Unix is an Operating System (OS). There are many popular Unix flavors such as BSD Unix, Coherent Unix, Data General DGUX, Digital UNIX (formerly OSF/1), Linux, Hewlett Packard HP-UX, IBM AIX, QNX, SGI IRIX, SCO Unix, Sun Microsystems Solaris, etc. Most Unix flavors can be identified with their use of the letter 'X' in the Operating System name. Unix has been ported to almost every computing hardware platform.

Unix was invented by Ken Thompson of AT&T's Bell Laboratories in 1969, as a Digital PDP minicomputer alternative to the General Electric multi-user mainframe running MIT's Multics (Multiplexed Information and Computing Service). Originally spelled Unics, Unix is an acronym for UNiplexed Information and Computing System. Thus, Unix was originally a pun on its predecessor’s (Multics) name. The word 'Unix' has become an anacronym and is no longer an acronym.