The CPC classification system arranges subject matter into hierarchical arrays.

1. (A) The highest array or level is the Section.
2. (B) Each section is subdivided into Classes.
3. (C) Each class is subdivided into one or more subclasses.
4. (D) Each subclass is broken down into Groups (main groups and subgroups).

Each part of this hierarchical structure is identified by classification symbols. Specifics about each element of the classification symbol are described below.

(A) Section Symbol – Each section is designated by one of the capital letters A through H and has an associated section title. There are nine sections, eight of which correlate to the sections of the International Patent Classification (IPC). The ninth section is used for classifying documents covering subject matter pertaining to a plurality of the sections. The table below shows the sections with their associated CPC and IPC section titles.

(B) Class Symbol – Each class symbol consists of the section symbol followed by a 2 digit number (e.g., C07). Each class symbol is associated with a title.

(C) Subclass Symbol – Each subclass symbol consists of the class symbol followed by a letter (e.g., C07D). Each subclass symbol is associated with a title.

(D) Main Group Symbol – Each main group symbol consists of the subclass symbol followed by a one- to four- digit number, the oblique stroke, and the number 00 (e.g. C07D 203/00). Each main group number is associated with a main group title which precisely defines a field of subject matter within the scope of its subclass and a definition.

(E) Subgroup Symbol – Each subgroup symbol consists of the main group symbol, but the number "00" in the main group symbol is replaced with an alternative number of up to six digits (e.g. C07D 203/02). Each subgroup symbol is associated with a title and definition.

Example:

CPC Symbols C07D 203/00 or C07D 203/02

The title associated with a CPC symbol defines the scope of the subject matter covered by that symbol. In general, the title of every CPC organizational division is read as including the titles of all its superior organizational units. For example, the title of a CPC subgroup is interpreted as including the title of its parent group and that parent’s group title all the way up to, and including, the section title.

Titles in the CPC system are generally in the form of single part or multipart titles which are described below.

1. (A) Single part title -- Defines or represents the subject matter of a single concept or information.
2. Example:
3. A47C 1/00 Chairs adapted for special purposes
4. (B) Multipart title (separated by semicolons) -- A semicolon in a CPC title delineates coverage of two distinct and separate information entities that should be considered stand-alone things for purposes of coverage.
5. Example:
6. F25D REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT COVERED BY ANY OTHER SUBCLASS
7. The three semicolons in the above example inform us that the subclass covers four distinct and separate entities: 1) refrigerators, 2) cold rooms, 3) ice boxes, and 4) other types of cooling or freezing apparatus not covered by any other subclass, therefore it is a residual to all cooling and freezing apparatus not elsewhere classified in CPC.

References are statements enclosed within parentheses in titles. The references point to other classification places that may be of interest. References apply to the classification place they appear and to all hierarchically lower classification places, unless stated otherwise.

Examples of References:

Example:

B64C AEROPLANES; HELICOPTERS (air-cushion vehicles B60V)

(A) Limiting references

A limiting reference is found in the group titles of the scheme and exclude specific subject matter from the scope of the classification place, when this subject matter would otherwise fulfill all the requirements of the classification place (or would be covered by that place). Limiting references are pertinent for classification purposes. Limiting references limit the scope of a place, thereby avoiding overlap.

Example:

A01F 7/02 . With rotating tools (threshing cylinders or concaves A01F 12/18)

(B) Precedence references

A precedence reference is a special example of a limiting reference that always refers to another group or groups taking "precedence" within the same subclass. The purpose of a precedence reference is to remove overlap between two similar groups.

Example:

G02B 1/00 Optic elements

1/04 . made of organic materials (1/08 takes precedence)

Notes are supplementary statements that follow a CPC class, subclass, main group, or subgroup title. Instruction in a "Note" is applied only to the CPC place where it appears, including all its hierarchically lower places. For example, a note after a class title applies to the entire class. A note after a subclass title applies only to the subclass, a note after a main group applies only to the main group, etc. Notes may be used to explain the scope, define terminology, or indicate specific classification rules.

A warning is used in CPC schemes for signaling deviations from IPC or incomplete classification. A warning may include a listing of IPC groups not included within CPC and the CPC group which covers the relevant subject matter. A warning also may be used to indicate the deletion or transferring of CPC groups and reclassification notices.

Guidance headings may be provided as follows:

1. (A) When a large part of a subclass relates to a common subject matter, a guidance heading indicating that subject matter may be provided at the beginning of that part.
2. (B) As a title, without any associated symbol, of subject matter preceding several main groups.
3. (C) To describe common subject matter of several main groups.