Classification systems make arranging materials on library shelves easier and likewise make locating materials on library shelves easier. Most systems of classification are based on subject categories and typically move from the general to the specific in their organization. The classification for American Literature, for example, breaks down into numerous subdivisions. Even this partial classification may seem awfully complicated at first glance, but if you were to try locating a single book by a certain author out of a collection of only 100,000 books without a classification system, you might spend weeks searching. Just as an accounting system groups income and expenditures by types, a library system groups knowledge by categories.
Organization is the operational concept behind library classification systems.
The ultimate goal of classification is ease of access. If all knowledge could be computerized, classification might seem less necessary, but even the smallest computer database relies on indexes to retrieve data. Without a more clearly delineated system of organization a single search of the word history, for example, might retrieve millions of occurrences. Clearly a subject arrangement makes locating materials easier even on a computer. The LC system provides very specific subject arrangement of all materials recording human knowledge.