Length itself could also be stored with variable length encoding.

That's what I mean though - if you standardize, as part of the language, that you can have 2 bytes for the string length because at the time no machine could handle anything larger, how do you move forward once 4 or 8 bytes is not a big deal without breaking everything?

Best solution would be something like SDNV. Short strings (up to 127 characters) have no length penalty and you can handle strings of any length.

I don't think these were invented back when K&R were designing C, but it feels like something any smart computer language designer could invent if the need arose.

N-bit machines can use N-bit lengths for strings in memory. If you're storing strings your storage format has to specify a way to decide the prefix length (or you can use some other system).

For example `std::string` uses `std::size_t` as a length which is 32-bit on 32-bit machines and 64-bit on 64-bit machines. When you serialise a string to protobuf (for example) it uses a variable-length prefix. Other formats could have fixed 4-byte prefixes or whatever they want (even null-terminated).