A bulletin board system is, at its simplest, a computer that waits by a telephone. The host runs BBS software attached to a modem, and when a caller dials the number, the two modems negotiate a connection and the caller is dropped into a text interface running on the host. From there the caller can read messages other people have left, post replies of their own, upload and download files, and on many boards play simple games. The name is literal: the system is an electronic version of a cork bulletin board in a hallway, a place where a community pins up notes for one another. The defining constraint of the era was that almost every board had a single phone line, so only one caller could be connected at a time and everyone else got a busy signal.
The first recognizable BBS was the Computer Bulletin Board System, or CBBS, built in Chicago by Ward Christensen and Randy Suess during a 1978 blizzard and described by them in the November 1978 issue of Byte under the heading “Hobbyist Computerized Bulletin Board.” Their article in that issue, archived in scanned form, lays out the idea plainly: a computer that members of a club could phone to leave and retrieve messages without a human operator in the loop. CBBS was assembled from an S-100 bus microcomputer, a modem, and software Christensen wrote to answer the phone, detect the carrier, and present a menu, automating what until then had required a person to relay messages by hand.
The model spread because it was cheap to replicate. A hobbyist with a spare computer, a modem, and the willingness to tie up a phone line could become a sysop, short for system operator, and run a board out of a spare room. Through the 1980s the number of boards grew into the tens of thousands, ranging from tiny single-line hobby boards to large multi-line commercial services. Each board was its own island, reachable only by dialing its specific number, which meant that calling a board in another city or country incurred long-distance charges and gave local boards a strong gravitational pull on their communities.
Technically a BBS combined several pieces that the early online world had to invent or borrow. Message bases organized public discussion into topics. File areas held programs and text that callers uploaded and downloaded, and moving those files reliably over noisy phone lines required a transfer protocol, which is why Christensen’s XMODEM became a near-universal companion to BBS software. Door programs let a board hand control off to a separate game or utility, and many boards ran elaborate text-mode interfaces decorated with ANSI escape codes for color and crude graphics. Later, store-and-forward networks such as FidoNet linked the islands together so that mail and discussion could hop from board to board across the world overnight.
The bulletin board system was, for roughly fifteen years, how ordinary people first went online. It predated the public Internet for most users and established many of the social patterns later taken for granted: usernames and login prompts, threaded public discussion, file sharing, online games, and the figure of the moderator or administrator who set the rules of a small online place. When dial-up access to the Internet and then the World Wide Web arrived in the mid-1990s, the single-line BBS could not compete with a globally interconnected network, and the boards faded. But the basic shape they pioneered, of dialing into a shared host to join a conversation, is the direct ancestor of the online services and forums that followed.