Re: Recovering data from audio tapes

[Mike <moose@rocknet.net.au>]

Metroplex wrote:

> Hi,
>
>     I am trying to help someone recover some very old data that
> was saved into audio tapes using an Apple II. Unfortunately, it is
> rather difficult to get hold of an Apple II around here. If you could
> help me with this task, I would greatly appreciate it. In particular,
> I have the following questions:-

I think you would really need to hook the tape player up to a real Apple ][
to achieve the transfer.

I did use a tape deck with my Apple ][ very extensively from 1980 to 1983,
before I could finally afford to buy a disk drive at home - boy did I love
my disk drive after using tapes .... ;)

Anyway, I did do heaps of work in saving and loading data, basic programs,
and also machine code games onto and off from tape.  Sometimes, I could
borrow an Apple ][ drive for the weekend and use it to transfer games,
programs, data to tape, and also backup what was on the tapes I had written
already.  These weekends were spent saving all my games / programs onto
tape because I may not get the lend of the drive again for another 6-12
months.

If you are loading saving data or basic programs, you should have no
problems with the tape - apart from the real possibility of data loss due
to age and inherrent problems with the tape format.

If you are loading and saving / loading machine code games, you could run
into problems.

For people who never loaded / saved machine code to / from tape, it
involved a few monitor commands, and some hex manipulation, but it didn't
always work - especially with games.

For basic programs, simply LOAD and SAVE were fine.  For machine code, it
was an entirely different kettle of fish.

Let's see, it has been 17+ years, but I still remember some of it :

] BLOAD binary-game    (to load the game from disk)
]CALL -151                    (for a good time !!)
*AA62
(then you would hit return twice and write down some HEX numbers)
*AA70
(then you would hit return twice and write down some HEX numbers)
Then you would do some manipulations on these HEX numbers, add them up so
something.
Then there was a write command - something with a W at the end.

You would then use the HEX numbers generated above to do the LOAD back from
tape, so you had to write them somewhere safe otherwise what was on tape
would be unloadable !

It really was wierd !!  The trouble was that some games gave different
answers depending on wether you loaded them from disk or tape - one game I
remember that caused me problems was Crystal Caves.  My disk version of it
became corrupt in ~1984.  So, I remembered I had it on tape (from my tape
only days) but could never get it saved back to disk again from tape - I
could never find out why.  It would load from tape OK, and play perfectly
from tape, but when I used the commands to save it back to disk, it wrote a
short file instead of one the right length, which wouldn't load from disk.
I contacted loads of people about it - Computer Land, all my Apple ][
friends, etc, but no-one could figure out what was going wrong.