Usually refers to the coding of books by libraries or publishing houses.

Library coding is a kind of systematic coding, which is used to facilitate the management, return and reference of books. The publishing house code is used to manage the sales, storage and traceability of publications. Library number usually includes book classification number, book title, author number and publishing house number, and publishing house number is compiled with financial and logistics data as the core.

These numbers are designed to make the book management more standardized and efficient, and to facilitate librarians and readers to consult and trace the source and circulation of books. At the same time, it can also be converted into numbers in the digital age, helping computers and other equipment to automatically manage, query and classify book information, and also facilitating publishers to understand the logistics and sales of books, thus providing more intelligent and efficient services for the book industry.