The United States dollar (sign: $; code: USD) is the unit of currency of the United States. The U.S. dollar is normally abbreviated as the dollar sign, $, or as USD or US$ to distinguish it from other dollar-denominated currencies and from others that use the $ symbol. It is divided into 100 cents (200 half-cents prior to 1857). The U.S. dollar is the currency most used in international transactions. Several countries use it as their official currency, and in many others it is the de facto currency. The U.S. dollar bill uses the decimal system, consisting of 100 equal cents (symbol ¢). In another division, there are 1,000 mills or ten dimes to a dollar, or 4 quarters to a dollar....