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.

CAD. computer aided design.

CAM. computer aided manufacturing.

CASE. computer aided software engineering.

CCITT. Consultive Committee for International Telephony and Telegraphy.

CD-ROM. compact disc - read only memory.

CISC. complex instruction set computer.

CMOS. complementary metal-oxide semiconductor.

CO-AX. coaxial cable.

COTS. configurable, off-the-shelf software.

CP/M. Control Program for Microcomputers.

CPU. central processing unit.

CRC. cyclic redundancy [check] code.

CRT. cathode ray tube.

C. A general purpose high-level programming language. Created for use in the development of computer operating systems software. It strives to combine the power of assembly language with the ease of a high-level language.

C++. An object-oriented high-level programming language.

calibration. Ensuring continuous adequate performance of sensing, measurement, and actuating equipment with regard to specified accuracy and precision requirements. See: accuracy, bias, precision.

call graph. (IEEE) A diagram that identifies the modules in a system or computer program and shows which modules call one another. Note: The result is not necessarily the same as that shown in a structure chart. Syn: call tree, tier chart. Contrast with structure chart. See: control flow diagram, data flow diagram, data structure diagram, state diagram.

cathode ray tube. An output device. Syn: display, monitor, screen.

cause effect graph. (Myers) A Boolean graph linking causes and effects. The graph is actually a digital-logic circuit (a combinatorial logic network) using a simpler notation than standard electronics notation.

cause effect graphing. (1) (NBS) Test data selection technique. The input and output domains are partitioned into classes and analysis is performed to determine which input classes cause which effect. A minimal set of inputs is chosen which will cover the entire effect set. (2) (Myers) A systematic method of generating test cases representing combinations of conditions. See: testing, functional.

central processing unit. The unit of a computer that includes the circuits controlling the interpretation of program instructions and their execution. The CPU controls the entire computer. It receives and sends data through input-output channels, retrieves data and programs from memory, and conducts mathematical and logical functions of a program.

certification. (ANSI) In computer systems, a technical evaluation, made as part of and in support of the accreditation process, that establishes the extent to which a particular computer system or network design and implementation meet a prespecified set of requirements.

change control. The processes, authorities for, and procedures to be used for all changes that are made to the computerized system and/or the system's data. Change control is a vital subset of the Quality Assurance [QA] program within an establishment and should be clearly described in the establishment's SOPs. See: configuration control.

change tracker. A software tool which documents all changes made to a program.

check summation. A technique for error detection to ensure that data or program files have been accurately copied or transferred. Basically, a redundant check in which groups of digits; e.g., a file, are summed, usually without regard to overflow, and that sum checked against a previously computed sum to verify operation accuracy. Contrast with cyclic redundancy check [CRC], parity check. See: checksum.

checksum. (IEEE) A sum obtained by adding the digits in a numeral, or group of numerals [a file], usually without regard to meaning, position, or significance. See: check summation.

chip. See: integrated circuit.

client-server. A term used in a broad sense to describe the relationship between the receiver and the provider of a service. In the world of microcomputers, the term client-server describes a networked system where front-end applications, as the client, make service requests upon another networked system. Client-server relationships are defined primarily by software. In a local area network [LAN], the workstation is the client and the file server is the server. However, client-server systems are inherently more complex than file server systems. Two disparate programs must work in tandem, and there are many more decisions to make about separating data and processing between the client workstations and the database server. The database server encapsulates database files and indexes, restricts access, enforces security, and provides applications with a consistent interface to data via a data dictionary.

clock. (ISO) A device that generates periodic, accurately spaced signals used for such purposes as timing, regulation of the operations of a processor, or generation of interrupts.

coaxial cable. High-capacity cable used in communications and video transmissions. Provides a much higher bandwidth than twisted wire pair.

