第6章例6-5

#include<stdio.h>
int main(void)
{
	char ch;

	printf("input characters:");
	ch=getchar();

	while(ch!='
'){
		if(ch>='A'&&ch<='Z')
			ch=ch-'A'+'a';
		else if(ch>='a'&&ch<='z')
			ch=ch-'a'+'A';
		putchar(ch);
		ch=getchar();
	}
	return 0;
}