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History of UNIX

The history of UNIX may surprise you since UNIX was not originally intended to be a commercial product.  The UNIX operating system was created by a group of computer scientists at AT&T's Bell Labs in the late 1960's after AT&T pulled out of a costly joint project with General Electric and MIT. UNIX was patterned after a multiuser operating system named MULTICS that was being developed as part of this joint project.

The original goal of the computer scientists was to develop a computing environment for computer science research and development, but instead the operating system took on a life of its own. After the group developed a text processing system for it, the Bell Labs Patent Office selected to use the UNIX operating system over other available commercial systems to fulfill their text processing needs.

[ If you are new to UNIX and need an overview of the key commands, check out our Basic UNIX Commands with Examples Tutorial ]

In the early 1970's, the high-level programming language C was developed so that it would be easier to port UNIX to other hardware platforms. The first version of UNIX written using C was developed in 1973. If it were not rewritten in C, it would have been difficult to run the operating system on machines other than the one it was originally developed on.

Before long, demand for the UNIX operating system outside of Bell Labs appeared. Since AT&T was a regulated monopoly at the time, and unable to sell it commercially because of this, they made it available on a limited basis to universities for educational purposes. The source (program) code was distributed with the operating system binaries (compiled program code) allowing recipients to make modifications and redistribute the operating system with their changes.

The most significant version of UNIX external to AT&T was developed at the University of California at Berkeley. Their modified distribution of the operating system was known as the Berkeley Software Distribution, or BSD for short. During the 1980's, BSD was used as the basis for a number of computer vendors' commercial version of UNIX. The computer vendors would take BSD and make changes to it to support their proprietary hardware platforms before selling both products to their customers.

After the breakup of the Bell System in 1984, AT&T was free to sell UNIX commercially. After using different operating system naming conventions internally, AT&T standardized on the name System V (read "system five"). The letter S is commonly used in place of "system," and new releases are suffixed with the letter R (for "release") and a release number.

All versions of the UNIX operating system can trace their roots to one of these two major strains (AT&T System V and BSD). Although these are two distinct branches, there are many overlapping pieces between the two. AT&T's System V Release 4 (SVR4) is often described as a merger of the System V and BSD lines.

If you enjoyed this brief introduction to the history of UNIX, you should watch Bell Labs' Ken Thompson and Dennis Ritchie (the creators of UNIX) talk about the birth of UNIX.