what is area code

An area code is a set of digits forming the most significant part of a telephone number, which is prefixed to each telephone number issued in its service area. It is used to designate geographic regions in a telephone numbering plan, allowing for the unique identification of subscribers in a specific area. In North America, area codes consist of three digits and are used as part of a ten-digit dialing sequence to reach a telephone subscriber. They are often necessary only when dialed from outside the code area or from mobile phones. Area codes are also assigned for non-geographic purposes, and some are reserved for special uses, such as toll-free numbers. The rules for numbering NPAs (Numbering Plan Areas) do not permit the digits 0 and 1 in the leading position, and area codes with two identical trailing digits are easily recognizable codes (ERC) .