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Library of Congress (LC) Classification System


  • System of Call Numbers and **Subject Headings - which are connected to each other
  • Used by academic libraries
  • Libraries use classification systems to organize the books on the shelves. A classification system uses letters and/or numbers (call numbers) to arrange the books so that books on the same topic are together. This arrangement results in "serendipitous browsing:" you find one book in the catalog, go to the shelf, and, other useful books are shelved near that book. In a library catalog, most books have multiple subject headings. The first subject heading is the main focus of the book. The call number corresponds to the first subject heading :
Classic Library Catalog Library Catalog - CATQuest

What is the Purpose of Call Numbers? (though it starts with letters, it is called a number )

Each book has a unique call number, which provides an address or location for the item, and also provides valuable information about it, such as the subject, first letter of the author’s last name, and date of publication.

Call numbers appear on the spine of books and in the Library Catalog:

In the LC Classification System for Literature, here is a sampling of how the call number would begin:

P     Language and Literature
PN  General Literature
PR  English Literature
PS  American Literature

The letter-and-decimal section of the call number often represents the author’s last name. The last section of a call number is often the date of publication.

Anatomy of a Call Number for the book Jane Austen and Bath by Emma Austen-Leigh
PR Subject Classification (British literature) Alphabetical
4036 Main Subject (Austen) Numerical
.A77 Author's last name (first initial : Austen-Leigh) Alphabetical
1977 Date of Publication Numerical

Read call numbers line by line.
Read the first line in alphabetical order: A, B, BF, C, D... L, LA, LB, LC, M, ML P, PA...PN, PQ, PR...

Read the second line as a whole number: 1, 2, 3, 45, 100, 101, 1000, 2000, 2430...

The third line is a combination of a letter and numbers.
Read the letter alphabetically.
Read the number as a decimal, eg: .B29 = .29 .B724 = .724
Some call numbers have more than one combination letter-number line, e.g., Z92.

The last line is the year the book was published.
Read in chronological order: 1985, 1991, 1992...2014, 2015...

When you reach the top of the stairs on the 3rd floor, turn to the right. Then turn right again until you're standing in the aisle between the stack rows, where the majority of the books on this floor are shelved (see image left).

The call number guide card at the end of each stack row tells you the call number range in that row. For example, PR 3588 .I - PR 4469 tells you that any call number that comes between PR 3588 .I and PR 4469 (e.g., PR 3991 .A1 H68 2012) is on the shelf in that stack row.

NOTE! The books are shelved in a "zig-zag" pattern. As you look at the call number guide card at the end of a stack, note the last call number in that stack. To find books immediately following that call number, first look to the row on the other side of the aisle. In the image above, note the gap between PR 4469 on one guide card and PR 5530 on the other guide card. Look across the aisle to find the stack that has books with call numbers ranging from PR 4470 - PR 5529.

When you reach the top of the stairs on the 2nd floor, the floor map on the wall is opposite you.
Look to the left and you'll see the stacks at the beginning of the call number range. (See next image below)

The card at the end of each stack row tells you the call number range in that row. For example, B 3776 .W564 N - BD 111 .P tells you that any call number that comes between B 3376 .W564 .N and BD 111 .P (e.g., B 4023 .L) is on the shelf in that stack row.

Why is it Important to Know the Structure of a Call Number?

Although the most efficient way to locate materials on a particular topic is usually to perform a subject or keyword search in the Library Catalog and then note the call number for each retrieved item, browsing the shelves can also help you locate material appropriate for your topic.

Since books are classified by subject, you can often find several helpful books on the same shelf, or nearby.
For example, within the subject classifications PR 4034-PR 4038, you will find books by and about Jane Austen.