A defined condition expression tests if a compilation variable is currently defined.
- An IS DEFINED condition evaluates as TRUE if compilation-variable-name-1 is defined.
- If compilation-variable-1 was defined via a DEFINE Compiler option, but preceding the defined condition in the program there
is neither a corresponding DEFINE directive with the AS PARAMETER phrase nor a DEFINE directive without the OFF phrase for
the compilation variable, then the defined condition for the compilation variable evaluates to FALSE.
- An IS NOT DEFINED condition evaluates as TRUE if compilation-variable-name-1 is not defined.
- If the most recent definition of compilation-variable-name-1 is via a DEFINE directive with the OFF phrase, it is considered
to be not defined.