Power key

The power key (or power button) was on all keyboards sold with Macs as of the 1980s. The key had the icon ◃ (⌽ or an open O with a letter I coming out of it, on newer Macs).

Use
The power key was of no use whatsoever on keyboards connected to the Macintosh Classic (although not the Macintosh Colour Classic), Macintosh LC, and other earlier (1990s) Macs.

However, as of the late 1990s Macs, it gradually was more and more useful. Before it was removed in the newest Apple keyboards (around 2002), it could completely turn on and off Macs connected to it.

Additional use

 * Press command and the power key (Classic Mac OS only). You've just invoked the interrupt switch. Type G at the resulting dialogue box (debugger) -- if you can, that is, because sometimes the system won't wake up after an interruption via this switch (e.g. if it is seriously hosed).


 * Press command-shift and the power key (all Mac OS versions). The Mac will restart -- you've just invoked the reset switch. This tip is good for Mac OS X, too.