Date   : Wed, 20 Jul 2005 01:23:56 +0100
From   : jgh@... (Jonathan Graham Harston)
Subject: Re: floppy discs

John Kortink <kortink@...> wrote:
> >Why not make GoMMC respond to service call 13 and 14 and
> >make it appear as a tape filing system image in ROM? No
> >patching of the OS required.
> 
> Because a lot of games have a habit of liberally
> peppering their code with things like *TAPE, *FX140
> and *FX143,12,3 and/or their OS_Byte equivalents.
 
*TAPE issues OsByte 140. Trap OsByte and whenever OsByte 140 goes
past, change it to OsByte 141 - *ROM
 
> The way it all works now (because it already does,
> see previous message) is (because the tape and ROM
> filing system use largely the same code, with a few
> switches here and there) that the OS is changed to
> do the ROM FS byte-get service call 14 at four
> strategic places, and GoMMC catches that. Works
> a treat.
 
That's a good way of doing it. Then, the data is still accessible
to an un-patched OS by selecting the ROM filing system.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
BBC BASIC for Windows and Internationalisation
  See http://mdfs.net/Software/BBCBasic/Windows/ProgTips