Pre-Defined Shell Variables

A Predefined Shell Variable is a data variable that exists when your csh is started. These variables are set in one of two ways:

set var=value
  or,
set var

These variables help you customize your environment by controlling where to look for executable files, the appearance of the prompt, whether you are notified when you receive mail, etc.

Pre-defined shell variables are only meaningful within your current shell.

NOTE: These variable names are all lower-case.