[sebhc] h17 and h8d disk images

Dave Dunfield dave04a at dunfield.com
Wed Sep 1 19:38:30 CDT 2004

> There is one thing I've thought would be good to
>add to the h8d format. I think we could add one byte
>to the end that would be the volume number.
>This could be optional since HDOS disk already include
>this in the first track data. Adding one more byte
>would cause allocation of another disk block on
>most files systems ( like DOS or Windoze ). That
>is a reasonable waste of space to always use.
> This information could be determined by any program as
>simply checking the file size. One byte longer than the
>100K bytes and it must have a volume number attached.
>If exactly 100K bytes, the first track information could
>be used.
> I believe that most current programs would just ignore
>this last byte. I'm relatively sure my program would.
>I currently buffer a track at a time. This should keep
>it backwards compatible.
> What do others think?

I don't actually read the file size (I just open it), however
I could just attempt a seek to the "extra byte" and if it fails,
assume HDOS and use the volume id from block 9 (IIRC), otherwise
use the volume ID in the "extra byte" (essentually a feature to
allow for non-HDOS disks?)

Sounds reasonable.

dave04a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools: www.dunfield.com
com             Vintage computing equipment collector.

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