### What is “Encapsulated PostScript” (“EPS”)

PostScript has over the years become a lingua franca of powerful printers; since PostScript is also a powerful graphical programming language, it is commonly used as an output medium for drawing (and other) packages.

However, since PostScript is such a powerful language, some rules need to be imposed, so that the output drawing may be included in a document as a figure without “leaking” (and thereby destroying the surrounding document, or failing to draw at all).

Appendix H of the PostScript Language Reference Manual (second and subsequent editions), specifies a set of rules for PostScript to be used as figures in this way. The important features are:

- certain “structured comments” are required; important ones are the identification of the file type, and information about the “bounding box” of the figure (i.e., the minimum rectangle enclosing it);
- some commands are forbidden — for example, a `showpage` command will cause the image to disappear, in most TeX-output environments; and
- “preview information” is permitted, for the benefit of things such as word processors that don’t have the ability to draw PostScript in their own right — this preview information may be in any one of a number of system-specific formats, and any viewing program may choose to ignore it.

A PostScript figure that conforms to these rules is said to be in “Encapsulated PostScript” (EPS) format. Most (La)TeX packages for including PostScript are structured to use Encapsulated PostScript; which of course leads to much hilarity as exasperated (La)TeX users struggle to cope with the output of drawing software whose authors don’t know the rules.

This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=eps