Re: ProDOS Plus

["Michael J. Mahon" <mjmahon@aol.com>]

Andy McFadden wrote:
> mdj <mdj.mdj@gmail.com> wrote:
>
> > > Sparse files were available already in Apple DOS 3.3 as well as in CP/M-80,
> > > both of which predated ProDOS.
> >
> > Curious. I never saw one in DOS 3.3, and didn't do a lot with CP/M.
>
>
> Random-access text files can be sparse.  For example, in the CiderPress
> tutorial sample disk image (an 800K disk with a DOS partition), there's a
> sparse file called "RANDOM:L128":
>
>  Name                             Type Auxtyp Modified         Format   Length
> ------------------------------------------------------------------------------
>  TestFiles                        DIR  $0000  17-Jan-03 19:27  ProDOS      512
>  TestFiles:SPARSE                 NON  $0000  11-Jan-03 16:24  ProDOS 16777215
>  TestFiles:EMPTY.SPARSE           NON  $0000  11-Jan-03 15:54  ProDOS    43969
>  TestFiles:EMPTY.SPARSE.R         NON+ $0000  11-Jan-03 15:51  ProDOS     6844
> [...]
>  _DOS001:RANDOM:L128              TXT  $0000  [No Date]        DOS      384030
>
>
> I hadn't realized that was possible until I had to implement them. :-)

ProDOS sparse files are actually pretty well known.

I use binary sparse files as large virtual address spaces for various
purposes.  BSAVE and BLOAD with the B and L parameters allow truly
random access to any kind of file (if the T parameter is used, too).

I'd just never run across one (knowingly) in DOS, where only a random
text file can be sparse.

-michael

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