Re: "Packed disk" format...

[Andy McFadden <fadden@fadden.com>]

Michael J. Mahon <mjmahon@aol.com> wrote:
> I have a 5.25" DOS disk that contains two large files, each purporting
> to be a "packed" version of a full disk side.  The largest of these
> files is 337 sectors, and the file name is suffixed with "<337>".
> 
> None of the contents is "readable" text, though each file starts off
> with the hex sequence:  00 00 00 00 10 00 ....
> 
> Does anyone know what program might have been used to "pack" these
> disk sides?

DDD created files with that sort of name; the number is the length in
sectors.  If so, they should open with CiderPress.

A comment from diskimg/DOS33.cpp:

 * To handle DDD 2.x files correctly, we need to identify them as such by
 * looking for 'B' with address=0 and length=0, a T/S count of at least 8
 * (the smallest possible compression of a 35-track disk is 2385 bytes),
 * and a '<' in the filename.  If found, we start from offset=0
 * (because DDD Pro 1.x includes the 4 leading bytes) and include all
 * sectors, we'll get the actual file plus at most 256 garbage bytes.

The DOS 3.3 code in CiderPress looks for candidate files, and gives
them an artificial length, so that the DDD expansion code doesn't have
to do the guessing.

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