To fully use the functionality of a Postscript printer on Unix, the system needs a Postscript Printer Description (PPD) file, which is a file in a standard format defined by Adobe. It describes the options the printer has and how to control them.
When a print dialog is presented to the user (either by an explicit call to
, or by printing), the system uses the PPD file to find what additional options to present, and how to communicate them to the printer.
A PPD file should be supplied by the manufacturer with the printer itself. Otherwise, it is normally possible to obtain the PPD file from the website of the manufacturer. The name of a PPD file should be printername.ppd.
When the user configures a new printer, the first thing the system does is to show the user all the PPD files that it can find under the
(directly, or one level of directories below it). The application should set this variable to the appropriate directory.
If the value of
, the system looks at the directory obtained by evaluating
If the printer does not have a PPD file, the user can still use it by selecting the default button in the print dialog. This means that the system will let the user change only the basic properties of the printer, without using its more complex features.