the standard also defines the relationship between the major currency unit and any minor currency unit. often, the minor currency unit has a value that is 1/100 of the major unit, but 1/1000 is also common. some currencies do not have any minor currency unit at all. in others, the major currency unit has so little value that the minor unit is no longer generally used (e.g. the japanese "sen", 1/100th of a yen). this is indicated in the standard by the currency exponent. for example, usd has exponent 2, while jpy has exponent 0. mauritania does not use a decimal division of units, setting 1 ouguiya (um) = 5 khoums, and madagascar has 1 ariary = 5 iraimbilanja.