This part of ISO 639 provides two sets of three-letter alphabetic codes for the representation of names of languages, one for terminology applications and the other for bibliographic applications. The code sets are the same except for twenty-five languages that have variant language codes because of the criteria used for formulating them (see 4.1). The language codes were devised originally for use by libraries, information services, and publishers to indicate language in the exchange of information, especially in computerized systems. These codes have been widely used in the library community and may be adopted for any application requiring the expression of language in coded form by terminologists and lexicographers. The alpha-2 code set was devised for practical use for most of the major languages of the world that are most frequently represented in the total body of the world's literature. Additional language codes are created when it becomes apparent that a significant body of literature in a particular language exists. Languages designed exclusively for machine use, such as computer programming languages, are not included in this code.