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From: madams@ecst.csuchico.edu (Michael E. Adams)
Newsgroups: comp.sys.ibm.pc.misc,alt.msdos.programmer,comp.os.msdos.programmer
Subject: Re: Writing my own print spooler
Message-ID: <1990Dec31.090454.13869@ecst.csuchico.edu>
Date: 31 Dec 90 09:04:54 GMT
References: <CHAS.90Dec27202731@tira.uchicago.edu> <uV5wu2w163w@ozonebbs.UUCP> <1990Dec30.160422.27898@xrtll.uucp>
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<uV5wu2w163w@ozonebbs.UUCP> steven@ozonebbs.UUCP (Steven Rubin) writes:
>$I don't know if this is the "correct" way to do a spooler, but The way I do 
>$it would be something like this
>$1) Capture int 1Ch.
>$2) Every clock tick, print x amount of characters from the file
>$3) return control to the other program.

<1990Dec30.160422.27898@xrtll.uucp> silver@xrtll.UUCP (Hi Ho Silver) writes:
>  Well, there isn't a "right" way and a "wrong" way; there are ways which
>don't work, and there are ways which do work with varying degrees of
>efficiency.
>
>   A more efficient, though slightly more difficult, way might be to set
>up the printer port to interrupt the CPU whenever it's ready for another
>character. ... see int 0Fh.

Silver:
  Good posting!  I liked what you had to say, but my DOS reference
guide seems to think that int 0Fh should be AVOIDED!

"On the PC, int 0Fh was assigned to the printer controller to
detect printer errors and print completion.  Programmers typically
do not use it because many controllers DO NOT generate it RELIABLY.
Generaly, you can ignore this interrupt.  The IRQ7 request can also
be generated as a default by the 8259 Priority Interupt Controller,
if the controller is unable to determin which device requested service.
Thus, it is NEVER SAFE to assume that an interrupt reaching this
handler was originated by the Printer; it could originate anywhere."

This is not a flame, just somthing to think about :-)

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