Operating System

Part II: Introduction to the Unix Operating System (The Evolution of Unix)

Introduction to the Unix Operating System

The Evolution of Unix Utilities and Shell Programming Systems Calls

The Evolution of Unix

First version was developed by Ken Thompson (1969) being part of the Research Group in Bell Laboratories

Developed in PDP-7 (which was idle at that time)

Soon joined by Dennis Ritchie (worked on MULTICS)

The Evolution of Unix

Thompson and Ritchie worked for so many years

Moved to PDP-11/20 for the second version Third version: used C (developed in Bell Labs

to support Unix) instead of assembly language

The Evolution of Unix

Multiprogramming and other enhancements added when the system moved to PDP-11/45 and PDP-11/70 (both hardware support multiprogramming)

Version 6 (1976): first version distributed outside of Bell Labs

The Evolution of Unix

Version 7 (1978)– Developed for the PDP-11/70 and Interdata 8/32– Considered “ancestor” of most modern Unix

systems– Also ported to VAX (appeared as 32V)

The Evolution of Unix

Because of clean design of early Unix Systems– Led to Unix-based work at other computer science

organizations Rand, University of Illinois, Harvard, Purdue University of California in Berkeley (most influential non-

Bell, non-AT&T)

The Evolution of Unix

1978– First Berkeley VAX Unix work (addition of virtual

memory, demand paging, & page replacement to 32V

– Bill Joy & Ozalp Babaoglu worked together to produce 3BSD (BSD - Berkeley Software Distributions) Unix

– First implementation of such functionality– Allowed large programs to run in Unix

The Evolution of Unix

Memory management work convinced DARPA (Dept. of Advanced Researched Projects Agency) to fund Berkeley

Develop standard system for government use

The Evolution of Unix

Project led to release of 4BSD– Supported by notable people from Unix &

networking community– One of the goals is provide networking for DARPA

Internet networking protocols (TCP/IP)

The Evolution of Unix

Release 4.2BSD– Possible to communicate among diverse network

facilities (LANs, WANs)– Adopted features from contemporary O/S (new user

interface -- C shell, new text editor -- vi, etc.)– Culmination of original Berkeley DARPA Unix

project

The Evolution of Unix

Release 4.2BSD (continued)– Reason for current popularity of mentioned

protocols– 1984 -> 60 connected networks– 1993 -> 8,000 connected networks, 10 million users

The Evolution of Unix

1993 -> 4.4 BSD– last Berkeley release– includes x.25 networking, new file system

organization, enhanced security, improved kernel structure

– Berkeley stopped its research after this release

The Evolution of Unix

Currently not limited to Bell, AT&T, Berkeley Moved to many different computers

– Sun Microsystems ported BSD to their workstations– DEC - Ultrix, OSF/1– Microsoft Xenix; Windows/NT heavily influenced by

Unix– Santa Cruz Operations - SCO Unix (PCs); Linux

(Red Hat, Caldera, etc.)

The Evolution of Unix

Many standardization projects for Unix environments

IEEE, ISO, ANSI, etc. 1989: ANSI standardized C programming

language (ANSI C)