The control key, often labeled “Ctrl” or “Ctl” on a computer keyboard, is a special type of key called a modifier key that is intended to be pressed down in combination with one or more other keys. Its exact function depends on the software and operating system being used, but it most often performs common functions like saving documents, printing, and copy/paste procedures. The control key’s name comes from its original purpose in teletype machines, where it was used to control aspects of the machine’s operation.