🚀 go-pugleaf

The question I responded to specified a parallel interface.  Ctrl-D's are
only for parallel and serial interfaces, and as many of you have pointed
out, have no place in network sessions such as Appletalk, Ethernet, or
whatevernet.  It is true that the Ctrl-D character is not part of the
PostScript language itself.  The PostScript language has no convention
for marking the end of a job!  If you are connected to a network, then
finding the end of the job is no problem, since the protocol implies that
information (end of file == end of job).  If you are connected to serial
or parallel, then the printer itself (or other graphics device) needs to
know when the job ends.  All Adobe PostScript implementations on every
device I have ever heard of use the Ctrl-D to mark the end of the job
on parallel or serial channels.  This does not mean that it's part of the
language -- but it seems to be a part of Adobe's implementation of the
PostScript language.

In reference to what actually happens: before running a job, the PostScript
interpreter's "server loop" does a "save".  When PostScript gets a
Ctrl-D (over the parallel or serial port) it does a "restore" (thereby
reclaiming VM) and then another "save" for the next job.  That's why
you have to exit the server loop to make changes that persist from job
to job.

BTW, the Ctrl-C character (over parallel or serial) "cancels" the current
job, but I'm not completely sure what is meant by that, nor whether it
is implemented the same in all cases.  On the serial channel only, you
can send a Ctrl-T and it will send a short status string back.  This is
also clearly not part of the PostScript language, but it is there in
most implementations.

Well, there's the can of worms.  Everybody dig in...



-- 
Jeff D. Pipkins (uunet!cpqhou!pipkinsj)

My disclaimer: My opinions do not necessarily reflect those of my employer.
Papaw's disclaimer: I've already told you more than I know.