Glossary of Computer Software Development Terminology

The terms are defined, as much as possible, using available standards. The source of such definitions appears immediately following the term or phrase in parenthesis, e.g. (NIST).

The source documents are listed at the bottom of this page.

BIOS. basic input/output system.

bps. bits per second.

band. Range of frequencies used for transmitting a signal. A band can be identified by the difference between its lower and upper limits, i.e. bandwidth, as well as by its actual lower and upper limits; e.g., a 10 MHz band in the 100 to 110 MHz range.

bandwidth. The transmission capacity of a computer channel, communications line or bus. It is expressed in cycles per second [Hz], and also is often stated in bits or bytes per second. See: band.

bar code. (ISO) A code representing characters by sets of parallel bars of varying thickness and separation that are read optically by transverse scanning.

baseline. (NIST) A specification or product that has been formally reviewed and agreed upon, that serves as the basis for further development, and that can be changed only through formal change control procedures.

BASIC. An acronym for Beginners All-purpose Symbolic Instruction Code, a high-level programming language intended to facilitate learning to program in an interactive environment.

basic input/output system. Firmware that activates peripheral devices in a PC. Includes routines for the keyboard, screen, disk, parallel port and serial port, and for internal services such as time and date. It accepts requests from the device drivers in the operating system as well from application programs. It also contains autostart functions that test the system on startup and prepare the computer for operation. It loads the operating system and passes control to it.

batch. (IEEE) Pertaining to a system or mode of operation in which inputs are collected and processed all at one time, rather than being processed as they arrive, and a job, once started, proceeds to completion without additional input or user interaction. Contrast with conversational, interactive, on-line, real time.

batch processing. Execution of programs serially with no interactive processing. Contrast with real time processing.

baud. The signalling rate of a line. It's the switching speed, or number of transitions [voltage or frequency change] made per second. At low speeds bauds are equal to bits per seconds; e.g., 300 baud is equal to 300 bps. However, one baud can be made to represent more than one bit per second.

benchmark. A standard against which measurements or comparisons can be made.

bias. A measure of how closely the mean value in a series of replicate measurements approaches the true value. See: accuracy, precision, calibration.

binary. The base two number system. Permissible digits are "0" and "1".

bit. A contraction of the term binary digit. The bit is the basic unit of digital data. It may be in one of two states, logic 1 or logic 0. It may be thought of as a switch which is either on or off. Bits are usually combined into computer words of various sizes, such as the byte.

bits per second. A measure of the speed of data transfer in a communications system.

black-box testing. See: testing, functional.

block. (ISO) (1) A string of records, words, or characters that for technical or logical purposes are treated as a unity. (2) A collection of contiguous records that are recorded as a unit, and the units are separated by interblock gaps. (3) A group of bits or digits that are transmitted as a unit and that may be encoded for

error-control purposes. (4) In programming languages, a subdivision of a program that serves to group related statements, delimit routines, specify storage allocation, delineate the applicability of labels, or segment parts of the program for other purposes. In FORTRAN, a block may be a sequence of statements; in COBOL, it may be a physical record.

block check. (ISO) The part of the error control procedure that is used for determining that a block of data is structured according to given rules.

block diagram. (NIST) A diagram of a system, instrument or computer, in which the principal parts are represented by suitably annotated geometrical figures to show both the basic functions of the parts and the functional relationships between them.

block length. (1) (ISO) The number of records, words or characters in a block. (2) (ANSI) A measure of the size of a block, usually specified in units such as records, words, computer words, or characters.

block transfer. (ISO) The process, initiated by a single action, of transferring one or more blocks of data.

blocking factor. (ISO) The number of records in a block. The number is computed by dividing the size of the block by the size of each record contained therein. Syn: grouping factor.

blueprint. An exact or detailed plan or outline. Contrast with graph.

bomb. A trojan horse which attacks a computer system upon the occurrence of a specific logical event [logic bomb], the occurrence of a specific time-related logical event [time bomb], or is hidden in electronic mail or data and is triggered when read in a certain way [letter bomb]. See: trojan horse, virus, worm.

boolean. Pertaining to the principles of mathematical logic developed by George Boole, a nineteenth century mathematician. Boolean algebra is the study of operations carried out on variables that can have only one of two possible values; i.e., 1 (true) and 0 (false). As ADD, SUBTRACT, MULTIPLY, and DIVIDE are the primary operations of arithmetic, AND, OR, and NOT are the primary operations of Boolean Logic. In Pascal a boolean variable is a variable that can have one of two possible values, true or false.

boot. (1) (IEEE) To initialize a computer system by clearing memory and reloading the operating system. (2) To cause a computer system to reach a known beginning state. A boot program, in firmware, typically performs this function which includes loading basic instructions which tell the computer how to load programs into memory and how to begin executing those programs. A distinction can be made between a warm boot and a cold boot. A cold boot means starting the system from a powered-down state. A warm boot means restarting the computer while it is powered-up. Important differences between the two procedures are; 1) a power-up self-test, in which various portions of the hardware [such as memory] are tested for proper operation, is performed during a cold boot while a warm boot does not normally perform such self-tests, and 2) a warm boot does not clear all memory.

bootstrap. (IEEE) A short computer program that is permanently resident or easily loaded into a computer and whose execution brings a larger program, such an operating system or its loader, into memory.

boundary value. (1) (IEEE) A data value that corresponds to a minimum or maximum input, internal, or output value specified for a system or component. (2) A value which lies at, or just inside or just outside a specified range of valid input and output values.

