Within a collection, materials are typically organized by subject. Librarians
assign a call number based on a work's subject. The sources are then shelved
by 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 call numbers are assigned for
the book, Battle in Seattle by Janet Thomas,
printed in 2000, about the demonstrations during the WTO summit
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