Message-ID:	<35748C42.7BFAE427@usa.net>
Date:	Tue, 02 Jun 1998 16:35:30 -0700
From:	ToolsSmith <ToolsSmith AT usa DOT net>
Reply-To:	ToolsSmith AT usa DOT net
MIME-Version:	1.0
To:	Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
CC:	djgpp AT delorie DOT com
Subject:	Re: Newbie application question.
References:	<Pine DOT SUN DOT 3 DOT 91 DOT 980602191952 DOT 20326S-100000 AT is>

Eli Zaretskii wrote:
> 
> On Tue, 2 Jun 1998, ToolsSmith wrote:
> 
> > I want to build some protected mode services that are callable via
> > software interrupts from real-mode applications. These protected mode
> > services, because of their potential size, need to reside in extended
> > memory. This must be transparent to the real-mode MS-DOS applications.
> 
> Please explain more what exactly do you want to accomplish.  And example
> of an application that needs this would be nice.  Specifically, please
> tell what protected-mode services would you like to access from the
> real-mode program.

We have a large real-mode application compiled in a LARGE memory model
using Microsoft C 6.0a. From this application we want to make a
real-mode software interrupt (e.g. INT 10) to a protected mode handler
resident in extended memory. We are not permitted to modify the existing
real-mode application in any manner. It is the intent that this
real-mode application NOT be aware that it is using protected mode
services located in extended memory. All this in an MS-DOS V6.22
environment.

So, using the DJGPP tools the following questions arise:
 - What DPMI services are required?
 - Are any other services (e.g. himem.sys, emm386) required?
 - What DPMI functions would a client need to use to install itself
   in extended memory as an interrupt handler callable from real-mode?
 - What would be needed to install multiple handers?

Thanks,
Steve

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