A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
A

ACCESS TIME - The length of time required for a binary WORD in the memory section of a computer to be read by the CENTRAL PROCESSING UNIT (CPU), or the time to read data from a peripheral data storage area.

ACCUMULATOR - An interface REGISTER (memory) in the ARITHMETIC LOGIC UNIT (ALU), that stores interim arithmetic information for future processing. The accumulator is interface between the ALU and other sections of the computer.
 

ADDER - The digital logic circuits in the ALU section of a computer which implements the adding process (sum and carry) of two or more binary numbers.
 

ADDRESS - The location of digital information in the MEMORY UNIT of a computer, or a digital code that designates this location.
 

ALGORITHM - The sequence of operations that defines a solution to a problem in logic.
 

ALPHANUMERIC - The term that defines the letters of the alphabet (A to Z) and the ten numerals (0 to 9). The term is generally used to mean any text data.
 

AMERICAN STANDARD CODE FOR INFORMATION INTERCHANGE (ASCII) - A 7-bit binary code, providing 128 different binary combinations for standard American keyboards. ASCII is used to encode all 26 letters of the alphabet (upper and lower case), all ten decimal digits (0 to 9), punctuation marks, standard graphics, and special control codes into machine language. Although ASCII has 128 different codes, only 7 bits are needed for each different code. ASCII characters are generally stored inside 8-bit bytes, providing room for the 128 ASCII codes plus another 128 codes, totaling 256 characters. This 8-bit code is referred to as EXTENDED ASCII.
 

ANALOG COMPUTER - A non-digital system that manipulates linear, or continually changing data.
 

AND GATE - See LOGIC GATES
 

ARITHMETIC LOGIC UNIT (ALU) - The section of a computer that contains a large amount of logic circuitry and performs the four basic arithmetic functions (addition, subtraction, multiplication, and division). Larger units contain circuitry for higher mathematical functions, such as: quadratic equations, etc.
 

ASCII DATA (ASCII FILE) - Data, or the file containing the data, that is constructed with letters of the alphabet, numerals, punctuation marks, and the standard ASCII formatting commands, such as: "carriage return" or "line feed". These terms refer to text information.
 

ASSEMBLER - A software program that converts (translates) each symbolic instruction written in ASSEMBLY LANGUAGE into the MACHINE LANGUAGE (binary code) of a computer.
 

ASSEMBLY LANGUAGE - A programming language (source code) that consists of a group of coded letters or labels, called mnemonics. A mnemonic is a memory assist to help recall data. Each mnemonic represents a single instruction that is translated into the binary code of machine language. Mnemonics are easier to use than machine language instructions. For example, the mnemonic "MUL" tells the computer to "MULtiply".
 

ASYNCHRONOUS - A term that describes a non-clocked, or free-running digital signal that triggers successive computer instructions; the completion of one instruction triggers the next. The speed of operation depends only on the speed of the signal generated through the circuit or network. In contrast with SYNCHRONOUS operation, the computer clock controls the speed of the signals in the system.
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B

BACKPLANE - A part of a computer into which the system's PC boards are plugged to provide a common voltage supply, reference, and SYSTEM BUS for all computer sections. A backplane is often called a MOTHERBOARD.
 

BASIC - The acronym for Beginner's All-purpose Symbolic Instruction Code. BASIC is an easy to use programming language, originally intended for educational purposes; it is available for personal computers in varying degrees of complexity.
 

BAUD RATE - A measure of speed (up to 2400 bits per second) of transferring information between two or more sections of a computer system, or between two or more computers.
 

BAUDOT CODE - A 5-bit digital code having 32 possible combinations of binary "0s" and "1s"; for Teletype (Telex) communications systems.

BENCHMARK - The specifications for measuring the characteristics of a computer system, or parts of the system, under clearly-defined conditions.
 

BINARY CODED DECIMAL (BCD) - A coding system in which each decimal system numeral (0 to 9) is represented by a 4-digit (4-bit) binary code.
 

BINARY SYSTEM (BASE 2) - A numbering system consisting of only two digits (0 and 1), as contrasted with a DECIMAL SYSTEM that uses ten digits (0 to 9). In electronics, "binary" and "two-state" are synonymous.
 

BINARY DIGIT (BIT) - The term "BIT" is the contraction of Binary DigiT and is part of a binary WORD that consists of combinations of "0s" and/or "1s". There are only two numerals in binary arithmetic (base 2) and is the basis for binary code (Machine Language), the language of the computer. A "bit" has the same significance in binary arithmetic that a decimal digit has in the more familiar decimal (base 10) arithmetic system.
 

BISTABLE MULTIVIBRATOR - A digital circuit having two stable electrical states. The output signal of this circuit will remain in either state (0 or 1) indefinitely until an external input signal causes the circuit to switch to its other output state. This circuit is generally called a FLIP-FLOP.
 

BIT - See BINARY DIGIT.
 

BLACK BOX - A term that refers to an electronic circuit or system within an enclosure without necessarily providing details of its internal elements. The black box concept often offers a useful approach in the design of a system or in the interconnect between two circuits or systems.
 

