Understanding Call Numbers




This tutorial is intended to give you an overview of different Call Numbering systems and how they work. By the end of this tutorial, you will understand how items are classified within each system, what the call numbers mean and how to find an item based on it's call number.

Call Numbers - An Introduction

Materials in libraries have to be organized in some way so that things can be found once they have been placed on a shelf.

Each item is assigned a unique code, called a call number, to help with organization.
  • Call numbers are usually made up of numbers and letters and sometimes include punctuation marks like colons or dots
  • Call numbers determine each item's exact location within a library
  • Call numbers are assigned to items so that they bring together materials which are alike in some way, usually by subject
Classification Systems are the rules used to determine call numbers. Most libraries, like public and academic libraries use standardized classification systems, but some (mostly special libraries) come up with their own classification system unique to their own needs and collections.

This tutorial will give a brief breakdown and explanation of several call number systems with tips on how to read the various numbers properly. A basic understanding of call numbers is necessary in order to find materials, and ultimately the information you need, in the library.

The most frequently use classification systems are :
  • Dewey Decimal Classification System (Dewey) - Used by most public and school libraries.
    Dewey call numbers begin with a three digit number.
    In the online catalog, typical Dewey call numbers look like:
    • 813 AL355L 1987

    On book spines, or labels on other materials, Dewey call numbers are arranged vertically and would typically look like:
    • 813
      AL355L
      1987

  • Library of Congress Classification System (LC) - Used by most academic libraries and in other larger libraries.
    LC call numbers begin with letters.
    In the online catalog, typical LC call numbers look like:
    • PS 1017 L5 1983

    On book spines, or labels on other materials, LC call numbers are arranged vertically and would typically look like:
    • PS
      1017
      L5
      1983

  • Superintendent of Documents (SuDocs) - Used by libraries with extensive collections of materials published by the United States Government
    SuDocs call numbers begin with letters and always include a colon.
    SuDocs call numbers typically look like:
    • HE 20.3002:R 24/5
Libraries may use one or all of these systems, based on the collections they own.
LSU Libraries use all of the above systems, as well as some other classification systems which are specially suited to certain special collections.

gold bar

Dewey Decimal Call Numbers

The Dewey Decimal Classification System is subject based, classifying and arranging items by the subject matter involved. LSU Libraries uses Dewey call numbers for materials in the Educational Resources Center, for theses and dissertations, and for older items which are used infrequently and are kept in compact storage.
  • Dewey call numbers begin with a three digit number

  • The Dewey system is broken into 10 primary classes, or general subject areas, represented by the first digit of that number
    • 000 - Generalities
    • 100 - Philosophy & Psychology
    • 200 - Religion
    • 300 - Social sciences
    • 400 - Language
    • 500 - Natural sciences & Mathematics
    • 600 - Technology
    • 700 - The arts
    • 800 - Literature & Rhetoric
    • 900 - Geography & History

  • The Dewey system further breaks these subjects into subclasses by the addition of the next two digits, and then often even adding a decimal point and more numerical digits. For example:
    • 500 Dewey call numbers deal with Natural Sciences & Mathematics
    • 590 Dewey call numbers deal with Zoological Sciences
    • 599 Dewey call numbers deal with Animals
    • 599.884 Dewey call numbers deal with Gorilla Behavior

  • For a list of the major classes and subclasses of the Dewey Decimal classification system, click HERE.

  • The second part of a Dewey call number is based on the Author's last name.
    • Some libraries use only the author's name, or the first letters of the author's name.
      For example, the call number for Gorillas in the Mist, by Dian Fossey would be:
      599.884 FOS
    • Some libraries use the first letter, or letters of the author's name followed by numbers representing the author and the particular item.
      In this case, the call number for Gorillas in the Mist is:
      599.884 F752g

  • Frequently a Dewey call number will include a third part which represents the year that the item, or particular issue of an item, is published.
    Again, the call number for Gorillas in the Mist:
    599.884 F752g 1983
gold bar

Library of Congress Call Numbers

The LC Classification System is also subject based, classifying and arranging items by the subject matter involved. LSU Libraries uses LC call numbers for most of it's books.
  • The LC system is broken into 21 primary classes, or general subject areas, represented by letters.

