Historical use of "traps"
dillon at apollo.backplane.com
Thu Jun 9 09:33:18 PDT 2005
:I was wondering about the historical meaning of the word "trap" today,
:in context of hardware and software traps. I have learned that creating
:a trap generally means an interrupt is created by one means or another.
: So, does "trap" mean "a trap for the kernel to fall into and handle?"
We need a historian. I do remember that on the 6502 instruction code
00 was a BRK instruction. People would often use this to insert hooks
into eproms or proms without erasing them. Simply program the location
to 00 and it would trap into software which would then implement the
In modern times TRAPs, EXCEPTIONS, and INTERRUPTs are nearly the same,
except that TRAPs typically mean synchronous entry into the supervisor
context (e.g. TRAP instruction), EXCEPTIONS mean (usually) synchronous
entry into a theupervisor due to an instruction fault, and INTERRUPTs
mean asynchronous entry into the supervisor.
<dillon at xxxxxxxxxxxxx>
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