What does the MARC tag 900 refer to in library cataloging?

The MARC tag 900 specifically refers to a Local Call Number in library cataloging. This tag is utilized by libraries to indicate a unique call number assigned to an item within their own collection, allowing for efficient retrieval and organization of materials. The use of tag 900 provides flexibility for libraries to create and manage their own local cataloging practices, which may not conform to standard classification schemes but serve specific local needs.

Other tags serve different purposes in the MARC format. For instance, the title proper is linked to a different tag, and subject added entries are indicated by yet another set of tags. Personal name entries also have their designated tags, distinct from the purpose served by tag 900. By correctly identifying the function of tag 900, one understands how local practices contribute to the broader context of library cataloging standards.