What Is UNIX?
This section provides a quick introduction of UNIX operating system, a multi-tasking and multi-user operating system.
UNIX is a multi-tasking and multi-user operating system,
originally developed on a PDP-11/20 computer by a team of AT&T Bell Labs employees,
including Ken Thompson, Dennis Ritchie, Douglas McIlroy and Rudd Canaday in 1970.
UNIX was initially called "Unics", because it was based on a previous
experimental operating system called "Multics".
The first version of UNIX was written in PDP-11/20 assembly language and had
only two application programs: a text formatting program called "roff" and a text editor.
In 1973, UNIX was rewritten in the C programming language and became a portable operating system.
Since them, UNIX has been ported to a wide range of computers.
Main features of UNIX operating systems:
- UNIX Is Portable - UNIX kernel is written in C language instead of assembly language.
Porting UNIX from one hardware platform to another is easy, requiring only a small amount of
machine-dependent code to be replaced.
- UNIX Supports Virtual Memory - A portion of the hard disk space is used to extend the physical memory
using memory paging and swapping techniques.
- UNIX Supports Hierarchical File System - All storage devices and some other resources are organized
into a single directory tree structure.
- UNIX Systems Are Open - UNIX systems use industry-standard technologies, like
TCP/IP protocols for communication, X-Windows for user interface, and NFS for remote storage sharing.
- UNIX Supports Multi-Tasking - Each user can perform multiple tasks simultaneously, like
formatting a disk, running a large numeric simulation program, and editing a file at the same time.
- UNIX Supports Multi-User - Multiple users can log in to a single UNIX system
and performing their own tasks at the same time.
- UNIX Kernel Is Small - Command interpreter (shell) and user commands are provided as separate programs
to keep the kernel small and allow new command interpreters and commands to be added easily.
- UNIX Supports Command Pipelines - Multiple commands can be linked with data producer-consumer relations.
The picture below shows a PDP-11/20 computer, on which UNIX was originally developed
Table of Contents
About This Book
1957 - FORTRAN Language Developed by IBM
►1970 - UNIX Operating System Developed by AT&T Bell Labs
►What Is UNIX?
Command Interpreters and Command Pipelines
UNIX File System Hierarchy
1971 - FTP Protocol Created by Abhay Bhushan
1972 - C Language Developed by Dennis Ritchie
1976 - vi Text Editor Developed by Bill Joy
1977 - Apple II Designed by Steve Jobs and Steve Wozniak
1977 - The Bourne Shell Developed by Stephen Bourne
1978 - The C Shell Developed by Bill Joy
1978 - Bash (Bourne-Again Shell) Developed by Brian Fox
1979 - The Tcsh (TENEX C Shell) Developed by Ken Greer
1983 - "Sendmail" Mail Transfer Agent Developed by Eric Allman
1984 - Macintosh Developed by Apple Inc.
1984 - X Window System Developed a MIT Team
1991 - WWW (World Wide Web) Developed by Tim Berners-Lee
1991 - Gopher Protocol Created by a University of Minnesota Team
1995 - Java Language Developed by Sun Microsystems
1995 - PHP: Hypertext Preprocessor Created by Rasmus Lerdorf
2002 - .NET Framework Developed by Microsoft
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