program save_data
      real x(2001), y(2001)

      dx = (6*2*3.1415 - 0)/2000
      do i=1,2001
        x(i)=(i-1)*dx
        y(i)=sin( x(i) )
      end do

      open(unit=15,file='sin.dat')
      write(15,*)2001
      do i=1,2001
        write(15,*) x(i), y(i)
      end do
      close(15)
      write(*,*)'The file sin.dat has been wriiten.'
      end