What are the different versions of UNIX? The first efforts at developing a multi-user, multi-tasking operating system were begun in the 1960s in a development project called MULTICS. While working for Bell Telephone Laboratories in 1969 and 1970, Ken Thompson and Dennis Ritchie began to develop their own single-user, multi-tasking small operating system and chose the name UNIX.
Their initial goal was simply to operate their DEC PDP machines more effectively. In 1971, UNIX became multi-user and multi-tasking, but it was still being developed by a small group of programmers who were trying to take advantage of the machines they had at hand. In 1973, Dennis Ritchie rewrote the UNIX operating system in C, a language he had developed. In 1975, the portability of the C programming language was used to port” UNIX to a wide variety of hardware platforms. For legal reasons, Bell Labs was not able to market UNIX in the 1970s, though they did share this operating system with many universities, most notably UC-Berkeley. This led to some of the variations in UNIX which we see today.
After the divestiture of the Bell System, its parent company AT&T became much more interested in marketing a commercial version of UNIX. Today, many companies have licensed their own versions, including AT&T’s System V, SCO’s Xenix, IBM’s AIX, Berkeley’s UNIX (called BSD” for “Berkeley System Development”), and versions of Berkeley UNIX such as Sun Microsystems’ SunOS, DEC’s Ultrix, and Carnegie Mellon University’s Mach (used on the NEXT).
