请高手帮忙检查下，谢谢。我刚开始学单片机

#include<reg52.h>
#define uchar unsigned char
#define uint unsigned int
void delayms(uint xms)
{ uint i,j;
for(i=xms;i>0;i--)
for(j=110;j>0;j--);
}
void main()
{ uchar temp,aa;
P3=0xfe;
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
delayms(10);
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{ temp=P3;
switch(temp)
{
case 0xee:
aa=0xfe;
break;
case 0xde:
aa=0xfd;
break;
case 0xbe:
aa=0xfb;
break;
case 0x7e:
aa=0xf7;
break;
}
while(temp!=0xf0)
{
temp=P3;
temp=temp&0xf0;
}

P1=aa;
}
}

P3=0xfd;
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
delayms(10);
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
temp=P3;
switch(temp)
{ case 0xed:
aa=0xef;
break;
case 0xdd:
aa=0xdf;
break;
case 0xbd:
aa=0xbf;
break;
case 0x7d:
aa=0x7f;
break;
}
while(temp!=temp&0xf0)
{
temp=P3;
temp=temp&0xf0);
}
P1=aa;
}
}
}