The first line of a PostScript file

The first line of a PostScript file must start with the two characters %!. The rest of the line can be blank, but for in order to take advantage of some environments, more is needed.

In some circumstances, an extra phrase like PS-Adobe-2.0 comes immediately after the first two characters. This tells programs that read and manipulate the file that it satisfies certain document structure conventions. In addition, a phrase like EPSF-3.0 means the file satisfies rigid requirements for Encapsulated PostScript.