United States telephone numbering

The United States telephone numbering system assigns each phone number a unique 10-digit code: a three-digit area code, a three-digit central office (or exchange) code, and a four-digit station number. The area code indicates a geographic region, while the central office code specifies a local exchange within that region. Together with the station number, they route calls accurately. This system allows for efficient numbering, scalability, and support for the large volume of phone users across the country, all coordinated under the North American Numbering Plan.