Computer Power Switches

IBM PS/2 from the late 1980s, with a mechanical switch. The computer's power state cannot be controlled by the operating system software (such as Microsoft Windows), and turning off the switch will immediately cut power to the computer.

Generic IBM-compatible tower computer, with a toggle button labeled "Power". This is also a mechanical switch.

Late 1990s computer with a modern power button. Pressing this power button will send a signal to the operating system software to initiate a graceful shutdown.

Modern power button on an iMac DV from 2000.

Modern power button on a MacBook Pro from 2011.

Power button on an Acer Aspire X from 2014.