This is Octothello by PC Solutions in 1992

REVERSI is traditionally played on an 8 by 8 board, with square A1 at top left and H8 at bottom right with OCTOTHELLO you may alter the board size/shape

Your object is to capture your opponents pieces by sandwiching them in a diagonal, horizontal, or vertical line. So if you have a piece on C5 and I have one on C4 you can move to C3, capturing mine on C4

This is easier to see than describe, so have a go you can view legal moves with F1, or even hit F3 for an automatic demo! Note that a move is only legal if it captures pieces you cannot just move TO any old vacant square. If you have no moves at all, you must PASS a go, by hitting F1. When neither side can move, the game is over and the higher score wins unless you selected play-to-lose mode!

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Code: PC Solutions