BOOLEAN ALGEBRA - Named after George Boole, a 19th century English mathematician, who first formulated theorems that included a mathematical analysis of the laws of human logic. It uses algebraic-like notation to describe the interaction of variables having only two states - "true" and "false". In electronics, the states are often referred to as "1" and "0" or, "high" and "low". The terms "high" and "low" refer to the voltage levels of the input and output signals of a logic gate (logic circuit). Boolean algebra is used in the design of logic circuits in computers and similar digital systems. The logic gates called AND, OR, and NOT are the three basic logic gates in Boolean algebra. NAND, NOR, XOR and others are combinations of the three basic logic gate operations.
 

BOOTSTRAP (BOOT) - A software program for initiating the operation of a computer. The function of the program is to set up the input and output (I/O) devices and load the OPERATING SYSTEM from a disk, cassette, or built-in READ ONLY MEMORY (ROM).
 

BREAKPOINT - Location of a place in a program where program execution can be stopped to permit a visual test, printing, or other performance analyses.
 

BUBBLE MEMORY - A high-density memory medium upon which a magnetic film is grown on a gadolinium-gallium garnet substrate. A small permanent magnet is mounted inside its package, perpendicular to the surface of the substrate. When an external magnetic field is created with an external coil, magnetic "bubble" domains are formed on the internal magnetic film which represent patterns of "1s". The absence of magnetic bubbles will represent patterns of "0s".
 

BUFFER - 1. A digital logic circuit inserted between other digital circuits to reduce circuit interaction and/or to provide amplification of a digital signal. 2. An intermediate storage circuit used to compensate for a difference in baud rate or, to compensate for different times of occurrence of different events or instructions. 3. A circuit for converting input or output voltages for signal level compatibility when transmitting data from one device to another.
 

BUNDLED - A term describing a computer system that includes all necessary hardware and software that will allow the system to operate as advertised.
 

BUS (BUSS) - A series of transmission lines connecting the various elements of a computer for distribution of data, control signals, addresses, and/or voltage supply(s) within a computer. See SYSTEM BUS.
 

BUS CONTROLLER - A circuit that generates commands and control signals for sequencing and timing of the data transmitted on a bus.
 

BYTE - A set (group) of consecutive binary digits (bits) that forms a unit (word) or sub-unit of digital information in a computer. Depending on the size of the computer, a digital word may contain one or more bytes. Through common usage, a byte is generally accepted as containing eight bits.
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C

CACHE - A high-speed buffer memory that is similar to a SCRATCH PAD MEMORY, but has a larger capacity; it is located in the CENTRAL PROCESSING UNIT. It is filled from the main memory at low speed with instructions and programs and is operated at a higher speed. A cache can also serve as a storage section between the CPU and a hard disk to speed up access of data on the hard disk.
 

CD-ROM (COMPACT DISK READ-ONLY MEMORY) - An aluminized disk, 4.72" in diameter that provides an optical storage medium for digital data up to 650 Megabytes. A laser beam permanently burns data into its surface which cannot be over-written, altered, or erased, providing read-only memory capability. Larger size disks are generally called "laser disks".
 

CD-R or WORM (COMPACT DISK, WRITE ONCE, READ MANY MEMORY) - A blank disk that can be programmed once, permanently storing up to 650 Megabytes of digital data. Once programmed, it has essentially the same features as a CD-ROM.
 

CD-E or CD R/W (COMPACT DISK, ERASABLE, READ/WRITE MEMORY) - Capable of storing up to 650 Megabytes of digital data. It uses a magneto-optical technology that combines the storage capacity and reliability of optical disks and the eras ability of magnetic media.
 

CENTRAL PROCESSING UNIT (CPU) - The section(s) in which all the processing circuits of a computer are located. It incorporates a CONTROL UNIT and an ALU.
 

CHARACTER GENERATOR - A circuit that accepts digital data and forms the corresponding letters and numerals for a monitor or printer.
 

CLOCK - A digital pulse generator that controls the timing of a computer and, to a great extent, determines the speed (number of instructions per second) capability of the computer. Generally, it is located in the CPU.
 

CMOS LOGIC - A CMOS technology monolithic IC "logic family" characterized by low power dissipation per gate, high chip density, and relatively high propagation delay per gate compared with bipolar IC logic families.
 

COMPILER - A software program that converts (translates) a complete software program written in high-level language SOURCE CODE (such as PASCAL or FORTRAN) into machine language. The entire source code is edited, compiled, and run at one time as compared to an INTERPRETER that is run one line at a time.
 

COMPLEMENT - Reversal of bit values: "1s" become "0s" and "0s" become "1s".
 

CONCURRENCY - The independent execution of two or more sequences of events that are either occurring, or appearing to occur simultaneously.
 

CONSOLE - The term referring to a combination of a DISPLAY and KEYBOARD.
 

CONTROL BUS - A set of transmission lines whose function is to carry synchronization signals and control data as part of the SYSTEM BUS.
 

CONTROL UNIT (CU) - Part of the CPU containing the CLOCK, PROGRAM COUNTER and INSTRUCTION REGISTER. The CONTROL UNIT also generates control signals and manages the CONTROL BUS.
 

COUNTER - A circuit whose output(s) change state in a specified sequence on receiving appropriate input signals. The circuit can provide a required output pulse after receiving a specified number of input pulses.
 

CRASH - The term that describes a situation when a part of, or the complete computer, stops working because of a hardware and/or software malfunction. A head-crash in a disk system refers to the accidental impact of the read/write head on the surface of the disk.
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D

DAISY-WHEEL PRINTER - An impact printer that uses a print element shaped like a flat disk or large thimble to form the alphanumerics and punctuation marks that are part of its print element. Unlike dot-matrix, ink-jet, and laser printers, daisy-wheel printers can not print graphics. See LETTER-QUALITY PRINTER.
 

