Date: Wed, 20 Dec 1995 08:15:46 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Justin Ward <ward AT escape DOT com>
Cc: gcc <djgpp AT sun DOT soe DOT clarkson DOT edu>
Subject: Re: Drive errors under protected mode..


On Tue, 19 Dec 1995, Justin Ward wrote:

> I have this program that uses BIOS calls to read the sectors of a
> disk.  biosdisk() works just fine, except when there's some disk error
> (disk not in drive, read error, write error, write protected disk,
> etc). I have a feeling the error arises because when there's a disk
> error, int 0x13 (I think) is called. And of course this makes a whole
> big mess of anything running in protected mode. So, how can I fix this

Most probably, your assumption that Int 13h is making a mess out of 
protected mode is wrong, and the real problem is how does your program 
handle disk errors.  DJGPP programs don't usually have any trouble 
whatsoever with Int 13h, or else they'd crash each time you read or write 
to a disk file.  Moreover, `biosdisk' itself calls Int 13h from protected 
mode, and it does work.

Handling errors which happen in Int 13h calls is a bit tricky.  It is 
described in the Interrupt list 
(ftp://ftp.coast.net/SimTel/msdos/info/inter48?.zip), under the various 
Int 13h functions.  Or you can post a part of your pogram which deals 
with this together with an explanation of how does it fail and in what 
circumstances exactly, and somebody will have an answer for you.