Access protection is a technological protection measure that restricts unauthorized access to a copyright work. It is usually in the form of a software program and/or hardware as part of a computer, an audiovisual or audio device. It allows programmers to restrict access to members of the class. Access-protection measures include means of preventing information, films or sound recordings stored on certain optical disks from being played on certain players. It also include systems that use encryption or a software key to access material or information stored on a digital format.