The Dewey Decimal System, which puts books of the same subject together, is the most frequent technique to organize books in a library. Every book is categorized into ten major sections using this approach. A librarian can find any book in the library by searching the appropriate section.
Code books are lists of subjects and titles that allow patrons to look up information about books they want to read but do not know yet. They are found in public libraries where readers can search by author or topic as well as in university and college libraries. Code books were once called catalogues because they served a similar function for scholars as catalogs do for shoppers. Today, they are often called bibliographies because they contain descriptions of more than one work by the same author or on related topics.
Code books list many different types of information about books, including authors, titles, publishers, dates, subjects, and locations where they can be found. They also include personal notes about the book and the person who wrote it. This last part is important because it allows librarians to match people with books they might be interested in despite there being no apparent connection between them. For example, if someone is studying history but also likes science fiction, the librarian will be able to point out other historical novels or sci-fi movies that may not have been obvious from just reading their name.
Nonfiction books are organized by subject to make it simpler to discover a book on a given topic. Melvil Dewey devised the technique that most libraries use to arrange books, which is known as the Dewey Decimal System. Each book is issued a three-digit call number based on its subject matter. For example, a book on astronomy would have a call number of 8.0 3.4.
Libraries often provide access to electronic resources instead of or in addition to physical copies. These can be divided into two main types: digital and analog. Digital resources include e-books, databases, and archives of some kind. Analog resources include microfilm and microfiche.
E-books are digital versions of a print book that can be read on many different computer devices using a software application called a reader. E-books are easy to add to and remove from; they do not go out of date like paper books do. However, e-books require more storage space than paper books, and their batteries need recharging from time to time. Databases are searchable collections of articles or other documents including peer-reviewed journals, magazines, newspapers, and encyclopedias. They can be searched online via a web browser. Archives are repositories that preserve materials for future reference or research. The two main kinds of archives are personal and institutional. Personal archives contain letters, notebooks, and other items belonging to an individual person.
The Dewey Decimal Classification System is the most extensively used system in libraries for categorizing books. Each book is assigned a number and is arranged on the shelf in numerical order. Books with the same number are arranged alphabetically by the author's surname. The DDC is summarized in three parts. Part one is the category number. This indicates what general subject area of knowledge the publisher believes will be of interest to readers. For example, psychology has categories from A-K. Category A covers human biology while K covers social sciences. Part two is the division number. This number ranges from 0 to 9 and indicates what group of divisions within the department, jurisdiction, or agency that issued the copyright license that are interested in the topic covered by the book. For example, division J of the U.S. Copyright Office is responsible for issuing licenses for works of literary art; division G deals with government publications; and so forth. Part three is the series number. This number ranges from 1 to 899 and indicates which collection of volumes or supplements of the parent publication are being made available. For example, series I covers volumes 1-24 of Henry Ford's History of the American Worker, while series III covers volumes 103-125.
Books are assigned numbers in four different ways: by object, subject, title, or author. If a book has multiple titles, each can have its own number.
As of 2015, the Dewey Decimal System is used to mark and classify books by topic area in the majority of public and elementary school libraries. The Library of Congress Classification system is used in college and university libraries. By the number of classes, the Dewey system implies ten major groupings of subjects. Each book is assigned to one or more of these groups.
Using this classification system makes it easy to find information about books that you're not sure about. For example, if you see a book with topics such as "cooking" and "gardening" on its cover, you can be certain that it's relevant to your life even if you have no idea what either person does or how they might differ from other people.
Books are also classified according to the type of material they contain. For example, fiction works have authors who write stories, novels, etc. Non-fiction works have authors who write about various topics through interviews, studies, and so forth. Textbooks are a special kind of non-fiction work; they usually include instructions on how to perform tasks related to their subject. Reference books provide information on topics without telling you to do anything with it. They often include articles on history, politics, science, and entertainment as well.
Classification also has many other uses beyond helping readers find interesting books.