You shouldn't need to define any codes, but just write the text as it is. You can write unicode russian, arabic, hebrew, etc...
Then you just give your string as a parameter to a function like str16to8() and it will convert it to ascii characters which are matching the Font Studio dds file.
When I wrote the arabic text, I had no idea or need to know what codes they actually are, I just wrote the text in english and used google translator to translate it to arabic.