Chess Software increase in playing strength each year. This is partly due to the increase in processing power that enables calculations to be made to ever greater depths in a given time. Programming techniques have improved enabling the softwares to be more selective in the lines that they analyse and to acquire a better positional understanding.
Some chess software use endgame tablebases to increase their playing strength during the endgame. An endgame tablebase is a database of all possible endgame positions with small groups of material. Each position is conclusively determined as a win, loss, or draw for the player whose turn it is to move, and the number of moves to the end with best play by both sides. Endgame tablebases in all cases identify the absolute best move in all positions included (identifying the move that wins fastest against perfect defense, or the move that loses slowest against optimal opposition). Such tablebases are available for all 3-6 man positions (counting the kings) and some 7-man combinations. When the manoeuvering in an ending to achieve an irreversible improvement takes more moves than the horizon of calculation of a chess engine, an engine is not guaranteed to find the best move without the use of an endgame tablebase, and in many cases can fall foul of the 50 move rule as a result. Some experts have pointed out the potential for faulty use of endgame tablebases by programmers, leading to worse play.