I just found out that in old planes, flight computers were programmed with audio cassette tapes 😯 which now makes me want to look up how data recording on MCs worked on the C64 (before my time).
I remember that in the 90s, I tried to run "play.exe word.doc" to get my SoundBlaster card to write to my cassette tape. Which of course didn't work.
I bet there is a FOSS project that backups and restores to audio cassettes.
Well, I guess now I know how I'll spend my…