/sys$common/syshlp/helplib.hlb PASCAL, Attributes, Parameter, CLASS_S  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  The CLASS_S attribute causes a formal parameter to be passed  by
  a  single  descriptor  form  that  is  used  for scalar data and
  fixed-length strings.  This attribute allows routines written in
  Compaq  Pascal  to  accept actual parameters from languages that
  generate CLASS_S descriptors.

  See the  "Compaq  Pascal  Language  Reference  Manual"  for  the
  complete description of using the CLASS_S attribute.