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Perhaps the best compromise between power and simplicity is the High–Low, or the Complete Point Count, which appears in the 1966 revised edition of Beat the Dealer. Still used today by top professionals, this is the simplest possible point count in that cards get values of −1, 0, or +1 only. You start with the count at 0. As the “small” cards 2, 3, 4, 5, 6 are used, they each add +1 to the cumulative count. The intermediate cards 7, 8, and 9 are counted as 0 so their appearance doesn’t affect the total count. Big cards—Aces and Ten-value cards—count as −1 so they each reduce the total by one. Suppose the player using the High–Low count sees these cards in the first round of play: A, 5, 6, 9, 2, 3. Then the count, which started with zero, becomes −1 + 1 + 1 + 0 + 1 + 1 = +3. With this count in a one-deck game—and with reasonably favorable rules—the player has an edge on the next deal. As cards are dealt, the count goes up and down around zero. When the count is positive the player benefits, and when it is negative it helps the casino.
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Edward O. Thorp (A Man for All Markets: From Las Vegas to Wall Street, How I Beat the Dealer and the Market)