! Get the file name and echo it back to the user.
    write(*,*) 'Please enter input file name:'
    read(*,*) filename
    write(*,10) filename
10  format(1x, 'The input file name is : ' , A)

! Open the file and check for errors on open
    open(3,file=filename,status='old',action='read', &
          iostat=status)
    openif: If(status == 0) then
      ! open was OK. Read values
      readloop: do
         read(3, *, iostat = status) value
         if(status /= 0) Exit
         nvals = nvals + 1
         write(*, 20) nvals, value
20       format(1x, 'Line' , I6, ' : Value = ' , F10.4)
      end do readloop

      ! The while loop has terminated. Was it because of a
      ! read error or because
      ! of the end of the input file?
      readif: if(status > 0) then
        write(*, 30) nvals + 1
30      format(1x, 'An error occurred reading line' , I6)
      else
        write(*, 40) nvals
40      format(1x, 'End of file reached. There were ', &
               I6, 'values in the file.')
      end if readif
    else openif
      write(*, 50) status
50    format(1x, 'Error opening file: IOSTAT = ' , I6)
    end if openif
    close(3)
    end program read