subroutine errio (stdout,subnam,mess,ios)
c
c=======================================================================
c                                                                    ===
c  This routines determines the error status from the given iostat   ===
c  value.                                                            ===
c                                                                    ===
c  ------                                                            ===
c  Input:                                                            ===
c  ------                                                            ===
c                                                                    ===
c  STDOUT   Unit number for standard output.      (integer)          ===
c  SUBNAM   Name of calling subroutine/function.  (string)           ===
c  MESS     Error message to print.               (string)           ===
c  IOS      IOSTAT value to test.                 (integer)          ===
c                                                                    ===
c  Calls:  EXITUS                                                    ===
c                                                                    ===
c=======================================================================
c
c-----------------------------------------------------------------------
c  Define local data.
c-----------------------------------------------------------------------
c
      integer ios,stdout
      character*(*) mess,subnam
c
c=======================================================================
c  Begin executable code.
c=======================================================================
c
      if (ios .gt. 0) write (stdout,10) subnam,'error',mess,ios
      if (ios .lt. 0) write (stdout,10) subnam,'end-of-file',mess,ios
c
      if (ios .ne. 0) call exitus (subnam)
c
      return
c
 10   format (/'***Error:  ',a,' - ',a,' occured while ',a/11x,
     &         'error code = ',i10)
c
      end