DATA BASE - A collection of structured information for creating a specific format out of some, or all, of the collected data.
 

DATA-BASE MANAGEMENT SYSTEM (DBMS) - A software program that controls and supervises the updating, editing, and execution of items from multiple files in a data base environment.
 

DEBUG - The process of detecting, locating, and correcting a problem in a software program or hardware.
 

DECREMENT - The reduction of the numerical contents of a counter. A decrement of 1 is usually assumed, unless otherwise specified. It is the complementary operation of INCREMENT.
 

DEVICE - In a computer system, this term refers to a unit of processing equipment external to the CPU. It is sometimes synonymous with the term PERIPHERAL.
 

DIODE-TRANSISTOR LOGIC (DTL) - One of the first bipolar monolithic IC families of logic gates. A diode in an IC logic gate performs the required logic with a transistor amplifying and inverting the output. The DTL family has been made obsolete by the Transistor-Transistor Logic (TTL) family.
 

DIRECT ADDRESS - A memory accessing mode in which the contents of the accessed location is called the OPERAND.
 

DIRECT MEMORY ACCESS (DMA) - A method of transferring blocks of data directly between an external device and the computer system memory without the need for intervention by the CPU. This method significantly speeds up the data transfer rate, improving system efficiency.
 

DISC or DISK (DISKETTE) - A thin, flexible, plastic, circular memory medium, coated on both sides with metal oxide and enclosed in a protective jacket. Data is stored magnetically in binary digital form on its surface(s). See FLOPPY DISK.
 

DISK DRIVE - The mechanical/electronic section that can accept and operate a compatible floppy or hard disk. It may include several motors (for disk rotation and reading/writing head positioning), position sensors, and control circuits.
 

DISK EMULATOR - See RAM Disk.
 

DISPLAY - A peripheral device serving as a computer readout, such as a cathode-ray tube (CRT), flat-panel (generally for laptop computers), or other readout devices. The screen can be amber, green, or full-color display. Also called a MONITOR.
 

DISK OPERATING SYSTEM (DOS) - A software program on a disk which coordinates the operation, transfer of data, supervision, and control of a computer. This software program must first be booted into the working memory of the computer from the disk before it can operate.
 

DISK STORAGE - A method of storing software programs and data on a rotating circular disk (either a floppy or hard disk) coated with magnetic material, such as iron oxide. Data is written (stored) and read (retrieved) by movable read/write heads positioned over data tracks on the surface of the disk. Addressable portions of the disk can be selected for read or write operations.
 

DOCUMENTATION - Information that explains how to use computer hardware or software. It is usually provided as a manual or stored on a disk.
 

DOT-MATRIX PRINTER - An impact printer with a computer-driven, multi-pin print element (print-head). It create images by imprinting a series of tiny dots on a paper to print a wide variety of character styles and/or finely detailed graphics. Generally, these printers are extremely fast and are used for draft-quality documents and precise graphics.
 

DOTS PER INCH (DPI) - The measurement of density on dot-matrix printers or other dot-matrix devices. As the DPI increases, image clarity increases.
 

DOWNLOAD - The transfer of files or data from a source of data to a remote computer. See UPLOAD.
 

DOWN TIME - A period of time during which a computer is not functioning. It is inoperable because of temporary or permanent failure of hardware or software, or when routine hardware or software maintenance procedures are indicated.
 

DYNAMIC RANDOM ACCESS MEMORY (DRAM) - A type of semiconductor memory in which the presence or absence of a capacitive charge in each element of the memory represents the state of the bit (1 or 0). This charge must be periodically recharged (refreshed) to maintain the desired binary state of the element.
See RANDOM ACCESS MEMORY.
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E

 

EDITOR - A program for preparing and/or modifying a SOURCE PROGRAM or other file by addition, deletion, or change.
 

EMITTER-COUPLED LOGIC (ECL) - A bipolar monolithic IC logic gate family characterized by very high speed operation and relatively high power dissipation compared with other monolithic IC logic families.
 

EMULATION - The process of imitation (simulation) of one computer system by another. The imitating program, or device (emulator), accepts the same data, executes the same programs, and achieves the same results.
 

EPROM (ERASABLE PROGRAMMABLE READ-ONLY MEMORY). A general term for a non-volatile, semiconductor memory that can be programmed, erased, and reprogrammed many times without damage to the device. More specific types of EPROMs include: EAPROM (ELECTRICALLY ALTERABLE PROM), EEPROM (ELECTRICALLY ERASABLE PROM) and UV-EPROM (ULTRAVIOLET ERASABLE PROM). Either memory is suitable for prototype and computer development, or to change memory data when new conditions dictate the change.
 

EVENT - An occurrence during the execution of a task, such as the completion of an input/output operation.
 

EXECUTE - The command to run a specified instruction or software program.
 

EXTENDED BINARY CODED DECIMAL INTERCHANGE CODE (EBCDIC) - An 8-bit code developed by IBM for their mainframe computers, providing 256 bit-pattern equivalents of standard keyboard symbols.
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F

FAN-IN - The maximum number of output terminals from other logic gates that can be connected to an input terminal of a specified logic gate.
 

