NLM Classification Fundamentals

Classification (Class) Numbers

Call Numbers vs. Classification Numbers

neighborhood street showing row of houses

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Libraries use unique call numbers to organize resources by subject areas. The call number of a resource acts like a house's street address. It is a unique identifier that locates the item sequentially within a larger group of similar resources (much like the other houses on a block may have a similar design, shape, size, etc.).

The National Library of Medicine employs MARC (MAchine-Readable Cataloging) Coding to standardize the format of call numbers in bibliographic records. For information on formatting call numbers in bibliographic records, visit the NLM Policy on Classification.

Example

NLM call number: 060 00 $a WA 540 AA1 $b B8p 1972 v. 32

In a MARC bibliographic record, an NLM call number (e.g., 060 00 $a WA 540 AA1 $b B8p 1972 v. 32) consists of the following basic components, when applicable:

MARC Coding Example
Call Number Label	Example
Classification Number	WA 540
Table G (Geographic Notation)	AA1
Cutter Number	B8
Workmark	p
Year of Publication	1972
Volume or Issue Number	v. 32 (Note: volume or issue number may also precede year of publication)

Call number 060 00 $a WA 540 AA1 $b B8p 1972 v. 32 broken down by MARC Coding example

We will discuss how to determine the first two components of a call number:
Classification Number and Table G (Geographic Notation).

For information about the rest of the components of a call number, visit this page on Shelflisting Procedures.