Students are debating what is an input device. Are the power and volume buttons on an iPhone input devices or just buttons like on and off switches. Going farther if the keyboard is a input device is each key itself a separate device or just a “button” on one larger device?
Another question is whether headphones are an input device because the plug that you put into the computer. The jack has to somehow know that it is headphones vs something else and the jack has to decide whether to play sound through the headphones versus the speakers.