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From: drk@well.UUCP (Doug Kaye)
Newsgroups: net.micro.pc
Subject: Re: (Orphan) Re: How does SideKick work?
Message-ID: <297@well.UUCP>
Date: Sun, 24-Nov-85 02:37:06 EST
Article-I.D.: well.297
Posted: Sun Nov 24 02:37:06 1985
Date-Received: Mon, 25-Nov-85 07:50:00 EST
References: <233@well.UUCP.UUCP> <26700005@ISM780B.UUCP>
Reply-To: drk@well.UUCP (Doug Kaye)
Organization: Whole Earth Lectronic Link, Sausalito CA
Lines: 21


I've had significant response to my own question.  Here's the basic scheme...
SK detects its activation keys via INT 9.  It then sets a flag meaning
"Try to become active".  SK then awaits an INT 28h (the undocumented
interrupt used by the PRINT spooler).  When an INT 28h comes in, SK knows
that the machine is in a safe state (ie, no DOS disk calls are in progress)
so it comes up!  If INT 28h isn't called, SK is also on the timer interrupt
and will "chirp" for a few seconds telling you that it can't activate
since things aren't safe.  If an INT 28h occurs during this time, SK will
stop chirping and will activate.  THe key here is, if you want SK to
be able to come up over your program, make sure to call INT 28h!  This is
done by DOS, apparently, during such calls as "read string from keyboard".
 
If more info is needed, let me know.

	Doug Kaye
	Rational Data Systems
	5725 Paradise Drive
	Corte Madera, CA 94925
	415/924-0840
	ihnp4!hplabs!well!drk