第4章例4-2

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

	num=0;
	total=0;
	count=0;
	printf("Enter grade:");
	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\n",total/num);
		printf("Number of failures is %d\n",count);
	}
	else
		printf("Grade average is 0\n");

	return 0;
}