Re: Applesoft 1?

[dempson@actrix.gen.nz (David Empson)]

lyricalnanoha <lyricalnanoha@usotsuki.hoshinet.org> wrote:

> On Sun, 30 Nov 2008, David Empson wrote:
> 
> > lyricalnanoha <lyricalnanoha@usotsuki.hoshinet.org> wrote:
> >
> >> I've managed to find Applesoft 1, the original buggy version, and I'm
> >> trying to reverse-engineer it to port since the "7-in-1 MS 6502 BASIC"
> >> produces broken output - but I've got a big question...
> >>
> >> ...what memory space does it load into? (Stupid obfuscated BASIC loaders.)
> >> I can't seem to figure out the info I'd need to be able to save it or to
> >> export it so I can extract the binary and feed it to IDA or something...
> >
> > I wasn't using the Apple II that far back but it seems reasonable to
> > assume the original version of Applesoft would have been loaded from
> > tape into main memory, either near $0800 or at the top of main memory.
> >
> > Putting it at the bottom would have been easier because it wouldn't need
> > to relocate depending on the amount of RAM installed.
> >
> > It predated the language card, so that area is out of the question. DOS
> > may not have been in the picture either, but it may have gone to some
> > trouble to respect Integer BASIC's LOMEM and/or HIMEM.
> 
> I've heard it loads at $800, it does seem to have code around there but
> the entry point's not down there.  Hm.

It might load at $7F8 (or thereabouts) and jump to the correct entry
point (which is likely to be the equivalent of $E000).

Is it possible to have a two-stage tape loader? If so, perhaps there is
a front end loaded somewhere else (maybe somewhere in $0200-$03EF), and
the main image is loaded at $0800, with the front end jumping to the
"cold" entry point.

-- 
David Empson
dempson@actrix.gen.nz