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Because PostScript is a language and PostScript printers are expecting print requests written in that language, some applications may produce standard print requests that may not be intelligible to PostScript printers. The following are examples of print requests that may not be interpreted by some PostScript printers.
Non-PostScript content types
| Content Type | Type of Print Request |
|---|---|
| simple | Print an ASCII (``simple'') text file. |
| troff | Print output from the troff command. |
| daisy | Print files intended for a Diablo 630 (``daisy-wheel'') printer. |
| dmd | Print the contents of a bit-mapped display from a terminal. |
| tek4014 | Print files formatted for a Tektronix 4014 device. |
| plot | Print plot-formatted files. |
Filters are provided with the print service to translate print requests with these formats to the PostScript language. For example, to convert a file containing ASCII text to PostScript code, the filter takes that text and writes a program around it, specifying printing parameters such as fonts and the layout of the text on a page.
Once the PostScript filters are installed,
they will be invoked automatically by
the print service
when a user specifies a content type
for a print request with the
-T
option.
For example,
if a user enters the command
lp -d psprinter -T simple report2
the ASCII file report2 (a file with an ``ASCII'' or ``simple'' format) will be converted to PostScript automatically, as long as the destination printer (psprinter) has been defined to the system as a PostScript printer.