program exam_pgplot
      implicit none
      integer pgopen, ngrids, i
      parameter (ngrids=1000)
      real x(ngrids), y(ngrids), delta_x, xmin, xmax
      
      xmin = -10.0
      xmax = 10.0

      if(pgopen('/xwin').le.0) stop

      call pgenv (xmin, xmax, -1.0, 1.0, 0, 0)

      delta_x = (xmax-xmin)/(ngrids-1)


      x(1) = xmin
      y(1) = sin(x(1)) * (1/ (1+(x(1)**2)) )
      do i=1, ngrids-1
        x(i+1) = x(i) + delta_x 
        y(i+1) = sin(x(i+1)) * (1/ (1+(x(i+1)**2) ))
      end do

      call pgline(ngrids, x, y)

      call pgclos

      end