  • By breaking items into 21 subject areas rather than the 10 of Dewey, the LC classification system allows libraries to classify and arrange larger collections.
    • A - General Works
    • B - Philosophy. Psychology. Religion
    • C - Auxiliary sciences of history
    • D - History
    • E,F - History in Americas
    • G - Geography
    • H - Social Sciences
    • J - General legislative and executive papers
    • K - Law
    • L - Education
    • M - Music and Books on Music
    • N - Fine Arts
    • P - Language and Literature
    • Q - Science
    • R - Medicine
    • S - Agriculture
    • T - Technology
    • U - Military Science
    • V - Naval Science
    • Z - Bibliography. Library Science

  • The LC system further breaks these subjects into subclasses by the addition of one or two letters followed by numbers up to four digits plus several decimal places in length. For example:
    • LC call numbers beginning with Q Science
    • LC call numbers beginning with QL deal with Zoology
    • LC call numbers beginning with QL 700 deal with mammals
    • LC call numbers beginning with QL737 deal with Gorilla Behavior
      The LC call number for Gorillas in the mist , by Dian Fossey is:
      QL737 P96 F67 1983

  • For a list of the major classes and subclasses of the LC classification system, click HERE.

  • The second part of an LC call number includes a code representing the author and the particular item. This part of the call number begins with a letter followed by numbers, and them sometimes another letter followed by numbers.
    For example, Gorillas in the Mist:
    QL737 P96 F67 1983

  • Frequently an LC call number will include a final part which represents the year that the item, or particular issue of an item, was published.
    Again, Gorillas in the Mist:
    QL737 P96 F67 1983
gold bar

Here is a comparison of another work classified using both Dewey and LC systems. The work, Little Women, by Louisa May Alcott, would be classified as follows:
  • in DC, as 813 AL355L 1987 and
  • in LC, as PS 1017 L5 1983
Dewey Decimal Library of Congress
Classification Number
813
 
Classification Number
PS
1017
Author and Book Number AL355L Author and Book Number L5
Year of publication (for this issue) 1987 Year of publication (for this issue) 1987


gold bar

Superintendent of Documents Classification System

SuDocs call numbers are issued by the United States Government Printing Office, for items published by the U. S. Government. The SuDocs Classification System is not a subject based system, rather, items are arranged by the department or the agency issuing the publication, such as the FBI or the Department of Health. As a Regional Depository for Government Documents, LSU Libraries uses the SuDocs Classification System for all government documents.
For more information on Government Documents, see the Government Documents Tutorial
  • SuDocs call numbers begin with letters which stand for the issuing government agency
  • For a list of SuDoc department classification system, click HERE.
  • After the department, other codes are added which represent agencies, the specific item, and date.
For example, the call number C 3.134/2 : C 83/2/994 can then be broken down as follows:

SuDocs Call Number
Issuing Department C Commerce Department
Subagency 3 Bureau of the Census
Series 134/2 : Statistical Abstract Supplement
Title and date C 83/2/994 County and City Data Book, 1994

Note the COLON in the center of the call number. No other call number has a colon, so this is a quick and easy way to tell if the number is a SuDocs number.

gold bar

Distinguishing features

Once you have a call number for an item you need, you will need to know what type of call number is in order to actually find that item.

Characteristics to help easily identify, the system used:

  • Dewey Decimal - begins with series of 3 numbers
    Examples:
    • 302 H789I 1993
    • 781.62 D184I
    • 917.3 D141G
  • Library of Congress - begins with one or two letters, followed by numbers
    Examples:
    • E 174 U58
    • LB 1062 B37
    • Z 1037 A2 C67 2004
  • Superintendent of Documents - begins with one or two letters, includes a colon (:)
    Examples:
    • PM 1.9:1998
    • GA 1.13:GGD
    • Y 4.F 76/2:C 16/2/1993

gold bar

How to Read the Call Numbers

Once you have a call number, and you know which kind of call number you are dealing with, what do you do with it?
You use that call number to figure out where the item is and to actually find it on the shelf. To do that, it is necessary to read those call numbers in correct order.

