Tony Duell wrote:
> > The commodore tape drive system apparently put a header at the start of each
> > file. You could fast forward through the tape manually until you got to about
>
> Yes, most systems did that. The home computers using normal audio tapes
> (that you had to position manually) generally had a header per file. The
> But if you don't have automatic fast forward (and some way to judge the
> approximate postiion of the tape automatically), then finding a
> particular file is consists of rewinding the tape to the start and then
> reading the tape (at normal speed) until you find the file you want.
> Which, using one side of a C90 cassette, could take 45 minutes. This is
> going to get boring fast.
Oops, interesting conversation you have here. I used C90 cassettes or
whatever in my datasette and I could position the thing quite
easily using the mechanic position counter. Didn't you have that
on your device? May be the PET 2001 didn't have a counter, but the
datasette I got with my C=64 did have that counter. The counter
wouldn't work accross two different devices, the one in school
counted at different speed than the one I had at home ... but I
suppose I could have found a conversion factor if need had been.
Now, for the more modern times, a 2GB DAT tape doesn't have a counter
and doesn't have a directory. But it has a start-of-file marker
that you can fast forward to (at amazing speeds!). You can do the
same backwards and on a per-block basis. On UNIX with "mt fsf $n"
you can forward by $n number of files. I found it impossible to
update a directory at the start of the tape, since each write would
leave an end-of-tape-mark at the end so that the rest of the tape
was lost. So, again I use the simple manually kept directory with
a pencil and the tape cover/label.
-Gunther
--
Gunther Schadow, M.D., Ph.D. gschadow_at_regenstrief.org
Medical Information Scientist Regenstrief Institute for Health Care
Adjunct Assistent Professor Indiana University School of Medicine
tel:1(317)630-7960 http://aurora.regenstrief.org
Received on Mon May 21 2001 - 21:21:16 BST