PostScript is not portable

Andii Inston wrote:

PostScript is platform independent i.e. it depends on the printer.It is not device independent for a number of important reasons.

1. The PostScript language has evolved and improved. Something generated specifically for a "level 3" printer may not print on an older level 1 printer.

2. Each printer has options like various paper trays. The way in which these are used is not standardised. The codes used to control one device can fail in another.

3. Some printers like extra control sequences, which are not strictly PostScript. This will cause errors in other printers.

Those who claim PostScript is device independent may have several reasons for doing so:

• ignorance of the above facts
• full knowledge of the above, but possession of applications which generate a generic, "lowest common denominator" PostScript that works with most devices. (These are not usually windows).
• an academic argument that pure PostScript is device dependent which they do not wish to sully with discussions of the kind of real world files which pass for PostScript!

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Aandi Inston  quite@dial.pipex.com

Rupert Mazzucco added:

Postscript programs can be be device- and platform-independent -- Adobe even gives a lot of hints how to make this happen -- but needn't be.

Windows printer drivers in particular usually don't seem to bother about *-independence, but rather try to make a program that prints as fast and pretty as possible on the corresponding printer. To this end, they even put printer-specific garbage at the beginning of the file that isn't Postscript at all, like the duplex stuff posted yesterday(?).

That said, there is often a switch hidden somewhere in the printing dialogue, where you can select something like "optimize for portability". In the Unix world, Postscript has a history of being used as interchange format, so things usually go a bit better there.

Regards, Rupert maz@doppler.thp.univie.ac.at (Rupert Mazzucco)