1, library classification: this is the classification compiled by library science experts according to the rules. Theoretically, there are two kinds, system method and combination method. System method refers to listing detailed categories, and the actual operation is classification. The rule of collocation is to put books with the same nature or category together. This classification is widely used in libraries and can effectively manage and search books.

2. Subject classification: This classification is based on the subject of books, such as literature, science and history. The advantage of this classification is that books related to specific topics can be found quickly, but the disadvantage is that cross-topic problems will occur, so appropriate adjustments should be made in the classification process.

3. Author classification: This classification is based on the author of the book. The advantage of this classification is that all works by the same author can be found quickly, but the disadvantage is that the problem of authors with the same name will appear, and appropriate adjustments should be made in the classification process.