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 languageshis paper discusses the nature and implementation of the file system and of the user command interface. CACM July, 1974 Ritchie, D. M. Thompson, K. time-sharing, operating system, file system, command language, PDP-11 4.30 4.32 CA740702 JB January 17, 1978 1:40 PM 2299 4 2629 2501 4 2629 2629 4 2629 2629 4 2629 2868 4 2629 2915 4 2629 2928 4 2629 2951 4 2629 3114 4 2629 1502 5 2629 2380 5 2629 2626 5 2629 2629 5 2629 2629 5 2629 2629 5 2629 2786 5 2629 2840 5 2629 2919 5 2629 3017 5 2629 3110 5 2629 3174 5 2629 1471 6 2629 1746 6 2629 1746 6 2629 2194 6 2629 2358 6 2629 2377 6 2629 2436 6 2629 2536 6 2629 2593 6 2629 2625 6 2629 2626 6 2629 2629 6 2629 2629 6 2629 2629 6 2629 2629 6 2629 2629 6 2629 2629 6 2629 2629 6 2629 2858 6 2629