#include <stdio.h>
#include <string.h>

int main(void) {
    char s[] = "Hallo";
    char *p;
    printf("%s\n", s);
    printf("sizeof(s) = %d\n", sizeof(s));
    printf("strlen(s) = %d\n", strlen(s));
    p = strchr(s, 'a');
    if (p != NULL) {
        *p = 'e';
    }
    printf("%s\n", s);
    fflush(stdin);
    getchar();
    return 0;
}