═══ 1. General help ═══ Backgammon is a game of both skill and luck in which two player move their "men" in an obstacle race around the board, trying to get their men off the board before their opponent does. OS/2 TD-Gammon lets you play against one of the strongest backgammon players in the world - an artificially intelligent player called TD-Gammon. At its easiest skill levels, OS/2 TD-Gammon will help you learn the ancient and intriguing game of backgammon as if you were playing against a novice at the game. At its highest skill levels, only a few of the best backgammon players in the world stand a chance of beating TD-Gammon consistently. Are you up to the challenge? Further information is available on: o What is TD-Gammon? o Starting the OS/2 TD-Gammon program o How to play OS/2 TD-Gammon o Setting the skill level o Starting a new game o Exiting the program o Rules of backgammon ═══ 1.1. What is TD-Gammon? ═══ TD-Gammon is a world-famous computer program that has revolutionized the game of backgammon. Based on breakthrough research in Artificial Neural Network technology, TD-Gammon actually taught itself to play backgammon, starting from scratch. It learned to play so well that it is now one of the very best backgammon players in the world. OS/2 TD-Gammon is a special edition of TD-Gammon that uses the facilities of OS/2 to bring this world-class game to you. It was developed by Gerald Tesauro and Keith Weiner at the world-famous IBM Thomas J. Watson Research Center, where it started as an experiment in artificial intelligence. Tesauro started with an artificial neural network, a computer simulation inspired by the human brain, that knew only the basic rules of backgammon: what moves were legal, when the game is over, how to keep score, and so on. He then put this neural network through a "training procedure" in which it played many games against itself, and learned from the outcome of each game. At the start of training, the network only knew how to choose randomly from the list of legal moves. Over the course of many thousands of training games, the network gradually improved its playing ability. After millions of games of experience, the neural network is now playing at the level of today's top human experts. Now you can play against this amazing computer opponent. Good luck! Further information is available on: o For further reading ═══ 1.1.1. For further reading ═══ There are many good books available on backgammon strategy. Two-time World Backgammon Champion Bill Robertie wrote a particularly fine book for beginners: Bill Robertie, "Backgammon for Winners," Cardoza Publishing, ISBN: 0-940685-42-6. Bill Robertie has also written an article describing his experience in playing against TD-Gammon: B. Robertie, "Carbon versus Silicon: matching wits with TD-Gammon," Inside Backgammon, Volume 2, No. 2, pp. 14-22 (1992). Inside Backgammon is a newsletter which can be obtained from The Gammon Press, P. O. Box 294, Arlington, MA 02174. A detailed technical article by Dr. Gerald Tesauro, the IBM Research scientist who developed the neural network used by TD-Gammon, describes the techniques it uses: G. Tesauro, "Temporal Difference Learning and TD-Gammon," Communications of the ACM, Volume 38, No. 3, pp. 58-68 (March 1995). ═══ 1.2. Starting the OS/2 TD-Gammon program ═══ To start OS/2 TD-Gammon, double-click on its icon. Or, from an OS/2 session, switch to the directory in which OS/2 TD-Gammon is installed and type TDGAMMON. For instance, if OS/2 TD-Gammon is installed in C:\GAMES, you would type: [C:\] CD \GAMES [C:\GAMES] TDGAMMON A window will appear containing a graphical display of a backgammon board set up in the standard starting configuration. TD-Gammon has the blue checkers, and they move in the counter-clockwise direction. You have the red checkers, and they move in the clockwise direction. Your home board is the lower left quadrant, and TD-Gammon's home board is the upper left quadrant. ═══ 1.3. How to play OS/2 TD-Gammon ═══ You play OS/2 TD-Gammon just like a regular backgammon game, except that you use the mouse to move your pieces on the board. You move your pieces, and OS/2 TD-Gammon moves its pieces. Further information is available on: o The starting board position o Rolling your dice o Moving your checkers o Offering a double o Accepting or declining a double o Keeping score o Rules of backgammon ═══ 1.3.1. The starting board position ═══ At the start of each game, the doubling cube has a value of 1, and is positioned in the middle, indicating that either player can double. Also at the start of each game, the players each roll a single die to determine who goes first. The player who rolled the higher value gets to play the combination. Your dice are red, and TD-Gammon's dice are blue. If TD-Gammon gets to play first, you will see it make a move, and then the dice will disappear. If you get to play first, you must make a legal move corresponding to the dice