Screen lock typically serves one or both of two purposes:
- To conserve battery power; and/or
- To protect against unauthorized, or unintended access to the device.
Screen lock is a state where the screen of a device is powered off. It is distinctly different then other machine power states because the device may still be running background processes even though the screen is powered off. When unlocking a screen, it is typical that a hardware button must be pressed, or some other type of activity must be used to notify the machine to turn on the display. Often, but certainly not always, the user must enter some form of authentication, after the display is on, before having complete access to the device.