Berkeley Software Distribution (BSD, sometimes called Berkeley Unix) is the Unix derivative distributed by the University of California, Berkeley, starting in the 1970s. The name is also used collectively for the modern descendants of these distributions.
BSD was widely identified with the versions of Unix available for workstation-class systems. This can be attributed to the ease with which it could be licensed and the familiarity it found among the founders of many technology companies during the 1980s. This familarity often came from using similar systems—notably DEC's Ultrix and Sun's SunOS—during their education. While BSD itself was largely superseded by the System V Release 4 and OSF/1 systems in the 1990s (both of which incorporated BSD code), in recent years modified open source versions of the codebase (mostly derived from 4.4BSD-Lite) have seen increasing use and development.