What does the universal code of ancient books in China mean?

Cataloging classification and naming. The universal code of ancient books in China refers to a set of code system for cataloguing, classifying and naming all kinds of ancient books, classics and documents related to the traditional cultural heritage of China, which is used to sort out, protect and inherit the ancient cultural heritage of China. The coding system was jointly developed by the National Library of China and China Ancient Books Protection and Restoration Center, and was officially released in 2006. It uses a combination of numbers and Chinese characters. * * * There are three levels of codes, including ten categories, fifty subcategories and two hundred and fifty subcategories, and each code has its own independent meaning and cultural connotation.