Shareware is a software distribution practice whereby a piece of software is distributed freely, and sharing of that software is encouraged. Some shareware is fully featured, while some is either time-limited, has built-in limitations (often called crippleware). Users of shareware are then encouraged to register the software, either to get a full and unrestricted copy, or just to support the author. Unlike freeware, you are expected to pay if you use the software, and unlike open source software, you are not allowed to modify the software. Unlike public domain software, the software is copyrighted and that particular copyright is owned by the author. A good analogy for shareware software is "try before you buy". Shareware is very often used for computer games.