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Understanding driver output

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  Understanding driver output idol programmer <idprog@trust.com> - 2014-08-06 11:51 +0100
    Re: Understanding driver output ken <ken@spamcop.net> - 2014-08-06 16:14 +0100
      Re: Understanding driver output rodd@panix.com (Rod Dorman) - 2014-08-06 19:06 +0000
        Re: Understanding driver output Ross Presser <rpresser@gmail.com> - 2014-08-06 12:13 -0700
          Re: Understanding driver output ken <ken@spamcop.net> - 2014-08-07 07:57 +0100
    Re: Understanding driver output luser- -droog <mijoryx@yahoo.com> - 2014-08-06 22:47 -0700

#1950 — Understanding driver output

In my quest to understand a bit more about postscript  I've been looking 
at what comes out of a Windows Postscript printer driver.

Here's an example:

5582 1340 M (Hello)S
6149 1340 M (World)S

I think this displaying the text Hello World,  but it's using M and S 
instead of moveto and show.

These "aliases" seem to have been defined at the top the file:

%%BeginResource: file Pscript_Win_Basic 5.0 0
/d/def load def/,/load load d/~/exch , d/?/ifelse , d/!/pop , d/`/begin 
, d/^
/index , d/@/dup , d/+/translate , d/$/roll , d/U/userdict , d/M/moveto 
, d/-
/rlineto , d/&/currentdict , d/:/gsave , d/;/grestore , d/F/false , 
d/T/true ,
d/N/newpath , d/E/end , d/Ac/arc , d/An/arcn , d/A/ashow , 
d/D/awidthshow , d/C
/closepath , d/V/div , d/O/eofill , d/L/fill , d/I/lineto , d/-c/curveto 
, d/-M
/rmoveto , d/+S/scale , d/Ji/setfont , d/Lc/setlinecap , d/Lj/setlinejoin ,
etc.


I assume this is done to try and reduce the file size?  Is this normal 
practice elsewhere?

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#1951

In article <53e208bb$0$49555$c3e8da3$fdf4f6af@news.astraweb.com>, 
idprog@trust.com says...
 
> In my quest to understand a bit more about postscript  I've been looking 
> at what comes out of a Windows Postscript printer driver.

Umm, that's a bit like trying to understand assembly language by looking 
at what comes out of a compiler. Machine generated PostScript isn't easy 
to follow.

 
> Here's an example:
> 
> 5582 1340 M (Hello)S
> 6149 1340 M (World)S
> 
> I think this displaying the text Hello World,  but it's using M and S 
> instead of moveto and show.
> 
> These "aliases" seem to have been defined at the top the file:

They aren't what I would call aliases. PostScript is a programming 
language, so you can define routines and call them in your program.

In this case you have routines called 'M' and 'S' (PostScript is case 
sensitive)

> I assume this is done to try and reduce the file size?  Is this normal 
> practice elsewhere?

Its normal practice everywhere for printer drivers/application output, 
yes. There's much less excuse for it since we all stopped using 9600 bps 
serial lines to send PostScript to printers, but old habits never die.



			Ken

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#1953

In article <MPG.2e4c5699fe9e4e669898c5@usenet.plus.net>,
ken  <ken@spamcop.net> wrote:
>In article <53e208bb$0$49555$c3e8da3$fdf4f6af@news.astraweb.com>, 
>idprog@trust.com says...
>>   ... 
>> I assume this is done to try and reduce the file size?  Is this normal 
>> practice elsewhere?
>
>Its normal practice everywhere for printer drivers/application output, 
>yes. There's much less excuse for it since we all stopped using 9600 bps 
>serial lines to send PostScript to printers, but old habits never die.

It was also handy back when the only network you had was Sneakernet
and you had to make it fit on a floppy.

-- 
					-- Rod --
rodd(at)polylogics(dot)com

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#1954

On Wednesday, August 6, 2014 3:06:19 PM UTC-4, Rod Dorman wrote:
> In article <MPG.2e4c5699fe9e4e669898c5@usenet.plus.net>, ken
> <ken@spamcop.net> wrote:
> >In article <53e208bb$0$49555$c3e8da3$fdf4f6af@news.astraweb.com>,
> >idprog@trust.com says...
> >>   ...  I assume this is done to try and reduce the file size?
> >>   Is this normal practice elsewhere?
> >
> >Its normal practice everywhere for printer drivers/application
> >output, yes. There's much less excuse for it since we all stopped
> >using 9600 bps serial lines to send PostScript to printers, but
> >old habits never die.
> 
> It was also handy back when the only network you had was
> Sneakernet and you had to make it fit on a floppy.

It can also be handy, still, during development. If your generated
Postscript doesn't work for whatever reason, you can tweak the M
routine in one place, instead of globally searching for moveto and
adding extra code everywhere.

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#1958

In article <28946358-edf6-409a-8f17-ace4079dee1b@googlegroups.com>, 
rpresser@gmail.com says...

> It can also be handy, still, during development. If your generated
> Postscript doesn't work for whatever reason, you can tweak the M
> routine in one place, instead of globally searching for moveto and
> adding extra code everywhere.

You can do that anyway, just redefine /moveto

		Ken

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#1956

On Wednesday, August 6, 2014 5:51:31 AM UTC-5, idol programmer wrote:
> In my quest to understand a bit more about postscript  I've been looking 
> at what comes out of a Windows Postscript printer driver.
> 
> Here's an example:
> 
> 5582 1340 M (Hello)S
> 6149 1340 M (World)S
> 
> I think this displaying the text Hello World,  but it's using M and S 
> instead of moveto and show.
> 
> These "aliases" seem to have been defined at the top the file:
> 
> %%BeginResource: file Pscript_Win_Basic 5.0 0
> /d/def load def/,/load load d/~/exch , d/?/ifelse , d/!/pop , d/`/begin 
> , d/^
> /index , d/@/dup , d/+/translate , d/$/roll , d/U/userdict , d/M/moveto 
> , d/-
> /rlineto , d/&/currentdict , d/:/gsave , d/;/grestore , d/F/false , 
> d/T/true ,
> d/N/newpath , d/E/end , d/Ac/arc , d/An/arcn , d/A/ashow , 
> d/D/awidthshow , d/C
> /closepath , d/V/div , d/O/eofill , d/L/fill , d/I/lineto , d/-c/curveto 
> , d/-M
> /rmoveto , d/+S/scale , d/Ji/setfont , d/Lc/setlinecap , d/Lj/setlinejoin ,
> etc.
> 
> 
> I assume this is done to try and reduce the file size?  Is this normal 
> practice elsewhere?

Yes, it's very much the common way to structure a postscript program 
to separate it into a Prolog and a Script. It helps get you into the
mindset of aggressively factoring your code. As others have commented
this practice also helps reduce the size of the program, and thus
storage and transmission requirements. In the past, storage and
transmission efficiency were more vital than they are now.

But the benefit for the programmer has always been -- and remains --
the power of abstraction to reduce the level of detail necessary to
write or review an implementation of an algorithm. So the Prolog+Script
style is merely good Structured Programming technique made into a
convention.

I highly recommend you read the Glenn Reid books: the Green Book,
and Thinking in Postscript. He gives an excellent overview of how
to write postscript code for a printer driver.

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