An international call prefix or dial out code is a trunk prefix used to select an international telephone circuit for placing an international call. It is often referred to as IDD Prefix (International Direct Dialing)—a country will typically have a NDD Prefix as well (National Direct Dialing). The international dialing prefix must be dialed before the country calling code and the destination telephone number. It is synonymous with international access code or exit code. The international call prefix is part of the telephone numbering plan of a country for calls to another country.