Re: DSK format specification

[pausch@saaf.se (Paul Schlyter)]

In article <myqdnVYa1ach4o2iXTWJhw@comcast.com>,
Bill Garber <willy46pa@comcast.net> wrote:
 
> You all are making DSK too complicated. All they are is this.
> Track 1, sector 1, byte 1 is byte 1 of the file, and so on each byte
> from the disk is sequential in the file. Nothing more.
 
Well, first of all, the track/sector/byte numbering stars with 0,
not with 1.
 
However, even though Track 0, sector 0, byte 0 was the first byte of
the DSK/.DO/.PO disk images, subsequent sectors (such as sector 1)
could be positioned differently.  When you say "sector 1", do you
mean physical sector 1 or logical sector 1?  If the latter, there
were three major sector interleaving schemes: Apple DOS 3, Apple
Pascal (which also was used by ProDOS), and Apple CP/M.  Thus,
"sector 1" could have four different meanings.
 
In .DSK/.DO/.PO disk images logicla sector numbers were used.  .DO
images used DOS 3 sector interleaving while .PO images used
Pascal/ProDOS sector interleaving.  .DSK images _usually_ used DOS 3
sector interleaving, but could sometimes use Pascal/ProDOS sector
interleaving.  I've never seen CP/M sector interleaving be used in
these disk images.  The Apple II Oasis emulator emulates Microsoft's
Z80 card too and thus can run Apple II CP/M -- it runs fine from disk
images with DOS 3 sector interleaving.
 
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