Good point Carol.  And this hardware still exists today...not sure about
the software.

John Lee
Vaske Computer Solutions




At 04:41 PM 6/22/05 -0400, Carol Darnell wrote:
>Actually, it also depends upon whether your 'controller' is a pc or a
>traditional dumb terminal.  The solution I used a number of years ago (and
>think was discussed here in the distant past) was the old 'P31' technique
>using dumb terminals which were dual-port.  We had very specific label
>requirements (this was producing thermal barcode labels for a poultry
>processor, where every label was unique, and allowed me to control a
>million+ label inventory), and had to use non-hp rugged-weather printers.
>The application was written in TRANSACT, with the printer driver written
>in COBOL - the code could 'program' the printer with one set of escape
>sequences displayed to the 2nd port, or download specific data and request
>the needed label using a different set.
>
>In this case, though, each station had a dedicated printer hard-wired to
>the terminal, and the OS had no idea that the printers even existed.  I
>maintained a configuration 'file' which told the application whether a
>particular port had a printer attached.
>
>So yes, it can be done, but it is VERY hardware specific and you would
>need to develop and maintain a 'configuration' matrix independent of the
>OS to build into the application the ability to tailor its output for the
>various hardware possibilities.
>
>I suppose a shared printer might be managed using IPC files, with the
>individual stations writing to one or more IPC files which were fed via an
>independent server to the appropriate printer(s) - in which case the
>server would have hot control over the printer(s).  There are probably
>several other approaches available... but I know these do, or at least
>did, work and work well.
>
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