OPAC: The full name of online public retrieval catalog is called "online public catalog query system" in library science. Readers can use the World Wide Web to find and borrow books. Extended materials originated in American universities and public libraries in the early 1970s, which means the' automation' of traditional readers' directory query. It is an online retrieval system for searching the information resources of the library through the network, and users can query the OPAC resources of various libraries without the limitation of space and place.

Matters needing attention in using OPAC

1. Readers can query books, periodicals, e-books, audio-visual materials, special resources, etc. Collected by many libraries. Choosing an appropriate retrieval method can also limit multiple conditions at the same time and narrow the query scope.

2. When selecting the retrieval method of book title, author and keywords, the system will use any word matching method after inputting the retrieval words.

3. If readers have books for special inquiry, it is suggested to limit the scope from the beginning to save time. Pay attention to the specified library when searching, and don't choose to search all.