Although tcsh stores variable values as strings, you can work with these variables as numbers. Expressions in tcsh can use arithmetic, logical, and conditional operators. The @ builtin can also evaluate arithmetic expressions but can work only with integers.
This section uses the term numeric variable to describe a string variable that contains a number that tcsh uses in arithmetic or logical arithmetic computations. However, no true numeric variables exist in tcsh.
A tcsh variable name consists of 1 to 20 characters, which can be letters, digits, and underscores (_). The first character cannot be a digit but can be an underscore.
Three builtins declare, display, and assign values to variables: set , @ , and