program read_n_plot
      character*20 user_filename

      write(*,*)'Which file to plot?'
      read(*,*)user_filename

      open(unit=10,file=user_filename)

      read(10,*)n

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