Re: Reference for layout of ProDOS and DOS 3.3. sector ordering?

[Andy McFadden <fadden@fadden.com>]

schmidtd <schmidtd@my-deja.com> wrote:
> Well, hmmm.  The book says that block 0 maps to _physical_ sectors 0
> and 2, but _DOS 3.3_ sectors 0 and E.  ADT pulls sectors off the disk
> sequentially (in reverse) using RWTS - which I assume uses DOS 3.3
> numbering and not physical numbering.  Right?  I guess my question
> really is... which sectors am I really pulling if I use RWTS so I know
> how to relate them to ProDOS ordering in the table? :-)

The sectors in a .do file, which is what ADT creates, are tracks 0 through
34 and sectors 0 through 15, in ascending order, *as DOS sees them*.
So the question you have to answer is, if I'm in ProDOS and read block N,
which two *DOS* sectors do I get?

The way I addressed this in CiderPress was to convert from the file's
ordering to "physical" and then "physical" to the requested sector in
the current mode.  If you can convert ProDOS blocks to physical sector
numbers, and DOS sector numbers to physical sector numbers, then you can
convert between ProDOS blocks and DOS sectors with two calculations.

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