What's the difference between international code, national code and area code?

Question

I need those 3 kinds of codes of some countries like: the US, the UK, Germany, France, Ireland,.....
Where can I find the definitions of those codes and the codes of all the countries in the world?

Answer 1

Area code is the numerical code to reach a certain place in a country. International Code is the numerical code to reach a country. For example: if you want to call Shanghai, China you dial numbers in the following sequence:
International Code for China + Area Code for Shanghai + Phone Number in Shanghai.
I am not sure what a national code and I never use one when making international calls.
Check out this link for an exhaustive list of all the country codes and the area codes for each country:
http://www.the-acr.com/codes/cntrycd.htm
Hope this helps.

Answer 2

The international code is the 3-digit code used to get an international line. The national code is the next 2-3-digit code which signifies which country you are calling. The area code comes next, and describes the region you are calling. In the US, the area code usually doesn't cross state lines.

Answer 3

To answer the last part of your question first, [and this depends on where you are in the world] but a lot of telephone books carry this information.

Now to the first part of your question, international code is the country you are calling, national code is usually the state you are calling and area code is the town
good luck