• An OPAC, (Online Public Access Catalog) is an online bibliography of a data collection from the library in the form of books, authors, genre, etc, that is available to the public. Online Public Access Catalogue (OPAC) or simply a Library Catalogue is a digital database of materials such as text files, e-books, journals, etc held by a library or group of libraries. Patrons can use the online library cataloguing software to find out any item under control of a library. It displays the query search results in an easy-to-understand format to enable patrons to find digital material quickly. An Online Public Access Catalog (OPAC) is an online reserve of library collections that is made available for public use. In the initial stages, OPAC was developed as standalone online catalogs, from VT100 terminals to a mainframe library catalog. The globally located library authorities or librarians have the provision to update the catalogue which usually requires a small amount of time.