Library of Congress Control Number

Library of Congress Control Number (in English, abbreviated: LCCN, roughly translated: Library of Congress Control Number) is a system serial number to number the library cataloging records at Library of Congress of United States.

History
The LCCN numbering system has been in use since 1898. At that time, LCCN stood for  Library of Congress Card Number  (roughly translated: Library of Congress Card Number). Sometimes people call it the Library of Congress Catalog Card (roughly translated: Library of Congress Catalog Card). Library of Congress makes business-use bibliographic cards cataloging and can sell copies of those card sets for letters Other libraries that need library cataloging. This practice is known as centralized cataloging. Each card set is given a serial number that identifies it.

Although most bibliographic information today has been electronicized during creation, storage and sharing with other libraries, there is still a need to identify specific records individually. Therefore, LCCN continues to do that function.

Employees librarians around the world use this unique identifier number when cataloging most books published in the United States. The LCCN gives them access to accurate cataloging data (also known as cataloging records) posted directly by the Library of Congress and by third parties on the Internet and other media.

In February 2008, Library of Congress introduced a service  LCCN Permalink  which provides a stable URL leading to all LCCNs.

Format
The most basic LCCN has a format that includes the year and serial numbers.
 * Code for the year is written in two digits for years in the period 1898-2000 and four digits for years from 2001 onwards. Three-year coincidences are distinguished by serial number size. There were some unusual cases of year codes beginning with "7" as a result of an unsuccessful experiment in 1969-1972.
 * Serial number is a six-digit sequence and may begin with the number "0". Between the number for the year and the serial number there is usually hyphen to separate it, but is not required. Recently, the Library of Congress instructed publishers not to add hyphens.