International Direct Dialing
International Direct Dialing (IDD) is an international telephone call dialed by the caller rather than going via an operator. Since late in the twentieth century, most international calls are direct dialed.
International calls are made by dialing the international call prefix for the country one is in, followed by the country calling code for the country one wishes to call, then the phone number within that country. When phone numbers are published for use abroad, they include the country calling code, but replace the international call prefix with "+" to signify that the caller should use the prefix appropriate for their country.