Postal code


A postal code is a series of letters or digits or both, sometimes including spaces or punctuation, included in a postal address for the purpose of sorting mail.
the Universal Postal Union lists 160 countries which require the use of a postal code.
Although postal codes are usually assigned to geographical areas, special codes are sometimes assigned to individual addresses or to institutions that receive large volumes of mail, such as government agencies and large commercial companies. One example is the French CEDEX system.

Terms

There are a number of synonyms for postal code; some are country-specific:
The development of postal codes happened first in large cities. Postal codes began with postal district numbers within large cities. London was first subdivided into 10 districts in 1857, WC, four were created to cover Liverpool in 1864; and Manchester/Salford was split into eight numbered districts in 1867/68. By World War I, such postal district or zone numbers also existed in various large European cities. They existed in the United States at least as early as the 1920s, possibly implemented at the local post office level only although they were evidently not used throughout all major US cities until World War II.
By 1930 or earlier, the idea of extending the postal district or zone numbering plans beyond large cities to cover even small towns and rural locales had started. These developed into postal codes as they are defined today. The name of US postal codes, "ZIP Codes", reflects this evolutionary growth from a zone plan to a zone improvement plan, "ZIP". Modern postal codes were first introduced in the Ukrainian Soviet Socialist Republic in December 1932, but the system was abandoned in 1939. The next country to introduce postal codes was Germany in 1941, followed by Singapore in 1950, Argentina in 1958, the United States in 1963 and Switzerland in 1964. The United Kingdom began introducing its current system in Norwich in 1959, but it was not used nationwide until 1974.

Presentation

Character sets

The characters used in postal codes are:
originally did not use the letters 'F', 'I', 'O', 'Q', 'U' and 'Y' for technical reasons. But as almost all existing combinations are now used, these letters were allowed for new locations starting 2005. The letter combinations "SS", "SD", and "SA" are not used, due to links with the Nazi occupation in World War II.
Postal codes in Canada do not include the letters D, F, I, O, Q, or U, as the optical character recognition equipment used in automated sorting could easily confuse them with other letters and digits. The letters W and Z are used, but are not currently used as the first letter. The Canadian Postal Codes use alternate letters and numbers, formatted ANA NAN.
In Ireland, the eircode system uses the following letters only: A, C, D, E, F, H, K, N, P, R, T, V, W, X, Y. This serves to avoid confusion in OCR, and to avoid accidental double-entendres by avoiding the creation of word lookalikes, as Eircode's last four characters are random.

Alphanumeric postal codes

Most of the postal code systems are numeric; only a few are alphanumeric. Alphanumeric systems can, given the same number of characters, encode many more locations. For example, while a two digit numeric code can represent 100 locations, a two character alphanumeric code using ten digits and twenty letters can represent 900 locations.
The independent nations using alphanumeric postal code systems are:
Countries which prefix their postal codes with a fixed group of letters, indicating a country code, include Andorra, Azerbaijan, Barbados, Ecuador and Saint Vincent and the Grenadines.

Country code prefixes

country codes were recommended by the European Committee for Standardization as well as the Universal Postal Union to be used in conjunction with postal codes starting in 1994, but they have not become widely used. Andorra, Azerbaijan, Barbados, Ecuador, Latvia and Saint Vincent and the Grenadines use the ISO 3166-1 alpha-2 as a prefix in their postal codes.
In some countries the numeric postal code is sometimes prefixed with a country code when sending international mail to that country.

Placement of the code

Postal services have their own formats and placement rules for postal codes. In most English-speaking countries, the postal code forms the last item of the address, following the city or town name, whereas in most continental European countries it precedes the name of the city or town. When it follows the city, it may be on the same line or on a new line.
In Japan, it is written at the start of the address when written in Japanese, but at the end when the address is written in the Latin alphabet.

Geographic coverage

Postal codes are usually assigned to geographical areas. Sometimes codes are assigned to individual addresses or to institutions that receive large volumes of mail, e.g. government agencies or large commercial companies. One example is the French Cedex system.

Postal zone numbers

Before postal codes as described here were used, large cities were often divided into postal zones or postal districts, usually numbered from 1 upwards within each city. The newer postal code systems often incorporate the old zone numbers, as with London postal district numbers, for example. Ireland still uses postal district numbers in Dublin. In New Zealand, Auckland, Wellington and Christchurch were divided into postal zones, but these fell into disuse, and have now become redundant as a result of a new postcode system being introduced.

Codes defined along administrative borders

Some postal code systems, like those of Ecuador and Costa Rica, show an exact agreement with the hierarchy of administrative divisions.
Format of six digit numeric postal codes in Ecuador, introduced in December 2007: ECAABBCC
Format of five digit numeric Postal codes in Costa Rica, introduced in 2007: ABBCC
In Costa Rica these codes were originally used as district identifiers by the National Institute of Statistics and Census of Costa Rica and the Administrative Territorial Division, and continue to be equivalent.
The first two digits of the postal codes in Turkey correspond to the provinces and each province has assigned only one number. They are the same for them as in ISO 3166-2:TR.
The first two digits of the postal codes in Vietnam indicate a province. Some provinces have one, other have several two digit numbers assigned. The numbers differ from the number used in ISO 3166-2:VN.

Codes defined close to administrative boundaries

In France the numeric code for the departments is used as the first two digits of the postal code, except for the two departments in Corsica that have codes 2A and 2B and use 20 as postal code. Furthermore, the codes are only the codes for the department in charge of delivery of the post, so it can be that a location in one department has a postal code starting with the number of a neighbouring department.

Codes defined indirectly to administrative borders

The first digit of the postal codes in the United States comprises discrete states. From the first three digits one can infer the state, with a few exceptions where an area is served by a central office in an adjacent state.
Similarly, in Canada, the first letter indicates the province or territory, although the provinces of Quebec and Ontario are divided into several lettered sub-regions, and the Northwest Territories and Nunavut share the letter X.

Codes defined independently from administrative areas

The first two digits of the postal codes in Germany define areas independently of administrative regions. The coding space of the first digit is fully used ; that of the first two combined is utilized to 89%, i.e. there are 89 postal zones defined. Zone 11 is non-geographic.
Royal Mail designed the postal codes in the United Kingdom mostly for efficient distribution. Nevertheless, people associated codes with certain areas, leading to some people wanting or not wanting to have a certain code. See also postcode lottery.
In Brazil the 8-digit postcodes are an evolution of the five-digit area postal codes. In the 1990s the Brazilian five-digit postal code, DDDDD, received a three-digit suffix DDDDD-SSS, but this suffix is not directly related to the administrative district hierarchy. The suffix was created only for logistic reasons.
file:QuadraExemplo-CEP-pnt.png|thumb|220px|In the code spatialization it is an error to associate the postal code to an individual land lot area: a lot may have 0, 1, 2 or more delivery points, with different codes.
The postal code assignment can be assigned to individual land lots in some special cases – in Brazil, they are named "large receivers" and receive suffixes 900–959. It is an error to associate the postal code with the whole land lot area. A postal code is often related to a land lot, but postal codes are usually related to access points on streets. Small or middle-sized houses, in general, only have a single main gate, which is the delivery point. Parks, large businesses such as shopping centers and big houses, may have more than one entrance and more than one delivery point.