1. < operating system > (Originally from Multics , widely propagated via Unix ) 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.
The commonest Unix shells are the c shell ( csh ) and the Bourne shell ( sh ).
2. (Or "wrapper") 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.
[ Jargon File ]
(1995-05-11)