The safe bet would be on corporate/academic mainframe software. While lots have been patched or replaced, I bet there's code from the 70s (perhaps 60s) still ru

The safe bet would be on corporate/academic mainframe software. While lots have been patched or replaced, I bet there's code from the 70s (perhaps 60s) still running out there somewhere. Let's put it this way: there's a market for teaching people how to program like it was 1975. Nobody around can do it anymore, and the code base is large enough that both the teaching and skillset are highly valued in some circles.