FAN-OUT - The maximum number of input terminals that can be connected to the output terminal of a specified logic gate.

FETCH - The command to obtain an instruction from a stored program.
 

FILE - A collection of related data treated as a single unit. In a computer, a file can exist on a disk, magnetic tape, or as an accumulation of information in memory.

FIRMWARE - A combination of a software program in hardware, such as a READ-ONLY MEMORY (ROM), or a disk that has files or software programs written on its surface.
 

FIRST IN, FIRST OUT (FIFO) - The term refers to the sequence of entering and then retrieving data from a data storage section of a computer. The first data entered is the first data retrieved.
 

FLAG - An indicator of a specific condition that informs a section of a program that this condition has already occurred and is identified by the presence or absence of the flag. A flag can be implemented in software and/or hardware.
 

FLASH MEMORY (FLEXIBLE ARCHITECTURE for SHARED MEMORY) - Non-volatile semiconductor memory with access time approximately that of EEPROM or EAPROM and density similar to that of an EPROM. FLASH memory is generally limited to about 100,000 erase cycles. Usually packaged in PCMCIA for plugging into a laptop computer card slot.
FLIP-FLOP CIRCUIT - A logic circuit having two stable output states. It has the ability to change from one state to the other when an input pulse is applied in a specified manner. It is also called a BISTABLE MULTIVIBRATOR.
 

FLOATING-POINT ARITHMETIC - A method in which the decimal point location of a number in an arithmetic operation is determined by the number's exponent value in base 10. All exponents are equalized prior to the operation to set a decimal point in its proper location in the final computation. Floating-point arithmetic extends a computer's mathematical capability beyond the limit imposed by a fixed word length and contributes to easier programming.
 

FLOPPY DISK (DISKETTE) - A relatively inexpensive, flexible, plastic disk for storing digital data on both sides of its magnetic surface. The amount of data depends on the diameter of the disk and the technology for recording the data. See DISK STORAGE.
 

FLOW CHART - A symbolic representation of the processing steps performed by a software program or a graphic sequence of logic operations implemented in hardware. A flow chart helps to visualize the procedure(s) necessary to design a software program or a final hardware system.
 

FONT - A style of print typeface having a specific form and size.
 

FORMAT - An orderly, structured arrangement of data elements (bits, bytes, and/or fields) that is necessary to produce a larger entity, such as: a list, record, table, file, or dictionary. Also, it is the term that describes the preparation of a magnetic disk to allow it to accept digital data.
 

FORTRAN - A science-oriented high-level software language, derived from the contraction of the terms FORmula TRANslator.
 

FREQUENCY SHIFT KEYING (FSK) - A technique of digitally keying (modulating) an audio tone (carrier wave) so that a commercial telephone line can carry digital data.
See MODEM.
 

FULL DUPLEX - A data transmission mode that provides simultaneous and independent transmission and reception. A conventional telephone communication is an example of this technique. See HALF DUPLEX.
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G

GATE - See LOGIC GATE.
 

GATE ARRAY - A group of standard logic gates that can be interconnected into a complete circuit or system. Also called LOGIC ARRAY.
 

GENERAL PURPOSE INTERFACE BUS (GPIB) - A BUS specification

standard (IEEE 488) for controlling peripheral devices.
 

GIGO (GARBAGE IN, GARBAGE OUT) - The term describing the output of a computer whose operation or accuracy is faulty.
 

GRAPHICS - Schematic drawings, pictures, line drawings, and/or diagrams generated by data entered into a computer via a keyboard or a data base.
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H

HALF-DUPLEX - A communications mode that allows transmission and reception of digital data between computers, but not simultaneously.
 

HANDSHAKING - A communications synchronizing technique carried out before and after any transfer of digital data. It consists of a sequence of signals for non-clocked (asynchronous) systems in which a reply is needed to complete a data transfer operation.
 

HARD COPY - A printed copy of a file, message, or graphic of the visual display on the screen of a computer monitor.
 

HARD-DISK DRIVE - A sealed unit containing high-density, high-speed, rigid metal disks, and recording heads to store digital data. It reads and writes data faster than floppy disks.
 

HARDWARE - The physical equipment of a computer system consisting of mechanical and electrical/electronic components.
 

HEXADECIMAL - The base 16 number system using 16 symbols (0 to 9 and A to F) to represent 16 decimal numerals (0 to 15).
 

HIGH-LEVEL LANGUAGE (HLL) - A programming language (source code) consisting of a unique group of symbols and command statements representing a series of machine operations. A COMPILER or INTERPRETER translates (converts) a HLL into MACHINE LANGUAGE. BASIC, FORTRAN, PASCAL, ALGOL, and ADA are some examples of high-level languages.
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I

IEEE 488 - See GENERAL PURPOSE INTERFACE BUS
 

IMPACT PRINTER - A computer-driven mechanical imprinting device where the characters are formed by the printer-head key striking a ribbon to imprint the character's image onto a paper.
 

INCREMENT - The increase in the numerical contents of a counter. An increment of one is usually assumed, unless otherwise specified. See DECREMENT.
 

INK-JET PRINTER - A printer that forms characters by electrostatically aiming and depositing a tiny patterned drop of ink onto the paper to be printed.
 

INPUT/OUTPUT (I/O) SECTION - The section that interfaces between the computer's SYSTEM BUS and the peripherals feeding data into and taking data out of the computer. Depending on the number of peripherals in a system, the I/O sections can have a single PORT or multiple ports.
 

