In 1969, Ken Thompson, one of the researchers at Bell Laboratories of AT&T, assisted by Dennis Ritchie developed a new operating system on the PDP-7, using the structure of a file system that had been designed Thompson, Ritchie and Rudd Canaday.
They created a multitasking operating system that could support two simultaneous users and included a file system, a shell and some utilities for the PDP-7. This new operating system in 1970 called Unics subsequently renamed UNIX and is the name that remains today.
In 1973, Ritchie and Thompson rewrite the core system using the C language that was easier maintenance and portability to other machines. The growing popularity of UNIX because of its innovations as it was written compactly on a high-level language code that allowed be modified according to individual preferences. AT&T offered the UNIX system commercially because at that time was not in the business of information technology. However, it allowed the availability of UNIX universities, commercial firms and government at a nominal cost. The number of machines running UNIX in 1977 totaled 600, mainly at Bell Labs and universities. It appears the seventh version of the system in 1979 and is the direct ancestor of the current system. The system III, based on the seventh version, became in 1982 the first commercial version of UNIX AT&T system. System III, the different editions of research and experimental versions were distributed to colleges and other research laboratories. Often impossible for computer whether a particular feature was part of the main structure of this system or was just part of one version. To eliminate this confusion about the varieties of UNIX system, AT&T introduced in 1983 System V version 1. With this AT&T version is first committed to maintaining compatibility with future versions.
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