program square
      real x(5),y(5)
      x(1)=-1
      y(1)=1
      x(2)=1
      y(2)=1
      x(3)=1
      y(3)=-1
      x(4)=-1
      y(4)=-1
      x(5)=x(1)
      y(5)=y(1)

      i_dummy=pgopen('/xwin')
      call pgenv(-5.0,5.0,-5.0,5.0,1,0)
      call pgline(5,x,y)

      call pgclos
      end