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Path: utzoo!utgpu!cunews!bnrgate!bwdls58!mlord
From: mlord@bwdls58.bnr.ca (Mark Lord)
Newsgroups: alt.msdos.programmer,comp.os.msdos.programmer
Subject: Re: Propagating Device Driver error status into C runtime errno variable.
Keywords: DOS, Device Driver
Message-ID: <3951@bwdls58.UUCP>
Date: 21 Aug 90 15:04:14 GMT
References: <163@matrix.UUCP>
Sender: mlord@bwdls58.UUCP
Reply-To: mlord@bwdls58.bnr.ca (Mark Lord)
Distribution: na
Organization: Bell-Northern Research, Ottawa, Canada
Lines: 17

In article <163@matrix.UUCP> venkat@matrix.UUCP (D Venkatrangan) writes:
>
>Who sets the Carry Flag for the return from int21h and what should the driver's
>interrupt routine do for that flag to be set?
>
The IRET instruction does an implicit POPF, which restores the carry flag
and all other flags to the values they had before the interrupt.  Instead
of doing an IRET, do a POPF, set the carry flag manually, and then do
the appropriate type of RET   (FAR ?).  Or twiddle the saved carry bit
on the stack before doing an IRET.

Have Fun.
-- 
 ___Mark S. Lord__________________________________________
| ..uunet!bnrgate!bmerh724!mlord | Climb Free Or Die (NH) |
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