Re: A85: Pixel mover

To: assembly-85@lists.ticalc.org
Subject: Re: A85: Pixel mover
From: "A.K.A. TheWiz" <dankna@bergen.org>
Date: Wed, 12 Nov 1997 07:48:10 -0500 (EST)
In-Reply-To: <19971111.152544.9614.0.egillespie@juno.com>
Reply-To: assembly-85@lists.ticalc.org

> i probably know this but can't think of what the answer is
> why would
> 
> add a, $F9
> 
> subtract 7 from a?

  Because the last bit would overflow the byte and wind up in the carry.
$F9 is what's called a "two's-complement number" of 7: invert all the bits,
then add 1.  Repeate to get 7 back.


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References:

Re: A85: Pixel mover

From: egillespie@juno.com (Erik L Gillespie)

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