The UNIX Time-Sharing system 
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: (1) a hierarchical file system
incorporating demountable volumes; (2) compatible 
file, device, and inter-process I/O; (3) the ability to
initiate asynchronous processes; (4) system command 
language selectable on a per-user basis; and (5) over
100 subsystems including a dozen languages.This 
paper discusses the nature and implementation of the
file system and of the user command interface.
CACM July, 1974
Ritchie, D. M.
Thompson, K.
