VMS Help PASCAL, Predeclared Routines, Transfer, UINT64  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  The UINT64 function converts the  value  of  the  parameter  and
  return its UNSIGNED64 equivalent.

  Syntax:

     UINT64(x)

  The parameter 'x' must be of an ordinal type.

  No error results if 'x' is an integer and has a negative  value.
  The value returned is x MOD 2**64.