第四章例4-2

/* 输入一批学生的成绩，以负数作为结束标志，计算平均成绩，并统计不及格人数 */
#include<stdio.h>
int main(void)
{
    int count,num;
    double grade,total;

    num=0;
    total=0;
    count=0;
    printf("Enter grades:");
    scanf_s("%lf",&grade);

    while(grade>=0){
        total=total+grade;
        num++;
        if(grade<60)
            count++;
        scanf_s("%lf",&grade);
    }
    if(num!=0){
        printf("Grade average is %.2f\n",total/num);
        printf("Number of failures is %d\n",count);
    }
    else
        printf("Grade average is 0\n");

    return 0;
}