为什么这段程序会出现这种错误

#include<stdio.h>
int main()
{
int i,a[i],s,b;
s=0,b=0;
for(i=1;i<10;i++)
{
scanf("%d",&a[i]);
printf("The score of No. %d(1-Pass, 2-Not pass):\n",i);
if(a[i]==1)
s++;
else
b++;

}
printf("Pass:%d,Not pass:%d",s,b);
if(s>=8)
printf("Too easy");
return 0;

}

int i,a[i],s,b;
数组a[i]大小未知。你这应该是a[10]