Wirt writes:

>There are an
>infinity of things that can be created on a PostScript printer that cannot be
>created on a PCL printer.

Wait a minute... for a 600dpi printer, there are only about 10^(10^7)
different images that can be created on a U.S. letter-sized piece of
paper. Are you really claiming that some of those images can be specified
only in PostScript? In any case, since the number of possible images is
finite, there can't be "an infinity" more PostScript-accessible images. I
think you're exaggerating again.

>>  The
>>  computational expense for a PCL form is incurred once, when the form is
>>  first created; thereafter, it's simply downloaded. Moreover, it's
>>  downloaded only once per job -- unlike PostScript, where it's downloaded
>>  with each page.
>
>That's not quite true, either. PostScript Level 2 allows forms caching
>(download once/reuse often

As I mentioned, there are restrictions on what can be cached, and the
caching is partially "advisory" -- that is, the printer is free to decide
not to cache a frame, but to re-execute it for every page. What the
printer actually does in this case is determined by such factors as the
amount of memory the printer has, the number of fonts in the job and so
on.

>I relatively quickly discovered that almost all of the inefficiencies
>associated with PS on a Mac are due to the manner by which Apple mediates
>PostScript libraries on the Macintosh. An enormous amount of unused
>information is downloaded with every print job on a Macintosh. Framemaker
>files, for example, consume a megabyte on each download that would be only a
>few K if generated in QueryCalc. B

This is actually application-dependent. PostScript is a programming
language, not a sequence of control characters; developers of PostScript
tools write extensive subroutine libraries to make their programmers'
lives easier. When you print from sophisticated publishing tools like
FrameMaker or PageMaker, the application downloads its subroutine library
to the printer first. The libraries also specify abbreviated encodings
for PostScript reserved words when binary encoding won't or can't be
used. The PC or Unix version of FrameMaker would have downloaded exactly
the same thing.

There is a small prefix, about 12kbytes, that is prepended by the Mac
PostScript driver (and in fact, by the Windows PostScript driver as
well). The prefix includes some subroutines that the PostScript driver
uses, as well as some specially-structured comments. This is done to
improve the portability of PostScript programs, so that you can take your
PostScript file over to a completely different output device and be
reasonably assured that the output you get from the $10/page color
proofer has the same layout as what you got from your $0.05/page color
inkjet.

>Does quality of output matter? If you're the electric company and need to
>print 500,000 invoices -- and you don't give a hoot what the invoices look
>like because you've got the customers over a barrel anyway -- then probably
>not. But if you're printing only 1000 invoices, and you want to impress your
>customers with the level of care and quality that you put into every
>aspect of
>your business, then it most likely matters a great deal.

I also value good design; I'm one of those people who looks at the design
of every piece of paper that crosses my desk, to see what I can learn
from it. But good design has absolutely nothing to do with the hardware
on which it's printed. A well-designed form can printed in PCL or
PostScript, and the recipient will never know the difference. So can a
badly-designed form, since PostScript does not yet have an operator that
critiques the aesthetics of its frame buffer.

The point of this conversation, if there is one, is that the important
thing is what the output looks like, not what printer language produced
it. Buying a PostScript printer because you think it'll make your output
look better is like buying an expensive pen because you think it'll make
your prose sound better.

-- Bruce



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