Path: utzoo!attcan!uunet!bu.edu!shelby!mcnc!uvaarpa!haven!uflorida!mlb.semi.harris.com!trantor.harris-atd.com!charybdis!sonny
From: sonny@charybdis.harris-atd.com (Bob Davis)
Newsgroups: comp.os.msdos.programmer
Subject: Is BIOS Reentrant?
Message-ID: <4844@trantor.harris-atd.com>
Date: 12 Nov 90 19:41:48 GMT
Sender: news@trantor.harris-atd.com
Reply-To: sonny@trantor.harris-atd.com (Bob Davis)
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Organization: Advanced Technology Dept., Harris ESS, Melbourne, FL
Lines: 22


	In what I read about designing TSRs, warnings are issued
about monitoring the "InDOS" flag and/or "DOSOK" (Int28h) to determine when
DOS function calls can safely be made. The impression is usually
left on me that BIOS calls are OK without such monitorings.

	Is this true? Is BIOS reentrant?

	May I safely use ALL Interrupts below 20h without checking
	on ANY such flags or indicators in TSRs?

	Is it ONLY when I need to use Interrupts above 20h that the
	tedious checks to avoid re-entering DOS are necessary?

Thanks.
 
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