I've always wondered: who actually wrote the software for IMPs and such? Who debugged the lower-level (but still essential) operational issues? Was it the peopl

I've always wondered: who actually wrote the software for IMPs and such? Who debugged the lower-level (but still essential) operational issues? Was it the people we've heard of, or others whose contributions we've forgotten? I'm guessing the latter, but it's hard to be sure this much later.