Patents are classified according to the technical content of the invention in groups and subgroups according to the International Patent Classification (IPC). The classification includes 8 technical areas marked with letters A to H) divided in subgroups further divided into classes and subclasses. Good to the applicant of the patent submission to the designated classification of the invention. But if it is not able to do it, then make the classification of patent examiners office.
The entire contents of the classification of English and French can be found on the website of the World Intellectual Property Organization (WIPO): www.wipo.int/classifications/en/.