How does one indicate undetermined languages using the ISO 15924 script codes?
There are two possibilities for coding undetermined languages. The first is to use three blanks (Space or blank, which is Hex 20). This implies that a language code is not applicable because there is no sung, spoken, or written textual content. The second possibility is to use a code that is available in the ISO 15924 list: Und (Undetermined) This code is used if the language associated with an item cannot be determined or specified It is not recommended to use nulls, since they may cause problems because of special use in programming as a control character.