Wanted: prodos prog selec

[jeff.blakeney@canrem.com (Jeff Blakeney)]

Subject: Wanted: prodos prog selector2run dos3.3games

 LLC> many old DOS 3.3 games will run under prodos, provided they don't
    > run out of buffer space while loading, and this happens a lot when
    > run from basic.system.  but if we're just running a program
    > selector there'll be more memory available to load the program
    > yes?

 LLC> perhaps someone knows simply how to patch the prodos file selector
    > so that it will load the program at its native location instead of
    > $2000?

I'm not sure if this helps or not but I thought I'd throw it in anyways.

If the problem you are experiencing is a NO BUFFERS AVAILABLE error
message if you try to BRUN a DOS 3.3 game from BASIC.SYSTEM on a ProDOS
disk, you are probably running into ProDOS's memory protection system.

ProDOS actually has a bit map of what sections of memory can be used and
if you try to load something into a protected part of memory, you get a
NO BUFFERS AVAILABLE error message.  When I was converting some DOS 3.3
games to ProDOS, I ran into this problem and discovered that what was
happening was that the DOS 3.3 game was trying to over the text screen
($400).  Under ProDOS, this area is protected and will cause the error.
If the program didn't load into this area, it would work fine.

What I ended up doing was adding some code to my Applesoft BASIC program
selector to modify the ProDOS bit map to say that the text screen was
not protected.  Then all the programs that were giving me problems
started working.

If you want, I could post the relevant code or my entire selector here
or to your e-mail address.  The program selector is pretty basic; reads
the directory and displays the names in multiple columns on the screen
with numbers beside them.  You type the number of the program you want
to execute and press return.  I always meant to go back and finish the
user interface up but it was working and I had other things to do so I
never did finish it.

 * 2qwk! 2.0 * Tg Ln Lite - 30% lss chrctrs