I'm having a hard time working out how this works. If process A is swapped out, and then B, B has to be swapped in before A can be? But only one process is ever in core at a time? To get A in, B has to be moved out? But then B would be the last one out, and would have to come in before A? Anyway, I don't understand why the OS could/would care which order processes we swapped in - unless it's something like the 'onion skin' memory allocation algorithm of CTSS (which also had only a single process resident at a time, IIRC), where, when a small process had to be swapped in, and a large one was already in, it only swapped out enough of the large one to make room for the small one. The process could recurse, hence the name. And I don't follow that either... V1 ran on the 11/20 without memory management hardware, though, right? (Although there's that cryptic reference to the KS11 in "Odd Comments and Strange Doings in Unix", although I've never been able to find out anything else about the KS11.) So presumably one would not have wanted more than one process resident at a time, as that decreases the odds of a buggy program trashing another process? Noel