Within a library collection, materials are typically organized by subject.
Librarians assign a call number based on a work's subject and sources
are then shelved by that call number so that anyone browsing the shelves will
find most of the titles on a subject together.
There are 2 main subject classification systems that translate a work's
subject and author or title into a code (call number) that determines
where it will be shelved.
The examples below illustrate how the two main subject classification
systems, Library of Congress and Dewey Decimal, are used to assign call numbers for the book, Battle
in Seattle by Janet Thomas, published in 2000, about
the demonstrations during the WTO summit in Seattle.
Library of Congress: Used in
most college, university, and research libraries because it handles
Dewey Decimal: Used in most
public and school libraries because it is more effective for smaller