VMS Help FORTRAN, Built-in Functions, %DESCR  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  %DESCR (arg)
  Forces an actual argument in a CALL statement or function reference
  to be passed by descriptor:  the address of a descriptor of the
  argument is passed to the subprogram.  By default, Fortran passes
  all character values by descriptor.