Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!trantor.harris-atd.com!charybdis!sonny
From: sonny@charybdis.harris-atd.com (Bob Davis)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Serial line TSR - help needed please?
Keywords: serial TSR how nasty DOS stuff
Message-ID: <5163@trantor.harris-atd.com>
Date: 31 Dec 90 16:59:22 GMT
References: <6517@crash.cts.com> <1990Dec30.041551.4685@micor.OCUnix.On.Ca>
Sender: news@trantor.harris-atd.com
Reply-To: sonny@trantor.harris-atd.com (Bob Davis)
Organization: Advanced Technology Dept., Harris ESS, Melbourne, FL
Lines: 27

In article <1990Dec30.041551.4685@micor.OCUnix.On.Ca> gwaigh@micor.OCUnix.On.Ca (Geoffrey Waigh) writes:
>This may not apply to you, but if you try writing to disk with a DOS call
>(which is the easy way to access the file system) in the background, it will
>not behave.  DOS is extremely non-rentrant (sp?) and does not like people 
>trying to do two things at once.  You will have to do something to be sure
>that DOS is not doing it's thing when you want to flush your buffer.  I would
>guess that grabbing INT 21 (ugh :-() may help but some Guru here may know a
>better kludge.
>
	No guru here, but I would suggest reading the sections on the InDOS
flag and the Critical Error flag, as well as on the "DOS Idle" interrupt,
Int28h, in a good DOS programmer's reference. I like:

	DOS Programmer's Reference, 2nd Edition
	by Terry Dettmann (w/ 2nd Ed. revisions by Jim Kyle)
	Published by QUE (C) 1989
	ISBN:0-88022-458-4

The recommended topics will help you stay out of DOS's way as far as
re-entrancy is concerned (no mean feat!).

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