I used a VAX in college, and the DEC operating system had built-in support for file versions. E.g., something like: when you write to a file, that creates FILEN

I used a VAX in college, and the DEC operating system had built-in support for file versions. E.g., something like: when you write to a file, that creates FILENAME.EXT.5 where before there were FILENAME.EXT.1 through 4. Compared to Unix it was harder to accidentally wipe your data. (It's been so long, and I didn't use it so much, that I won't opine on how much harder. But the Unix Haters Handbook ragged on Unix quite a bit for this sort of thing.)