Making Call Numbers Work For You

A call number is like your home address. An address helps you find a specific house within a city; a call number helps you find the exact location of a book on the library shelf.

The 2 most commonly used classification systems for devising the call numbers are Dewey Decimal Classification and Library of Congress Classification. Public libraries tend to use Dewey, while university libraries tend to use Library of Congress. The underlying principles are similar, but the actual call numbers look very different.

There are 2 basic parts to a call number: the SUBJECT part and the AUTHOR part.

In the Dewey Decimal Classification...

Subject - This part is made up of all numbers, ranging from 3 to 10 or more digits (depending on how narrowly focused the topic of the book).

Author - This part begins with a letter that matches the first letter of the author's last name, followed by 2 or 3 numbers, and then usually another letter that matches the first letter of the first word of the title.

In the Library of Congress Classification...

Subject - This part is made up of 2 letters plus 1 to 4 (or more) digits.

Author - This part begins with a letter that corresponds to the first letter of the author's last name, followed by a series of numbers.

For example, if you had a book by Jeffrey Pfeffer entitled The Human Equation: Building Profits by Putting People First,

The Dewey call number might be 658.314 P524h

The Library of Congress call number might be HF 5386 .P5468

It's the same book, but different libraries give it different call numbers depending on the classification system they use.

Let's break down those numbers a bit so you can see how they work.


658.314 = The number for books about motivating employees
P524h = P524 stands for the author's last name (Pfeffer); "h" for the first word of the title (Human)

Library of Congress

HF = The section for books about commerce
5386 = Books about success in business
.P5468 = Represents the author's last name

These are the 10 major divisions of the Dewey classification system.

000 Computers and Information Science
100 Philosophy & Psychology
200 Religion
300 Social Sciences
400 Language
500 Science & Mathematics
600 Technology
700 The Arts
800 Literature
900 Geography & History

Under each major division are 10 subdivisions, to break down the broad topic areas into smaller topics. So, for example, you will find these subdivisions of the 600s (Technology).

610 Medicine
620 Engineering
630 Agriculture
640 Home Economics

650 Management
660 Chemical Engineering
670 Manufacturing
680 Manufacturing for Specific Uses
690 Buildings

The 650s are further subdivided into these categories.

651 Office Services
652 Processes of Written Communication
653 Shorthand
657 Accounting

658 General Management
659 Advertising & Public Relations

Many Dewey call numbers have a decimal point after the first 3 numbers, followed by more numbers after the decimal. That's because the Dewey Decimal system allows you to continue subdividing the topic - by adding more digits - until you arrive at a number that precisely describes the topic of the book.

The 658s can be subdivided even more to show these topics.

658.1 Organization and Finance
658.2 Plant Management
658.3 Personnel Management
658.4 Executive Management
658.5 Management of Production
658.7 Management of Materials
658.8 Marketing

That's how you come up with an outrageous number like 658.312402854678 for books about using the Internet to train employees.

That same book (about training employees using the Internet), in a library using Library of Congress Classification (LCC), would probably have a call number like this: HF5549.5.T7. Let's break that down so you can see how the LC classification works.

HF = Commerce
5001-6182 = Business
5549-5549.5 = Personnel management
5549.5 = Subdivisions under Personnel management
.T7 = Training of employees

In this case, the .T7 doesn't represent the author's name; that part of the call number was needed in order to provide more subdivisions. The author's name would be represented by another line, possibly D743 for a last name of Driscoll. (Yes ... even in libraries, there are exceptions to the rules!)

The book used for this example is Web-based Training : Using Technology to Design Adult Learning Experiences, by Margaret Driscoll.

Dewey has 10 basic number groups (000s to 900s) into which to subdivide all the knowledge of the world -- a daunting task! LCC has 26 letters of the alphabet to use, and these are then subdivided by numbers. That's why LCC numbers aren't as long as Dewey numbers can sometimes be.

You can see that Dewey and LCC are structured very differently, but the underlying principle is the same: You take a broad subject area and keep breaking it down into smaller subdivisions until you get a precise topic that corresponds with the topic of the book.

So, what does this mean to you? If you understand a little bit about how the books are organized, you can go directly to the correct section of a library collection and browse around until you find something on your topic.

You are at the end of Module 1!


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