shell
:shell: n. [orig. Multics
techspeak, widely propagated via Unix] 1.
[techspeak] The command interpreter used to pass commands to an
operating system; so called because it is the part of the operating
system that interfaces with the outside world. 2. More generally, any
interface program that mediates access to a special resource or server
for convenience, efficiency, or security reasons; for this meaning, the
usage is usually `a shell around' whatever. This sort of program is also
called a `wrapper'. 3. A skeleton program, created by hand or by another
program (like, say, a parser generator), which provides the necessary
incantation
to set up some task and the control flow to drive it (the
term driver
is sometimes used synonymously). The user is meant to fill
in whatever code is needed to get real work done. This usage is common
in the AI and Microsoft Windows worlds, and confuses Unix hackers.
Historical note: Apparently, the original Multics shell (sense 1) was
so called because it was a shell (sense 3); it ran user programs not by
starting up separate processes, but by dynamically linking the programs
into its own code, calling them as subroutines, and then dynamically
de-linking them on return. The VMS command interpreter still does
something very like this.
Jargon File Version 4.3.1, 29 JUN 2001 =
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