How Do International Dialing Codes Work
Every country in the world has a unique country dialing code. This means that telephone calls can be made from anywhere in the world to anywhere in the world without and problems. Before you dial an international country dialling code, it is necessary to tell the telephone system you want to do so - see the instructions on how to make an international call for more information.
Composition of country dialing codes
Most countries have a 2-digit calling code, the code for the United Kingdom is 44; France is 33. The United States is an exception as the code is 1. Some smaller countries (in terms of people, not area) have a three-digit country dialling code, such as the Republic of Ireland (353).
Representation of international phone numbers
Because you need to dial different codes to make international calls in different countries, it is recommended not to write an international phone number starting with 0 or 00. It is much better to use the + sign to represent the code needed. So, a number in the United Kingdom might be represented as +44 1296 999999.
National dialing codes when calling internationally
In some countries, it may be necessary (when dialling a number from within the country) to add a zero - or depending on how you look at it - take the zero out when calling the number internationally. For example:
To call the above number in the UK, you would need to dial 01296 999999. The 01296 is the national area code (in this case the Aylesbury area in the South-East of England).
To call this number from outside of the United Kingdom, it is necessary to not dial the 0 at the beginning of the area code, so in this example it would become 1296 999999. You then add the country code onto the front of the number (it is 44 for the UK), eg 44 1296 999999.
If you wanted to call the number from France, you would need to dial 00 first as this is the was in France to initiate an international call. Putting it all together for this example: 00 44 1296 999999.