Re: Weird Output for Question #2

Ed Casas (edc@ece.ubc.ca) Thu, 19 Oct 2000 07:34:45 -0700 

Date: Thu, 19 Oct 2000 07:34:45 -0700
From: Ed Casas <edc@ece.ubc.ca>
Subject: Re: Weird Output for Question #2



> When I run my compiled code in the Windows Virtual Dos Machine,
> I have the following output:
> 
> ????:
>             :????
> ????:
>             :
>             :
>             :
>             :
> ????:????
> ????:????
> ????:????
> ????:????
>             :????
>             :
>             :
> ????:????
>             :
> 
> I am asumming that this might due to the difference between the
> memory management of Dos and Windows. In another word, the
> interrupt vectors are stored somewhere else in the memory
> rather than the lower 1024 bytes under the Windows protective
> mode.
> 
> Can anyone tell me if I am right?

Well, yes and no.

The interrupt mechanism is indeed different when the processor is
in protected mode and the processor does have a different set of
interrupt vectors (with a much more complicated structure, which
is why we're sticking with real mode interrupts in this course).

However, the program running in ``virtual 8086'' mode in the DOS
box will still see 256 interrupt vectors starting at address 0
that it can read and print out.

-- 
Ed Casas   edc@ece.ubc.ca   http://casas.ece.ubc.ca   +1 604 822-2592