boundary value analysis. (NBS) A selection technique in which test data are chosen to lie along "boundaries" of the input domain [or output range] classes, data structures, procedure parameters, etc. Choices often include maximum, minimum, and trivial values or parameters. This technique is often called stress testing. See: testing, boundary value.

box diagram. (IEEE) A control flow diagram consisting of a rectangle that is subdivided to show sequential steps, if-then-else conditions, repetition, and case conditions. Syn: Chapin chart, Nassi-Shneiderman chart, program structure diagram. See: block diagram, bubble chart, flowchart, graph, input-process-output chart, structure chart.

branch. An instruction which causes program execution to jump to a new point in the program sequence, rather than execute the next instruction. Syn: jump.

branch analysis. (Myers) A test case identification technique which produces enough test cases such that each decision has a true and a false outcome at least once. Contrast with path analysis.

branch coverage. (NBS) A test coverage criteria which requires that for each decision point each possible branch be executed at least once. Syn: decision coverage. Contrast with condition coverage, multiple condition coverage, path coverage, statement coverage. See: testing, branch.

bubble chart. (IEEE) A data flow, data structure, or other diagram in which entities are depicted with circles [bubbles] and relationships are represented by links drawn between the circles. See: block diagram, box diagram, flowchart, graph, input-process-output chart, structure chart.

buffer. A device or storage area [memory] used to store data temporarily to compensate for differences in rates of data flow, time of occurrence of events, or amounts of data that can be handled by the devices or processes involved in the transfer or use of the data.

bug. A fault in a program which causes the program to perform in an unintended or unanticipated manner. See: anomaly, defect, error, exception, fault.

bus. A common pathway along which data and control signals travel between different hardware devices within a computer system. (A) When bus architecture is used in a computer, the CPU, memory and peripheral equipment are interconnected through the bus. The bus is often divided into two channels, a control channel to select where data is located [address bus], and the other to transfer the data [data bus or I/O bus]. Common buses are: ISA [Industry Standard Architecture] the original IBM PC 16 bit AT bus; EISA [Extended Industry Standard Architecture] the IBM PC 32 bit XT bus [which provides for bus mastering]; MCA [MicroChannel Architecture] an IBM 32 bit bus; Multibus I & II [advanced, 16 & 32 bit respectively, bus architecture by Intel used in industrial, military and aerospace applications]; NuBus, a 32 bit bus architecture originally developed at MIT [A version is used in the Apple Macintosh computer]; STD bus, a bus architecture used in medical and industrial equipment due to its small size and rugged design [Originally 8 bits, with extensions to 16 and 32 bits]; TURBO Channel, a DEC 32 bit data bus with peak transfer rates of 100 MB/second; VMEbus [Versa Module Eurocard Bus], a 32 bit bus from Motorola, et.al., used in industrial, commercial and military applications worldwide [VME64 is an expanded version that provides 64 bit data transfer and addressing]. (B) When bus architecture is used in a network, all terminals and computers are connected to a common channel that is made of twisted wire pairs, coaxial cable, or optical fibers. Ethernet is a common LAN architecture using a bus topology.

byte. A sequence of adjacent bits, usually eight, operated on as a unit.

Source Documents

1. The New IEEE Standard Dictionary of Electrical and Electronics Terms, IEEE Std. 100-1992.
2. IEEE Standards Collection, Software Engineering, 1994 Edition, published by the Institute of Electrical and Electronic Engineers Inc.
3. National Bureau of Standards [NBS] Special Publication 500-75 Validation, Verification, and Testing of Computer Software, 1981.
4. Federal Information Processing Standards [FIPS] Publication 101, Guideline For Lifecycle Validation, Verification, and Testing of Computer Software, 1983.
5. Federal Information Processing Standards [FIPS] Publication 105, Guideline for Software Documentation Management, 1984.
6. American National Standard for Information Systems, Dictionary for Information Systems, American National Standards Institute, 1991.
7. FDA Technical Report, Software Development Activities, July 1987.
8. FDA Guide to Inspection of Computerized Systems in Drug Processing, 1983.
9. FDA Guideline on General Principles of Process Validation, May 1987.
10. Reviewer Guidance for Computer Controlled Medical Devices Undergoing 510(k) Review, Office of Device Evaluation, CDRH, FDA, August 1991.
11. HHS Publication FDA 90-4236, Preproduction Quality Assurance Planning.
12. MIL-STD-882C, Military Standard System Safety Program Requirements, 19JAN1993.
13. International Electrotechnical Commission, International Standard 1025, Fault Tree Analysis.
14. International Electrotechnical Commission, International Standard 812, Analysis Techniques for System Reliability - Procedure for Failure Mode and Effects Analysis [FMEA].
15. FDA recommendations, Application of the Medical Device GMP to Computerized Devices and Manufacturing Processes, May 1992.
16. Pressman, R., Software Engineering, A Practitioner's Approach, Third Edition, McGraw-Hill, Inc., 1992.
17. Myers, G., The Art of Software Testing, Wiley Interscience, 1979.
18. Beizer, B., Software Testing Techniques, Second Edition, Van Nostrand Reinhold, 1990.
19. Additional general references used in developing some definitions are:
20. Bohl, M., Information Processing, Fourth Edition, Science Research Associates, Inc., 1984.
21. Freedman, A., The Computer Glossary, Sixth Edition, American Management Association, 1993.
22. McGraw-Hill Electronics Dictionary, Fifth Edition, 1994, McGraw-Hill Inc.
23. McGraw-Hill Dictionary of Scientific & Technical Terms, Fifth Edition, 1994, McGraw-Hill Inc..
24. Webster's New Universal Unabridged Dictionary, Deluxe Second Edition, 1979.

The bulk of this information was obtained from FDA.gov.