The call number is not printed on the book, but the library numbers the books for the convenience of book management and readers' borrowing. It is written (or printed) on the label and then attached to the spine of the book. The capital letter at the beginning of the call number indicates the book classification number of the library (the category of books on the shelf will be marked at both ends of each shelf, for example, C stands for China ancient literature works, etc. ), the number behind should be the year of publication of the book or the number in this kind of book. The telephone number is very continuous. Generally, the books on the shelves are arranged in the order of call numbers, so it is easier for readers to find the corresponding books by checking the call numbers before borrowing books.