A library catalogue is a registry of some type of collection that a particular library possesses or shares with a group of libraries. Card catalogues were originally how a library stored information about its collections. Small cards were filled out with a book's pertinent information, such as title, author, year of publication, publisher, Dewey Decimal and ISBN numbers, and these cards were then housed in drawer-filled cabinets that were accessible to library patrons. With very few exceptions, library catalogues are now fully automated and the same type of information that was formerly available in small drawers is much more easily accessed on a computer terminal.
OPACs (Online Public Access Catalogs) were the result when libraries made the switch to automation. Not only do OPACs enable more current and accurate content maintenance but accessing a library's holdings is now far more swift and efficient no matter which of the many types of available library catalogues you wish to access. Prior to automation, libraries would have to maintain multiple manual catalogues, such as author catalogues, subject catalogues and title catalogues, which are the types of information most commonly searched at public and academic libraries. With the advent of OPACs, a library customer can customize his search with the simple click of a mouse.
Perhaps you are researching your family's history or you are an art historian investigating the origins of an obscure painting. Maybe you are interested in learning more about sociology, political life in the twentieth century or the life cycle of a grasshopper. Do you need an historical photograph to complete a report? There is a library catalogue available to help you find the relevant information you are seeking. The Library of Congress is a vast repository of information and is a gateway to a multitude of special-collection catalogues.
Legal research differs greatly from the type of research conducted at a public or academic library. Those in the field of law may have to investigate previous law cases or statutes that are relevant to a case they are building. Law-related library catalogues offer the user many ways to search, including by type of law, legal jurisdiction and citations.
Medical researchers may want to delve into articles on clinical trials for a medication or for protocol used by other medical professionals in dealing with a rare malady. Along with those in the legal field, medical researchers have the ability to conduct highly detailed searches using library catalogues designed specifically for providing the meticulous information they need to help their patients.