CVS check out i get four options. What do they mean?

When I am checking out an application i get four options HEAD, Branches, Versions and Dates what do they mean? What is the difference between eac开发者_开发技巧h of them?

A code repository is a tree of versions, each of which represents the state of the code at some particular point. It's possible to create a new branch of the tree from any point. Thus…

• HEAD is the tip of the main trunk of the tree.
• A branch is some other route through the tree of versions (e.g., to support a particular set of releases or develop a feature). If you ask to check out a branch, you typically get the tip of that branch.
• A version represents an exact state of the code. In CVS, versions are per-file. (Other source control systems have global versioning.)
• A date-based checkout represents getting the state of the code at a particular moment. This can be very useful for tracking down bugs.

The other thing that you'll see is a tagged version. That's where a name is given to a particular state of the tree (e.g., to represent an exact release).

Please take a look at Open Source Development with CVS, especially the Branches chapter. That explains how CVS works and what the head revision is and what branches are.