What Is UNIX

Computer History Notes - Herong's Tutorial Notes

∟1970 - UNIX Operating System Developed by AT&T Bell Labs

∟What Is UNIX

This section provides a quick introduction of UNIX operating system, a multi-tasking and multi-user operating system.

What Is UNIX? - 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.