Power key

They are also found on an increasing number of Microsoft Windows keyboards,[citation needed] sometimes supplanted with additional keys for sleep.

This peripheral bus was intended to connect low-speed input devices like keyboards and computer mice.

Power keys remain on some modern Macs, including the MacBook Air, but most others have replaced it with an "eject" key, formerly used to open the now-non-existent CD drive.

In Windows, this can be configured to enter one of the "sleeping modes", i.e. "suspend to RAM" (with fast wake up by pressing any key) or "suspend to disk" (i.e. hibernation, where waking up will require pressing the power button, restoring all running applications in their current running state), or to shutdown the PC completely (closing all running applications and services, pressing the power button will reboot the PC, possibly in "fast boot" mode if enabled in BIOS/EFI settings and Windows settings).

Pressing any of these keyboard or case buttons, or using the desktop Start menu to simply "shutdown" the PC will not apply pending system updates immediately (as it could be lengthy and could use too much energy if the battery power level is too low), but will delay them until the next "restart" menu option is selected, or an administrative update for Windows instructs the PC (with a sufficient battery level or connected to an AC power source) to restart to apply updates during the shutdown, and normal restart (with fast boot temporarily disabled to terminate all system updates preinstalled during the shutdown phase).

The Apple Keyboard featured a prominent power key above the standard keyboard keys. The triangle icon was used to represent power on in these earlier models.
The modern MacBook Air includes a power key with the "1 in a circle" icon.
This multifunction keyboard has separate keys for sleep, wake and power on/off.
On PC keyboards, power keys were often based on rubber mechanisms, like this Yahoo-branded example.