Date   : Thu, 20 Oct 1994 11:51:40 +0000
From   : lamcw <lamcw@...>
Subject: re: BBC: Disk Handling

"Chris L. Rae" wrote

;My gut feeling is that an emulator should emulate the *whole* machine, if 
;possible. 

but that means REAL HARD work!!

;That means disks too. So I think that if you have a BBC 
;emulator, you should be able to stick BBC disks in it.

ideally it's a nice thought. but as david barnett said, it's not really
necessary. i'm just trapping the CFS (cassette filing system) using
OSFILE and OSFSC to load and save blocks of data.

the hassle is that no directory is maintained. so okay, you can't have it
both ways. i put the load & exec addresses in a 10 byte header at the start
 of the file,i.e.

   &FF    (fixed value as a check)
   LO1
   HI1    (load addr)
   LO2
   HI2    (exec addr)
   CHK    (a simple check, (LO1+HI1+LO2+HI2)&255  )
    0
    0
    0
    0     (reserved for possible future expansion)


the commands SAVE and *SAVE will create these headers as well. one nice
advantage is that PAGE can stay at &E00.


chris lam.