algorithms. Also called cache memory, memory cache. See also cache, central processing unit, VCACHE.
n. 1. The smallest unit of time recognized by the central processing unit (CPU)--typically a few hundred-millionths of a second. 2. The time required for the CPU to perform the simplest instruction, such as fetching the contents of a register or performing a no-operation instruction (NOP). Also called clock tick.
n. An electric fan usually placed directly on a central processing unit (CPU) or on the CPU's heat sink to help dissipate heat from the chip by circulating air around it. See also central processing unit, heat sink.
n. A relative measure of the data-processing capacity of a particular central processing unit (CPU), usually measured in megahertz. See also central processing unit.
n. In multiprocessing, the amount of time during which a particular process has active control of the central processing unit (CPU). See also central processing unit, multiprocessing.
n. On the Internet, the major geographic domain specifying that an address is located in Costa Rica.
n. See carriage return.
n. A person who overcomes the security measures of a computer system and gains unauthorized access. The goal of some crackers is to obtain information illegally from a computer system or use computer resources. However, the goal of the majority is to merely break into the system. See also hacker.
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.
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.
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.
n. See Web browser.
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.
n. Acronym for cyclical (or cyclic) redundancy check. A procedure used in checking for errors in data transmission. CRC error checking uses a complex calculation to generate a number based on the data transmitted. The sending device performs the calculation before transmission and sends its result to the receiving device. The receiving device repeats the same calculation after transmission. If both devices obtain the same result, it is assumed that the transmission was error-free. The procedure is known as a redundancy check because each transmission includes not only data but extra (redundant) error-checking values. Communications protocols such as XMODEM and Kermit use cyclical redundancy checking.
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.
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.
n. A scaled-down or functionally reduced version of hardware or software, distributed for demonstration purposes. See also demo.
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).
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.
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.
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.
n. 1. Lines drawn at the edges of pages to mark where the paper will be cut to form pages in the final document. See also registration marks. 2. Lines drawn on photographs or illustrations to indicate where they will be cropped, or cut. See also crop.
n. An assembler that executes on one hardware platform but generates machine code for another. See also assembler, compiler, cross-compiler, cross development.
vb. To check the accuracy of a calculation by using another method to verify the result. Compare cross-foot.
n. A compiler that executes on one hardware platform but generates object code for another. See also assembler, compiler, cross-assembler, 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.
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.
n. Intersecting lines used by some computer input devices to locate a particular xy-coordinate.
n. Shading made up of regularly spaced, intersecting lines. Cross-hatching is one of several methods for filling in areas of a graphic.
n. In Windows 95, Windows 3.x, and MS-DOS, a file-storage error occurring when one or more sections, or clusters, of the hard drive or a floppy disk have been erroneously allocated to more than one file in the file allocation table. Like lost clusters, cross-linked files can result from the ungraceful exit (messy or abrupt termination) of an application program. See also file allocation table, lost cluster.
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.
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.
n. Interference caused by a signal transferring from one circuit to another, as on a telephone line.
n. Acronym for cathode-ray tube. The basis of the television screen and the standard microcomputer display screen. A CRT display is built around a vacuum tube containing one or more electron guns whose electron beams rapidly sweep horizontally across the inside of the front surface of the tube, which is coated with a material that glows when irradiated. Each electron beam moves from left to right, top to bottom, one horizontal scan line at a time. To keep the screen image from flickering, the electron beam refreshes the screen 30 times or more per second. The clarity of the image is determined by the number of pixels on the screen. See also pixel, raster, resolution (definition 1).
n. The part of a video adapter board that generates the video signal, including the horizontal and vertical synchronization signals. See also video adapter.
vb. See surf.
vb. To process information. See also number crunching.
adj. Involving the use of superconducting electronics kept in a cryogenic environment at very low temperatures.
n. The decoding of electronically encrypted information for the purpose of understanding encryption techniques. See also cryptography, encryption.
n. The use of codes to convert data so that only a specific recipient will be able to read it, using a key. The persistent problem of cryptography is that the key must be transmitted to the intended recipient and may be intercepted. Public key cryptography is a recent significant advance. See also code1 (definition 2), encryption, PGP, private key, public key.
n. On the Internet, the major geographic domain specifying that an address is located in the former Czechoslovakia.
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.
n. See Compressed SLIP.
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.
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.
n. A facility that provides e-mail directory information through the CSO system. See also CSO.
n. See cascading style sheets.
n. See cascading style sheets.
n. See Communications Terminal Protocol.
n. Acronym for computer-telephony integration. The practice of using a computer to control one or more telephone and communications functions.
n. Short for control. See control character (definition 2), Control key.
or Ctrl Short for control. A designation used to label the Control key on computer keyboards. See also control character (definition 2), Control key.
n. A three-key combination used with IBM and compatible computers to restart (reboot) the machine. Pressing Ctrl-Alt-Del (Control-Alt-Delete) causes a warm boot in MS-DOS--the computer restarts but does not go through all of the internal checks involved when power to the system is switched on (cold boot). In Windows 95 and Windows NT, Ctrl-Alt-Del provides a dialog box from which the user may choose to shut down the computer or end any current tasks.
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.
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.
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.
n. On the Internet, the major geographic domain specifying that an address is located in Cuba.
n. See Common User Access.
n. See character user interface.
A fanciful shorthand notation meaning "See you later," sometimes seen in Internet discussion groups as a farewell by a participant temporarily leaving the group.
n. See smart quotes.
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.
n. See active cell.
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).
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.
n. See program counter.
n. A type of circuit design in which the transistors operate in unsaturated (amplifying) mode.
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.
n. The rate at which a cursor on screen flashes on and off. See also cursor (definition 1).
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.
n. See arrow key.
n. A videoconferencing program developed at Cornell University. It was the first program to give Windows and Mac OS users the ability to engage in real-time videoconferencing over the Internet, but it requires a lot of bandwidth (at least 128 Kbps speed) to function properly.
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.
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.
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.
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.
n. On the Internet, the major geographic domain specifying that an address is located in Cape Verde.
n. See computer vision.
n. See campuswide information system.
n. On the Internet, the major geographic domain specifying that an address is located in Cyprus.
or cyber café n. 1. A coffee shop or restaurant that offers access to PCs or other terminals that are connected to the Internet, usually for a per-hour or per-minute fee. Users are encouraged to buy beverages or food to drink or eat while accessing the Internet. 2. A virtual café on the Internet, generally used for social purposes. Users interact with each other by means of a chat program or by posting messages to one another through a bulletin board system, such as in a newsgroup or on a Web site.
n. See e-money.
n. See IRC.
n. A person who investigates criminal acts committed online, especially fraud and harassment.
n. Apple's Internet suite for HTML browsing and e-mail, based on OpenDoc for easy integration with other applications. See also OpenDoc.
n. One who spends copious time online, exploring the Internet. Also called Internaut. See also cyberspace.
n. The study of control systems, such as the nervous system, in living organisms and the development of equivalent systems in electronic and mechanical devices. Cybernetics compares similarities and differences between living and nonliving systems (whether those systems comprise individuals, groups, or societies) and is based on theories of communication and control that can be applied to either or both. See also bionics.
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.
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.
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.
n. Software used at some libraries that allows one to query a database through the use of an interactive search engine.
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.
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).
n. See CRC.
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.
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.
n. On the Internet, the major geographic domain specifying that an address is located in the Czech Republic.