COBOL. Acronym for COmmon Business Oriented Language. A high-level programming language intended for use in the solution of problems in business data processing.

code. See: program, source code.

code audit. (IEEE) An independent review of source code by a person, team, or tool to verify compliance with software design documentation and programming standards. Correctness and efficiency may also be evaluated. Contrast with code inspection, code review, code walkthrough. See: static analysis.

code auditor. A software tool which examines source code for adherence to coding and documentation conventions.

code inspection. (Myers/NBS) A manual [formal] testing [error detection] technique where the programmer reads source code, statement by statement, to a group who ask questions analyzing the program logic, analyzing the code with respect to a checklist of historically common programming errors, and analyzing its compliance with coding standards. Contrast with code audit, code review, code walkthrough. This technique can also be applied to other software and configuration items. Syn: Fagan Inspection. See: static analysis.

code review. (IEEE) A meeting at which software code is presented to project personnel, managers, users, customers, or other interested parties for comment or approval. Contrast with code audit, code inspection, code walkthrough. See: static analysis.

code walkthrough. (Myers/NBS) A manual testing [error detection] technique where program [source code] logic [structure] is traced manually [mentally] by a group with a small set of test cases, while the state of program variables is manually monitored, to analyze the programmer's logic and assumptions. Contrast with code audit, code inspection, code review. See: static analysis.

coding. (IEEE) (1) In software engineering, the process of expressing a computer program in a programming language. (2) The transforming of logic and data from design specifications (design descriptions) into a programming language. See: implementation.

coding standards. Written procedures describing coding [programming] style conventions specifying rules governing the use of individual constructs provided by the programming language, and naming, formatting, and documentation requirements which prevent programming errors, control complexity and promote understandability of the source code. Syn: development standards, programming standards.

comment. (1) (ISO) In programming languages, a language construct that allows [explanatory] text to be inserted into a program and that does not have any effect on the execution of the program. (2) (IEEE) Information embedded within a computer program, job control statements, or a set of data, that provides clarification to human readers but does not affect machine interpretation.

compact disc - read only memory. A compact disk used for the permanent storage of text, graphic or sound information. Digital data is represented very compactly by tiny holes that can be read by lasers attached to high resolution sensors. Capable of storing up to 680 MB of data, equivalent to 250,000 pages of text, or 20,000 medium resolution images. This storage media is often used for archival purposes. Syn: optical disk, write-once read-many times disk.

comparator. (IEEE) A software tool that compares two computer programs, files, or sets of data to identify commonalities or differences. Typical objects of comparison are similar versions of source code, object code, data base files, or test results.

compatibility. (ANSI) The capability of a functional unit to meet the requirements of a specified interface.

compilation. (NIST) Translating a program expressed in a problem-oriented language or a procedure oriented language into object code. Contrast with assembling, interpret. See: compiler.

compile. See: compilation.

compiler. (1) (IEEE) A computer program that translates programs expressed in a high-level language into their machine language equivalents. (2) The compiler takes the finished source code listing as input and outputs the machine code instructions that the computer must have to execute the program. See: assembler, interpreter, cross-assembler, cross-compiler.

compiling. See: compilation.

complementary metal-oxide semiconductor. A type of integrated circuit widely used for processors and memories. It is a combination of transistors on a single chip connected to complementary digital circuits.

completeness. (NIST) The property that all necessary parts of the entity are included. Completeness of a product is often used to express the fact that all requirements have been met by the product. See: traceability analysis.

complex instruction set computer. Traditional computer architecture that operates with large sets of possible instructions. Most computers are in this category, including the IBM compatible microcomputers. As computing technology evolved, instruction sets expanded to include newer instructions which are complex in nature and require several to many execution cycles and, therefore, more time to complete. Computers which operate with system software based on these instruction sets have been referred to as complex instruction set computers. Contrast with reduced instruction set computer [RISC].

complexity. (IEEE) (1) The degree to which a system or component has a design or implementation that is difficult to understand and verify. (2) Pertaining to any of a set of structure based metrics that measure the attribute in (1).

component. See: unit.

computer. (IEEE) (1) A functional unit that can perform substantial computations, including numerous arithmetic operations, or logic operations, without human intervention during a run. (2) A functional programmable unit that consists of one or more associated processing units and peripheral equipment, that is controlled by internally stored programs, and that can perform substantial computations, including numerous arithmetic operations, or logic operations, without human intervention.

computer aided design. The use of computers to design products. CAD systems are high speed workstations or personal computers using CAD software and input devices such as graphic tablets and scanners to model and simulate the use of proposed products. CAD output is a printed design or electronic output to CAM systems. CAD software is available for generic design or specialized uses such as architectural, electrical, and mechanical design. CAD software may also be highly specialized for creating products such as printed circuits and integrated circuits.

