program rotate_object
c     implicit none
      real x(5),y(5),xold(5),yold(5)

      xold(1)=1.0
      yold(1)=1.0
      xold(2)=-1.0
      yold(2)=1.0
      xold(3)=-1.0
      yold(3)=-1.0
      xold(4)=1.0
      yold(4)=-1.0
      xold(5)=xold(1)
      yold(5)=yold(1)

      if(pgopen('/xwin')<=0)stop
      call pgenv(-3.0,3.0,-2.0,2.0,1,0)

      dtheta = 0.0001
      do j=1,100000
        do i=1,5
          x(i)=xold(i)*cos(dtheta)+yold(i)*(-1)*sin(dtheta)
          y(i)=xold(i)*sin(dtheta)+yold(i)*cos(dtheta)
        end do
        call pgbbuf
        call pgsci(0)
        call pgline(5,xold,yold)
        call pgsci(1)
        call pgebuf
        call pgline(5,x,y)
        do i=1,5
          xold(i)=x(i)
          yold(i)=y(i)
        end do
      end do
      end