Subj : Re: zero page allocation for Forth
To   : chitselb
From : Harry Potter
Date : Thu Aug 10 2017 17:08:56

On Thursday, August 10, 2017 at 3:48:55 PM UTC-4, chitselb wrote:
> If you needed 141 bytes of zero page on a C-64, what addresses would you use? 
 BASIC is switched out, Kernal is still switched in, so anything BASIC uses can 
be reallocated.  Having it all be contiguous so I can go in and out of BASIC is 
important too.
>
> On a PET (4.0 ROM) I'm just using $00-$8C (everything below jiffy clock) and 
there's a little ML routine ('aloha') to swap the half page in and out, but I 
want to port PETTIL to the C=64

On a C64, the BASIC ROM uses ZP addresses $02-$8F, but you can use kernal ZP 
locations you don't need in your program.  For example, $83-$8B and $AE-$B6 are 
used for tape and RS232 and $F7-$FF are for RS232 and free space.  Does this 
help?

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