Library of Congress Classification

The Library of Congress Classification is a system for organizing library materials by subject using letters and numbers. It arranges topics into broad classes and increasingly specific subclasses.

Main classes of the Library of Congress Classification: The twenty-one top-level subject divisions of the Library of Congress Classification, designated by single letters or letter combinations. These divisions provide the system’s first subject-based sorting step.
Herbert Putnam: American librarian who served as Librarian of Congress from 1899 to 1939 and oversaw major institutional changes. Putnam’s administration initiated the classification project that produced the system.
Dewey Decimal Classification: A general library classification system that organizes knowledge into ten main classes subdivided using decimal notation. Dewey uses a decimal hierarchy, unlike the Library of Congress system’s lettered main classes.
Library catalog: An organized record of a library’s holdings, with details that help identify and locate materials. Catalog records commonly include classification call numbers for locating physical items.
Library of Congress Classification maintenance: The ongoing revision and publication of changes to Library of Congress Classification schedules. Continuous maintenance lets schedules respond to new subjects and changing terminology.
Library of Congress call number: A shelf identifier built from classification letters and numbers, often combined with a date or other item details. The completed call number translates a classified subject into an item’s shelf address.
Charles Martel: American librarian who helped develop the Library of Congress Classification in the early twentieth century. Martel directed early work on schedules for the new classification.
Universal Decimal Classification: A faceted classification system derived from Dewey Decimal Classification that uses decimal notation and auxiliary symbols. Its notation supports combining topics more explicitly than standard Library of Congress schedules.
Online public access catalog: A searchable digital interface for exploring a library’s catalog records and holdings. Catalog interfaces can expose classification numbers alongside searchable bibliographic details.
Library of Congress Classification and knowledge organization: The system’s representation of subjects through hierarchical classes, subdivisions, and assigned relationships. Its schedules make particular choices about which topics are grouped and how they relate.

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