The power button is round or square. Almost all electronic devices have power buttons or switches. Normally, the device turns on when this button is pressed and off when it is pressed again.
Is the i/o on or off? Simple hack to remember forever!
A hard power button is mechanical: you feel a click when you press it, and you can usually see a difference in depth when the switch is on versus when it’s not. A soft power button, which is much more common, is electrical and looks the same when the device is on and off.
Some older devices have an on/off switch that functions like a hard power button. Flipping the switch one way turns the device on, and flipping the switch the other way turns it off.
Power buttons and switches are usually marked with the symbols "I" and "O". This marking is sometimes I/O or the characters "I" and "O" on top of each other as one character, as in this photo.