INSTRUCTION - A software statement that specifies a machine operation. Also called a COMMAND.
 

INSTRUCTION SET (INSTRUCTION REPERTOIRE) - A description of the total operational capabilities of a computer provided by the computer or the CPU (MPU) manufacturer. It consists of a listing of binary words for each executable commands. It is sometimes called the computer's MICROCODE.
 

INTERPRETER - A high-level language translator that converts individual high-level computer language program instructions (source code) into machine instructions. It translates and executes each statement line-by-line during the running of the program.
 

INTERRUPT - The suspension of normal program execution to perform a higher priority service routine as requested by a peripheral device. After completion of the service routine operation, the interrupted program routine is resumed at the point where it was interrupted.
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J

JUMP - An instruction that causes the computer to fetch the next instruction to be executed from a location other than the next sequential location in memory.
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K

KEYBOARD - A peripheral device consisting of alphanumerics, punctuation marks, and other special function keys that are mechanically arranged to allow the entry of data, commands, and other information into the system.
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L

LAN - See LOCAL-AREA NETWORK.

LANDSCAPE - A printer feature, generally controlled by software, which rotates the output image by 90º to print across the length rather than the width of the paper.
 

LASER (LIGHT AMPLIFICATION by STIMULATED EMISSION of RADIATION) - A system that generates high-intensity, highly-focused light for many purposes, including printers, high-density memory media, and a light generator for fiber optic transmission systems.
 

LASER DISK - See CD-ROM

LASER PRINTER - A computer-driven photocopier that creates an original image of the text or graphics from the output of the computer. A computer-controlled laser beam "paints" the desired image inside the photocopier and then prints the image on a sheet of paper.
 

LAST-IN, FIRST-OUT (LIFO) - A method of storing and retrieving data in a stack, table, or list.
 

LIGHT PEN - A light-sensitive stylus for forming graphics by touching coordinates on a display screen, thereby seeming to draw directly on the screen.
 

LIBRARY - A collection of standard software instructions, programs, routines, and subroutines in a computer's memory.
 

LINKAGE - Instructions that connect one program to another, providing continuity of executions between the programs.

LOCAL AREA NETWORK (LAN) - A combined hardware/software technique for interconnecting company related multiple computers or computer terminals through a high-speed networking system.
 

LOGIC GATE - A digital circuit resulting in an output whose state (0 or 1) depends on the specific combination of the states of input signals. Definitions of the more commonly used logic gates are listed below:
 

AND - All inputs must be in a "1" state to produce a "1" state output.
 

NAND (NOT AND) - All inputs must be in a "1" state to produce a "0" state output.
 

OR (NOT OR) - Any one input, or more, in a "1" state will produce a "0" state output.
 

NOT (INVERTER) - A logic gate having only one input and one output. If the input is in a "1" state, the output is in a "0" state and vice versa.
OR - Any one input, or more, in a "1" state will produce a "1" state at the output.
 

XOR (EXCLUSIVE OR) - If any of the inputs are in a "1" state, but not if two or more inputs are "1", the output is in a "1" state.
 

LOOK AHEAD - 1. A feature of a CPU which allows the masking of an interrupt request until the current sequential instruction has been completed. 2. A feature of an adder circuit in the ALU section which allows the circuit to look ahead to see that all the generated arithmetic carrys are available for addition.
 

LOOPING - The repetition of program instructions until a conditional exit situation is encountered.
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M

MACHINE LANGUAGE - Sets of numeric binary code instructions in a computer which execute its operations. All other programming languages (SOURCE PROGRAMS) must be translated into machine language (OBJECT PROGRAM) before entering the CPU.
 

MACRO - A combination of commands, instructions, or keystrokes which may be stored in a computer's memory to be executed as a single command by a single keystroke or a simultaneous combination of keystrokes.
 

MACROASSEMBLER - An assembly language translator that converts macro expressions into several machine language instructions. Although macros simplify program coding and speed up execution of a program, a code for each macro must also be generated.
MAINFRAME COMPUTER - Second largest of the computer family, in capability and, generally, in size, having a WORD-WIDTH of 32 bits and higher. The largest computer is the SUPER COMPUTER with a WORD WIDTH of 64 to 128 bits.
 

MEMORY - A data storage structure in a computer that accepts binary information for storage in electrical, mechanical, or magnetic form, and retains the information for as long as needed. Selected data can be written, moved, displayed, copied, or erased. The variety of memory media includes: paper, magnetic, bubble, optical laser, and semiconductor memory. Each one has a different method of operation and a specific criterion for being selected.
See STORAGE.
 

MICROCOMPUTER - A microprocessor-based computer, consisting of an MPU, internal semiconductor memory, input and output sections, and a system bus, all on one, or several monolithic IC chips inserted into one or several PC boards. The addition of a power supply and connecting cables, appropriate peripherals (keyboard, monitor, printer, disk drives, etc.), an operating system and other software programs can provide a complete microcomputer system. The microcomputer is generally the smallest of the computer family, however, the improvement in performance capability of newer microcomputer systems can make the microcomputer as powerful as larger systems.
 

MICROPROCESSOR UNIT (MPU) - The Central Processor Unit (CPU) implemented in monolithic IC technology, usually, but not necessarily, on one VLSI chip. In many cases, the SYSTEM BUS is also included on the MPU chip.
 

