Access time. The amount of time it takes for information to be read from or written to a disk. The sum of search time plus seek time.
Accumulator. A register used to temporarily store data being manipulated by the CPU.
Acoustic modem. A modem using a coupler into which the telephone handset is plugged. Also called an acoustic coupler.
Acronym. A word formed by taking the first letters or sounds of each word in a phrase and capitalizing them. For example, RAM (pronounced as a word) is an acronym for random-access memory.
Ada. A U.S. Defense Department-sponsored high-level programming language named after Augusta Ada (Countess of Lovelace), the world's first programmer and Charles Babbage's associate.
Adder. The circuitry that performs addition on data received by the CPU.
Address. (1) A location in memory where data are stored and can be retrieved. (2) The part of an instruction that identifies the specific location of the data to be operated on by that instruction.
Address bus. An electrical pathway that carries the addresses of data from memory to the processor.
Address register. A register containing the storage location of the next data item to be retrieved from memory.
Aliasing. The jagged or stair step appearance of the edges of diagonal lines or curves on a display screen. It occurs because pixels on the screen are arranged in rows and columns, and is clearly visible on low-resolution screens.
Algorithm. A predetermined set of instructions for solving a problem in a finite number of steps. (See also Heuristic).
Alphanumeric. Data represented in both alphabetic (the letters A-Z) and numeric (the numbers 0-9) form.
ALL. An acronym for arithmetic/ logic unit. The component of the CPU that is responsible for performing arithmetic and logic operations.
Analog. (1) Pertaining to the representation of numerical quantities, such as the measurement of speed by an analog speedometer. (2) A type of signal used in some telephone and television networks, as well as some VCRs. cassette tapes, and plastic records.
Analog computer. A type of computer that is designed to process data obtained directly from measurable quantities, such as voltages, resistances, or rotations.
Analog-to-digital converter. A device that converts analog quantities, such as voltages, resistances, rotations, light. pressure, or temperature, into digital numbers for processing by a computer.
Analytical graphics. Graphics that are intended to help the user of a computer analyze data from spreadsheets and databases. Usually includes simple bar, line, and pie charts.
Antenna. A device for sending, and receiving electromagnetic waves.
APL. An acronym for a programming language. An interactive scientific programming language designed for on-line use.
Application. What is done with a computer system.
Application generator. A program that writes other programs based on the user's input combined into a single module of software.
Application programmer. A person who writes computer programs, such as spreadsheets, word processors, database programs, and specific application programs (e.g., accounting or inventory programs). There are two categories: business-application programmers and scientific- or engineering-application programmers.
Application software, A computer program or set of programs intended to perform a specific function, such as accounting, payroll, word processing, spreadsheet calculating, or database management.
Application-specific integrated circuit (ASIC). An integrated circuit designed to fill the specific requirements of an application.
Architecture. A term used by computer designers to designate the structure of complex information-processing systems. It includes the kinds of instructions and data used, the memory organization and addressing, and the methods by which the system is implemented.
Arithmetic/logic unit. See ALU.
Arithmetic operator. A symbol that tells the computer to perform an arithmetic operation. The operators are (+) for addition. (-) for subtraction. (*) for multiplication. (/) for division, and (**) for exponentiation.
Arithmetic unit. The functional unit of a central processing unit that performs adding, subtracting, multiplying, dividing, and shifting of numbers.
Array. A type of data structure that consists of two or more related data elements identified by a single name.
Artificial intelligence (Al). The branch of computer science that attempts to understand the nature of intelligence and produces new classes of intelligent machines. Areas of study include robotics, speech recognition, image recognition, natural-language processing, and expert systems.
Artificial language. A language whose syntax, grammar, and rules were developed prior to its use. Programming languages are examples of artificial languages. .
Artificial life. A lifelike process in an artificial medium such as a computer model, simulation, or robot. Artificial life simulations have been developed that synthesize some of the processes (e.g., reproduction, growth, learning, and evolution) exhibited by biological systems of life. Ascending order. Sequential arrangement from lowest to highest. A telephone book, for example, lists names in ascending order.
ASCII. An acronym for American Standard Code for Information Inter-change. A seven- or eight-bit code that specifies a unique set of binary digits that represent a character set.
Assembler. A program that translates an assembly-level language into machine language.
Assembly-level language.A low-level computer language consisting of symbolic instructions and addresses that translate into machine codes on a one-to-one basis.
