It's a place to store "strings", that is, bits of text or numbers, for use in menus and speech. For example, if the marshall says "I want you to patrol around {reg12}, {reg13} and {reg14}", you can be sure there's a bit of code beforehand that defines which settlements should be mentioned.
It goes up to reg65 iirc, but that's just a vague guess based on what I've seen.
It goes up to reg65 iirc, but that's just a vague guess based on what I've seen.