computer aided manufacturing. The automation of manufacturing systems and techniques, including the use of computers to communicate work instructions to automate machinery for the handling of the processing [numerical control, process control, robotics, material requirements planning] needed to produce a workpiece.

computer aided software engineering. An automated system for the support of software development including an integrated tool set, i.e., programs, which facilitate the accomplishment of software engineering methods and tasks such as project planning and estimation, system and software requirements analysis, design of data structure, program architecture and algorithm procedure, coding, testing and maintenance.

computer instruction set. (ANSI) A complete set of the operators of the instructions of a computer together with a description of the types of meanings that can be attributed to their operands. Syn: machine instruction set.

computer language. (IEEE) A language designed to enable humans to communicate with computers. See: programming language.

computer program. See: program.

computer science. (ISO) The branch of science and technology that is concerned with methods and techniques relating to data processing performed by automatic means.

computer system. (ANSI) a functional unit, consisting of one or more computers and associated peripheral input and output devices, and associated software, that uses common storage for all or part of a program and also for all or part of the data necessary for the execution of the program; executes user-written or user-designated programs; performs user-designated data manipulation, including arithmetic operations and logic operations; and that can execute programs that modify themselves during their execution. A computer system may be a stand-alone unit or may consist of several interconnected units. See: computer, computerized system.

computer system audit. (ISO) An examination of the procedures used in a computer system to evaluate their effectiveness and correctness and to recommend improvements. See: software audit.

computer system security. (IEEE) The protection of computer hardware and software from accidental or malicious access, use, modification, destruction, or disclosure. Security also pertains to personnel, data, communications, and the physical protection of computer installations. See: bomb, trojan horse, virus, worm.

computer word. A sequence of bits or characters that is stored, addressed, transmitted, and operated on as a unit within a given computer. Typically one to four bytes long, depending on the make of computer.

computerized system. Includes hardware, software, peripheral devices, personnel, and documentation; e.g., manuals and Standard Operating Procedures. See: computer, computer system.

concept phase. (IEEE) The initial phase of a software development project, in which user needs are described and evaluated through documentation; e.g., statement of needs, advance planning report, project initiation memo. feasibility studies, system definition documentation, regulations, procedures, or policies relevant to the project.

condition coverage. (Myers) A test coverage criteria requiring enough test cases such that each condition in a decision takes on all possible outcomes at least once, and each point of entry to a program or subroutine is invoked at least once. Contrast with branch coverage, decision coverage, multiple condition coverage, path coverage, statement coverage.

configurable, off-the-shelf software. Application software, sometimes general purpose, written for a variety of industries or users in a manner that permits users to modify the program to meet their individual needs.

configuration. (IEEE) (1) The arrangement of a computer system or component as defined by the number, nature, and interconnections of its constituent parts. (2) In configuration management, the functional and physical characteristics of hardware or software as set forth in technical documentation or achieved in a product.

configuration audit. See: functional configuration audit, physical configuration audit.

configuration control. (IEEE) An element of configuration management, consisting of the evaluation, coordination, approval or disapproval, and implementation of changes to configuration items after formal establishment of their configuration identification. See: change control.

configuration identification. (IEEE) An element of configuration management, consisting of selecting the configuration items for a system and recording their functional and physical characteristics in technical documentation.

configuration item. (IEEE) An aggregation of hardware, software, or both that is designated for configuration management and treated as a single entity in the configuration management process. See: software element.

configuration management. (IEEE) A discipline applying technical and administrative direction and surveillance to identify and document the functional and physical characteristics of a configuration item, control changes to those characteristics, record and report change processing and implementation status, and verifying compliance with specified requirements. See: configuration control, change control, software engineering.

consistency. (IEEE) The degree of uniformity, standardization, and freedom from contradiction among the documents or parts of a system or component. See: traceability.

consistency checker. A software tool used to test requirements in design specifications for both consistency and completeness.

constant. A value that does not change during processing. Contrast with variable.

constraint analysis. (IEEE) (1) Evaluation of the safety of restrictions imposed on the selected design by the requirements and by real world restrictions. The impacts of the environment on this analysis can include such items as the location and relation of clocks to circuit cards, the timing of a bus latch when using the longest safety-related timing to fetch data from the most remote circuit card, interrupts going unsatisfied due to a data flood at an input, and human reaction time. (2) verification that the program operates within the constraints imposed upon it by requirements, the design, and the target computer. Constraint analysis is designed to identify these limitations to ensure that the program operates within them, and to ensure that all interfaces have been considered for out-of-sequence and erroneous inputs.

