This paper is a general overview of Unix operating system. It starts by presenting a brief history of the early development of Unix. It concentrates on main aspects of Unix operating system. Key concepts covered are interactive multi-user operating systems, the design objectives of Unix, file-store organization, text processing and programming, the role of C programming language with regard to portability and reliable system software, process control (signals and fork), error logging and recovery from system failures, modifiability and application.
Introduction of Unix
History of Unix
Interest in Unix
The Design Objectives of Unix, File-store Organization, Text Processing, and Programming. a.
Benefits of text files
The Role of the C Programming Language with Regard to Portability and Reliable System Software a.
Important features of C
Process Control: Signals and Fork
State of a process
Unix event handling sequence
Non-Unix event handling
Unix process control allows maximum flexibility
Error Logging and Recovery From System Failures
Unix recovery features
Advantages of recovery procedures
Modifiability and Application Programmer Interface (API). a.
The User's Perspective on Unix.
Strictly speaking, UNIX (in capitals) has been a registered trademark of UNIX System Laboratories (first owned by AT&T, then sold, in 1993, to Novell, Inc., then sold, in 1995, to SCO). The Open Group currently owns the Unix® Trademark. But the word "Unix" has also come to refer to a collection of very closely related operating systems (e.g. AT&T UNIX System V, BSD 4.3 Unix, Sun Microsystems' Solaris, Silicon Graphic's Irix, DEC/Compaq Tru-64 Unix, IBM's AIX, Hewlett-Packard's HP Unix, FreeBSD, NetBSD, SCO UNIX, Minix, Linux, and many others) which have found use on a wide variety of computing platforms, ranging from single-user personal computers to large network server multi-processor machines. Many of these variants are proprietary, but others have source code freely available. For the purposes of this paper, features of the Unix operating system will refer to those features that are common to almost all modern versions of Unix. It is helpful to give a brief outline of Unix history. UNIX was the creation of a group of researchers at Bell Laboratories (now Lucent Technologies) during the years 1969-1970. The desire was to produce a multi-user, multiprocessing operating system which would support research in computer science, but which had modest hardware requirements (unlike the earlier MULTICS project). Users were expected to connect to the system primarily via terminals over RS-232 serial communication lines. Additional improvements were made over the next few years. The kernel was rewritten in C in 1973. By 1974 Bell Laboratories Version 5 of the UNIX system was available for a nominal charge with full source code and quickly became a popular choice within academic computer science programs. Interest in UNIX spread overtime and spurred modifications that added functionality. One of the most significant milestones was the addition (in version BSD 4.2 in 1983) of TCP/IP networking via the software abstraction of a network socket. This made it possible for application programmers to write portable code that accessed a network. The mature version of this line of development was BSD 4.3 Unix. An attempt at consolidation and the adoption of a standard for Unix in the late 1980's produced two camps. One group was formed by the AT&T and Sun Microsystems agreement to merge features of both their systems as System V Release 4 (SVR4). This was marketed by Sun under the Solaris name. A second group (including Apollo Computer, Digital Equipment Corporation, Hewlett-Packard, and...
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