演示通过中断INT0方式处理键盘输入的方法。对4X4的键盘矩阵定义了16个键名分别是0，1。。。E，F。某个键被按下就通过串口在模拟终端上输出。为了演示主循环与中断服务过程，在主循环中加了一条打印语句，用来演示程序的跳转。-Demo INT0 interrupt handling by keyboard input methods. The definition of the 4X4 matrix keyboard 16 keys, respectively 0,1. . . E, F. A key is pressed on through the serial port terminal in the simulation output. To demonstrate the main loop and interrupt service process, in the main loop added a print statement, to demonstrate the program jump.