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UNIX∗ is a general-purpose, multi-user, interactive operating system for the larger Digital Equipment Corporation PDP-11 and the Interdata 8/32 computers. It offers a number of features seldom found even in larger operating systems, including (i) A hierarchical file system incorporating demountable volumes, (ii) Compatible file, device, and inter-process I/O, (iii) The ability to initiate asynchronous processes, (iv) System command language selectable on a per-user basis, (v) Over 100 subsystems including a dozen languages, (vi) High degree of portability. This paper discusses the nature and implementation of the file system and of the user command interface.
Ritchie et al. (Sat,) studied this question.