Let's put the following Dewey Decimal call numbers in order:
823
D653e
798.24
M1265a
823
B189e
821
L196
798.2
H985t
823
D553d
824
G987

Begin by comparing the entire number on the first line and put them in order from smallest to largest. So...
The "700" call numbers come before the "800" call numbers.
Then 798.2 is before 798.24, 821 is before the 823s and 824 is last.
798.2
H985t
798.24
M1265a
821
L196
823
D653e
823
B189e
823
D553d
824
G987

The second line of the call number is considered a decimal so is compared letter by letter, digit by digit. So...
Of those 823 call numbers, the B comes before the Ds.
798.2
H985t
798.24
M1265a
821
L196
823
B189e
823
D653e
823
D553d
824
G987

Of the remaining two call numbers, first line 823, second line beginning with D, compare the next digit. 5 comes before 6.
798.2
H985t
798.24
M1265a
821
L196
823
B189e
823
D553d
823
D653e
824
G987

gold bar

Let's put the following Library of Congress call numbers in order:
PS
2552
O874 A6
2001
PK
2198
G4 A233
1999
M
1613.3
B94 L6
1990Z
PN
1994
M78
1996
PS
3568
A486 W56
2001
PS
3
A47
1967

The first step is the easiest. Putting he first letters in correct order you get this:
M
1613
.3 B94 L6
1990Z
PK
2198
G4 A233
1999
PN
1994
M78
1996
PS
2552
O874 A6
2001
PS
3568
A486 W56
2001
PS
3
A47
1967

The next step is a little more tricky. The first set of numbers you come to are treated as a WHOLE number, and shelved in order from smallest to largest. So... 3 is before 2552 which is before 3568, which means PS 3 is before PS 2552 which is before PS 3568.
M
1613
.3 B94 L6
1990Z
PK
2198
G4 A233
1999
PN
1994
M78
1996
PS
3
A47
1967
PS
2552
O874 A6
2001
PS
3568
A486 W56
2001


gold bar

Remember, the first leter(s) and the first set of numbers represent the subject of the item. The previous example deals with correctly ordering the subject portions of the call number, and if you can get to that area of the shelves, you will at least be in the right area to find materials in your subject area.

If you are looking for a specific item it is important to understand the correct order for all parts of the call number. After the first set of letter(s) and the first set of numbers, the call number is read differently. Rather than whole numbers, the rest of the call number is treated as a decimal, and each digit is read individually.

If you had the following call numbers:
C
3
R3
C
3
R279
C
3
R2
C
3
R21
C
3
R1
C
3
R275
C
3
R38

It might help to think of them as:
C 3 R3
C 3 R279
C 3 R2
C 3 R21
C 3 R1
C 3 R275
C 3 R38
Or even:
C 3 R300
C 3 R279
C 3 R200
C 3 R210
C 3 R100
C 3 R275
C 3 R380

gold bar

The first set of letters are all the same (C)
The first set of numbers are all the same (3)
The second set of letters are the same (R)...

Second set of numbers - First digit.
Move the "1" to top, group the "2"s then the "3"s:
Second set of numbers - Second digit. Within the "2"s, the "0" is first, then the "1" then the "7"s. Within the "3", the "0" is first, then the "8".
C 3 R100


C 3 R279
C 3 R200
C 3 R210
C 3 R275


C 3 R380
C 3 R300
C 3 R100


C 3 R200
C 3 R210


C 3 R279
C 3 R275


C 3 R300
C 3 R380

gold bar

Finally, within the ".27_" set,
the third digit, "5" then the "9".
C 3 R100
C 3 R200
C 3 R210
C 3 R275
C 3 R279
C 3 R300
C 3 R380
Or...
C 3 R1
C 3 R2
C 3 R21
C 3 R275
C 3 R279
C 3 R3
C 3 R38

Or finally...

C
3
R1
C
3
R2
C
3
R21
C
3
R275
C
3
R279
C
3
R3
C
3
R38


gold bar

This is the end of the Understanding Call Numbers Tutorial.

If you have questions, or need help with anything in the library be sure to ask a librarian. At LSU Libraries there are a number of ways to find help:
  • Visit the Research Desk in room 141 Middleton Library
  • Telephone the Research Desk at (225) 578-8875 during regular hours
  • Text the Research Desk at (225) 245-3667 during regular hours
  • Use Ask Us! to contact us via live chat, e-mail, or to search our FAQ