uchar 不能放在程序中間？？

#include <reg52.h>
#define uchar unsigned char
#define uint unsigned int
uchar code table[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};
sbit duan=P2^6;
sbit wei=P2^7;

void delay(uint z);

void main()

{
   
    duan=1;
  P0=0x00;
  duan=0;
  uchar num;
     while(1)
   {
      for(num=0;num<15;num++)
     {
    wei=1;
     P0=table[num];
    wei=0;
    delay(1000);
   }
   }
}

void delay(uint z)
{
  uint x,y;
  for(z=x;x>0;x--)
    for(y=110;y>0;y--);
}

uchar 放在這兒就不行，放在sbit duan=P2^7;下一行或放在 duan=1;上一行就可以,這是為什么呀？