%LOC (arg)
 Returns the actual storage address of a data element.  The argument
 can be any data value.  The result is an INTEGER*8 data type on
 Alpha AXP processors, or an INTEGER*4 data type on RISC processors.

 In the case of global symbols, %LOC returns the value of the symbol
 rather than its address.

 %REF (arg)
 Forces an actual argument in a CALL statement or function reference
 to be passed by reference:  the address of the argument is passed
 to the subprogram.  By default, Fortran passes all numeric values
 by reference.

 %VAL (arg)
 Forces an actual argument in a CALL statement or function reference
 to be passed by value:  the actual value of the argument is passed
 to the subprogram.  The argument must be 32 bits in size or less.
 If the argument is less than 32 bits in size, it is sign-extended
 to that size.