/tops-ten/ DEC' s proprietary Os for the fabled PDP-10 machines, long a favourite of hackers but now effectively extinct. A fountain of hacker folklore. see also ITs, TOPs-20, TWENEX, VMs, operating system. TOPs-10 wassometimes called BOTs-10 (from "bottoms-ten") as a comment on the inappropriateness of describing it as the top of anything. [Jargon File]