The key combination in Windows that enables a user to terminate an unresponsive application. When all three keys are pressed at the same time, the Task Manager utility is launched, which displays all open applications. It also enables the user to shut down the computer.
First used to reboot DOS PCs, the keystrokes were chosen by IBM in 1981 to ensure users would not accidentally press them. The delete key is at the opposite end of the keyboard from the Ctrl and Alt keys. See Command-Option-Escape
and Win Task Manager
End a Task in Windows 8.1
Pressing Ctrl-Alt-Del in Windows 8.1 displays a menu in which Task Manager is one of the options.