Revision control

Definition
Revision control (also known as version control or source control) is the management of changes to documents, programs, and other information stored as computer files.

Software
It is most commonly used in software development, where a team of people may change the same files. Changes are usually identified by a number or letter code, termed the "revision number," "revision level," or simply "revision." For example, an initial set of files is "revision 1". When the first change is made, the resulting set is "revision 2", and so on. Each revision is associated with a timestamp and the person making the change. Revisions can be compared, restored, and with some types of files, merged.