请帮我为以下代码添加注释#include <REGX52.H> NixieTable[]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F,0x77,0x7c,0x39,0x5e,0x79,0x71}; int MatrixKeyNum; void Delay(unsigned int xms) { unsigned char i, j; while(xms--) { i = 2; j = 239; do { while (--j); } while (--i); } } void Nixie(unsigned char Location,Number) { switch(Location) { case 1:P2_4=1;P2_3=1;P2_2=1;break; case 2:P2_4=1;P2_3=1;P2_2=0;break; case 3:P2_4=1;P2_3=0;P2_2=1;break; case 4:P2_4=1;P2_3=0;P2_2=0;break; case 5:P2_4=0;P2_3=1;P2_2=1;break; case 6:P2_4=0;P2_3=1;P2_2=0;break; case 7:P2_4=0;P2_3=0;P2_2=1;break; case 8:P2_4=0;P2_3=0;P2_2=0;break; } P0=NixieTable[Number]; } unsigned char MatrixKey() { unsigned char KeyNumber=0; P1=0xFF; P1_3=0; if(P1_7==0){Delay(20);while(P1_7==0);Delay(20);KeyNumber=1;} if(P1_6==0){Delay(20);while(P1_6==0);Delay(20);KeyNumber=5;} if(P1_5==0){Delay(20);while(P1_5==0);Delay(20);KeyNumber=9;} if(P1_4==0){Delay(20);while(P1_4==0);Delay(20);KeyNumber=13;} P1=0xFF; P1_2=0; if(P1_7==0){Delay(20);while(P1_7==0);Delay(20);KeyNumber=2;} if(P1_6==0){Delay(20);while(P1_6==0);Delay(20);KeyNumber=6;} if(P1_5==0){Delay(20);while(P1_5==0);Delay(20);KeyNumber=10;} if(P1_4==0){Delay(20);while(P1_4==0);Delay(20);KeyNumber=14;} P1=0xFF; P1_1=0; if(P1_7==0){Delay(20);while(P1_7==0);Delay(20);KeyNumber=3;} if(P1_6==0){Delay(20);while(P1_6==0);Delay(20);KeyNumber=7;} if(P1_5==0){Delay(20);while(P1_5==0);Delay(20);KeyNumber=11;} if(P1_4==0){Delay(20);while(P1_4==0);Delay(20);KeyNumber=15;} P1=0xFF; P1_0=0; if(P1_7==0){Delay(20);while(P1_7==0);Delay(20);KeyNumber=4;} if(P1_6==0){Delay(20);while(P1_6==0);Delay(20);KeyNumber=8;} if(P1_5==0){Delay(20);while(P1_5==0);Delay(20);KeyNumber=12;} if(P1_4==0){Delay(20);while(P1_4==0);Delay(20);KeyNumber=16;} return KeyNumber; } void main() { while(1) { MatrixKeyNum=MatrixKey(); if(MatrixKeyNum) Nixie(1,MatrixKeyNum); } }

这段代码是一个基于单片机的数码管键盘输入程序，以下是代码的注释：

//引入头文件regx52.h
#include <REGX52.H> 
//定义数码管的显示表
NixieTable[]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F,0x77,0x7c,0x39,0x5e,0x79,0x71}; 
//定义全局变量MatrixKeyNum
int MatrixKeyNum; 

//定义延时函数
void Delay(unsigned int xms) 
{ 	
	unsigned char i, j; 	
	while(xms--) 	
	{ 		
		i = 2; 		
		j = 239; 		
		do 		
		{ 			
			while (--j); 		
		} while (--i); 	
	} 
} 

//定义数码管显示函数
void Nixie(unsigned char Location,Number) 	
{ 	
	switch(Location) 	
	{ 		
		case 1:P2_4=1;P2_3=1;P2_2=1;break; 		
		case 2:P2_4=1;P2_3=1;P2_2=0;break; 		
		case 3:P2_4=1;P2_3=0;P2_2=1;break; 		
		case 4:P2_4=1;P2_3=0;P2_2=0;break; 		
		case 5:P2_4=0;P2_3=1;P2_2=1;break; 		
		case 6:P2_4=0;P2_3=1;P2_2=0;break; 		
		case 7:P2_4=0;P2_3=0;P2_2=1;break; 		
		case 8:P2_4=0;P2_3=0;P2_2=0;break; 	
	} 	
	P0=NixieTable[Number];  	
}  

//定义矩阵键盘扫描函数
unsigned char MatrixKey() 
{ 	
	unsigned char KeyNumber=0; 	 	
	P1=0xFF; 	
	P1_3=0; 	
	if(P1_7==0){Delay(20);while(P1_7==0);Delay(20);KeyNumber=1;} 	
	if(P1_6==0){Delay(20);while(P1_6==0);Delay(20);KeyNumber=5;} 	
	if(P1_5==0){Delay(20);while(P1_5==0);Delay(20);KeyNumber=9;} 	
	if(P1_4==0){Delay(20);while(P1_4==0);Delay(20);KeyNumber=13;} 	 	
	P1=0xFF; 	
	P1_2=0; 	
	if(P1_7==0){Delay(20);while(P1_7==0);Delay(20);KeyNumber=2;} 	
	if(P1_6==0){Delay(20);while(P1_6==0);Delay(20);KeyNumber=6;} 	
	if(P1_5==0){Delay(20);while(P1_5==0);Delay(20);KeyNumber=10;} 	
	if(P1_4==0){Delay(20);while(P1_4==0);Delay(20);KeyNumber=14;} 	 	
	P1=0xFF; 	
	P1_1=0; 	
	if(P1_7==0){Delay(20);while(P1_7==0);Delay(20);KeyNumber=3;} 	
	if(P1_6==0){Delay(20);while(P1_6==0);Delay(20);KeyNumber=7;} 	
	if(P1_5==0){Delay(20);while(P1_5==0);Delay(20);KeyNumber=11;} 	
	if(P1_4==0){Delay(20);while(P1_4==0);Delay(20);KeyNumber=15;} 	 	
	P1=0xFF; 	
	P1_0=0; 	
	if(P1_7==0){Delay(20);while(P1_7==0);Delay(20);KeyNumber=4;} 	
	if(P1_6==0){Delay(20);while(P1_6==0);Delay(20);KeyNumber=8;} 	
	if(P1_5==0){Delay(20);while(P1_5==0);Delay(20);KeyNumber=12;} 	
	if(P1_4==0){Delay(20);while(P1_4==0);Delay(20);KeyNumber=16;} 	 	
	return KeyNumber; 
}  

//主函数
void main() 
{ 		
	while(1) 	
	{ 		
		MatrixKeyNum=MatrixKey(); 		
		if(MatrixKeyNum)	Nixie(1,MatrixKeyNum); 	
	} 
}