The CLASS_A attribute causes a formal parameter to be passed  by
  an  array  descriptor that describes contiguous arrays of atomic
  data types or contiguous arrays of fixed-length  strings.   This
  is  the  default  mechanism  for  conformant array parameters on
  OpenVMS VAX systems.  This attribute is illegal on parameters of
  schema types.

  See the "HP Pascal Language Reference Manual" for  the  complete
  description of using the CLASS_A attribute.