Looking for programs on audio tape/cassette containing programs for Sinclair ZX80 PC?

Question

OK, so back before ice age, I recall having a Sinclair ZX80 PC (with TV as a display, and a cassette tape player as storage device).

Obviously, the programs on cassette tapes made a very distinct sound (er... noise) when playing the tape... I was wondering if someone still had those tapes?

The reason (and the reason this Q is programming related) is that IIRC different languages made somewhat different pitched noises, but I would like to run the tape and listen myself to confirm if that was really the case...

Answer 1

I know these come up on auction sites like Ebay quite frequently - if you want to buy them yourself. If you get someone else who owns one to listen then you are going to get their subjective opinion :)

In any case, the language used to save it would be the secondary cause of the pitch changes - it will be related to the data. IOW you could probably create a straight binary data file that sounded very similar to a BASIC program (the BASIC would have been saved as text, as it is interpreted).

Answer 2

I know the threads old but... I was playing about with something similar last night and I've got a wav of an old zx81 game if you're still interested? pm me and I'll post it somewhere.

Answer 3

You can use something like http://www.wintzx.fr/ or pick something from http://www.worldofspectrum.org/utilities.html#tzxtools to convert an emulator file to an audio file and then you can just play it on your PC. Some tools also allow you to play the file directly. Emulator files can be found at http://www.zx81.nl/files.html and many other places.

Answer 4

I have the tapes but they've been stored in the garage at my parents' house and the last thirty years hasn't been kind to them.

You can get images here though: http://www.zx81.nl/dload if that's any use. Perhaps there is a tool out there for converting from the bytes back to the audio ;)

Edit: Perhaps here: http://ldesoras.free.fr/prod.html#src_ay3hacking

Answer 5

On the ZX80, ZX81 and ZX Spectrum, tape output is achieved by the CPU toggling the output line level between a high state and a low state. Input is achieved by having the CPU watch an input line level. The very low level of operation was one of Sir Clive's cost-saving measures; rival machines like the BBC Micro had dedicated hardware for serialisation and deserialisation of data, so the CPU would just say "output 0xfe" and then the hardware would make the relevant noises and raise an interrupt when it was ready for the next byte. The BBC Micro specifically implements the Kansas City Standard, whereas the Sinclair machines in every instance use whatever adhoc format best fitted the constraints of the machine.

The effect of that is that while almost every other machine that uses tape has tape output that sounds much the same from one program to the next by necessity, programs on a Sinclair machine could choose to use whatever encoding they wanted, which is the principle around which a thousand speed loaders were written. It's therefore not impossible that different programs would output distinctively different sounds. Some even used the symmetry between the tape input and output to do crude digital sampling, editing and playback, though they were never more than novelties for obvious reasons.

That being said, the base units of the ZX80 and ZX81 contained just 1kb RAM so it's quite likely that programmers would just use the ROM routines for reading and writing data, due to space constraints if nothing else. Then the sound differences would just be on account of characteristic data, as suggested by slugster.