combination that is shown. ═══ 1.3.2. Moving your checkers ═══ Checkers are moved by clicking on them with the left mouse button, dragging them to the desired location, and then releasing the mouse button. If you attempt to move to an illegal location, the computer will beep and the checker will reappear at the starting location. If the computer has hit any of your checkers, they will be on the bar (the gray strip in the middle of the board). Checkers on the bar must re-enter the board in the opponent's home quadrant before other checkers can be moved. Once you have gotten all your checkers into your home quadrant, you can begin bearing them off the board. To bear checkers off, drag them to the gray border area on the left edge of the board. Checkers that have been borne off are shown stacked up edgewise. Before you have finished making a complete legal move, you are allowed to take back some or all of the component moves that you have made so far. To take back a move, simply drag the checker back to the starting location. ═══ 1.3.3. Offering a double ═══ Each time that it is your turn to play, you can offer a double if the doubling cube is in the middle or on your side of the board. To offer a double, click on the doubling cube with the left mouse button. If TD-Gammon accepts the double, the cube will appear on TD-Gammon's side of the board, and will be set to twice the previous value. If TD-Gammon declines the double, a message will appear indicating that you have won the game; congratulations! Once you have doubled, you cannot double again, as TD-Gammon has the exclusive right to make the next double. If you do not wish to offer a double, simply click anywhere on the board, and your dice roll will appear. Once your dice have been rolled, you cannot double until your next turn. ═══ 1.3.4. Accepting or declining a double ═══ When TD-Gammon offers you a double, the cube will be turned to twice its previous value, and will be moved toward your side of the board. To accept the double, click on the doubling cube and drag it to the notched cube-holding location on your side of the board. To decline the double, click on the doubling cube and drag it towards the middle of the board. ═══ 1.3.5. Keeping score ═══ OS/2 TD-Gammon keeps a running total of your score in the lower right-hand corner of the window. You start out with a score of 0. When you win a game, the number of points you win in that game is added to your score. If TD-Gammon wins the game, the number of points it wins is subtracted from your score. If you have won more points that TD-Gammon, your score will be positive (greater than zero). If TD-Gammon has won more points, your score will be negative (less than zero). If you close TD-Gammon and open it again later, your score will be reset to 0. ═══ 1.4. Setting the skill level ═══ OS/2 TD-Gammon has five possible skill settings: o Novice o Beginner o Intermediate o Advanced o Expert To set the desired skill level, select the Options menu and a pull-down menu will appear showing the five possible levels. Select the desired skill level from this menu. The skill level can be reset at any time during a game, except while the computer is moving or thinking. ═══ 1.5. Starting a new game ═══ To start a new game, select the New menu item from the File menu. The board will be reset to the starting position. ═══ 1.6. Exiting the program ═══ To exit OS/2 TD-Gammon, double-click on the system icon in the OS/2 TD-Gammon window, or select Exit from the File menu. When you exit the program, the settings will be saved, but the current game will not be saved. ═══ 2. Rules of backgammon ═══ Backgammon is an obstacle race between two armies of 15 men each. Each man is called a "checker", and moves around a track divided into 24 triangular-shaped divisions known as "points". The goal of the game is to be the first player to bring all of your men around the board and then off the board. Further information is available on: o The backgammon board o Object of the game o Starting a game o Moving your men o Doublets o Making points o Blots o Closed board o Compulsory moves o Bearing off o Gammon and backgammon o The doubling cube o Hints for successful play ═══ 2.1. The backgammon board ═══ The backgammon board is divided down the center by a partition, known as the "bar" (See Diagram 1), into an outer and a home (or inner) board. The side nearest you is your outer and home boards; the side farther away is your opponents outer and home boards. The arrows indicate the direction of play. For purposes of convenience we have numbered the points in the diagram. Though the points are not numbered on the actual board, they are frequently referred to during play to describe a move or a position. Your (X's) 4-point or 8-point will always be on your side of the board; your opponent's (O's) will always be on the other side of the board. A move from your 9-point to your 5-point is four spaces (the bar