Since PDP-11 Unix became operational in February, 1971, over 600 installations have been put into service. Most of them are engaged in applications such as computer science education, the preparation and formatting of documents and other textual material, the collection and processing of trouble data from various switching machines within the Bell System, and recording and checking telephone service orders. Our own installation is used mainly for research in operating systems, languages, computer networks, and other topics in computer science, and also for document preparation.
– Dennis Ritchie and Ken Thompson, The UNIX Time-Sharing System, The Bell System Technical Journal, July – August 1978.
In the early years of the ARPANET in the 1970’s, Tenex/TOPS20 was the most widely used operating system on the network. However, since the 1980’s, variants of Unix have become the most widely used operating systems on the Internet.
Unix caused the creation of the popular C programming language, and helped establish Internet networking in academic environments. After spawning a number of somewhat incompatible varieties over the years, the Unix operating system family now shows signs of standardization on a free open source software version called Linux. The following subsections provide more information.