The introduction of the shot clock is one of the key changes that have shaped the game of basketball as we know it today. The shot clock--requiring teams to take a shot in a limited amount of time--was introduced to keep teams from stalling. The NBA had the shot clock for years before it was adopted into the college game.
At times teams would stall, or hold the ball, to slow a game down and keep a superior team from getting the ball. It was a strategy that worked at times, but it slowed the game and made it less interesting.
In 1986 the NCAA adopted a 45 second shot clock for men's basketball. In 1992 the rule was modified to reset the shot clock after the ball hit the rim instead of when it left the shooter's hand. In 1994 the shot clock was reduced to 35 seconds, which is where it is today.
The NCAA women installed a 25 second shot clock in the early 70s.
Once a team gains possession, it has 35 seconds to take a shot. If the shot is made, the other team starts with the ball and a new shot clock. If the shot is missed, the team that rebounds gets a new shot clock of 35 seconds. The shot must hit the rim or the backboard to be considered a shot. If the ball hits neither and stays in bounds, it is not considered a shot, and the shot clock continues if the shooting team retains possession.
A team can gain possession after the other team has scored, on a rebound, on a jump ball or by getting the ball in a loose ball situation. The shot clock begins when the official signals that the inbound player has touched the ball on a throw in.
The shot clock stops when the official's whistle sounds for any reason. The shot clock is turned off when there is a reset situation and there are less than 35 seconds left in the game, or 25 seconds in a womens' game.
The shot clock continues to run in a loose ball situation.
Resetting the clock
The shot clock is reset when there is a change of possession. The new team in control gets a new 35 seconds on the shot clock. There is also a full reset when there is a personal foul, a technical foul on a defensive player, a violation other than kicking or hitting the ball with the fist, or if there is an inadvertent whistle with no team in control.
The shot clock is to be reset at 15 seconds when the ball is intentionally kicked or hit with a fist with 14 seconds or less left in the possession.
The shot clock is not reset if the offense retains possession on a held ball or out of bounds play. The shot clock is also not reset when the ball is intentionally kicked with 15 seconds or more left in the possession. Other stoppages that do not result in a reset clock are for an injured player, a timeout, a double foul, a technical foul on the offense, or an inadvertent whistle with the ball under control.