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

PostScript has been for many years a lingua franca of powerful printers (though modern high-quality printers now tend to require some constrained form of Adobe Acrobat, instead); 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:

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