<P> While there are many variations in detail, handicap systems are generally based on calculating an individual player's playing ability from his recent history of rounds . Therefore, a handicap is not fixed but is regularly adjusted to increases or decreases in a player's scoring . </P> <P> In the United States, handicaps are calculated using several variables: The player's scores from his most recent rounds, and the course rating and slope from those rounds . A handicap differential is calculated from the scores, using the course slope and rating, and the player's handicap differentials are used to calculate the player's handicap . </P> <P> A golfer whose handicap is zero is called a scratch golfer . A golfer whose handicap is approximately 18 is called a bogey golfer . </P> <P> In the United States each officially rated golf course is described by two numbers: the course rating and the slope rating . The course rating of a particular course is a number generally between 67 and 77 that is used to measure the average "good score" by a scratch golfer on that course . The slope rating of a particular course is a number between 55 and 155 that describes the relative difficulty of a course for a bogey golfer compared to a scratch golfer . These two numbers are used to calculate a player's handicap differential, which is used to adjust a player's score in relation to par according to the slope and rating of the course . The slope rating for a golf course of average difficulty is 113 . </P>

One who has a handicap of zero in golf is known as