Multics (was Re: getcwd() and friends.)

[Dave Collier-Brown]

  Actually the cost of a system-call equivalent in Multics was/is
comparable to system calls in Unix, as one usually had a ring crossing
required to do anything major (ie, something other than returning one's
process id).  This meant calling a gate, having it double-check you, then
set up a new stack frame, then do the work.
  The old call sequence was...

	eaplp	-*,ic
	aos	2,ic
	tra	linq-*,ic*
	arg	0

  which means "do all sorts of stuff, then branch" (:-)).

  Seriously, though, there were lots of good, subtle ideas in Multics. Some
deserve to be reinvented.  Others deserve to be recorded as "classic, elegant
stupidity".


--dave

  

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