Originally, a two-letter abbreviation for a particular country, generally used as a top-level domain.

Originally, as the name implies, country codes were meant just for countries; but over time, country codes were allocated for many areas (mostly islands) that aren't countries -- such as Antarctica (aq), Christmas Island (cx) and Saint Pierre et Miquelon (pm).

Country codes are based on ISO 3166 and are used as the top level domain for Internet hostnames in most countries but hardly ever in the USA (code "us").

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