#include<stdio.h>
#include<ctype.h>
int main(void)

{
    char answer='N';
double total=0.0;
double value=0.0;
unsigned int count=0;
printf("\nthis program calculates the average of"
"any number of values.");
for( ;; )
{
    printf("\nenter a value:");
    scanf("%lf",&value);
    total+=value;
    ++count;


    printf("do you want to enter another value?(Y or N0):");
    scanf("%c",&answer);

if(tolower(answer)=='n')
   break;}
   

printf("\nthe average is %.2lf\n",total/count);        
        return 0;
}

在每个scanf前面加一句flushall();

谢谢，搞定了，我看着书上输入的，出现了这个问题，刚开始学习，请多指教。

scanf("%c",&answer); 改为
scanf(" %c",&answer);