3

代码说明：

说明：  系统由单片机、显示器等部分组成，利用显示器来显示密码锁输入的相关信息，系统上电时内部默认三组数字密码（4位或4位以上）；密码输入正确则打开密码锁(The system is made up of single-chip microcomputer, display and other parts. It displays relevant information of the password lock using the display. When the system is powered up, it acquiers three sets of digital Ciphers (4 bits or more than 4 bits). If the password is entered correctly, it will open the password lock.)