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How does a library catalog differ from a library classification system?

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British Museum: Reading Room — library Reading Room of the British Museum, designed by Sidney Smirke in collaboration with Anthony Panizzi and built in the 1850s. Illustration by Smirke, from the *Illustrated London News*, 1857.

While cataloging and classification are both essential indexing disciplines, they serve distinct functions in organizing a library collection.1

Library Cataloging
Cataloging focuses on identifying and describing the physical and topical nature of individual items. It involves extracting bibliographic elements—such as author names, titles, publishers, and dates—to create a record for each item. Conceptually, a catalog acts as a matrix where each entry provides specific keys to help users locate and identify materials within the collection.23

Library Classification
Library classification is the system used to arrange materials in a logical order, typically by subject, to enable patrons to find items easily. By assigning a call number, classification physically locates an item within the library’s shelves and within the broader realm of knowledge. Common systems include the Dewey Decimal Classification and the Library of Congress Classification.2

In short, while the catalog provides the descriptive information needed to identify an item, the classification system provides the framework for its physical arrangement and shelf placement.2