I’ve written a few posts [1, 2, 3] on the recently discovered Unix v4 tape. The tape is significant because it is the only known extant copy of Unix v4. Unix v4 is significant because it was the first copy of Unix to be written mostly in C. The TL;DR of those posts centers around the difficulty of reading the tape or even if it would be possible. In the end, of course, they did manage to read the tape and recover the code.
The Computer History Museum (CHM) has a very nice video featuring the people involved that recounts how hard recovering the tape was. It wasn’t possible to simply mount the tape on a drive and read it. Rather, they tapped into the electronics of the tape reader where the analog signals came off the tape head but before they were decoded into digital. The analog data was then processed by a program that recovered the digital information from the analog signals.
How they happened to have the technology to do this is an interesting story in itself and is told by the people who developed it along with the problem they were trying to solve when they did. We also hear from the people who discovered the tape and their evolving reactions to it. At first, they merely thought that finding the tape—an ancient technology at that time—was sort of cool but they didn’t think much of it. It wasn’t until after a bit of research that they realized what they had and got in touch with the CHM.
The video is 16 minutes, 37 seconds long but it tells an interesting story and is worth a quarter hour of your time.