HPF provides data mapping directives that are advisory in nature. The mapping inquiry subroutines allow the program to determine the actual mapping of an array at run time. It may be especially important to know the exact mapping when an EXTRINSIC subprogram is invoked. For these reasons, HPF includes mapping inquiry subroutines which describe how an array is actually mapped onto a machine. To keep the number of routines small, the inquiry procedures are structured as subroutines with optional INTENT (OUT) arguments.