Path: utzoo!attcan!uunet!samsung!dali.cs.montana.edu!ogicse!emory!hubcap!lsalomo
From: lsalomo@hubcap.clemson.edu (lsalomo)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Is BIOS Reentrant?
Message-ID: <11569@hubcap.clemson.edu>
Date: 13 Nov 90 15:09:08 GMT
References: <4844@trantor.harris-atd.com>
Distribution: na
Organization: Clemson University, Clemson, SC
Lines: 27

From article <4844@trantor.harris-atd.com>, by sonny@charybdis.harris-atd.com (Bob Davis):
> 
> 	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?

BIOS is not reentrant (OS/2 had to replace the BIOS routines because of this),
but I do believe that you can use up to int 9 with no problems (someone else
better verify this).

Cheers,
Q - the "Q"uestor for knowledge (, a degree, etc.)

lsalomo@hubcap.clemson.edu
ibmman@clemson.clemson.edu
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