Area code

Area code is a type of numbering scheme used in telecommunication to allocate telephone numbers to specific geographic areas. The structure and distribution of area codes can vary significantly from country to country, and in some cases, within a single country.

History

The concept of the area code was first developed and implemented by AT&T and Bell System in the United States in the mid-20th century, as part of a national direct dialing system. This system was known as the North American Numbering Plan (NANP), which was established in 1947.

Structure

An area code is typically a sequence of three digits. In the NANP, the first digit can be any digit from 2 through 9, the second digit can be any digit, and the third digit can be any digit from 0 through 9. This structure allows for a potential of 800 possible area codes.

Allocation

Area codes are allocated to specific geographic regions. In the United States, these regions can be as large as an entire state (for example, Alaska, Delaware, and Hawaii each have only one area code), or as small as a portion of a large metropolitan area.

Dialing

In many countries, including the United States and Canada, it is necessary to dial "1" before the area code when making a long-distance call. This is known as "1+" dialing. However, in some areas, particularly in large cities, it is necessary to dial the area code even for local calls.

Overlays and splits

When the existing area code of a region becomes exhausted due to population growth or the proliferation of cell phones and pagers, a new area code must be introduced. This can be done in one of two ways: by splitting the region into two or more regions each with its own area code (a "split"), or by overlaying a new area code onto the same geographic region as the existing area code (an "overlay").

See also

• List of North American Numbering Plan area codes
• Telephone numbering plan
• International call

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