A Breif History of Unix

A Brief History of Unix

HISTORY OF UNIX AND CAUSES FOR ITS POPULARITY

Most discussions of UNIX begin with the history of UNIX without explaining why the history of UNIX is important to understanding UNIX. The remainder of this document will describe some strengths and weaknesses of UNIX and attempt to explain why UNIX is becoming popular. All of UNIX's strengths and weaknesses can be directly related to the history of its development, hence a discussion of history is very useful.

UNIX was originally developed at Bell Laboratories as a private research project by a small group of people starting in 1969. This group had experience with a number of different operating systems research efforts in the 1970's. The goals of the group were to design an operating system to satisfy the following objectives:

Simple and elegant

Written in a high level language rather than assembly language

Allow re-use of code

Typical vendor operating systems of the time were extremely large and all written in assembly language.

UNIX Source Code

UNIX in HU 2006

Tree UNIX?

UNIX had a relatively small amount of code written in assembly language (this is called the kernel) and the remaining code for the operating system was written in a high level language called C.

The group worked primarily in the high level language in developing the operating system. As this development continued, small changes were necessary in the kernel and the language to allow the operating system to be completed. Through this evolution the kernel and associated software were extended until a complete operating system was written on top of the kernel in the language C.

UNIX APPLICATION PROGRAMMING INTERFACE

Many proprietary operating systems have a simplified view of application behavior. The typical application reads some data from disk, tape or a terminal and does some processing. Output is produced onto disk, tape,