Re: A89: operation size?

To: assembly-89@lists.ticalc.org
Subject: Re: A89: operation size?
From: TurboSoft@aol.com
Date: Thu, 3 Dec 1998 18:38:36 EST
Delivered-To: assembly-89-outgoing@towerguard.unix.edu.sollentuna.se
Reply-To: assembly-89@lists.ticalc.org

In a message dated 12/3/98 5:44:20 PM Eastern Standard Time, S43R80@aol.com
writes:

> when you afterincrement something, the operation size or something is then
>  added to a0 after the instruction is completed
>   ie: move (a0)+,d0
>  In this case 4 would be added to a0 afterwards...I know this because I read
>  it...BUT how do I know what the insruction size is...Why is it 4

Actually the move command should be move.l .  lf you had pushed a word into
the stack pointer at that place then when you popped it back into d0 then it
would be move.b (a0)+,d0 and that would increment the a0 register by 2.
moving a byte increases by 1, a word by 2, and a longword by 4.

>  Also what is unsigned/signed integers?  You used different branch 
> instructions
>  depending on what kind of integer, right?  Or something like that...I'm
just
>  typing off the top of my head rightn now...THANKS

signed means that if 00001011 has a zero as the first bit (which it does
there) then it  is a negative number.  However, if you said that 00001011 was
unsigned, then it doesn't matter whether the left-most bit is 0 or 1 because
it's going to be counted as positive anyway.  l think.