system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 How did patent offices make sure that they didn't register the same invention twice without the use of computers and modern search engines? Did the patent officers have to memorize every invention?
gpt
There's a very elaborate and detailed and thorough patent classification system still in use today that is designed to avoid this sort of thing.  The original system was adapted to work in digital storage.