연습문제 21-1

#include <stdio.h> #include <string.h> #include <ctype.h> int main(void) { char ipt=0; ipt=getchar(); if(65<=ipt && ipt<=90) { ipt=tolower(ipt); putchar(ipt); } else if(97<=ipt && ipt<=122) { ipt=toupper(ipt); putchar(ipt); } else printf("잘못된 입력!\n"); return 0; }