Re: [cc65] Remote display for the C64 using VNC

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From: Ullrich von Bassewitz (
Date: 2002-06-27 21:02:40


On Thu, Jun 27, 2002 at 08:34:14PM +0200, Adam Dunkels wrote:
> Uz - does cc65 work well with the BASIC interpreter? Are there any zeropage
> variables or anything eler that are trashed by either?

The cc65 runtime uses 24 bytes of the zero page. Since most of the zero page
is used by BASIC and the kernal, and the kernal is needed when a cc65 compiled
program is running, part of the variables used by BASIC are saved, used by the
program, and copied back when the program ends. This means that it is not
possible to use a cc65 compiled program and BASIC together without special

However... if the task switcher takes care of that, that is, if it manages a
local copy of the zero page locations used by both, switching threads would be
possible. It would also be possible to move the zero page space used by the
cc65 runtime into a range where more memory cells are unused. Starting at $9B
many locations are used for datasette and RS232, so moving the cc65 zero page
in that range would mean that these locations would not have to be copied when
switching threads (provided that you don't allow VNC users to access the
datasette of course).



Ullrich von Bassewitz                        
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