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;

}