[TUHS] Etymology of shell

[TUHS] Etymology of shell

[Warren Toomey]

So what is the etymology of "shell", then? I see that Multics has a shell. Was the CTSS user interface also called a shell?

Cheers, Warren
-- 
Sent from my Android phone with K-9 Mail. Please excuse my brevity.
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[TUHS] Etymology of shell

[John Cowan]

Warren Toomey scripsit:

> So what is the etymology of "shell", then? I see that Multics has a
> shell. Was the CTSS user interface also called a shell?

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 at 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)

[TUHS] Etymology of shell

[Noel Chiappa]

    > From: John Cowan

    > Rather than starting another process, the Multics shell mapped the
    > executable program the user requested into its own space .. then jumped
    > into it. The equivalent of exit() simply jumped back to the shell code.

This is from memory, so apply the proverbial grain, but ISTR that the
original concept for the Multics shell was just like that for Unix - i.e.
each command would be a separte child process. This was given up when Multics
processes turned out to be so computationally expensive, and they went to
commands being subroutines that were dynamically linked in (very easy with
Multics, where dynamic linking was a fundamental system capability) and
called from the shell.

	Noel