VMS Help PASCAL, Data Types, Real, H_FLOAT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  The H_FLOAT type denotes quadruple-precision real  values.   The
  H_FLOAT  type  is  synonymous with the QUADRUPLE type on OpenVMS
  VAX systems.

  H_FLOAT is supported only on OpenVMS VAX Systems.