#include<stdio.h>
int main() {
    char c;
    scanf("%c", &c);
    if ((c >='A' ) && (c<= 'Z')) {
        printf("字母为大写\n");
        printf("小写是%c\n", (c + 32));
    } else if ('a' <= c && c <= 'z'){
        printf("字母为小写\n");
    }
    return 0;
}

嗯~谢谢呀