菜鸟单片机求助。。

#include <reg52.h>
#define uchar unsigned char
#define uint unsigned int
sbit DULA=P2^0;
sbit WELA=P2^1;
sbit CS88=P2^2;
uchar code table[]={0x3f,0x06,0x5b,0x4f,
0x66,0x6d,0x7d,0x07,
0x7f,0x6f,0x77,0x7c,
0x39,0x5e,0x79,0x71};
uchar i,j,k;
void delay(uint);
void main()
{
EA=1;
EX0=1;
IT0=0;
WELA=1;
P0=0X00;
WELA=0;

  for(i=0;i<=15;i++)
  {
  
  DULA=1;
  P0=table[i];
  DULA=0;
  delay(1000);
  }
}
void delay(uint z)
{
uint x,y;
for(x=z;x>0;x--)
  for(y=110;y>0;y--);
}
void zd() interrupt 0
{
while(1);
}     


大神，为什么I 的值一直不变呢  = =