UNIX Time-Sharing System: UNIX on a Microprocessor

UNIX on a Microprocessor By H. LYCKLAMA (Manuscript received December 5, 1977) The decrease in the cost of computer hardware, brought about by the advent of the microprocessor and inexpensive solid-state memory, has brought the personal computer system to reality. Although the cost of software development shows no sign of decreasing soon, the fact that a large amount of software has been developed for the UNIX* time-sharing system in the high-level language, C, makes much of this software portable to another processor with rather limited hardware in comparison. A single-user UNIX system has been developed for the DEC LSI-11 microprocessor using 20K words of primary memory and floppy disks for secondary storage. By preserving the user-system interface of the UNIX system, it is possible to run almost all of the standard UNIX languages and subsystems on this single-user version of the UNIX system. A background process as well as foreground processes may be run. The file system is "UNIX-like, " but has provisions for dealing with contiguous files. Subroutines have been written to interface to the file system on the floppy disks. Asynchronous read/write routines are also available to the user. The LSI-UNIX system (LSX) has appeal as a stand-alone system for dedicated applications, as well as many potential uses as an intelligent terminal system. I. INTRODUCTION The UNIX operating system 1 has enjoyed wide acceptance as a powerful, general-purpose time-sharing system. It supports a large * UNIX is a t r a d e m a r k of Bell L a b o r a t o r i e s .