Specify how a dummy argument is to be passed.

  REFERENCE specifies a dummy argument's memory location is to be
  passed instead of the argument's value.

  VALUE specifies a dummy argument's value is to be passed instead of
  the argument's memory location.

  When a dummy argument has the VALUE property, the actual argument
  passed to it can be of a different type.  If necessary, type
  conversion is performed before the subprogram is called.

  When a complex (KIND=4, KIND=8, or KIND=16) argument is passed by
  value, two floating-point arguments (one containing the real part,
  the other containing the imaginary part) are passed by immediate
  value.

  Character values, substrings, assumed-size arrays, and adjustable
  arrays cannot be passed by value.

  If REFERENCE (only) is specified for a character argument, the
  string is passed but the length is not passed.

  If REFERENCE is specified for a character argument, and C (or
  STDCALL) has been specified for the routine, the string is passed
  but the length is not passed.  This is true even if REFERENCE is
  also specified for the routine.

  If REFERENCE and C (or STDCALL) are specified for a routine, but
  REFERENCE has not been specified for the argument, the string is
  passed with the length.

  VALUE is the default if the C or STDCALL property is specified in
  the subprogram definition.