Consultive Committee for International Telephony and Telegraphy. See: International Telecommunications Union - Telecommunications Standards Section.

control bus. (ANSI) A bus carrying the signals that regulate system operations. See: bus.

control flow. (ISO) In programming languages, an abstraction of all possible paths that an execution sequence may take through a program.

control flow analysis. (IEEE) A software V&V task to ensure that the proposed control flow is free of problems, such as design or code elements that are unreachable or incorrect.

control flow diagram. (IEEE) A diagram that depicts the set of all possible sequences in which operations may be performed during the execution of a system or program. Types include box diagram, flowchart, input-process-output chart, state diagram. Contrast with data flow diagram. See: call graph, structure chart.

Control Program for Microcomputers. An operating system. A registered trademark of Digital Research.

controller. Hardware that controls peripheral devices such as a disk or display screen. It performs the physical data transfers between main memory and the peripheral device.

conversational. (IEEE) Pertaining to a interactive system or mode of operation in which the interaction between the user and the system resembles a human dialog. Contrast with batch. See: interactive, on-line, real time.

coroutine. (IEEE) A routine that begins execution at the point at which operation was last suspended, and that is not required to return control to the program or subprogram that called it. Contrast with subroutine.

corrective maintenance. (IEEE) Maintenance performed to correct faults in hardware or software. Contrast with adaptive maintenance, perfective maintenance.

correctness. (IEEE) The degree to which software is free from faults in its specification, design and coding. The degree to which software, documentation and other items meet specified requirements. The degree to which software, documentation and other items meet user needs and expectations, whether specified or not.

coverage analysis. (NIST) Determining and assessing measures associated with the invocation of program structural elements to determine the adequacy of a test run. Coverage analysis is useful when attempting to execute each statement, branch, path, or iterative structure in a program. Tools that capture this data and provide reports summarizing relevant information have this feature. See: testing, branch; testing, path; testing, statement.

crash. (IEEE) The sudden and complete failure of a computer system or component.

critical control point. (QA) A function or an area in a manufacturing process or procedure, the failure of which, or loss of control over, may have an adverse affect on the quality of the finished product and may result in a unacceptable health risk.

critical design review. (IEEE) A review conducted to verify that the detailed design of one or more configuration items satisfy specified requirements; to establish the compatibility among the configuration items and other items of equipment, facilities, software, and personnel; to assess risk areas for each configuration item; and, as applicable, to assess the results of producibility analyses, review preliminary hardware product specifications, evaluate preliminary test planning, and evaluate the adequacy of preliminary operation and support documents. See: preliminary design review, system design review.

criticality. (IEEE) The degree of impact that a requirement, module, error, fault, failure, or other item has on the development or operation of a system. Syn: severity.

criticality analysis. (IEEE) Analysis which identifies all software requirements that have safety implications, and assigns a criticality level to each safety-critical requirement based upon the estimated risk.

cross-assembler. (IEEE) An assembler that executes on one computer but generates object code for a different computer.

cross-compiler. (IEEE) A compiler that executes on one computer but generates assembly code or object code for a different computer.

cursor. (ANSI) A movable, visible mark used to indicate a position of interest on a display surface.

cyclic redundancy [check] code. A technique for error detection in data communications used to assure a program or data file has been accurately transferred. The CRC is the result of a calculation on the set of transmitted bits by the transmitter which is appended to the data. At the receiver the calculation is repeated and the results compared to the encoded value. The calculations are chosen to optimize error detection. Contrast with check summation, parity check.

cyclomatic complexity. (1) (McCabe) The number of independent paths through a program. (2) (NBS) The cyclomatic complexity of a program is equivalent to the number of decision statements plus 1.

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.