Bulletin_board_system A Bulletin Board System, or BBS, is a computer system running software that allows users to connect and login to the system using a terminal program. Originally BBSes were accessed only over a phone line using a modem, but by the early 1990s some BBSes allowed access via a Telnet, packet switched network, or packet radio connection.Once logged in, a user could perform functions such as downloading or uploading software and data, reading news, and exchanging messages with other users, either through electronic mail or in public message boards.