does not count as a space). A move from White's 12-point to your 12-point, though it crosses from your opponent's board to yours, is but one space, for these two points are really next to each other. Diagram 2 shows the board set up ready for play. Each side has five men on the 6-point, three men on the 8-point, five men on the opponent's 12-point, and two men on the opponents' 1-point. Note that play proceeds in opposite directions, so that the men can be set up in two ways. Turn the diagram upside down to see the layout if play were proceeding in the other direction. <-----------------------------------------------+ | X moves this direction >-----------------------+ | | | | | 24 23 22 21 20 19 18 17 16 15 14 13 | | +------------------------------------------+ | | | . . . . . . | | . . . . . . | | | | . . . . . . | | . . . . . . | | | | . . . . . . | | . . . . . . | | | | . . . . . . | | . . . . . . | | | | . . . . . . | | . . . . . . | | | | | | | | | +----+ | Home Board |BAR| Outer Board | | | | 64 | | | | | | | +----+ | P O I N T S | | . . . . . . | | | Doubling | . . . . . . | | . . . . . . | | | Cube | . . . . . . | | . . . . . . | | | | . . . . . . | | . . . . . . | | | | . . . . . . | | . . . . . . | | | +------------------------------------------+ | | 1 2 3 4 5 6 7 8 9 10 11 12 | | | | <-------------------------------------------+ | | O moves this direction >--------------------------+ Diagram 1 (Numbered from X's point of view) 24 23 22 21 20 19 18 17 16 15 14 13 +------------------------------------------+ | X . . . . O | | . O . . . X | | X O | | O X | | O | | O X | | O | | X | | O | | X | +----+ | |BAR| | | 64 | | X | | O | +----+ | X | | O | | X | | X O | | O X | | X O | | O . . . . X | | . X . . . O | +------------------------------------------+ 1 2 3 4 5 6 7 8 9 10 11 12 Diagram 2 (Numbered from X's point of view) ═══ 2.2. Object of the game ═══ The object of Backgammon is for each player to bring all of his or her men into his or her home board, and then to bear them off the board. The first player to get all of his or her men off the board is the winner. ═══ 2.3. Starting a game ═══ Each player casts one die. The player with the higher number makes the first move, using the two numbers cast by the player's die and the opponent's. In the event that both players roll the same number, it is a standoff and each rolls another die to determine the first move. In the event of subsequent ties, this process is repeated until the dice turn up different numbers. ═══ 2.4. Moving your men ═══ Each player's turn consists of the roll of two dice. The player then moves one or more men in accordance with the numbers cast. If the dice roll is 4-2, the player can move one man six spaces, or one man four spaces and another man two spaces. Bear in mind that, when moving a single man for the total shown by the two dice, you are actually making two moves with the one man --- each move according to the number shown on one of the dice. ═══ 2.5. Doublets ═══ If the same number appears on both dice, for example, 2-2 or 3-3 (known as doublets), the caster is entitled to four moves instead of two. Thus, if the dice roll is 3-3, the player can move up to four men, but each move must consist of three spaces. The players throw and play alternately throughout the game, except in the case where a player cannot make a legal move and therefore forfeits a turn. ═══ 2.6. Making points ═══ A player makes a point by positioning two or more of his or her men on it. The player then "owns" that point, and the opponent can neither come to rest on that point nor touch down on it when taking the combined total of the dice with one man. ═══ 2.7. Blots ═══ A single man on a point is called a blot. If you move a man onto an opponent's blot, or touch down on it in the process of moving the combined total of your cast, the blot is hit, removed from the board and placed on the bar. A man that has been hit must re-enter in the opposing home board. A player cannot make any move until all of that player's men that were on the bar have been brought back into play. Re-entry is made on a point equivalent to the number of one of the dice cast, providing that point is not owned by the opponent. ═══ 2.8. Closed board ═══ A player who has made all six points in his or her home board is said to have a closed board. If the opponent has any men on the bar, the opponent will not be able to re-enter since there is no vacant point in the adversary's home board. Therefore, the opponent forfeits a turn, and continues to do so until such time as the player has to open up a point in the home board, thus providing a point of re-entry. ═══ 2.9. Compulsory moves ═══ A player is compelled to play both parts of the roll if there is any legal way to do so. Note that when bearing off, you can play the roll in such a way as to move fewer spaces than the larger die indicates by playing the smaller die first. This is legal as long as each