I was recently clearing out a drawer full of audio cassettes, some of which were unlabelled. So I decided to play them. (Yes, I've still got a cassette player!) I found that they were full of a series of tones, which was the only way (back in the mid-1980s) to save computer programs written on the BBC Model B computers at the school where I taught.
At least that was better though than the first computer programs I wrote at college. They were written in Fortran IV, and later in Basic, ready to be typed onto punched cards. Those cards then had to be POSTED(!) to the Polytechnic, so that the programs could be run on their computer, with the printed output being posted back to us. A single keying error when punching the cards could wreck a program, so I'd then have to type out another set of cards and put those into the post, praying that I'd not made any more errors!