Bell Labs found they needed an operating system for their computer center which at the time was running various batch jobs. The BESYS operating system was created at Bell Labs to deal with these needs.

Bell Labs was adopting third generation computer equipment and decided to join forces with General Electric and MIT to create Multics (Multiplexed Information and Computing Service).

By April 1969, AT&T made a decision to withdraw Multics and go with GECOS. When Multics was withdrawn Ken Thompson and Dennis Ritchie needed to rewrite an operating system in order to play space travel on another smaller machine (a DEC PDP-7 [Programmed Data Processor 4K memory for user programs). The result was a system which a punning colleague called UNICS (UNiplexed Information and Computing Service)--an 'emasculated Multics'.

Summer 1969 UNIX was developed. 

First edition of UNIX released 11/03/1971. The first edition of the "UNIX PROGRAMMER'S MANUAL [by] K. Thompson [and] D. M. Ritchie" is also dated "November 3, 1971". It includes over 60 commands like: b (compile B program); boot (reboot system); cat(concatenate files); chdir (change working directory); chmod (change access mode); chown (change owner); cp (copy file); ls (list directory contents); mv (move or rename file); roff (run off text); wc (get word count); who (who is one the system). The main thing missing was pipes.

Second edition of UNIX released 12/06/1972

Ritchie rewrote B and called the new language C.

UNIX had been installed on 16 sites (all within AT&T/Western Electric); it was publically unveiled at a conference in October.

Third edition of UNIX released 02/xx/1973

Forth edition of UNIX released 11/xx/1973

Fifth edition of UNIX released 06/xx/1974

Thompson went to UC Berkeley to teach for a year, Bill Joy arrived as a new graduate student. Frustrated with ed, Joy developed a more featured editor em.

Sixth edition of UNIX released 05/xx/1975

1UNIX released late 1977

2UNIX released mid 1978

Seventh edition of UNIXreleased 01/xx/1979

3UNIX released late 1979

4.0 BSD released 10/xx/1980

SGI introduces IRIX

SCO delivers its first packaged UNIX system called SCO XENIX System V for Intel 8086 and 8088 processor-based PCs.

Ultrix 1.0 was released.

Eighth edition of UNIX released 02/xx/1985

The GNU manifesto is published in the March 1985 issue of Dr. Dobb's Journal. The GNU project starts a year and a half later.

Ninth edition of UNIX released 09/xx/1986

HP-UX 2.0 released.

HP-UX 3.0 released.

SCO ships SCO UNIX System V/386, the first volume commercial product licensed by AT&T to use the UNIX System trademark.

HP-UX7.0 released.

Tenth edition of UNIX released 10/xx/1989

Sun unveils Solaris 2 operating environment, specially tuned for symetric multiprocessing.

Linux is introduced by Linus Torvald, a student in Finland. Who post to the comp.os.minix newsgroup with the words:

Hello everybody out there using minix -

I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu) for 386(486) AT clones.

HP-UX 8.0 released.

HP-UX 9.0 released.

FreeBSD 1.0 released December of 1993

Red Hat Linux is introduced.

Caldera, Inc was founded in 1994 by Ransom Love and Bryan Sparks.

NetBSD 1.0 released 10/26/1994

FreeBSD 2.0 released 01/xx/1995

SCO acquires UNIX Systems source technology business from NovellCorporation (which had acquired it from AT&T's UNIX System Laboratories). SCO also acquires UnixWare 2 operating system from Novell.

HP-UX 10.0 released.

4.4 BSD Lite Release 2 the true final distribution from the CSRG 06/xx/1995

HP-UX 11.0 released.

Caldera ships OpenLinux Standard 1.1 May 5, 1997, the second offering in Caldera's OpenLinux product line 

SCO delivers UnixWare 7 operating system.

Sun Solaris 7 operating system released.

FreeBSD 3.0 released 10/16/1998

FreeBSD 4.0 released 03/13/2000

Caldera Systems Inc. announces that Caldera Systems has entered into agreement to acquire the SCO Server Software Division and the Professional Services Division