A ZIP Code is the postal code used by the United States Postal Service, zip code maps free which always writes it with capital letters. ZIP codes also change when postal restrictions are realigned. ZIP is an ellipsis for the Zoning Improvement Plan, but was also cleverly meant to suggest that mail travels more efficiently (and therefore faster) when senders use it. The basic ZIP Code format consists of five geometric digits. Two-letter abbreviations were introduced for states, eliminating the need to write the state's name out in full. Similarly, US military addresses also have their own abbreviations. the 5-digit delivery city to zip code area, such as a city block, a group of apartments, an individual high-volume receiver of mail, or any other unit that could use an extra identifier to aid in efficient mail sorting and delivery. The ZIP Code is often translated into a barcode called POSTNET that is printed on the mail piece as well, to make it easier free zip code maps for robotic machines to sort the digital zip code maps mail. Unlike most barcode symbologies, POSTNET uses long and short bars, not thin and thick Zip Code Lookup bars. On business reply mail, the FIM code indicates whether the POSTNET bar code is included. The reason for ZIP codes precincts to not match city limits could be one of two reasons. First, the ZIP code was formed before it was part of any city. Second, the ZIP code provides a nonspecific boundary while the city limits can be complicated. Most significantly, in swiftly developing periphery, it is sometimes necessary to open a new sectional center facility, which must then be allocated its own three-digit ZIP-code prefix or prefixes. Such allocation can be done in various ways. Delivery services other than the USPS, such as Federal Express, United Parcel Service, and DHL require a ZIP code for the optimal internal routing of a package. This spares customers from being required to use some other routing designator, United States zip code map such as the IATA code of the destination airport or railhead