VAX-11 in the context of Berkeley Software Distribution

The Berkeley Software Distribution (BSD), also known as Berkeley Unix, is a discontinued Unix operating system developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berkeley. First released in 1978, it began as an improved derivative of AT&T's original Unix developed at Bell Labs, based on the source code. Over time, BSD evolved into a distinct operating system and played a significant role in computing and the development and dissemination of Unix-like systems.

BSD development was initially led by Bill Joy, who added virtual memory capability to Unix running on a VAX-11 computer. During the 1980s, BSD gained widespread adoption by workstation vendors in the form of proprietary Unix distributions—such as DEC with Ultrix and Sun Microsystems with SunOS—due to its permissive licensing and familiarity among engineers. BSD also became the most widely used Unix variant in academic institutions, where it was used for the study of operating systems. The BSD project received funding from DARPA until 1988, during which time BSD incorporated ARPANET support and later implemented the TCP/IP protocol suite, released as part of BSD NET/1 in 1988. By that time, the codebase had diverged significantly from the original AT&T Unix, with estimates suggesting that less than 5% of the code remained from AT&T. As a result, NET/1 was distributed without requiring an AT&T source license.