【51单片机利用外部中断编写程序用两个按键控制数码管显示从0到9,S1控制加计数0—9，S2控制减计数9—0。】

缘由https://ask.csdn.net/questions/7935097

#include "reg52.h"
unsigned char code SmZiFu[]={63,6,91,79,102,109,125,7,127,111,128,0};//共阴0-9.
unsigned char j=0,jj=0;
void smjia()
{
	unsigned char ys0=0,ys1=0;
	while(j<10)if(++ys0==0)
	{
		P0=SmZiFu[j];
		if(++ys1==0)++j;
	}
}
void smjian()
{
	unsigned char ys0=0,ys1=0;
	while(j)if(++ys0==0)
	{
		P0=SmZiFu[j-1];
		if(++ys1==0)--j;
	}
}
void main()
{//缘由https://ask.csdn.net/questions/7935097
	unsigned char ys0=0,ys1=0;
	EA=IT0=EX0=IT1=EX1=1;//下降沿触发，外部中断优先设置
	P1=0;
	while(1)
	{
	}
}
void WaiBuZhongDuan0() interrupt 0//外部中断引脚P3.2，INT0
{
   j=0;smjia();//调用函数可以移到主函数判断状态即可
}
void WaiBuZhongDuan1() interrupt 2//外部中断引脚P3.3，INT1
{
   j=10;smjian();
}