#include<stdio.h>
int main(void) {
    char ch;
    int words = 0, letters = 0;
    while ((ch = getchar()) != EOF)
    {
    if ((ch>='A' && ch <= 'Z') || (ch>='a' && ch <= 'z'))
        letters++;
    if (ch == ' ' || ch == ',' || ch == '.' || ch == '\n')
        words++;
    }
    printf("Totally %d words and %d letters!", words, letters);
    printf("Average = %f", (double)letters / (double)words);
    return 0;
}

为什么输入像"lala la lalala^Z"这样的，while循环不会结束，必须要换行之后输入^Z循环才会结束呢？