Evolution of UNIX

UNIX resulted from research at AT&T Bell Laboratories in the 1970s. The name is a pun: At the time, an operating system named MULTICS was in use at AT&T, and the inventors of UNIX made up their name to contrast their system with MULTICS. The early versions of the operating system were developed at Bell Labs through the early 1970s. Later, the UNIX code was released to various universities for further development. The most significant developments were made by the Computer Science laboratories at the University of California at Berkeley. At the same time, the commercial versions of UNIX continued to develop at AT&T. In the 1980s, the two strands of UNIX development

1. AT&T and
2. Berkeley

continued in parallel.

The Berkeley strand got a major boost from Sun Microsystems, which used the Berkeley code as the basis for its SunOS operating system. The AT&T strand was picked up by companies such as IBM and HP. The picture was further complicated by a series of "alliance wars" in the late 1980s. In these battles, various groups of companies (for example, AT&T and Sun versus IBM, HP, DEC, and others) formed associations with the goal of producing so-called UNIX standards.
The AT&T and Sun alliance produced UNIX System V, while the IBM/HP/DEC alliance (the Open Software Foundation) produced a system called OSF/1, which exists mostly as a set of standards without an implementation.
The Berkeley Software Distribution was an operating system based on Unix which was used for research, developed and distributed by the Computer Systems Research Group at the University of California, Berkeley.