The ICS (International Classification for Standards) is intended to serve as a structure for catalogues of international, regional and national standards and other normative documents, and as a basis for standing-order systems for international, regional and national standards. It may also be used for classifying standards and normative documents in databases, libraries, etc. The system was created by the ISO, International Organization for Standardization.
It is a hierarchical classification consisting of three levels.
Level 1 - covers 40 fields of activity in standardization, e.g. road vehicle engineering, agriculture, metallurgy. Each field has a two-digit notation.
Example:
43 ROAD VEHICLE ENGINEERING
Level 2 - subdivides the fields into 392 groups with level 1 and level two (a three-digit group number) separated by a point.
Example:
43.040 Road vehicle systems
Level 3 - further divides 144 of the 392 groups are 909 sub-groups with level 1, level 2, and a two-digit number (level 3) separated by a point.
Example:
43.040.20 Lighting, signaling and warning devices