#include<reg51.h>
#define uchar unsigned char
#define uint unsigned int
sfr P0M1=0x94;
sfr P0M0=0x93;
sfr P2M1=0x96;
sfr P2M0=0x95;
sfr P1M1=0x92;
sfr P1M0=0x91;
uchar code table[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90};   //0~9数组
uchar buff[4]={0,0,0,0};  //位
uchar code bittab[]={0x01,0x02,0x04,0x08}; //控制位
uchar temp,unm,unm1;
void xs();
uchar key();
void delay(uchar);
void main()
{
   P0M1=0xff;
   P0M0=0x00;
   P2M1=0xff;
   P2M0=0x00;
   P1M1=0xff;
   P1M0=0x00;
   P0=0XFF;
   P2=0X00;
   while(1)
       {           buff[0]=0;
           xs(key());
          
       }
}
void xs()      //显示
{  uchar i;
   P2=0x00;
   for(i=0;i<4;i++)
     {
     P2=bittab;
     P0=table[buff];
     delay(1);
     }
}
void delay(uchar z)
{
   uchar x,y;
   for(x=0;x<124;x++)
   for(y=0;y<z;y++);
}
/*uchar key()
{
    P3=0XFE;
    temp=P3; //读取
    temp=temp&0xf0; //是否有键按下
    while(temp!=0xf0)
        {
            delay(20);
            temp=P3; //读取
            temp=temp&0xf0; //是否有键按下
            while(temp!=0xf0)
                {
                    temp=P3;
                    switch(temp)
                        {
                            case 0xe0:unm=1;break;
                        }                }        }
        return unm;
}
  */
uchar key()
{
    uchar huoqu;
    P3|=0x07;
    temp=P3;
    if(temp&0x07==0x07){huoqu=0xff;return(huoqu);}
    delay(20);
    P3|=0x07;
    if(temp&0x07==0x07){huoqu=0xff;return(huoqu);}
    huoqu=temp&0x07;
    while(temp!=0X07)
    {
        switch(temp)
        {
          case 0x06:unm=2;break;
        }
    }
    return huoqu;
}
此帖出自小平头技术问答