part of the roll is played legally at the moment you play it. If only one part of the roll can be played legally, then you must play the higher die if possible; if not, play the lower die. ═══ 2.10. Bearing off ═══ Once a player has brought all of his or her men into the home board, the player can commence bearing off. Men borne off the board are not re-entered into play. The player who bears off all of his or her men first is the winner. A player cannot bear off men while that player has a man on the bar, or outside the player's home board. Thus if, in the process of bearing off, a player leaves a blot and it is hit by the opponent, the player must first re-enter the man in the opponent's home board, and bring it around the board into the player's own home board before the player can continue the bearing off process. In bearing off, you remove men from the points corresponding to the numbers on the dice cast. However, you are not compelled to remove a man. You can, if possible, move a man inside your home board a number of spaces equivalent to the number of a die. If you roll a number higher than the highest point on which you have a man, you can apply that number to your highest occupied point. Thus, if you roll 6-3 and your 6-point has already been cleared but you have men on your 5-point, you can use your 6 to remove a man from your 5-point. In some cases it might be advantageous to play the smaller die first before applying the higher die to your highest point (See Compulsory Move). For example, suppose you have one checker on your 5 point, and two checkers on your 2 point. Your opponent has a checker on the ace (one point) and on the bar. You roll 6-3. You can play the 3 to the 2 point then the 6 to bear a checker off the 2 point leaving your opponent no shots (no blots for the opponent to hit). The alternative, using the 6-3 to bear checkers off both the 5 and 2 points, would leave your opponent 20 out of 36 ways to hit your remaining blot. ═══ 2.11. Gammon and backgammon ═══ If you bear off all 15 of your men before your opponent has borne off a single man, you win a gammon, or double game. The number of points you win will be two times the number of the doubling cube. If you bear off all 15 of your men before your opponent has borne off a single man, and your opponent still has one or more men in your home board or on the bar, you win a backgammon, or a triple game. The number of points you win will be three times the number on the doubling cube. ═══ 2.12. The doubling cube ═══ The introduction of the doubling cube into the game is largely responsible for the leap in popularity of modern backgammon. Each face of the doubling cube bears a number to record progressive doubles and redoubles, starting with 2 and going on to 4, 8, 16, 32 and 64. At the commencement of play, the doubling cube rests on the bar, between the two players, or at the side of the board. At any point during the game, a player who thinks he or she is sufficiently ahead can, when it is the player's turn to play and before the dice are cast, propose to double the stake by turning the cube to 2. The opponent can decline to accept the double, in which case the opponent forfeits the game and loses 1 point, or accept the double, in which case the game continues with the stake at 2 points. The player who accepts the double now "owns" the cube --- which means that the accepting player has the option to redouble at any point during the rest of the game, but the opponent (the original doubler) can not. If, at a later stage the player exercises this option, the opponent is now faced with a similar choice. The opponent can either decline the redouble and so lose 2 points, or accept and play for 4, and he now "owns" the cube. A player can double even with men on the bar even if the opponent has a closed board and the player cannot enter. Though the player does not roll the dice, since no move is possible, the player still has the right to double. Note that a gammon doubles and a backgammon triples the stake of the cube. ═══ 3. Hints for successful play ═══ Backgammon is a game of both skill and luck. This section gives you a few hints at the basic strategies and tactics that are important in winning. For a more detailed discussion of strategy and tactics, see the references. Further information is available on: o Build blocking points o Hit the opponent's blots o Playing safe o Taking chances ═══ 3.1. Build blocking points ═══ One of the primary objectives in backgammon is to block the escape of the opponent's back men. Conversely, on the other side of the board, one of your main objectives is to escape your opponent's blockade. Blocking and escaping are important, because a player cannot begin bearing off until all of his or her men have been brought into his home board. The best blocking points to make are your 5 point, 7 point and 4 point. So, for example, in the opening position shown below in Diagram 3, you are X and have a roll of 3-1 to play. You should play 8-5, 6-5, making your 5 point. 