Logical

 Logical expressions can contain one or more logical operators and
 logical, integer, or relational operands.  The following are
 logical operators:

    Operator  Meaning
    ---------------------------
    .AND.     Logical conjunction: the expression A .AND. B
              is true if both A and B are true.

    .OR.      Logical disjunction (inclusive OR):  the ex-
              pression A .OR. B is true if either A, B, or 
              both, are true.

    .XOR.     Same as .NEQV.

    .NEQV.    Logical inequivalence (or exclusive OR): the
              expression A .NEQV. B is true if either A or 
              B is true, but false if both are true.

    .EQV.     Logical equivalence: the expression A .EQV. B
              is true if both A and B are true, or both are
              false.

    .NOT.     Logical negation: the expression .NOT. A is 
              true if A is false and false if A is true.