11.1. Introduction   

PostScript is a general-purpose programming language invented by John Warnock and Charles Geschke of Adobe Systems. Usually, though, it is used as a page-description language and has been designed specifically to communicate a description of a unit of output -- generally this is a page but can be a window or even a single graphic element from a computer-based composition system to a raster-output device.

A Page Description Language is an interpreted programming language which has very powerful graphics capabilities (Adobe 1990). Its main use is to describe the appearance of text, graphical shapes, and sampled images on a page. The graphics on the page is described by PostScript as a series of marks, either black or coloured, made on a white page. These marks can be overwritten to get the finished page on the output device.

The followings are some examples of the output device :-

The Page Description is a high-level description because it describes pages as a series of abstract graphic objects rather than as a series of detailed, device-dependent commands. ( Display PostScript Programming , David A. Holzgang, Addison- Wesley,1990)