Introducing UNIX and Linux

UNIX and Linux Design and Organisation

Overview
The Kernel and Shell
Files
      Networks
Technical Basics
      Bits, Bytes, Words and Characters
      ASCII Characters
How to get Linux
Summary

Files

On any machine there will be a large amount of information (or data) that must be stored, including programs, text, and the UNIX operating system itself. Each unit of data - which may be small (for instance, a few words of text) or large (like parts of the UNIX operating system itself) - is stored in a file. Files are simply sequences of bytes, stored somewhere on the system, perhaps on magnetic disks, CD-ROMs, or other storage devices. We are not interested in exactly where the file is stored, merely in its contents.

Each file has a name, which should consist of any letter, digit, or the characters . (period), - (minus sign), or _ (underscore). Other characters are also acceptable in a filename, but are discouraged in order to promote clarity. When we use files, we will normally refer to them by name. Some examples are:

test 11a My_File prog.c p-1