operating system [techspeak] n. (Often abbreviated `OS') The foundation software of a machine, of course; that which schedules tasks, allocates storage, and presents a default interface to the user between applications. The facilities an operating system provides and its general design philosophy exert an extremely strong influence on programming style and on the technical cultures that grow up around its host machines. Hacker folklore has been shaped primarily by the UNIX, ITS, TOPS-10, TOPS-20/TWENEX, WAITS, CP/M, MS-DOS, and Multics operating systems (most importantly by ITS and UNIX).