When devices turn on, they enter a state that’s valid and has been configured by the manufacturer. Eg. an mp3 player would want to start to play the first song in the playlist.
As they operate, a device can enter into a state that’s invalid due to bugs, or bad user input. Eg. going with the example above, the mp3 player would want to play song #57 on the playlist, but there are only 56 songs.
Restarting the device will mean that the device will exit the bad state, and return to the valid initial state.
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