Version Control (aka Revision Control) is the management of changes to data. Most often source code, documents, or other shared data. It also provides a means of quickly finding what exactly was changed which can be very useful when a bug has been introduced into a new version of a program, or concern is raised about a contributor.
In it's simplest form, it can be simply keeping copies of old files before making changes. Old versions can be compared to new versions with operating system tools like FC in DOS/Windows and DIFF for *nix.
Git, the defacto standard for version control; is a free and open source distributed version control system designed to handle everything from small to very large projects with speed and efficiency.
GitHub is a web-based Git repository hosting service, which offers all of the distributed revision control and source code management (SCM) functionality of Git as well as adding its own features. Unlike Git, which is strictly a command-line tool, GitHub provides a web-based graphical interface and desktop as well as mobile integration. It also provides access control and several collaboration features such as wikis, task management, and bug tracking and feature requests for every project
Modern, feature rich version control is supplied by programs like GIT^ or SourceGear Vault^, and is rapidly becoming an expected feature in online content storage systems like dropbox.com and Google Drive^. Drive however, has a very easy to use interface which allows collaboration and easy change tracking. Even Wikipedia.com maintains a list of past versions of each article.
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