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From: broehl@watserv1.waterloo.edu (Bernie Roehl)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Programming the Mouse
Message-ID: <1990Aug2.140351.4185@watserv1.waterloo.edu>
Date: 2 Aug 90 14:03:51 GMT
References: <1990Jul30.182430.7493@uokmax.uucp> <34725@ut-emx.UUCP> <1990Jul31.193800.18227@uokmax.uucp>
Organization: University of Waterloo
Lines: 14

In article <1990Jul31.193800.18227@uokmax.uucp> gene@uokmax.uucp (Gene E. Johannsen) writes:
>Anyway, I found my problem.  It is the 'int 21h' that freezes it.  I honestly
>don't know why.

It's because DOS is not re-entrant.  You may be in the midst of a DOS call
when a mouse interrupt comes along; you call DOS again from your handler,
and since DOS has only one internal stack you overwrite what was there
previously.  Your call completes, you get your *, then the handler returns
to a clobbered stack and your system goes to Sudbury.
-- 
	Bernie Roehl, University of Waterloo Electrical Engineering Dept
	Mail: broehl@watserv1.waterloo.edu OR broehl@watserv1.UWaterloo.ca
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