What is the composition structure of patent classification number?

A complete classification number consists of symbols representing a department, a large category, a small category, a large group or a small group. The red circle in the figure below is the complete representation of the patent classification number.

International patent classification is a general international patent literature classification. The classification number obtained by classifying patent documents (specifications) with the international patent classification table is called the international patent classification number, which is usually abbreviated as IPC number. IPC adopts the classification principle of combining function with application, with function as the main and application as the auxiliary. In the hierarchical form, the technical contents are marked as follows: Department-Division-Class-Class-Group-Group, and a complete classification system is gradually formed.