# 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("This program calculates the average of any number of value.\n");

    for(;;)
    {
        printf("\nEnter a value: ");
        scanf("%lf", &value);
        total = total + value;
        ++count;
        printf("Do you want to enter another value? ( Y or N):");
        scanf(" %c", &answer); // 为啥 %c前面要加空格？
        if(tolower(answer) == 'n')
            break;
    }
    printf("\nThe average is %.2lf\n", total/count);
    return 0;
}

还是不理解，，我在想想。。