The ACM Computing Classification System (CCS) is a subject classification system for computing devised by the Association for Computing Machinery (ACM). The system is comparable to the Mathematics Subject Classification (MSC) in scope, aims, and structure, being used by the various ACM journals to organise subjects by area.
The system has gone through seven revisions, the first version being published in 1964, and revised versions appearing in 1982, 1983, 1987, 1991, 1998, and the now current version in 2012.
The ACM Computing Classification System, version 2012, has a revolutionary change in some areas, for example, in "Software" that now is called "Software and its engineering" which has three main subjects:
Software organization and properties. This subject addresses properties of the software itself.
Software notations and tools. This subject covers programming languages and other tools for writing programs.
Software creation and management. This subject covers human activities including software management.
It is hierarchically structured in four levels. Thus, for example, one branch of the hierarchy contains: