New string variables declared on IF are initially set to a blank value and
are assigned the format specified on the STRING command that creates them.
Logical expressions are evaluated in the following
order: string functions, then relations, and then logical operators.
When more than one logical operator is used, NOT is evaluated first, followed by AND, and then OR. You can change the order of operations using parentheses.
If the transformed value of a string variable exceeds
the variable’s defined width, the transformed value is truncated.
If the transformed value is shorter than the defined width, the string
is right-padded with blanks.