You may be familiar with finding books in a public library or K-12 school library, but academic libraries at colleges and universities are organized differently.
Public libraries and K-12 school libraries use the Dewey Decimal Classification System to organize books by topic into 10 main categories identified by numbers (000s-900s).
Academic libraries use the Library of Congress (LOC) Classification System. Books are also organized by topic, but there are more than 10 categories, and it uses letters instead of numbers.