In 1965, Bell Telephone Laboratories (Bell Labs, a division of AT&T )Bell Labs was working with General Electric and Project MAC of MIT to write an operating system called Multics. To make a long story slightly shorter, Bell Labs decided the project wasn't going anywhere and broke out of the group. This, however, left Bell Labs without a good operating system.
Ken Thompson and Dennis Ritchie decided to sketch out an operating system that would meet Bell Labs' needs. When Thompson needed a development environment (1970) to run on a PDP-7, he implemented their ideas. As a pun on Multics, Brian Kernighan gave the system the name UNIX.
Later, Dennis Ritchie invented the ``C'' programming language. In 1973, UNIX was rewritten in C, which would have a major impact later on. In 1977, UNIX was moved to a new machine, away from the PDP machines it had run on previously. This was aided by the fact UNIX was written in C.
Unix was slow to catch on outside of academic institutions but soon was popular with businesses as well. The Unix of today is different from the Unix of 1970. It has two major versions: System V, from Unix System Laboratories (USL) , a subsiderary of Novell, and BSD, Berkeley Software Distribution. The USL version is now up to its forth release, or SVR4, while BSD's latest version is 4.4. However, there are many different versions of Unix besides these two. Most versions of Unix are developed by software companies and derive from one of the two groupings. Recently, the versions of Unix that are actually used incorporate features from both of them.
USL is a company that was `spun off' from AT&T , and has taken over the maintenance of UNIX since it stopped being a research item. Unix now is much more commericial than it once was, and the licenses cost much more.
Please note the difference between Unix and UNIX. When I say ``Unix'' I am talking about Unix versions in generally, whether or not USL is involved in them. ``UNIX'' is the current version of Unix from USL. The distinction is because UNIX is a trademark of X/Open. (Officially, anybody can create a UNIX operating system, as long as it passes tests from X/Open. Since the tests haven't been created yet and are likely to cost money, Linux is currently not a ``real'' UNIX.)
Current versions of UNIX for Intel PCs cost between $500 and $2000.