Variables Defining Constants

The following variables have fixed values that cannot be changed, i.e., are constant. These variables are the only ones permitted in a CASE statement WHEN command.

The $FALSE Variable

$\textbf{{\char36}FALSE}$

False logical value

Type: Logical, Read-only

The $FALSE variable stores the logical constant representing false. The macro compiler constant .FALSE. can be used in place of $FALSE.

The $NULL Variable

$\textbf{{\char36}NULL}$

“Not Used”, “Not Available” value

Type: $NULL, Read-only

The $NULL variable has a special fixed value, which is used to indicate not used or not available. $NULL has a value with a null data type: it is not a number, string, minor word or sequence. $NULL is therefore not equal to any number, string, minor word or sequence.

$P variables and some macro system variables will be set to $NULL to indicate that a value is not available or has yet to be specified.

The $PI Variable

$\textbf{{\char36}PI}$

PI Trigonometric value

Type: Numeric, Read-only

The $PI variable stores the PI trigonometric constant.

The $TRUE Variable

$\textbf{{\char36}TRUE}$

True logical value

Type: Logical, Read-only

The $TRUE variable stores the logical constant representing true. The macro compiler constant .TRUE. can be used in place of $TRUE.