第四章例4-2

#include<stdio.h>
int main(void)
{
   int count,num;
   double grade,total;

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