MPI procedures sometimes assign a special meaning to a special value of a basic type argument; e.g. tag is an integer-valued argument of point-to-point communication operations, with a special wild-card value, MPI_ANY_TAG. Such arguments will have a range of regular values, which is a proper subrange of the range of values of the corresponding basic type; special values (such as MPI_ANY_TAG) will be outside the regular range. The range of regular values can be queried using environmental inquiry functions (Section MPI Environmental Management ).