$IF/$ELSE/$ENDIF         Define Conditional Compilation

 $IF const
 .
 . [statements]
 .
 [$ELSE
 .
 . statements]
 .
 $ENDIF

    Defines a conditional compilation block.

       const    A named constant or a constant value. If const is nonzero
                (TRUE), the statements between $IF and $ELSE are compiled.
                If const is zero (FALSE), the statements between $ELSE and
                $ENDIF are compiled.

   --------------------------------------------------------------------------

      Notes:    $ELSE is optional. $ENDIF is required.

                Conditional compilation statements can be nested to 256
                levels.