Introduction

An introduction to UNIX was given in the chapter File Basics. In this section further information is supplied.

The first version of UNIX was written in assembler language by American Telephone and Telegraph (ATT) in 1969. By 1973 it had been rewritten in the high level language C making it portable to other machines, a prime reason for its popularity today. By 1979 Berkeley University had developed an extended version. Since then many versions have developed but fortunately only three command language forms (known as ``shells''), and extensions based upon them, are common:-

• The Bourne shell (sh) -- the original shell.

• The Bourne Again shell (bash) -- an extended version of the Bourne shell used by Linux..

• The C shell (csh) -- Standard for Berkeley Software Distribution (BSD).

• The T C shell (tcsh) -- an extended version of the C shell.

• The Korn shell (ksh) -- Standard for System V from ATT.

UNIX is the first choice for Reduced Instruction Set Computers (RISC). There are a number of full screen interfaces based on X Windows.In the department we use a Linux - a version of UNIX developed by the GNU Free Software Foundation.