anchor.diff:        open( 10, file = '_x20f_.bin', access = 'direct', recl = 1 )
         do i = 1,8
             write( 10, rec = 1, iostat = ierr ) string(1:i)
  -          if ( ierr /= 0 ) exit
  +          if ( ierr /= 0 ) call exit(1)
             bytes = i
         enddo
   
  
positive.code:               read( 10, rec = record ) (img(b), b = 1,bytes )
                first  = 1
            else
                exit
            endif
        enddo
  
  
negative.code:           record = record + 1
            read( 10, rec = record, iostat = ierr ) (img(i), i = 1,bytes )
            if ( ierr .ne. 0 ) then
                read_img = .false.
                return
            endif
  
            do i = 1,bytes
  