5.9 Operands, Operators, and Expressions
  An operand contains a value. An operand can be a scalar,
  subscripted variable, named constant, literal, and so on. An
  operator specifies a procedure to be carried out by one or
  more operands. An expression consists of operands separated
  by operators.

  The following are types of operators:

        Arithmetic
        String
        Relational
        Logical

  When combined with operands, these operators can produce:

  .
        Numeric expressions
  .
        String expressions
  .
        Conditional expressions

  For more information about operands, operators, and expres-
  sions, see the DEC BASIC and VAX BASIC for OpenVMS
  Systems Reference Manual .