Warren Toomey scripsit: I can't speak to CTSS, but my understanding is that the Multics shell was a shell in the same sense as an expert-system shell: that is, a fixed piece of code into which other code was loaded in order to customize it to do something. Rather than starting another process, the Multics shell mapped the executable program the user requested into its own space, as is done with shared libraries today, and then jumped into it. The equivalent of exit() simply jumped back to the shell code. -- John Cowan http://www.ccil.org/~cowan cowan(a)ccil.org The present impossibility of giving a scientific explanation is no proof that there is no scientific explanation. The unexplained is not to be identified with the unexplainable, and the strange and extraordinary nature of a fact is not a justification for attributing it to powers above nature. --The Catholic Encyclopedia, s.v. "telepathy" (1913)