請(qǐng)大神們解惑，關(guān)于C語言的問題

ID:111874 · 發(fā)表于 2016-7-2 11:20

//請(qǐng)問為什么在main函數(shù)中聲明變量一定要放在最前，詳細(xì)的疑問請(qǐng)看程序
#include <reg52.h>
#define uchar unsigned char
#define uint unsigned int
sbit key1 = P3^4;
sbit dula = P2^6;
sbit wela = P2^7;
uchar code table[]={
0x3f, 0x06, 0x5b, 0x4f, 0x66, 0x6d,
0x7d, 0x07, 0x7f, 0x6f, 0x77, 0x7c,
0x39, 0x5e, 0x79, 0x71
};
void main(void)
{
uchar num;//num變量放在這里申明，程序不會(huì)出錯(cuò)，放在下面注釋的位置就會(huì)出錯(cuò)？？？請(qǐng)大神解釋下
wela = 1;
P0 = 0xfe;
wela = 0;
//uchar num;///////num變量如果是在這里申明；那么程序就會(huì)出錯(cuò)，請(qǐng)問我們?cè)谏昝鱩ain函數(shù)中的變量的時(shí)候?yàn)槭裁匆欢ㄒ旁诘谝晃?
P3 = 1;

while(1)
{
if(key1 == 0)
{
num++;
}
dula = 1;
P0 = table[num];
dula = 0;
}
}