Sometimes, one might want to iterate through a large string, but string_char_at is slow, and the use scenario doesn't quite fit string_foreach. For these situations, I suggest a string_to_char_array, ...

Arduino Keypad Lock with Password Changing #include <Keypad.h> #include <Password.h> String newPasswordString; //hold the new password char newPassword [6]; //charater string of newPasswordString ...