Precursors[ edit ] A precursor to the public bulletin board system was Community Memory , started in August in Berkeley, California. Useful microcomputers did not exist at that time, and modems were both expensive and slow. Community Memory therefore ran on a mainframe computer and was accessed through terminals located in several San Francisco Bay Area neighborhoods. Community Memory allowed the user to type messages into a computer terminal after inserting a coin, and offered a "pure" bulletin board experience with public messages only no email or other features. It did offer the ability to tag messages with keywords, which the user could use in searches. The system acted primarily in the form of a buy and sell system with the tags taking the place of the more traditional classifications.