Library of Congress classification scheme

The Library arranges its collections of books and bound periodicals according to the Library of Congress Classification Scheme. Each book has a class mark consisting of letters and numbers which indicate its subject and determine where it is filed on the shelf.

The code usually begins with two letters

• The first letter represents the broad subject. For example, all D books (History) are on the Second Floor.
• The second letter specifies a narrower subject area within the broad category: within History (D), DA stands for British History.
• The next part of the class mark is a number, which gives a more precise definition of subject matter. Within a subject section, books are filed numerically, so DA 84 comes before DA 86 which comes before DA 226.
• The final part of the class mark refers to the author's name. It normally consists of a letter and a number. This part is filed in alphabetical order by letter, then by number in a decimal sequence, i.e. DA 84.C3 precedes DA 84.C35 which precedes DA 84.C4

In practice, class marks may be more complex, with extra letters and numbers giving a more precise definition of subject matter. In each case, read down the class mark, taking each element separated by a full stop as a separate unit.

The following list gives a more detailed breakdown of subjects and their class marks

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z