MINICOMPUTER - Considered to be more capable than a microcomputer but less powerful than a mainframe. Generally, the WORD-WIDTH of the minicomputer is between 12 to 32 bits.

MNEMONIC - A symbolic label or code reminder that assists the user in remembering a specific operation or command.
See ASSEMBLY LANGUAGE.
 

MODEL - A representation of a process or system that can be controlled to demonstrate the effects that various actions will have on the process or system.
 

MODEM - An acronym for MOdulator/DEModulator that refers to specific equipment that provides a means of communication between two computer systems over conventional telephone lines. Each remote computer requires its own MODEM and a compatible communications software program for proper interfacing.
See FREQUENCY SHIFT KEYING.
 

MONITOR - The visual readout device of a computer system. A monitor can be in several forms:, a cathode ray tube (CRT), a liquid crystal display (LCD), or a flat-panel, full-color display. See DISPLAY.
 

MOUSE - A manually operated input device for moving or entering positional information and other data or commands by accessing (pointing to) images on a monitor.
 

MULTITASKING - The technique of using several applications programs (tasks) in a computer system or on several terminals in a network at the same time. Multitasking can simultaneously work with several programs or interrelated tasks that share memories, codes, buffers, and files.
 

MULTIUSER - The term describing the capability of a computer system to be operated at more than one terminal at the same time.
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N

NEGATIVE LOGIC - This term refers to logic in which the negative voltage represents the "1" state and the zero voltage represents the "0" state.
See POSITIVE LOGIC.
 

NESTING - Embedding commands or data in levels of other data so that specific routines or instructions can be executed or accessed continuously in loops, without returning to the main program.
 

NIBBLE - A sequence of four adjacent bits, or a half-byte. A hexadecimal or BCD coded digit can be represented by a nibble.
 

NODE - The endpoint of a network branch or the junction of two or more branches.
 

NON-VOLATILE MEMORY - A memory where stored data remains undisturbed by the removal of electrical power.
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O

OBJECT CODE - Machine language code produced by a translator program, such as an assembler, interpreter, or compiler. Instructions in object code can be executed by a Central Processing Unit (CPU).
See SOURCE CODE.
 

OPERATING SYSTEM (OS) - A structured software program (set of programmed routines) that manages, controls, coordinates, and sequences the hardware and software resources of a computer system. See BOOTSTRAP. The operating system is sometimes called SYSTEMS SOFTWARE.
 

OPERATION CODE (OP-CODE) - Part of a computer instruction word that designates the function performed by a specific instruction. For example, op-codes for arithmetic instructions include: "ADD", "SUB", "MUL" and "DIV".
 

OVERFLOW - An error condition occurring in a computer when a mathematical operation produces a result having a magnitude that exceeds the capacity of the computer's arithmetic register.
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P

PASCAL - A high-level programming language that is structured to encourage efficient programming habits (documentation) and is used extensively in educational institutions and engineering environments.
 

PARALLEL OPERATION - A method of data transmission in which all bits of a digital word are handled simultaneously with each bit on a separate line. Although faster and simpler to install and operate than SERIAL OPERATION, this method requires more transmission lines (real estate).
 

PARITY - A method of verifying the accuracy of binary data after it has been transferred to or from a storage area.
 

PARTITIONING - The logical grouping of electronic functions within a given set of hardware components.
 

PCMCIA (PERSONAL COMPUTER MEMORY CARD INTERNATIONAL ASSOCIATION) A package in a plastic card form containing semiconductor memory, particularly FLASH. These cards are plugged into the card slot in laptop computers.
 

PERIPHERAL - A term designating the various kinds of machines and devices that work in conjunction with a computer but are not necessarily part of the computer structure. Typically, peripherals refer to: printers, keyboards, monitors, scanners, CD ROM drives, and plotters. A hard drive, floppy disk drive, and a MODEM are considered to be peripheral devices even though they may be physically located inside a computer.
 

PLUG-COMPATIBLE - A term that describes the ability of peripherals to be interchanged without modification.
 

POLLING - A process in which a number of peripheral devices, remote stations, or nodes in a computer network are interrogated, one at a time, to determine if service is required.
 

POP - The instruction that removes a word from the top of a stack.
See STACK.
 

PORT - An input/output channel (either parallel or serial), terminated at a connector on the computer. It interconnects the computer's input and/or output terminals to an appropriate source and/or destination.
 

PORTRAIT - A term that designates the position of conventional printing across the width of a page.

POSITIVE LOGIC - This logic represents the reverse of NEGATIVE LOGIC. It is the more commonly used form of logic. A positive voltage represents a "1" state and a negative (or zero) voltage represents a "0" state.
 

PRINT SPOOLER - A device for temporarily storing data to be printed when the printer is functioning. It provides uninterrupted data entry and editing while the printer is active and while other data awaits transmission to the printer.
 

PROGRAM - A complete sequence of computer software instructions necessary to provide an application, solve a specific problem, perform an action, or respond to external stimuli in a prescribed manner. As a verb, it means to develop a program.
 

PROGRAM COUNTER (PC) - A special-purpose register in the CPU which contains the address of the next instruction to be fetched and executed.
 

PROGRAMMABLE LOGIC ARRAY (PLA) - An unprogrammed, general-purpose logic structure in monolithic IC form consisting of an array of similar, and/or compatible logic gates. Also called PROGRAMMABLE ARRAY LOGIC (PAL).
 

