Date: Tue, 27 Apr 1999 13:54:02 -0400
Message-Id: <199904271754.NAA23027@envy.delorie.com>
From: DJ Delorie <dj AT delorie DOT com>
To: djgpp AT delorie DOT com
In-reply-to: <Pine.SOL.3.91.990427134359.3388A@travelers.mail.cornell.edu>
	(arh14 AT cornell DOT edu)
Subject: Re: Writing an OS
References:  <Pine DOT SOL DOT 3 DOT 91 DOT 990427134359 DOT 3388A AT travelers DOT mail DOT cornell DOT edu>
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> Bah!  If you are writing for an x86 system and have x86 code, why can't 
> you use it?

Go get Netscape for Linux and try to run it under plain MS-DOS, then
think about the question you just asked.  Why can't you just use it?
They're both ix86 systems, right?

> Build it on another computer, or just write in assembly and link in
> the stdlib, right?

If you link in DJGPP's stdlib, you *must* use MS-DOS, because that's
what DJGPP's stdlib uses.

> Then just jump to it...what's so hard about that?

There's not INT 0x21 in Linux.  Why can't I just do MS-DOS calls in
Linux?  What's so hard about that?  Sorry, it just won't work.

> Now if you're writing an OS for a totally *foreign* computer with
> different instruction set, yes, you will be up a creek...

Having a different OS on the same CPU is just as much a problem.
Consider trying to run Linux programs under Win/NT.  It's the same
CPU, right?  Why don't they just work?