"Classics and History Subsets" are four categories of ancient books divided by the ancients according to their contents. Some large-scale ancient books series often include four books and are named after them, such as Four Ku Quanshu, Four Series and Four Essentials. It can be seen that the four categories are of great significance to ancient books.
The four-part classification of classics, history, books and collections is the product of China traditional culture, which is suitable for traditional cultural classics. Familiarity with ancient books and further understanding of traditional culture is a key for us. Since the May 4th Movement, China has used the western book classification for reference and classified books according to the modern subject system. As of 20 13 10, the Chinese Library Classification revised in the 1990s is still widely adopted by all kinds of libraries in China. It is called Chinese Library Classification for short, but because many ancient books are difficult to be included in the classification system of Chinese Library Classification, the collection and retrieval of ancient books libraries (libraries) still adopt the traditional four-part classification.