program read_n_plot
      character*20 myfilename

      write(*,*)'Name of file to plot, please:'
      read(*,*)myfilename
      open(unit=10,file=myfilename,status='old')

      read(10,*)n

      if(pgopen('/xwin')<=0)stop
      call pgenv(0.0,10.0,-5.0,5.0,0,0)


      do i=1,n
        read(10,*)x,y
        call pgpt(1,x,y,20)
      end do

      call pgclos
      end