In many GUI environments, including Microsoft Windows and most desktop environments based on the X Window System, and in applications such as word processing software running in those environments, control-V can be used to paste text from the clipboard at the current cursor position. Control-V was one of a handful of keyboard sequences chosen by the program designers at Xerox PARC to control text editing. Presumably these particular keystrokes were chosen because of their location on a standard QWERTY keyboard, since the Z (undo), X (cut), C (copy), and V (paste) keys are located together at the left end of the bottom row of the standard QWERTY keyboard. The equivalent Mac OS key combination on Apple computers is Command-V.