CVS is widely used in both open source and proprietary software development projects, and is generally considered to be the best freely available, full-featured version control tool. The use of file merging rather than locking.
File locking prohibits other developers from accessing a file when someone else has checked it out.
CVS allows a multiple check-outs of a single file, and then combines all the changes. Remote access to source code file repositories. Developers can obtain and modify project files from virtually anywhere. CVS is a client-server system. This is the top-level module containing the entire source code tree for that particular module.