24 23 22 21 20 19 18 17 16 15 14 13 +------------------------------------------+ | X . . . . O | | . O . . . X | | X O | | O X | | O | | O X | | O | | X | | O | | X | +----+ | |BAR| | | 64 | | X | | O | +----+ | X | | O | | X | | X O | | O X | | X O | | O . . . . X | | . X . . . O | +------------------------------------------+ 1 2 3 4 5 6 7 8 9 10 11 12 Diagram 3 -- X to play 3-1 ═══ 3.2. Hit the opponent's blots ═══ When you have an opportunity to hit the opponent, it is usually (but not always) a good thing to do. Hitting accomplishes two important objectives. First, by sending the opponent blot to the bar, the opponent loses ground in the race to get all of one's men home and off the board. Second, the effectiveness of the opponent's next roll is diminished, as the opponent has to use half of the roll to re-enter the blot. And sometimes the opponent loses an entire turn if the opponent rolls a combination which does not permit the blot to re-enter. An illustration of the value of hitting is shown below in Diagram 4: 24 23 22 21 20 19 18 17 16 15 14 13 +------------------------------------------+ | X . . . O O | | O O . . . X | | X O O | | O X | | O | | X | | | | | | | | | +----+ | |BAR| | | 64 | | X | | O | +----+ | X | | X O | | X | | X O | | O X | | X O | | O . . . . X | | . X . . X O | +------------------------------------------+ 1 2 3 4 5 6 7 8 9 10 11 12 Diagram 4 -- X to play 6-1 In this diagram, you are X and you have rolled 6-1. In this position you have the opportunity to build a good blocking point by playing either 13-7, 8-7, or 11-5, 6-5. However, neither of these moves are as good as hitting the opponent blot by playing 24-23, 23-17* (the asterisk denotes a hit). ═══ 3.3. Playing safe ═══ If hitting the opponent's blots is usually a good thing to do, then logically, it follows that you should not give the opponent a lot of opportunities to hit you. It is often a good idea to minimize both the number of blots that you have, as well as the chances of each blot being hit. A good rule of thumb is that blots located 7 spaces or more away from the opponent's men are much less likely to be hit than those located 6 spaces away or less. 24 23 22 21 20 19 18 17 16 15 14 13 +------------------------------------------+ | X . . . . O | | . O . . O X | | X O | | O X | | O | | O X | | O | | X | | O | | | +----+ | |BAR| | | 64 | | | | | +----+ | X | | O | | X | | X O | | X | | X O | | O . . O X X | | . X . . X O | +------------------------------------------+ 1 2 3 4 5 6 7 8 9 10 11 12 Diagram 5 -- X to play 5-2 Diagram 5 above shows a position where a safe play is required. It is too wild to hit O here with a move like 6-1*, 6-4*. O would then be able to hit back with 2-2 or with any roll containing a 1, 4, or 5, for a total of 28 out of 36 possible dice combinations. Instead, you should play 8-3, 5-3. This leaves only one blot on the 11 point, located 7 spaces away from O's man on the 4 point, and 10 spaces away from O's man on the 1 point. O only has 8 dice combinations out of 36 that hit your blot (6-1, 5-2, 4-3 or 6-4). ═══ 3.4. Taking chances ═══ While it is good to play safe, one should not go overboard with minimizing chances of being hit. Especially in the early going, it is worth taking small chances to try to improve your position. An example is given in Diagram 6: 24 23 22 21 20 19 18 17 16 15 14 13 +------------------------------------------+ | X . . . . O | | . O . . . X | | X O | | O X | | O | | O X | | O | | O X | | O | | X | +----+ | |BAR| | | 64 | | X | | | +----+ | X | | O | | X | | X O | | X | | X O | | O O . . . X | | . X . . . O | +------------------------------------------+ 1 2 3 4 5 6 7 8 9 10 11 12 Diagram 6 -- X to play 5-2 In this position, you could play completely safe by moving 13-8, 8-6. However, this leaves you with a very inflexible position that is not likely to improve. A much better alternative is 13-8, 13-11. It is worth giving O a small chance to hit you with a combination of 6-3, 5-4, or 6-4 (6 chances out of 36) in order to give yourself a much better chance of building new points if you do not get hit. ═══ 4. Bearing Off ═══ When all of your checkers are in your home board, you can bear off checkers by dragging them to the lower "bin" on the left edge of the board. The player who bears off all of his or her checkers first, wins. ═══ 5. Bar ═══ The bar is the central area of the board. Whenever a checker is hit (landed upon by an opponent's checker), it is sent to the bar. Checkers that are on the bar must be brought back into play before any other moves can be made by that player. ═══ 6. Doubling ═══ Before a player rolls the dice, that player can offer a double if that player "owns" the doubling cube, or if neither player has doubled yet. To offer a double to TD-Gammon, drag the doubling cube upwards towards your opponent. When TD-Gammon offers a