Audio Cassette formats; Copy protection? - test-drb@ccmp.vtda.org

30 Nov 1998

...
 > Someone mentioned that there are copy protection
schemes for cassette tape,
...
   and I was
curious what these might be and how they might interfere with
 recording the tape onto my HD. 
 Some machines (the BBC micro is one IIRC) have a bit in the cassette
 block header that when set prevents you listing or saving the BASIC
 program. That's one trivial form of copy protection. I don't recall that
one on the BBC.  You could do that on the ZX81 due to
very strange operating system features.

The BBC had a header on each tape _block_ that said where the file would be
stored in memory, how long it was and an execution address.  One simple
scheme rested on the fact that the parameters the machine used were taken
...
 from the first block of the file and those it told the
user were taken from the last block...

I also saw a program which, when listed or saved, gave "bad program", but
would run OK.  Don't know how that was done...

Philip.