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The Unix Operating System The first version of Unix was developed at Bell Laboratories to use an otherwise idle PDP-7. He was joined by Dennis Ritchie. Thompson, Ritchie, and others in the Research Group produced the early versions of Unix. Ritchie had previously worked on the Multics project, the Multics was a strong influence on the newer operating system. Even the name Unix is merely a pun on Multics. The basic organization of the file system, the idea if the command interpreter (the shell) as a user process. the use of a separate process for each command, the original line-editing characters (# to erase the last character and @ to erase the entire line), and numerous other features came directly from Multics. Ideas from various other operating systems, such as MIT's CTSS and the KDS-940 system, were also used. Ritchie and Thompson worked quietly on Unix for many years. Their work on the first version allowed them to move it to a PDP-11/20, for a second version. A third version resulted from rewriting most of the operating system in the system programming language C, instead of the previously used assembly language. C was developed at Bell Labs to support Unix. Unix was also moved to larger PDP-11 models, such as the 11/45 and 11/70. Multiprogramming and other enhancements were added when it was rewritten in C and moved to systems (like the 11/45) with hardware support for multiprogramming. As Unix developed, it became widely used within Bell Labs and gradually spread to a few universities. The first version widely available outside Bell Labs was Version 6, in 1976. (the version number for early Unix systems corresponds to the edition number of the Unix Programmer's Manual that was current when distribution was made; the code and the manuals were revised independently.) In 1978, Version 7 was distributed. This Unix system ran on the PDP-11/70 and the Interdata 8/32, and is the ancestor of most modern Unix systems. In particular, it was soon ported to other PDP-11 models and to the VAX computer line. The version available on the VAX was known as 32V. After the distribution of Version 7 in 1978, the Unix Support Group (USG) assumed administrative control and responsibility from the Resarch Group for distributions of Unix within AT&T, the parent organization for Bell Labs. Unix was becoming a product, not simply a reseach control. The Research Group has continued with their own version of Unix to support their own internal computing, however. The system currently (1985) in development by the research group at Bell labs is Version 8, which is available only within Bell Labs. The small size, modularity, and clean design of early Unix systems led to Unix-based work at numerous other computer science organizations such as Rand, BBN, the University of Illinois,Harvard,Purdue, and even DEC. The most influential of the non-Bell Labs and non-AT&T Unix development groups, however, has been the University of California at Berkeley. The current set of Unix systems is not limited to Version 8, system V(Release 2), and 4.2BSD, however. As Unix has grown in popularity, it has been moved to many different computers and computer systems. A wide variety of Unix, and Unix-like, operating systems have been created. DEC supports its Unix (called Ultrix) for VAXes; Microsoft rewrote Unix for the Intel 8088 and called it Xenix; IBM has Unix on its PC and its mainframes. Unix is also available from Amdahl, Sun, NBI, MassComp, Hewlett-Packard, Gould, Data General, Perkin-Elmer, and a host of other vendors, including, of course, AT&T. Most of these systems are based on Version 7, System III, 4.2BSD, or system V.

Reference: Operating System Concepts Second Edition Author: James L. Peterson Abraham Silberschatz pages: 507-510