Concurrent version system (CVS) is a tool that manages different versions of software modules during software development. When a software developer needs to make changes to existing code, documentation, test cases, test plans, and other reports, a formal change request has to be issued for tampering with the module. CVS stores the main software module in a repository, allowing developers to make changes to their own, local copies. This allows various developers to make changes to a module while maintaining consistency. At the end of each day, software developers can store their new versions in the CVS repository as different versions of the existing module, a process known as check-in. This term is also known as a CVS repository or concurrent versioning system.
A CVS does not store every changed document separately. It only saves the changes between different documents. CVS also enables a merger of different versions of the same document made by different developers. The user can access the CVS repository using the provided command line interface. The CVS repository can be in the same machine as the developer’s working environment or can be accessed through an LAN or via the Internet.Two basic functions supported by CVS are check-in and check-out. In check-in, the desired module with the necessary changes is stored or transferred from the developer's local repository to the CVS server. In check-out, the developer downloads a copy of the module. This allows the development of that module in the local repository. Using its logging mechanism, the CVS manages all information regarding who has modified which module and at what time.The CVS manages consistency among different files using three concepts. File locking is used to ensure that the file is modified by one person at a time. The same file modified by different people can be monitored using the watch command. The CVS ensures appropriate policies to combat conflicts among files modified by the same developer. It supports an option to include the modified versions in the same file by using appropriate delimiters. CVS offers security by using password authentication or Kerberos with generic security services application program interface protocol. Finally, all changes made successfully can be saved using the "commit" command from the command line interface.
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