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;
}