Digital bookmarks on books usually refer to marks used for book classification and retrieval. These marks can be used to indicate the position of books in the classification table, which is convenient for readers to find and borrow. In China Library Classification, Chinese phonetic alphabet and Arabic numerals are used for mixed numbering, with one letter representing a major category, the alphabetical order reflecting the order of major categories, and the disciplines subdivided under major categories are composed of Arabic numerals. According to this classification method, digital bookmarks mark corresponding codes on books, so that readers can quickly find the books they need.