Asynchronous transmission. A mode of communication in which individual data packages are sent at random time intervals. (See also Synchronous transmission).
Attribute.A column in a two-dimensional database.
Audio digitizer hoard.board that plugs into a computer's expansion slot and turns analog sound waves into digital tiles for playback.
Authoring system. A specialized application generator that combines hardware and software tools for designing interactive programs.
Automatic teller machine (ATM).special-purpose computer that allows bank customers to perform routine banking transactions themselves, rather than having to wait for a bank employee.
Automation. Short for automatic operation. The process of mechanizing or computerizing functions so they perform without human intervention.
B-tree. A file in which the records BA are structured into an inverted tree based on a series of midpoints. For example, the root of the tree is the midpoint of a file, at the second level arc more midpoints, and so on.
Background study. The analysis Bat of an existing system for the purpose of performing a requirements analysis.
Backing up. Copying program or data files in case the original is Bailost or destroyed.
Backup file. A copy of a file made for safekeeping in case the Bid original is lost or damaged.
Band/belt/train printer. An impact printer that uses one striking mechanism for each character position across a line; sometimes called a line printer. Bin
Bandwidth. The term used as a measure of the capacity of a communication channel, expressed in bits per second.
Bank switching. A software technique used to increase a computer's memory by allowing different pieces of memory to occupy the same addresses.
Bar code. A series of thick and thin stripes used to represent numbers and characters.
BASIC. An acronym for Beginner's All-purpose Symbolic Instruction Code. A high-level programming language originally intended for time-sharing systems but now used primarily in conjunction with microcomputers.
Batch processing. A method by which a computer performs one job at a time, with no human interaction occurring during the job.
Baud. A unit of information transfer that is synonymous with one bit per second.
Bidirectional printing. Printing lines of output in alternate directions. For example, if the first line is printed left to right, the next line will be printed right to left.
Binary digit. The smallest unit of information capable of being represented in a computer or communication system.
Binary number. A number system that uses only the symbols 0 and 1 to represent digits (from the Latin binaries. meaning "two at a time").
Binary search. A search method in which a list of items is successively halved until the sought item is located.
Binary signal. A computer circuit that is represented by two different levels (high and low) of voltage.
Biometric device. An instrument that performs mathematical analysis of biological characteristics. Examples include analyzing speech, handwriting, fingerprints, or eye retina features.
BIOS. An acronym for basic input/ output system. The part of an operating system that links the specific hardware devices to the software.
Bistable. A hardware device, such as a switch, that can only assume two stable states, such as on or off.
Bit. Short for binary digit. (See also Binary digit).
Bit map. A technique for dividing a display screen into a very fine grid of pixels that uses a video memory, in which bits represent pixels on a display screen. With bit mapping, a grid of pixels on a display screen is represented by a light or dark point on the surface of the display screen. (See also Pixel).
Bits per second. The number of bits of information that pass a given point in one second. A measure of the carrying capacity of a channel; sometimes called baud rate.
Boolean algebra. An algebra that is used to manipulate symbols according to the operators and, or. and not. It allows logic to be handled as simply as mathematical formulas. Developed by George Boole in 1847.
Bootstrap loader. An initialisation program that sets up and readies the computer when it is turned on.
Bottom-up design. In software development, a technique that starts with the parts or most basic functional components and proceeds to build a whole or completed program.
Branch. A type of program instruction that performs a test on a register or flag and. depending on the results, continues on with the next instruction in sequence, or branches (or jumps) to another instruction in the program.
Buffer. A device (usually a memory) that temporarily stores data while it is being routed to a destination, such as a printer, mass storage, or a communication channel.
Bug. A computer term for an error. A software bug is a programming error, a hardware bug is a malfunction or design error in the computer or one of its components.
Bundled. A computer system sold as a complete system. A t\pi-cal bundled system would include all the necessary hardware components along with a variety of software programs for various applications; often called a turnkey system.
Bus. The electrical pathway used to transfer information from one point in a computer to another.
Bus network. system in which all computers or terminals communicate via a common distribution channel or bus.
Business systems analyst. A sys≠tems analyst who is in an or≠ganizational department other than the data-processing de≠partment.
Byte. A sequence of eight consecu -tive bits used in coding systems to represent one character of data or information.
C. A high-level programming language that is very popular with system programmers because of its transportability between computer systems.
Cache. A high-speed buffer memory filled from lower-speed mass storage. Frequently used instructions and data can be fed to and from the CPU much faster when located in a cache. Pronounced "cash".