How to read Library of Congress call numbers
In reading a call number, begin at the top line and read from left to right; then proceed to the next line reading again from left to right as if reading a book.
Starting with the letter(s) at the top left of the call number books are ARRANGED ALPHABETICALLY:
A AC AG AZ B BC BT
Books having the same letter(s) on the top line are all shelved together by the number group that follows the letter(s).
THESE NUMBERS ARE ARRANGED NUMERICALLY, NOT DECIMALLY:
F F F F F F F 1 21 75 101 175 200 2113
When both the letter(s) and the number group that follows are the same, then books are shelved ALPHABETICALLY by the next letter:
QM QM QM QM QM QM QM 23 23 23 23 23 23 23 .A .B .C .D .E .F .G
Books which are identical in first letter(s), in the number group that follows, and in the second letter, are then shelved by the next number group. THESE NUMBERS ARE ARRANGED DECIMALLY, NOT NUMERICALLY:
QM QM QM QM QM QM QM 23 23 23 23 23 23 23 .E6543 .E778 .E88 .E9 .E99 .E995 .E999
Oftentimes a call number will have a fourth line which contains a letter and a number or numbers. THE LETTER IN THIS LINE IS ARRANGED ALPHABETICALLY, WHILE THE NUMBER(S) IS/(ARE) ARRANGED DECIMALLY
QM QM QM QM QM QM QM 23 23 23 23 23 23 23 .E6543 .E778 .E88 .E9 .E99 .E995 .E999 A25 C6 F88 F885 F9 H92 K2
Note: The date of an edition frequently can be determined by its inclusion in the call number. However, the most accurate way of determining the edition date is to consult the information given in the preliminary pages of a particular volume.
Grateful acknowledgement is made to Gorgas Library, University of Alabama, Tuscaloosa, for granting permission to use this information developed at their institution.