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From: perkins@bnrmtv.UUCP (Henry Perkins)
Newsgroups: net.micro.pc
Subject: Re: why does program stop print spooler?
Message-ID: <699@bnrmtv.UUCP>
Date: Mon, 15-Sep-86 16:10:48 EDT
Article-I.D.: bnrmtv.699
Posted: Mon Sep 15 16:10:48 1986
Date-Received: Tue, 16-Sep-86 05:56:28 EDT
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Organization: Bell Northern Research, Mtn. View, CA
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> >I have a C program that stops the print spooler ( the PRINT command).
> >The spooler stops printing
> >whin this program is in control, and resumes normally when it exits.
> >
> Does the C-program grab interrupt 28h?  I believe that PRINT uses this
> interrupt to achieve a pseudo-form of multitasking.  When the machine
> is waiting around for you to type something, it ocassionally calls int
> int 28h when it is safe to do so.  See Best of BIX in the Sept issue
> of BYTE.
> 
More accurately, MSDOS raises INT 28H when it's in a keyboard input wait.
If the C program isn't doing keyboard input, or if the C doesn't use
MSDOS calls to read from the keyboard, you'd expect printing to stop.
This is why I have a HARDWARE print buffer.
-- 
{hplabs,amdahl,3comvax,okstate}!bnrmtv!perkins        --Henry Perkins

It is better never to have been born.  But who among us has such luck?
One in a million, perhaps.