Power management keys
|This article does not cite any references or sources. (May 2009)|
- The Power key is used both to power on and to power off the computer.
- The Sleep key is used to put the computer to sleep, when it uses significantly lower power than when it is active, but can be woken quickly.
- The Wake key wakes the system from standby.
The power saving modes and the transition between them is usually implemented using ACPI.
The placement of the three power management keys on a computer keyboard varies depending on the keyboard's model.
Ideally, these keys should be placed far enough from the rest of the keys, since the consequences of accidentally pressing one of them while using the computer (with the exception of the Wake key, which does nothing in this situation) can range from being annoying to causing data loss. For instance, if the user has edited a file, but not saved it yet, on some applications shutting down the system (which happens when a finger slip hits the Power key) can easily lose all the changes (although generally the more used operating systems ask the user to save the file before shut down). While the results of wrongly pressing the Sleep key aren't as extreme (unless the computer has problems returning from sleep), it can cause problems in real-time games or any application which depends on a network connection.
One common placement for these keys is in the right of the top row of the keyboard, replacing the Print Screen/SysRq, Scroll Lock, and Pause/Break keys, which are moved one row down. Hereby the 2x3 block of edit and navigation keys is made to occupy the empty space just above the arrow keys. This annoys some people, because it confuses their muscle memory.
Another common placement for these keys is just below the Delete, End, and Page down keys, in the empty space just above the Arrow keys. When used with normal-sized keys, this can cause a high probability of accidental keypresses, especially when the typist is used to a keyboard without any keys on that position, or with the alternate arrangement described above. This leads some people to physically remove the keycaps. Some keyboard models avoid this problem by using keys with a lower height and requiring a higher force to be pressed.
Many keyboards have found a solution to this problem, in that a specific key has to be held down while the power management key is pressed. Often, this is found in the top-right of the keyboard, to the right of the lock button lights, and can be described as "opposite the escape button". With this button, the power, sleep, and wake keys don't do anything when pressed alone, and the function key does nothing, either.
Most of the original ADB Apple Macintosh keyboards, as well as the first USB keyboard, had a key to turn the machine on in lieu of a physical power button on the computer itself. The symbol on it was usually a triangle pointing left (◁). On most keyboards it was located at the extreme upper-right corner, above the function keys and above the right most key, or in the same vertical position and in the center. The power button was replaced with a disc eject button when the Apple Pro Keyboard was introduced, and Apple removed the ability of Macs to be switched on from the keyboard. Pressing the power button when running Mac OS brought up the shutdown dialog box, on keyboards with an eject button the combination Control-Eject is used instead (for most x-Power keyboard combinations, x-Eject is used as the replacement combination).