A functional unit, consisting of one or more computers and associated software, that (a) 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, (b) executes user-written or user-designated programs, and (c) performs user-designated data manipulation, including arithmetic and logic operations. Note: A computer system may be a stand-alone system or may consist of several interconnected systems. Synonyms ADP system, computing system.