/sys$common/syshlp/helplib.hlb FORTRAN, Statements, INQUIRE, IOSTAT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  IOSTAT = ios

  ios  Is an integer scalar memory reference.

  IOSTAT is a control specifier rather than a property specifier.
  The "ios" is assigned a processor-dependent positive integer value
  if an error occurs during execution of the INQUIRE statement; it is
  assigned the value zero if there is no error condition.