multiple combinations can be tried in below style
printf("%d\n", case_insensitive_string_compare("HELLO", "hello"));
printf("%d\n", case_insensitive_string_compare("HeLLo", "hEllO"));
printf("%d\n", case_insensitive_string_compare("HELLO123", "hello1"));
printf("%d\n", case_insensitive_string_compare("HELLO", "hello123"));
printf("%d\n", case_insensitive_string_compare("", "hello"));
printf("%d\n", case_insensitive_string_compare("HELLO", ""));