program example
      integer i, pgopen
      real x(100), y(100), p_x(5),p_y(5), delta_x
      if(pgopen('/xwin') <= 0) stop
      delta_x = 5.0 /100 
      Do i=1, 100
        x(i) = i*delta_x
        y(i) = x(i)**2
      end do
      do i=1,5
        p_x(i) = i
        p_y(i) = i**2
      enddo
      call pgenv(0.0, 10.0, 0.0, 20.0, 0, 0)
      call pglab('x','y','parabolla')
      call pgline (100, x, y)
      call pgpt (5,p_x, p_y, 12)
      call pgclos
      end