将输入作为字符流读取，直到遇到isupper和islower函数的EOF

#include <stdio.h>  
#include <ctype.h>  
int main(void)  
{
    int ch;  
    unsigned long uct = 0;  
    unsigned long lct = 0;  
    unsigned long oct = 0;  

    while ((ch = getchar()) != EOF)  
        if (isupper(ch))  
            uct++;  
        else if (islower(ch))  
            lct++;  
        else  
            oct++;  
    printf(%lu uppercase characters read\n, uct);  
    printf(%lu lowercase characters read\n, lct);  
    printf(%lu other characters read\n, oct);  

    return 0;  
}