[Coco] 6809 CPU architecture

[jdaggett at gate.net]

Jim

Pointers are a fundamental entity in programming. The use of the 
pointer registers are important so that blocks of data or tables can be 
accessed more easily.

ex:

one has a table of 256 entries of one byte each. You can load the 
first address of the table in say the X register and then use either the 
A or B register to index into the table for the item you want. 

Pointers can be used to point data buffers arays. Say you are 
printing a line of text to a serial port. Accumaltor A can be a 
character counter to tell you when the line is done and say the X 
register can be the starting point in memory where the line of data 
needs to be printed. Register A tells you how many character to print 
and the X register tells you what to output to the serial port. 

Pointers and the use of the pointer registers is fundamental in any 
programming language. Even more so in C/C++.

james


On 22 Jan 2004 at 22:49, jimcox at miba51.com wrote:

From:           	<jimcox at miba51.com>
Subject:        	Re: [Coco] 6809 CPU architecture
To:             	CoCoList for Color Computer Enthusiasts 
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Date sent:      	Thu, 22 Jan 2004 22:49:52 -0800
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> On Fri, 23 Jan 2004 00:20:08 -0600
>   Roger Taylor <rtaylor at bayou.com> wrote:
> >At 10:17 PM 1/22/2004 -0800, you wrote:
> >>You're right, that reply was meant for Robert, but I'd 
> >>also like to thank you for your help too :)
> >>
> >>I think I'm missing something, but didn't Robert already 
> >>list X, Y, U, amd S?
> >
> >
> >
> >:)
> >
> >Think about it for a minute.
> >
> >
> 
> Can't think, brain hurts! :)  Hmmm, you listed them as 
> pointers, maybe that it or maybe I should start reading 
> one of the many books that I just dug out.  I take it the 
> one from Barden is the best (I have about six differnt 
> ones on 6809 assembly that I either purchased over the 
> years or were given to me)
> 
> Jim
> 
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