The power button is a round or square button that powers on and powers off a device. Typically, the device powers on when the switch is pressed in and powers off when the button is again pressed. Some devices instead have a power switch that accomplishes the same thing. A flip of the switch in one direction turns the device on and a flip in the other turns the device off.
Nearly all electronic devices have power buttons or power switches. In a typical computer setup, power buttons and switches appear on the front and sometimes back of the monitor and on the front and back of the case. The power switch on the back of the case is actually the power switch for the power supply installed in the computer.
Power buttons and switches are usually labeled with "I" and "O" symbols. The "I" represents power on and the "O" represents power off. This designation will sometimes be seen as I/O or as the "I" and "O" characters on top of each other as a single character.
Also Known As: power switch
Examples: "I spent ten minutes trying to figure out why my computer wasn't coming on before I realized that I hadn't flipped the power switch on the surge protector that my computer was plugged into!"