Re: A83: Negative numbers

To: Alan C Johnson <assembly-83@lists.ticalc.org>
Subject: Re: A83: Negative numbers
From: Linus Akesson <lairfight@softhome.net>
Date: Mon, 21 Sep 1998 18:27:36 +0100
Delivered-To: assembly-83-outgoing@towerguard.unix.edu.sollentuna.se
In-Reply-To: <19980920.160017.-191863.4.benjamin99@juno.com>
Reply-To: assembly-83@lists.ticalc.org

What, there a difference? Let's talk bytes here: -1 is the same as 255, right?
Because 255 + 1 = 0 and -1 + 1 = 0. Let's talk words: -1 is the same as 65535.
65535+1 = 0, -1+1=0, -1+65535 = 65534 = -2. You probably know all this before,
because this is the way numbers are stored anyway. The thing is, the assembler
doesn't make any difference between them. That is one great example of the
difference between c and asm: Asm will always work, although not necessarily
correctly.

Linus

On 20-Sep-98, Alan C Johnson wrote:

>How does the processor know when a number is negative?  How does TASM
>compile a negative number as opposed to an unsigned number?  Also, what
>are all of the system flagsand what are their purposes?  All I know now
>are zero, carry and parity.  Can any register set the parity flag?

>Thanks,
>Alan
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References:

A83: Negative numbers

From: benjamin99@juno.com (Alan C Johnson)

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