Dewey Decimal Classification

Call numbers in the Dewey Decimal Classification (Dewey) are evaluated one line at a time from top to bottom.

Example:
801.25
B78
1962


Line 1.

801.25 is the first line of the call number.  This is a decimal number and as such would find the following location among other Dewey Call numbers:

Note that 801.3 is considered a "larger" number than 801.125 in decimal ordering.

Line 2.

Once the 801.25 section of books is found, next narrow the search by further evaluating the second line of the call number.

Identify the first letter on the line.  In the example, the first letter is "B", so search within all the 801.25 books for the section with the second line beginning with "B".  This section will be found in a logical progression in alphabetical order.

Now evaluate the rest of the second line.  The number "78" in the example is a decimal number, so that within the "B" numbers, the following sequence would be correct:

The explanation in the second column should clarify what is not so obvious in the first column.

Although the example does not show this, there may be additional letters and numbers following the "B78" on the second line.  These will be ordered logically by processing one letter or number at a time until a difference is found.

Line 3.
The number 1962 represents a year of publication in this case.  This line will not always be present, but when it is, the order of shelving will be chronological.

Shelving order for "years"
No date (and "n.d.") is shelved before the same call number which has a date.
1906 comes before 1907, etc.

Line 4 and additional lines.
Some call numbers will have more lines.  These may designate a volume, copy, or part number.  These are ordered in traditional numerical order, with 1 coming before 2, 2 before 3, etc.
 


Introduction
Library of Congress Classification
AFA Library Toolbox