PROGRAMMABLE READ-ONLY MEMORY (PROM) - A blank read-only memory (ROM) that is programmed with external programming equipment after manufacture. Once programmed, it is not re-programmable and is considered to be a ROM.
 

PROPAGATION DELAY - The time required for the output of a logic gate to respond to a combination of input pulses.
 

PUSH - The instruction used to deposit a word on top of a stack.
 

PUSH-DOWN STACK - A dedicated temporary storage register in a computer, sometimes part of a system memory, structured so that data (words) in the stack are retrieved in reverse order of entry. See LIFO.
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R

RAM DISK (DISK EMULATOR) - A portion of a hard drive configured to emulate a RAM. It accesses information quickly, but its data must be saved in a non-volatile memory for future use. Otherwise, the information is lost when power is removed.
 

RANDOM ACCESS - A technique of accessing (reading) a word of data from a memory structure by the CPU. Since a word in the memory can be accessed directly, the time required is independent of its location (address) in the memory structure. It is sometimes called a "direct access" method.
 

RANDOM ACCESS MEMORY (RAM) - A volatile, semiconductor storage structure that accesses temporary data with a random or direct accessing method. It is more accurately referred to as "erasable read/write" memory. Data in this memory can be read by the CPU, edited, altered, erased, or new information written over existing data by computer commands. Its data must be saved for future access by writing it into a non-volatile memory. See NON-VOLATILE MEMORY and VOLATILE MEMORY.
 

READ-ONLY MEMORY (ROM) - A semiconductor memory whose data cannot be erased, or overwritten; it can only be accessed (read) for use by the CPU. The data in a ROM is of a permanent nature and is programmed by the ROM manufacturer. In many cases, its programmed information identifies the dedicated function of a computer. A ROM can also be in the physical form of a module (tape or disk) that is plugged into a computer to change its operation from one program to another.
 

REAL-TIME DATA - Time-dependent data processed by a computer whose output data is capable of controlling other time-related events, such as traffic control. Real time is the actual time it takes for an event to occur.
 

REGISTER - A temporary storage unit for quick, direct accessibility of a small amount of data for processing. Most computers include a set of internal registers that can be accessed more quickly than the system's main memory.
 

RESIDENT SOFTWARE - The program(s) residing in the main memory of a computer system. For convenience of operation, several software programs can reside in RAM after the computer is turned on and booted, and they can be accessed quickly from within another program.
 

RS-232-C - Identifies an interconnection standard for serial operation. It specifies the configuration and type of connectors in the computer's serial I/O port(s) and peripheral serial port(s).
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S

SCRATCH PAD MEMORY - A group of internal registers used for the temporary storage of data being collected and sorted for immediate processing. It is analogous to a pad of paper for quickly jotting down notes. SECTOR - A section of a recording track on a magnetic disk.
 

SEMICONDUCTOR MEMORY - Data storage devices formed with semiconductor components (generally monolithic ICs). See RAM, ROM, PROM, EPROM, EAPROM, EEPROM, and FLASH.
 

SERIAL OPERATION - A method of data transmission where the data is handled in sequence, one bit at a time.
See PARALLEL OPERATION.
 

SERVICE ROUTINE - A set of instructions for performing a programmed operation, typically, in response to an interrupt command.
 

SHIFT - A computer operation consisting of moving a group of adjacent data bits either to the left or to the right by a prescribed number of positions. The move is done in a SHIFT REGISTER for a carry-over operation.
 

SIMPLEX - A data transmission mode that provides transmission in one direction only.
See FULL DUPLEX and HALF DUPLEX.
 

SIMULATION - The imitation of a logical operation of one computer by another to measure and evaluate the operation of the computer being designed. Simulation is primarily intended to provide an analysis of program logic, independent of hardware environment, and is extremely useful for debugging a new software program prior to committing it to ROM.
 

SOFTWARE - Programs, languages, procedures, and documentation for a computer system. Software includes: operating systems (system software), language translators (assemblers, interpreters and compilers), subroutine libraries, application programs, and the information in instruction manuals.
 

SOURCE CODE (SOURCE PROGRAM) - A set of computer instructions in hard-copy or stored form. When written in a language other than machine language, the source code requires translation by an assembler (or macroassembler), interpreter, or compiler into object code.
See OBJECT CODE.
 

STACK - A dynamic, sequential data list usually contained in the computer system's main memory. It has special provisions to access data from either end. Storage and retrieval of data from the stack is performed automatically by the CPU.
 

STATIC MEMORY - A type of semiconductor read/write memory (RAM) that does not require periodic refresh cycles. As long as electrical power is ON, the data in a static memory is maintained.
 

STORAGE - This term is interchangeable with the term MEMORY.
 

SUBROUTINE - A short program segment that performs a specific function and is available for general use by other programs and routines.
 

SUPERCOMPUTER - The largest mainframe computer featuring exceptionally high speed operation while manipulating huge amounts of information.
 

SUPPORT CHIPS - Computer-related circuits other than the CPU. Examples are: main memory (RAM and ROM), I/O ports, and system bus.
 

STATE - The logic input or output condition of a binary digital circuit - the state is either a "0" or "1".
 

STORAGE CAPACITY - The amount of data that can be retained in a memory unit. It is expressed either by a number of bits or bytes (8-bit words).
 

