Control-Alt-Delete (often abbreviated to Ctrl-Alt-Del, also known as the “three-finger salute”) is a computer keyboard command on PC compatible systems that can be used to reboot the computer, and summon the task manager or Windows Security in more recent versions of the Microsoft Windows operating system. It is invoked by pressing the Delete key while holding the Control and Alt keys. It forces a soft reboot, brings up the task manager (on Windows, BeOS, and KDE-based Linuxes) or a jump to ROM monitor. These keys are sometimes referred to in computer manuals as interrupt keys, since they are often used to interrupt the operation of a malfunctioning program.
The interesting part is that David Bradley, who first implemented it spent just 1 minute 23 second in writing its source code, an invention (!) thats rescuing pcs in the world !