The Concept

Revision control (RC) or version control is a fairly simple concept. Most people do it by ``saving a file under a different name''. Revision control implies the following:

• There is a concept of version/revision. In other words, for the same file, there may be multiple versions. To get to a particular file, you need to supply the version number.
• There is a concept of ``repository''. This is a place where the system files for revision control are stored. A user normally does not need to know where such files are stored.
• There is a concept of ``control''. There are two main control actions: check in and check out. We'll talk about this in following sections.

The general idea is quite simple. Every time you make any important changes to your files (for debugging, enhancement or otherwise purposes), you create a new ``version'' out of the file(s). This way, you can track changes made to your file(s) between versions. Revision control allows you to ``diff'' (a computer geek verb that means ``finding the differences between'') different versions of the same file. This is very handy, because many visual tools can display the results in an intuitive fashion.

Revision control also allows you to check out an earlier version of a file. This is helpful if you decide that you want to restart from an older version of the file.

More complex operations include branching and merging. For some revision control system, you can also collaborate with others easily using a remote repository on a network (Internet or intranet).