program line_n_pt_pap_lab
      real x(101),y(101),xp(5),yp(5)
      if(pgopen('/xwin')<=0)stop
      call pgpap(4.0,0.75)
      call pgenv(0.0,4.0,0.0,25.0,0,0)
      call pglab('x','y','y=x**2')
c preapre data for y=x^2
      dx=(4.0-0.0)/100
      do i=1,101
        x(i)=(i-1)*dx
        y(i)=x(i)*x(i)
c       y(i)=x(i)**2
      end do 
      do i=1,5
        xp(i)=i
        yp(i)=i*i
      end do
      call pgline(101,x,y) 
      call pgpt(5,xp,yp,9)
      call pgclos
      end