Abbreviated BSD Unix, and also known as Berkeley Unix. BSD Unix was developed at the University of California at Berkeley by researchers working in the Computer Systems Research Group (CSRG) from the 1970s to 1993 when the group finally closed its doors. BSD added many significant advanced features to Unix, including the C shell, the vi editor, TCP/IP networking additions, and virtual memory.
Because the CSRG was an academic group producing state-of-the-art software with no support obligations, BSD Unix was not supported in the normal way; bug fixes were sometimes made available, but it was a hit-and-miss process at best. For this reason, BSD Unix appealed to the research community and scientific users rather than to commercial users who tended to use Unix from AT&T.
BSD Unix 4.1 through to the last release, version 4.4, and the related commercial products, including those from Sun Microsystems, DEC, and Mt Xinu, are still popular and in use in universities and commercial institutions all over the world.