利用51单片机设计一个密码锁，要求如下
1．密码输入正确后，输出一个电磁锁开锁信号与已开锁信号。
2．输错密码想要修改时，有整体清除密码和按位清除密码可供选择。
3．电磁锁打开后，能够通过按键关上密码锁。
4．用户可以自行修改密码。
5．修改的密码忘记后，可以恢复出厂设置，恢复原密码。(Use 51 single chip to design a password lock, which is required as follows
After the 1. password is correctly input, the output of an electromagnetic lock unlocking signal and the unlocked signal.
When the 2. error password is intended to be modified, there is an overall clear cipher and a bit scavenging password for selection.
3. when the electromagnetic lock is opened, the password lock can be closed by the key.
4. users can modify their passwords by themselves.
After the 5. modified password is forgotten, the factory settings can be restored and the original password can be restored.)