double to you, it will push the doubling cube downwards towards you. To accept the double, drag the doubling cube downward. To decline the double, drag the doubling cube upwards. If you accept the double, the stakes of the game are doubled. If you decline the double, you forfeit the game. ═══ 7. Dice ═══ When it is your turn, you can roll the dice by clicking on an open part of the board with the left mouse button. If you want to double, remember to do so before you roll the dice. ═══ 8. Help for New ═══ Select the New menu item from the File menu to end the current game and start a new game. ═══ 9. Help for Exit ═══ Select the Exit menu item from the File menu to close OS/2 TD-Gammon. The current settings will be saved, but the current game will not be saved. ═══ 10. Help for Settings ═══ Select the Settings menu item to open the Settings folder. The Settings folder lets you set the skill level, the animation speed, and the colors of the various parts of the TD-Gammon board. ═══ 11. Help for Novice ═══ Select the Novice level to tell TD-Gammon to play at the level of a novice backgammon player. At this level, TD-Gammon is fairly easy to beat, even for a player who is just learning backgammon. It knows the rules, and will generally try to hit your blots when it can, but it does not know very much strategy. This is the default skill level. ═══ 12. Help for Beginner ═══ Select the Beginner level to tell TD-Gammon to play at the level of a beginning backgammon player. At this level, TD-Gammon will play like a player who knows a few of the basic strategies of backgammon. It will make mistakes that would be obvious to a more experienced backgammon player. ═══ 13. Help for Intermediate ═══ Select the Intermediate level to tell TD-Gammon to play at the level similar to that of an intermediate backgammon tournament player. In some ways, it will be a stronger player than a human who is an intermediate tournament player. In other ways, it will be weaker. ═══ 14. Help for Advanced ═══ Select the Advanced level to tell TD-Gammon to play at the level similar to that of an advanced backgammon tournament player. In some ways, it will be a stronger player than a human who is an advanced tournament player. In other ways, it will be weaker. At this level, most people will find TD-Gammon difficult to beat consistently. When playing at the advanced level, TD-Gammon spends more time thinking about its moves than it does at lower levels. You might notice a delay when it is thinking about doubling, and when it is thinking about its move, especially on slower machines. ═══ 15. Help for Expert ═══ Select the Expert level to tell TD-Gammon to play at its highest level of skill. At this level, even expert human players will have difficulty beating TD-Gammon consistently. When playing at the expert level, TD-Gammon spends more time thinking about its moves than it does at lower levels. You will probably notice a delay when it is thinking about doubling, and when it is thinking about its move, especially on slower machines. ═══ 16. Help for Help index ═══ Select Help index from the Help menu for an index of the online help for OS/2 TD-Gammon. ═══ 17. Help for General help ═══ Select General help from the Help menu to see detailed information about OS/2 TD-Gammon. ═══ 18. Help for Using help ═══ Select Using help from the Help menu for information on the use of the online help facility. ═══ 19. Help for Keys help ═══ Select Keys help from the Help menu to view a list of keys that can be used to perform various actions from within OS/2 TD-Gammon. ═══ 20. Help for Rules ═══ Use Rules help from the Help menu to view a description of the basic rules of backgammon. ═══ 21. Help for Hints ═══ Select Hints from the Help menu for some helpful hints on playing backgammon well. ═══ 22. Help for Bearing off help ═══ Select Bearing off help from the Help menu for a description of bearing off your pieces after your home board is filled. ═══ 23. Help for Bar help ═══ Select Bar help from the Help menu for a description of the "bar" on the backgammon board. ═══ 24. Help for Doubling cube help ═══ Select Doubling cube help from the Help menu for a description of the doubling cube. ═══ 25. Help for Dice help ═══ Select Dice help from the Help menu for information on how to use the dice in OS/2 TD-Gammon. ═══ 26. Help for Product information ═══ Select Product information from the Help menu for information about OS/2 TD-Gammon, such as the version number and copyright information. ═══ 27. Keys help ═══ You can get help on any object on the backgammon board by clicking on that object with the right mouse button. To get help on the doubling cube, for instance, click on the doubling cube with the right mouse button. The following keys can be used in OS/2 TD-Gammon instead of using the mouse to click on menu items. Alt+F Display the File menu Alt+O Display the Options menu Alt+H Display the Help menu F1 Context-sensitive help