In the Library of Congress system, call numbers begin with one or two letters. Call numbers and library classification are intertwined because each field of study is represented by a call number. For example, in the Library of Congress system, the letter L represents education, the letter Q represents science, N represents the arts, and so forth. In the Dewey Decimal system, all books about education have call numbers in the 370's and all books about science have call numbers in the 500's. This is why books about the same discipline are together on the shelf.
Call numbers get longer as the subject represented become more specific.
Selective List of Academic Fields Knowing the academic field in which your topic falls can help you decide where to browse in the library. The study of all the processes and services, both nonfarm and farm, involved in producing plants and animals and their produces and in getting them to the consumer. The science concerned with man, both normatively and historically, dealing with his physical characteristics, his racial, geographical, and historical distribution, classification, and relationships, and his cultural, environmental, and social development and relationship. A study of the celestial bodies, their composition, distances, motions, and the laws which control them. The study of plant life.