Re: DSK format specification

[Andy McFadden <fadden@fadden.com>]

In comp.sys.apple2 Michael Pender <mpender@hotmail.com> wrote:
> Omigosh!!  ProBlock version 1.0 could do that back in 1990!!
> 
> Seriously though, I thought the format would be a bit more complex.

Nope.  Common Apple II disk formats:

- Universal Disk Images (.2mg)
  Spec available on www.a2central.com as FTN $e0/0130.
- DiskCopy 4.2 (.dsk)
  Spec available as FTN $e0/0005.
- Copy II Plus (.img)
  Unadorned sectors, but in "raw" order.
- Sim //e HDV images (.hdv)
  Unadorned sectors with a header.
- Dalton's Disk Disintegrator (DDD v2.1+, DDD Pro v1.1+) (.ddd)
  Not described anywhere, but a source code disassembly is available.
- Unadorned sector-format files (.po, .do, .raw, .hdv)
  The "DSK" format, which is usually in DOS or ProDOS sector order.
  DiskCopy 6 (.dc6) is usually just this.
- Unadorned nibble-format files (.nib, .nb2)
  Raw nibbles, with 6384 or 6656 bytes per track.
- ShrinkIt (NuFX) compressed disk images (.shk, .sdk)
  Spec available as $e0/8002.

There are a few others (e.g. Davex archived volumes, $e0/8004), and I think
Apple Oasis has its own.  The above are often stored with gzip compression
or (ick) in a ZIP archive on FTP sites.

The real trick is figuring out whether an unadorned 5.25" image is in
DOS, ProDOS, or "physical" order.  Also, don't make the mistake I made in
CiderPress 1.0 and assume that all volumes are going to be multiples of
something nice, like 4K.  It's possible to have odd-sized ProDOS volumes,
mostly from Windows/Mac/UNIX utilities that create a full-sized HD volume
but don't actually write the blocks until necessary.

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