Re: A83: DAA and BCD.
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Re: A83: DAA and BCD.
This is a followup to the post I made on the 10th...
Ok, so how would I create two numbers in BCD, add them, and put the result
in A?
Thanks, James.
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-----Original Message-----
From: John Kugelman <kugelman@mnsinc.com>
To: assembly-83@lists.ticalc.org <assembly-83@lists.ticalc.org>
Date: Thursday, December 10, 1998 9:12 PM
Subject: Re: A83: DAA and BCD.
>
>James Matthews wrote:
>>
>> Ok, can someone explain to me what is BCD format, and what does DAA do?!
>
>BCD means Binary Coded Decimal (there abouts). It's a numerical format
>used to express decimal numbers more conveniently in a binary system.
>Typically, a number will be represented as 1 or 2 decimal digits per
>byte. 1 digit per byte is very inefficient spacewise, but it's very
>easy to work with decimal numbers in this form. 2 digits per byte
>(packed BCD) is more efficient, but more difficult to work with.
>
>In either case, BCD is less efficient spacewise than storing the number
>in native binary, but this is the trade off for ease of use.
>
>The floating point format used in the TI-83 is similar to BCD format
>because it stores decimal digits individually, similarly to packed BCD.
>
>DAA, interpreting the instruction set list I'm reading, converts a into
>BCD after a BCD operation performed on a. Adding or subtracting BCD
>numbers isn't as simple as an add or sub instruction - I'm guessing that
>one must add the two numbers and then use DAA to convert the result back
>to BCD format.
>
>--
>John Kugelman. kugelman@mnsinc.com
>
>I believe we can change anything.
>I believe in my dream.
> - Joe Satriani
>