The Library of Congress system puts books in order by their subject. Each LC call number starts with a letter or letters of the alphabet, and books are then shelved in the alphabetical order of the call number. Here are the major LC classes:
A GENERAL WORKS
B PHILOSOPHY, PSYCHOLOGY, RELIGION
C AUXILIARY SCIENCES OF HISTORY
D
WORLD HISTORY AND HISTORY OF EUROPE, ASIA, AFRICA, AUSTRALIA, NEW ZEALAND, ETC.
E
HISTORY OF THE AMERICAS
F
HISTORY OF THE AMERICAS
G GEOGRAPHY, ANTHROPOLOGY, RECREATION
H SOCIAL SCIENCES
J POLITICAL SCIENCE
K LAW
L EDUCATION
M MUSIC AND BOOKS ON MUSIC
N FINE ARTS
P LANGUAGE & LITERATURE
Q SCIENCE
R MEDICINE
S AGRICULTURE
T TECHNOLOGY
U MILITARY SCIENCE
V NAVAL SCIENCE
Z
BIBLIOGRAPHY, LIBRARY SCIENCE, INFORMATION RESOURCES (GENERAL)