:trap: 1. n. A program interrupt, usually an interrupt caused by
some exceptional situation in the user program. In most cases, the
OS performs some action, then returns control to the program.
2. vi. To cause a trap. "These instructions trap to the
monitor." Also used transitively to indicate the cause of the
trap. "The monitor traps all input/output instructions."
This term is associated with assembler programming (`interrupt'
or `exception' is more common among {HLL} programmers) and
appears to be fading into history among programmers as the role of
assembler continues to shrink. However, it is still important to
computer architects and systems hackers (see {system},
sense 1), who use it to distinguish deterministically repeatable
exceptions from timing-dependent ones (such as I/O interrupts).
-- The AI Hackers Dictionary
UUO (you-you-oh) [short for "Un-Used Operation"] n. A DEC-10 system
monitor call. The term "Un-Used Operation" comes from the fact
that, on DEC-10 systems, monitor calls are implemented as invalid
or illegal machine instructions, which cause traps to the monitor
(see TRAP)....
