system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Before electronic banking, how did wealthy businessmen keep track of their earnings?
gpt
They had an army of accountants writing things in ledgers.  Double-entry bookkeeping was invented to accurately keep track of the money flowing in and out of various accounts, and it was common for large businesses to have entire _floors_ of accountants whose job it was to keep track of those entries.