说明：  中断程序的编写：在单片机系统的p1口上接有8个LED，LED的阳极接+5V，阴极接P1口的引脚。当P1口某一口线输出为0时，将LED点亮。在外部中断0输出引脚P3.2引脚上接上上拉电阻并接有一个按钮开关K1。用K1按钮来产生外部中断0的输入信号。定时器程序的编写：在AT89S51单片机的P1口上接有8个LED.下面采用定时器T0的方式一的定时中断方式，使P1口外接的8个LED每0.5秒闪亮一次。C51程序：在AT89S51的P1.0脚接有一只发光二极管，二极管的阴极接P1.0脚，阳极通过限流电阻接+5V，现在让发光二极管每隔800毫秒闪灭，占空比为50 。不使用函数strcat（），用字符指针变量作函数参数编程实现字符串连接函数strcat()的功能，将字符串srcStr连接到字符串dstSTR的尾部。用基本文件操作编写DOS下的TYPE命令，即把文件内容以ASCII码字符方式向标准输出设备输出。
(Write interrupt routine: on the SCM system p1 port connected with 8 LED, LED anode connected to+ 5V, the cathode connected to the P1 port pins. When a certain line P1 port output is 0, the LED lights. In the pull-up resistor connected to the external interrupt and then there is a button to switch on the K1 0 output pin P3.2 pin. With K1 button to generate an external interrupt 0 input signal. Write timer programs: On AT89S51 microcontroller P1 port is connected with 8 LED timer below using the timer T0 interrupt the way a way to make the P1 port 8 LED external flash once every 0.5 seconds. C51 Procedure: AT89S51 of P1.0 pin is connected with a light emitting diode is connected to P1.0 cathode and the anode through the current limiting resistor connected to+ 5V, now let the light emitting diode flash off every 800 ms, the duty cycle is 50 . Do not use the function strcat (), with the character pointer variable as a function parameter programming string concatenation function strcat () )