<Table> <Tr> <Td> </Td> <Td> This article possibly contains original research . Please improve it by verifying the claims made and adding inline citations . Statements consisting only of original research should be removed . (June 2017) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article possibly contains original research . Please improve it by verifying the claims made and adding inline citations . Statements consisting only of original research should be removed . (June 2017) (Learn how and when to remove this template message) </Td> </Tr> <P> ZIP Codes are a system of postal codes used by the United States Postal Service since 1963 . The term ZIP, an acronym for Zone Improvement Plan, was chosen to suggest that the mail travels more efficiently, and therefore more quickly (zipping along), when senders use the code in the postal address . The basic format consists of five digits . An extended' ZIP + 4' code, introduced in 1983, includes the five digits of the ZIP Code, a hyphen, and four additional digits that determine a more specific location within a given ZIP Code . </P> <P> The term ZIP Code was originally registered as a servicemark by the U.S. Postal Service, but its registration has since expired . USPS style for ZIP is all caps and the "C" in "Code" is also capitalized, although style sheets for some publications use sentence case or lowercase . </P>

What does the zip in zip code stand for