将给出一个实际的的Boot Loader程序，它可以配合Windows中的超级终端程序，采用Xmodem传输协议，通过RS232接口下载更新用户的应用程序。(This section will give a practical Boot Loader program, which can cooperate with the super terminal program in Windows and use Xmodem transport protocol to download and update user applications through RS232 interface.)