the outside edge of the arms and legs. The cylinder extends from the floor to the ceiling, allowing the player to jump upward. A player can occupy any cylinder not already occupied by the opponent. No one else is allowed to step or reach into this cylinder. A player must not extend his limbs or bend his body in a way that is not normal. If there is a breach of this principle that places the opponent at a disadvantage, the official may penalise it. The NBA does not use the cylinder principle to judge contact; it only says that a player may not bend or reach in a position that is not normal (nor push, hold, and so on). Elements of time and distance The elements of time and distance concern the reaction time and distance of another person. They apply only to players without the ball, not to the ball carrier. For example, a player cannot suddenly step in front of a sprinting player, even without invading the cylinder. Another example is when a player sets a screen directly behind a player: the player would not physically be able to react to the screen in enough time to avoid it. Types of foul Charging and blocking When significant illegal contact between the ball-carrier and a defender occurs, it usually means that either — The defender committed a blocking foul, or The ball-carrier committed the offensive foul of charging. Deciding between the two is complex, partly subjective, and often controversial. Generally, the ball-carrier committed a charge if all of the following are true: The defender was still, or moving sideways or backward but not forward, when contact occurred. The defender took a legal guarding position before the contact, that is, one with both feet on the floor. The defender was hit on the torso (as opposed to the arm or leg). In the NBA, in contact during a move to the basket, officials do not consider the position of the defender's feet, but decide whether the defensive player's torso was set in position before the offensive player began his upward motion. An exception is that a charging foul is usually not called if the ball-handler is within a 4-foot (1.22 m) radius around the center of the basket (known in the rules as the "restricted area" and sometimes colloquially as the "smiley face"). That is, if the ball-carrier is