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Manuscript Documentation Unit
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The UNIX Time-Sharing System
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Dennis M. Ritchie
Ken Thompson

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Bell Laboratories
Murray Hill, N. J. 07974
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ABSTRACT
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UNIX is a general-purpose, multi-user, interactive
operating system for the Digital Equipment Corporation
PDP-11/40 and 11/45 computers.
It offers a number of features
seldom found even in larger operating
systems, including
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1.	A hierarchical file system incorporating
demountable volumes,
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2.	Compatible file, device, and inter-process I/O,
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3.	The ability to initiate asynchronous processes,
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4.	System command language selectable on a per-user basis,
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5.	Over 100 subsystems including a dozen languages.
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This paper discusses the nature and implementation
of the file system and of the user command interface.
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Key words and phrases: time-sharing, operating system,
file system, command language, PDP-11
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CR categories: 4.30, 4.32
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