A dollar is the national monetary unit of the USA, along with some other countries, and the most common types of dollar are the US dollar, the Canadian dollar, the Australian dollar, etc. Most affairs are made with the use of USD and, besides that, after World War II, the US dollar has become the world’s primary reserve currency or worldwide currency. In 1971, the cancellation of the direct convertibility of the United States Dollar to gold was ordered by President Richard Nixon. In some countries the dollar has the status of being the de facto currency which allows using it instead of the official one. The right of issuing the US dollars belongs to the Federal Reserve System and all dollar bills that have been issued since 1861 are still legal.