Which electronic system is the automated version of a card catalogue?

### Why this is right An Online Public Access Catalogue (OPAC) is the computerized catalogue users search to identify library holdings. ### The concept A card catalogue records holdings on physical cards. An OPAC provides catalogue access electronically. The other identifiers listed identify books, serials, or digital objects rather than functioning as catalogues. ### The other options - **International Standard Book Number (ISBN)**: Identifies a book or book edition; it is not a catalogue. - **International Standard Serial Number (ISSN)**: Identifies a serial publication; it is not a catalogue. - **Digital Object Identifier (DOI)**: Identifies a digital object, often an article; it does not replace a library catalogue. ### Terms - **OPAC**: Online Public Access Catalogue, an electronic library catalogue. - **ISBN**: International Standard Book Number, an identifier for books. - **ISSN**: International Standard Serial Number, an identifier for serials. - **DOI**: Digital Object Identifier, an identifier for a digital object. ### Remember A catalogue helps find holdings; an identifier labels a particular publication or object.