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Computerworld - Ever wonder about how Unix got started, not to mention all the twists and turns it took along the way? Here are some milestones of the operating system's four-decade-long history.

1956

A U.S. Department of Justice consent decree enjoins AT&T from "engaging ... in any business other than the furnishing of common carrier communication services."

1969

Mar. -- AT&T-owned Bell Laboratories withdraws from development of Multics (Multiplexed Information and Computing Service), a pioneering but overly complicated time-sharing system. Some important principles in Multics will be carried over into Unix.

Aug. -- Ken Thompson at Bell Labs writes the first version of an as-yet-unnamed operating system, in assembly language for a DEC PDP-7 minicomputer.

1970

Thompson's operating system is named Unics, for Uniplexed Information and Computing Service and a pun on "emasculated Multics." (The name is later mysteriously changed to Unix.)

1971

Feb. -- Unix moves to the new Digital Equipment Corp. PDP-11 minicomputer.

Nov. -- The first edition of the "Unix Programmer's Manual," written by Ken Thompson and Dennis Ritchie, is published.

1972

Dennis Ritchie develops the C programming language.

1973

Unix matures. The "pipe," a mechanism for sharing information between two programs, which will influence operating systems for decades, is added to Unix. Unix is rewritten from assembler into C.

1974

Jan. -- The University of California at Berkeley receives a copy of Unix.

July -- "The UNIX Timesharing System," by Dennis Ritchie and Ken Thompson, appears in the monthly journal of the Association for Computing Machinery (ACM). The authors call it "a general-purpose, multi-user, interactive operating system." The article produces the first big demand for Unix.

1976

Bell Labs programmer Mike Lesk develops UUCP (Unix-to-Unix Copy Program) for network transfer of files, e-mail and Usenet content.