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

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

  X_FLOAT is supported only on OpenVMS Alpha Systems.