What Is a Power Button and What Are the On/Off Symbols?

The power button is a round or square button that powers an electronic device on and off. Nearly all electronic devices have power buttons or power switches. Typically, the device powers on when a user presses the button and powers off when they press it again. A hard power button is mechanical—you can feel a click when it's pressed and 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 appears the same when the device is on and off. Some older devices have a power switch that accomplishes the same thing as a hard power button. A flip of the switch in one direction turns the device on, and a flip in the other turns it off. On/Off Power Button Symbols (I & O) 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 I/O or the "I" and "O" characters on top of each other as a single ch...