Place one disc and a whole line can change colour. The immediate gain is easy to see; whether it leaves you a good position is harder to judge. That gap between following the rules and choosing a useful move made Reversi-style games interesting projects for early computer programmers.
Which rules?
Reversi was played in the nineteenth century, before computers. Historical research documents editions spreading internationally in the late 1880s, and Otto Maier publishing it with Rocco in 1893. Goro Hasegawa’s Othello became prominent in the 1970s.
The names are often used interchangeably in computing, but historical Reversi and modern Othello are not automatically identical rulesets. World Othello Federation writer Ben Seeley identifies differences in starting arrangements and passing rules. The rules below describe modern Othello, which many computer games labelled Reversi follow.
Two players use an eight-by-eight board. Black moves first from a fixed arrangement of four central discs. A legal move places a disc on an empty square and traps at least one unbroken line of opposing discs between it and a friendly disc. Lines may run horizontally, vertically or diagonally; all discs captured by that move must turn over.
A player passes only when no legal move exists. Play ends when neither player can move, even if empty squares remain. The player with more discs wins; equal totals produce a draw. Filling the board is a common ending, not a requirement.
More discs can be a worse position
A corner disc cannot be surrounded, so it cannot be flipped. Other edge discs are not automatically safe: they can still be trapped along the edge. A stable disc is one that cannot be flipped in any continuation of the position.
Brian Rose’s strategy book explains why corners can help build stable groups, and why available moves matter. Taking many discs immediately may leave the opponent good choices while restricting your own. The useful question is what the move permits next, not only how many discs it changes now.
Programming the opponent
Richard O. Duda published an Othello program in the October 1977 BYTE. Its BASIC listing stores the board in an array and checks eight directions. It offers a simple capture-counting strategy and another that adds a preference for outside positions. Duda explicitly invited readers to improve its play.
Peter W. Frey’s July 1980 BYTE article went further, discussing positional priorities, move options and searching the final moves. He offered versions for the TRS-80 and Apple, illustrating how the same rules could support different computer opponents.
These examples separate two jobs. Move validation establishes what is allowed. Evaluation and search try to choose well among those moves. A program can implement the first correctly and still play badly—a useful distinction for anyone learning to write board-game software.
Sources
- Peter Michaelsen, Kira Moss and Bjarne Toft, “Sophus Tromholt (1851–1896): A Neglected Danish Games Inventor”, Board Game Studies Journal 19, 2025, pp. 137–138: Reversi’s international editions and later Othello context. Historical research, not evidence for an exact 1883 invention date.
- Ben Seeley, “Reversi versus Othello”, World Othello Federation, posted 2020: differences between rulesets. Its broader origin claims are not adopted here.
- World Othello Federation, official rules: moves, passing and end conditions.
- Brian Rose, Othello: A Minute to Learn… A Lifetime to Master, 2005, chapters 1–3: rules, stable discs and mobility.
- Richard O. Duda, “Othello, a New Ancient Game”, BYTE, October 1977, pp. 60–62: explanation and published BASIC source listing.
- Peter W. Frey, “Simulating Human Decision-Making on a Personal Computer”, BYTE, July 1980, pp. 56–72: programming strategies and offered TRS-80/Apple versions.