6-4

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


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

    while(ch !='\n'){
        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;
}