Date   : Fri, 20 Nov 2009 22:48:40 +0100
From   : rick@... (Rick Murray)
Subject: Quine

Mick Champion wrote:

> CLC
> LDA byte1
> LDX #0
> .loop
> ADC byte1
> STA byte1
> BCC a
> INC byte2
> .a
> INX
> CPX#4
> BNE loop

Am I thick or do I not see what you are multiplying BY?
Are you trying 'byte1' times four? (LDX #0 --> CPX #4)?

As 4 is a power of two, a bit of shifting would prob. do that in less 
code/cycles, though for a more flexible multiplier you'll want to use 
variables in both cases.


If it is for a fixed sum in a program:
   If the number is a power of two, shift it. Like 'n' times 8.

   If the number isn't, cheat.
   Want to multiply by nine? It will probably quicker to shift to
   multiply by eight, and then add another, thus *9!


I Googled this for you:
   http://www.cyberroach.com/analog/an19/boot_camp.htm
Might help explain?


There's another cheat you can use. Count DOWN in your loop, not up. When 
you hit zero, the Z flag will be set so you can BNE loop (until zero...) 
disposing of the need to CMP.



Best wishes,

Rick.

-- 
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