Traditional UNIX programs and printing systems while using PostScript are largely not
PPD-aware. PPDs are “PostScript Printer Description” files. They enable you to specify and
control all options a printer supports: duplexing, stapling, and punching. Therefore, UNIX users for a long
time couldn't choose many of the supported device and job options, unlike Windows or Apple users. But now
there is CUPS. as illustrated in
Printing to a PostScript Printer.
Figure21.2.Printing to a PostScript Printer.
However, there are other types of printers out there. These do not know how to print PostScript. They use
their own PDL, often proprietary. To print to them is much more demanding. Since your UNIX applications mostly
produce PostScript, and since these devices do not understand PostScript, you need to convert the print files
to a format suitable for your printer on the host before you can send it away.