On 12.11-12:58, Girish Venkatachalam wrote:
[ ... ]
> Thanks. I definitely stand corrected. I definitely meant PDL and not
> PCL. My memory failed due to lack of proper understanding. Sorry...
often make the same error.
:-)
[ ... ]
> I want to know what happens behind the scenes when you type
>
> $ lpr foo.ps
>
> Assuming that foo.ps is the output of a2ps.
depends on the scenario. if your printer "supports postscript" then
nothing much. the lpd accepts the print job, queues it and
eventually routes it on to the correct device (sometimes across
another lpr session, sometimes via jetdirect, sometimes parallel
port, usb, etc, etc).
if it's not a postscript printer (e.g. an old hp laserjet that supports
PCL) then the lpr system needs to be configured with a filter. this
filter simply takes the input, processes it in some way and passes
it back to lpd for queuing. generally this filter is ghostscript
which processes the postscript to the correct printer language but we
used to write scripts and progs for various conversions (e.g.
EBCDIC->ASCII, XES->PCL) too, and there are still some examples out
there (probably one or too in the standard distribution if you look
under /usr/share somewhere).
i haven't used the filter program others mentioned but i would guess
that it installs itself as the standard lpd filter and is smart enough
to make the correct conversions (probably passing a lot of the work
to ghostscript for postscript input, hence the reason it asks for
which gs printer driver it should use for each device).
[ ... ]
> And what is the relation between PS and PDF?
>
> I hear that even PDF is some form of PDL. As you can see I am quite
> lost at this point. :)
then you need to do a little more research.
:-)
PDF is very similar to PostScript but it produces much smaller documents
(using JPEG compression and other tricks not normally used in PS as
they just cause the printer more work) and so is more suitable for
storing and exchanging documents in that format (it also has some
extensions relating to the "document" it's describing). i don't know
of any printers that support printing PDF documents directly but i'm
sure they're out there.
--
t
t
w
