Info Tech Guide

Postscript is a programming language that describes the appearance of a printed page. It was developed by Adobe in 1985 and has become an industry standard for printing and imaging. All major printer manufacturers make printers that contain or can be loaded with Postscript software, which also runs on all major operating system platforms. A Postscript file can be identified by its ".ps" suffix.

Before PostScript was introduced, publishing systems relied on proprietary typesetting systems, which often caused incompatibilities between computers and printing systems. In fact, before the days of PostScript, pages that incorporated text, images, and line art had to be manually assembled on a paste-up board and then photographed. The resulting picture was sent to a printing plate, which was used to make copies of the document pretty archaic compared to the simple printing options available today.

Postscript describes the text and graphic elements on a page to a black-and-white or color printer or other output device, such as a slide recorder, imagesetter, or screen display.

Postscript handles industry-standard, scalable typeface in the Type 1 and TrueType formats. Users can convert Postscript files to the Adobe Portable Document Format ( PDF ) using the Adobe Acrobat product. PDF files present the document's printed appearance on a display screen. (You'll find many PDF documents for downloading and viewing from Web sites; you'll need to download the Acrobat viewer as a plug-in .) Adobe sells a more sophisticated product called Supra for print-on-demand and production printing.

Adobe PostScript makes it possible to produce high quality page content that can include text, images, and line art in a standard format compatible with multiple devices. In fact, the evolution of PostScript led to the development of Adobe Acrobat, which creates PDF documents.

PostScript is an object-oriented language, meaning that it treats images, including fonts, as collections of geometrical objects rather than as bit maps. PostScript fonts are called outline fonts because the outline of each character is defined. They are also called scalable fonts because their size can be changed with PostScript commands. Given a single typeface definition, a PostScript printer can thus produce a multitude of fonts. In contrast, many non-PostScript printers represent fonts with bit maps. To print a bit-mapped typeface with different sizes, these printers require a complete set of bit maps for each size.

The principal advantage of object-oriented (vector) graphics over bit-mapped graphics is that object-oriented images take advantage of high-resolution output devices whereas bit-mapped images do not. A PostScript drawing looks much better when printed on a 600-dpi printer than on a 300-dpi printer. A bit-mapped image looks the same on both printers.