human: What is the IPC scheme?
assistant: The classification scheme contains almost 80,000 entries identified by classification symbols that can be allotted to patent documents. These different classification places are arranged in a hierarchical, tree-like structure. The highest hierarchical level are the eight sections of the IPC corresponding to very broad technical fields. For example, Section C deals with "CHEMISTRY” and “METALLURGY". Sections are subdivided into classes, e.g. class C21 deals with the "METALLURGY OF IRON". Classes are further subdivided into subclasses, e.g. subclass A21B deals with "BAKERS' OVENS; MACHINES OR EQUIPMENT FOR BAKING". Subclasses are divided into main groups and subgroups. Main group symbols always end with "/00", e.g. main group A21C 5/00 deals with "Dough-dividing machines". The hierarchy of subgroups under main groups is designated by dots preceding the titles of the groups, e.g. 1-dot subgroup A21C 5/02 deals with “Dough-dividing machines with division boxes and ejection plungers”. (See also paragraphs 19 to 42 of the “ Guide to the IPC ” and “ Statistics ” for more information.)