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.

LAN. local area network.

LSI. large scale integration.

ladder logic. A graphical, problem oriented, programming language which replicates electronic switching blueprints.

language. See: programming language.

large scale integration. A classification of ICs [chips] based on their size as expressed by the number of circuits or logic gates they contain. An LSI IC contains 3,000 to 100,000 transistors.

latency. (ISO) The time interval between the instant at which a CPU's instruction control unit initiates a call for data and the instant at which the actual transfer of the data starts. Syn: waiting time.

latent defect. See: bug, fault.

life cycle. See: software life cycle.

life cycle methodology. The use of any one of several structured methods to plan, design, implement, test. and operate a system from its conception to the termination of its use. See: waterfall model.

linkage editor. (IEEE) A computer program that creates a single load module from two or more independently translated object modules or load modules by resolving cross references among the modules and, possibly, by relocating elements. May be part of a loader. Syn: link editor, linker.

loader. A program which copies other [object] programs from auxiliary [external] memory to main [internal] memory prior to its execution.

local area network. A communications network that serves users within a confined geographical area. It is made up of servers, workstations, a network operating system, and a communications link. Contrast with MAN, WAN.

logic analysis. (IEEE) Evaluates the safety-critical equations, algorithms, and control logic of the software design. (2) Evaluates the sequence of operations represented by the coded program and detects programming errors that might create hazards.

longitudinal redundancy check. (IEEE) A system of error control based on the formation of a block check following preset rules.

low-level language. See: assembly language. The advantage of assembly language is that it provides bit-level control of the processor allowing tuning of the program for optimal speed and performance. For time critical operations, assembly language may be necessary in order to generate code which executes fast enough for the required operations. The disadvantage of assembly language is the high-level of complexity and detail required in the programming. This makes the source code harder to understand, thus increasing the chance of introducing errors during program development and maintenance.

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.