Core_Computer Studies: Postscript what is it?

When desktop printing started in the mid-eighties, the major complaint from professional printers and typesetters was that the spacing of type was uneven and inconsistent from printer to printer. They were right.

Adobe solved this problem with the creation of PostScript. When one wants to print a document, PostScript technology takes the information and sends it to a printer in the form of simple text commands. A printer with a PostScript interpreter can then translate the text information into images and text. The output is consistent with what is seen on-screen and with any number of other printers. It was also this technology that allowed fonts to be printed at a great variety of sizes without any decrease in quality. This is because a font's outline file contains vector outlines of the font characters which, like any vector art, can be re-sized without any loss in quality.

PostScript is the technology that really made professional desktop publishing and design possible. Before PostScript, designers working with computers didn't have the necessary control over printed output that exists today. PostScript is a Page Description Language (PDL) that was developed by Adobe. PostScript differs from other PDLs because it treats items on a page as geometric objects. When you print using a PostScript printer, PostScript commands are sent from your system in the form of text commands. These commands contain exact information about what is on the page. The commands are received, understood and translated by a PostScript interpreter in your printer. Because of the simplicity of text commands and consistency of PostScript interpreters, any PostScript printer will print the information in the same way. In other words sending the same Postscript information to fifty different printers would yield the same results.

PostScript font information follows the same principle which is why designers prefer them over their inexact counterparts, TrueType fonts.

If you're not using a PostScript-enabled printer, your output will not be consistent between other printers and Postscript-based graphics, like EPS files, will look different if not terrible.

These notes are written for students who undertake the Core Computer course at School of Art, Australian National University. Students of the course should feel free to contact any member of staff with comments questions and general suggestions..

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