#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
int main() {
while (1) {
printf("请输入一个字符!\n");
int enter = 0;
enter = getchar();
if (enter >= 'a'&&enter <= 'z') {
putchar(enter - 32);
printf("\n");
}
else if (enter >= 'A'&&enter <= 'Z') {
putchar(enter + 32);
printf("\n");
}
else if (enter >= 0 && enter <= 9)
printf("\n");
}
system("pause");
return 0;
}