u/LongUsernamein r/programming • Recommends
On “Secret C64 Program Found On A Christian Rock Band’s Vinyl Record”
The C64 used a magnetic tape audio cassette( link to this video to store it's program. The tapes could be played as weird audio on a regular tape player. You could also copy that audio then load it back into the computer.
So these people just copied the sound onto the record groves, then you could record it back to tape and load it into the computer.
Tape was common until the late 80's when diskettes became more common. Tape was common for backing up hard drives through the early 2000s and is still used in some data center applications.