Re: A85: Ram OS-new OS for 85
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Re: A85: Ram OS-new OS for 85
Mike Baker wrote:
>
> Umm sound interesting but the whole idea of phatOS was to be a small
> alternative shell. Making a shell like that run phatOS programs is a
> nice idea, but goes against the concept of PhatOS. Also have you any
> idea as to how one would multitask on the z80?. I know you could run
> an interrupt but with no way to read the PC (program counter, it
> points to the part of the program currently running) it would be
> impossible to switch tasks; plus what about data storage? you'd need
> to have text_mem backed up somewhere because every program would
> want to use it and would thus corrupt the data from the other
> programs. It doesn't sound to me like you are experienced in z80
> enough to overcome these problems.
>
> Mike Baker
> mbm00@hotmail.com
As far as multitasking, preemptive multitasking (where the shell
switches when it wants) would be impossible if you could not determine
the program counter, but having the program determine when it wants to
switch would not be impossible because the program would know where it
left off. You would implement this by calling a function, say once
every time through a loop, that hands control to the os which then gives
control to another program, or if no other programs are running, sends
control back to the calling program. The only difficulty with this is
that background programs could eat up too much time and make the
foreground program be too slow. One way to fix this would be to switch
to the foreground program more often than the others.
Well, that's what I think anyway.
--
Jonathan Anderson
sarlok@geocities.com
"I can't be wrong - my modem is error correcting."
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