What is the exchange code in a phone number?

The telephone exchange code is a numeric prefix in a telephone number that originally was used to identify the specific telephone switch that served that number. With number portability, the geographic zones are not as clear cut, but the exchange code still identifies the charging area.

In North America (USA, Canada, etc.), the exchange code is the first three digits after the area code. In other countries, the length of the exchange code may vary.