Editing Currency (section)

== Control and production ==
[[Image:South East Asia Exchange Rates (6031878489).jpg|thumb|A list of exchange rates for various base currencies given by a [[money changer]] in Thailand, with the Thailand Baht as the counter (or quote) currency. Note the Korean currency code should be KRW.]]
{{Most traded currencies}}
Commonly a [[central bank]] has the exclusive power to issue all forms of currency, including coins and banknotes ([[fiat money]]), and to restrain the circulation alternative currencies for its own area of circulation (a country or group of countries); it regulates the production of currency by banks ([[credit (finance)|credit]]) through [[monetary policy]].

An [[exchange rate]] is a price at which two currencies can be exchanged against each other. This is used for [[international trade|trade]] between the two currency zones. Exchange rates can be classified as either [[floating exchange rate|floating]] or [[fixed exchange-rate system|fixed]]. In the former, day-to-day movements in exchange rates are determined by the market; in the latter, governments intervene in the market to buy or sell their currency to balance supply and demand at a static exchange rate.

In cases where a country has control of its own currency, that control is exercised either by a [[central bank]] or by a [[Finance minister|Ministry of Finance]]. The institution that has control of monetary policy is referred to as the monetary authority. Monetary authorities have varying degrees of autonomy from the governments that create them. A monetary authority is created and supported by its sponsoring government, so independence can be reduced by the legislative or executive authority that creates it.

Several countries can use the same name for their own separate currencies (for example, a ''dollar'' in [[Australian dollar|Australia]], [[Canadian dollar|Canada]], and the [[United States dollar|United States]]). By contrast, several countries can also use the same currency (for example, the [[euro]] or the [[CFA franc]]), or one country can declare the currency of another country to be [[legal tender]]. For example, [[Panama]] and [[El Salvador]] have declared US currency to be legal tender, and from 1791 to 1857, [[Spanish dollars]] were legal tender in the United States. At various times countries have either re-stamped foreign coins or used [[currency board]]s, issuing one note of currency for each note of a foreign government held, as [[Ecuador]] currently does.

Each currency typically has a main currency unit (the [[dollar]], for example, or the [[euro]]) and a fractional unit, often defined as {{Frac|1|100}} of the main unit: 100 [[Cent (currency)|cents]]&nbsp;= 1&nbsp;[[dollar]], 100 [[centime]]s&nbsp;= 1&nbsp;[[franc]], 100 pence&nbsp;= 1&nbsp;[[Pound sterling|pound]], although units of {{Frac|1|10}} or {{Frac|1|1000}} occasionally also occur. Some currencies do not have any smaller units at all, such as the [[Icelandic króna]] and the [[Japanese yen]].

[[Mauritania]] and [[Madagascar]] are the only remaining countries that have theoretical fractional units not based on the decimal system; instead, the [[Mauritanian ouguiya]] is in theory divided into 5 [[khoums]], while the [[Malagasy ariary]] is theoretically divided into 5 [[iraimbilanja]]. In these countries, words like ''dollar'' or ''pound'' "were simply names for given weights of gold".<ref name="The Collapse of the Dollar">{{cite book |last1=Turk |first1=James |last2=Rubino |first2=John |title=The collapse of the dollar and how to profit from it: Make a fortune by investing in gold and other hard assets |edition=Paperback |year=2007 |orig-year=2004 |publisher=Doubleday |location=New York |isbn=978-0-385-51224-4 |oclc=192055959 |pages=43 of 252}}</ref> Due to [[inflation]] khoums and iraimbilanja have in practice fallen into disuse. (See [[non-decimal currencies]] for other historic currencies with non-decimal divisions.)