#include <stdio.h>
#define SUM 100000
int main  ()
{
    int i;
    float amount,aver,total;
    for (i=1,total=0;i<=1000;i++);
    {
        printf("please enter amount");
    scanf("%f",amount);
    total=total+amount;
    if(total>SUM) break;
    }
    aver=total/i;
    printf ("num=%d\naver=%10.2f\n",i,aver);
    return 0;
}

取址符

“for (i=1,total=0;i<=1000;i++);”分号结束了for循环体，所以break位置非法。

#include <stdio.h>
#define SUM 100000
int main  ()
{
    int i;
    float amount,aver,total;
    for (i=1,total=0;i<=1000;i++);   //去掉分号
    {
        printf("please enter amount");
    scanf("%f",&amount);        //加上取址符
    total=total+amount;
    if(total>SUM) break;
    }
    aver=total/i;
    printf ("num=%d\naver=%10.2f\n",i,aver);
    return 0;
}