From:	"Andrew D. Jones" <guln AT home DOT com>
Newsgroups:	comp.os.msdos.programmer,comp.os.msdos.djgpp
Subject:	Re: Porting DJGPP DPMI Apps-->Borland C++5.x
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Date:	Wed, 13 Dec 2000 14:44:01 GMT
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On Tue, 12 Dec 2000 15:19:30 -0700, Russ Magee
<rmageeNO_SPAM AT home DOT com> wrote:

[snip]

>1) If we use the 5.0 compiler and make 16-bit DOS apps, is it true we don't
>need DPMI at all, and can just call BIOS the traditional way, and bang
>on hardware directly?

Bang away!  DPMI is only required for protected-mode (DOS) programs as
an interface to the real-mode DOS operating system (and system BIOS)
on which it runs.

Not having to make calls through DPMI would actually simplify your
programs (no more need to call DPMI Simulate Real Mode Interrupt, you
just fill the registers and such and call the interrupt yourself.)

On the other hand, you lose the flat address space, and have to start
worrying about segments and such.

>2) If we use the newer compiler, and compile win32 console apps, can these
>access the BIOS and hit hardware directly as well? If so, does it look
>the same from the assembly-coder's standpoint (other than being able
>to use a flat address space, I suppose, which would be nicer)? The
>textbooks on PC Assembler/Hardware Architecture all use DOS apps in their
>examples of accessing hardware/BIOS directly. We NEED the development
>environment to be somewhat compatible with the textbook.

AFAIK, Win32 (GUI/console) programs cannot access the underlying
hardware themself.  You would need to write VxD's through which your
main program would access the hardware (the other side of that is that
you could use the existing Win32 API calls, but I don't think that
fits into what you have in mind.)

>3) And can we use VESA BIOS calls with either of the above schemes, without
>DJGPP? (IE, what kind of support for VESA calls is there in TASM, Borland
>C/C++)?

You seem to be a bit unclear about these things.  If your program runs
in DOS, no matter whether it's in real-mode or protected-mode, it can
access the VESA BIOS Extensions.  It's just a matter of how to do it.

TASM/BC++ itself doesn't "support" VESA.  You write the code to do it
yourself. :)  Although, I'd recommend using NASM over TASM, but that's
just my own opinion. :)

>I hope this is clearer. Thanks again in advance,

And I hope this helps a bit more.

-- 
Andrew Jones

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