OPEN(FIle=input, OLD, ERror=21) ! on error branch to label 21 (not shown)
OPEN(FIle=output)
    DO i = 1, 1E300 ! "infinite" loop, exited on end-of-file error
      READ( FIle=input,  ERror=22) buffer ! on error (end of file) branch to label 22
      WRITE(FIle=output, ERror=23) buffer ! on error branch to label 23 (not shown)
    ENDDO
22  WRITE(FIle=output, CLoSe=1)