 Most GUI's also allow the player to set up and edit positions, take back moves, offer and accept draws (and resign), have a "coach" function to recommend a move when the player is in doubt, and show the engine's analysis as the game progresses.There are a few chess engines such as Sargon, IPPOLIT, Stockfish, Crafty, Fruit and GNU Chess that can be downloaded (or source code otherwise obtained) from the Internet free of charge.Perhaps the most common type of chess software are programs that simply play chess.