STREAMER/STREAMING TAPES - A small tape recorder, usually in cassette form, is used to store data from a hard disk for the purpose of backing up this data.
 

SYNCHRONOUS COMMUNICATION - A method of transferring binary data, in serial form, between computers or between a computer and its peripherals. Transmission of data is at a rate set by the computer's clock with synchronization bits located at the beginning of each message or block of data.
 

SYNTAX - A set of grammatical rules defining valid use of specific commands or instructions in a computer language.
 

SYSTEMS SOFTWARE - A general term for software that supervises, sequences, and coordinates programs. Systems software may include programs, such as: operating systems, assemblers, interpreters, compilers, software debugging programs, text editors, utilities and peripheral drivers.
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TEXT EDITOR - See EDITOR.
 

THIRD-PARTY SOFTWARE - Software developed by a software company rather than by a computer manufacturer or user.
 

THROUGHPUT - The number of instructions executed per second, measured in millions of instructions per second (MIPS) or billions of instructions per second (BIPS).

TOGGLE - To switch back and forth between two states or conditions of operation, as in a toggle switch.
 

TOP-DOWN HIERARCHICAL DESIGN - A hardware and/or software design approach that starts at the most general level of a machine or software program. It proceeds, step-by-step, to lower levels, adding detail as the design progresses.
 

TRACK - A ring on the surface of a magnetic disk.

TRACTOR-FEED - A pin-fed device for advancing continuous form paper through a computer printer.

TRANSISTOR-TRANSISTOR LOGIC (T2L) - A logic gate family that provides higher-speed and higher-power than the obsolete DTL logic family. The first transistor in the circuit performs the required logic. Another transistor amplifies and inverts the output. Improved pin-compatible versions of this logic family are called TTL-Schottky (T2L-S) and Low Power TTL-S (LPT2L-S).
 

TRANSLATOR - See ASSEMBLER, MACROASSEMBLER, INTERPRETER, and COMPILER.
 

TRI-STATE LOGIC - The term that designates the possible conditions of a specific logic gate output: "0", "1" or "undefined".
 

TRUNCATE - The dropping of digits or characters from one end of a data item causing loss of accuracy or information.
 

TRUTH TABLE - A tabulation of all possible combinations of states at the inputs of a logic gate which will result in a specific logic state at the output of the gate.
 

TURNKEY SYSTEM - A complete computer system ready to operate without any hardware or software modification or addition.
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U

UNFORMATTED (UNINITIALIZED) DISK - A blank magnetic disk with no track/sector identification recorded on it that allows users to implement their own track/sector identifications.
 

USART - UNIVERSAL SYNCHRONOUS/ASYNCHRONOUS RECEIVER TRANSMITTER - A circuit that converts serial-to-parallel or parallel-to-serial operation for communication between two computers or between a computer and its peripherals.
 

USER-FRIENDLY PROGRAM - A software program that has been designed to easily direct the user through the operation or application of a program. A menu-driven program is considered to be "user-friendly".
 

UTILITY - A software program designed to perform a computer system's routine housekeeping functions, like copying, deleting files, and/or providing techniques to simplify the execution of a program.
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V

VOCABULARY - A list of operating codes or instructions available to the software programmer for writing a program in a specific language.
 

VOLATILE MEMORY - A memory whose contents are irretrievably lost when power is removed. If data in RAM must be saved after power shut-down, back-up in nonvolatile memory (magnetic disk, tape, or CD-R) is essential.
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W

WAIT STATE - An internal condition of delay in processing time executed by the CPU when a synchronizing control signal is not present. Wait states synchronize the timing of a CPU with the relatively slower access time of the computer's main memory.
 

WINCHESTER DRIVE - See HARD-DISK DRIVEWINDOWING - The ability of a program to divide a display screen into smaller sub-units that permit portions of different sections of a program, or different programs, to be displayed on the screen, edited, and copied independently.
 

WORD PROCESSING (WP) - The term refers to a program, that allows creating, editing, formatting, displaying, printing, and storage of text with great flexibility and ease. Different WP programs provide different, and sometimes, more desirable capabilities than others.
 

WORD - The set of binary bits handled by a computer as a primary unit of data. The width (number of bits) of a computer word depends on the hardware design. Wider words imply higher levels of precision, higher speed, and more intricate instructions. Typically, each location in memory contains one word.
 

WORM (WRITE-ONCE, READ-MANY) - A high-density optical disk memory available in a variety of formats from 5.25" to 14". The WORM can be programmed once, permanently saving a user's data. It then becomes an optical disk read-only memory having essentially the same features as a CD-ROM. Also called CD-R (CD-RECORDABLE).
 

WORKSTATION - The work area and/or equipment used for computer operations, including computer-aided design (CAD). The equipment generally consists of a monitor, keyboard, printer and/or plotter, and other output devices.
 

WRITE - The process of storing data into a memory.
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X

X-Y

PLOTTER - A computer-driven printing mechanism that draws coordinate points in graph form.
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Z

ZERO-WAIT STATE - A condition that results when no delays are inserted into the system software to deliberately detain operation of the CPU. This can be done with high-speed memory and proper design of computer architecture. Zero-wait state is desirable for the high-speed operation of a computer.
 

ZOOM - The process of proportionately enlarging or reducing an image displayed on a computer monitor.
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