Arithmetic expressions contain numeric data such as variables,
 record elements, array elements, constants, function references,
 and arithmetic expressions enclosed in parentheses.  The expression
 evaluates to a numeric value.  The numeric operators are as
 follows:

      Operator    Ranking     Description

         **        1          exponentiation (evaluated
                                  right to left)
         *         2          multiplication
         /         2          division 
         +         3          addition
         -         3          subtraction        

 You can use parentheses to force an order of evaluation.

 Character expressions consist of character elements and character
 operators.  Evaluation of a character expression yields a single
 value of character data type.  A character element may be a
 constant, variable, record element, array element, substring,
 expression (optionally enclosed in parentheses), or a function
 reference.

 A character expression has the form:

   character element[//character element]...

 The concatenation operator (//) is the only character operator.
 Concatenation is from left to right.

 Logical expressions may contain logical and integer data such as
 variables, record elements, array elements, constants, function
 references, expressions enclosed in parentheses, and relational
 expressions.  The expression evaluates to a logical value using the
 following operators:


       OPERATOR         PRECEDENCE
       **               First (Highest)
       *,/              Second
       +,-,//           Third
       Relational
         Operators      Fourth
       .NOT.            Fifth
       .AND.            Sixth
       .OR.             Seventh
       .XOR.            Eighth (Lowest)
       .NEQV.           Eighth
       .EQV.            Eighth

 Relational expressions consist of either two arithmetic or two
 character expressions separated by relational operators.  The
 expression is reduced to a logical value (true or false).

       OPERATOR      DESCRIPTION
        .LT.          Less than
        .LE.          Less than or equal to
        .EQ.          Equal to
        .NE.          Not equal to
        .GT.          Greater than
        .GE.          Greater than or equal to

 Expressions of COMPLEX data type can use only .EQ. and .NE.
 operators.