Oh, and by the way... SysRq, or System Request, is basically a key that lies between Control-Break and Control-Alt-Delete. It was on a key by itself on the 84-key AT keyboard, and was the one key added to make that keyboard 84 keys, instead of 83 keys like the original IBM PC keyboard.
Although current PC operating software does not make use of this, in standard PC hardware, pressing the System Request key activates a specific interrupt for the CPU. Thus, it could potentially be used to get out of difficult lock-up situations.