Substitute character actions than the last one can also be undone by pressing multiple times. 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. Substitute character A substitute character (␚) is a control character that is used in the place of a character that is recognized to be
ISO/IEC 9995 of the keytops; the standard defines their position independent of the characters of the primary layout. Thus, e. g. the Yen symbol “¥” occupies the shifted position on the 6th letter key of the second row, whether this is the Y key on a QWERTY keyboard (like the US layout) or the Z key on a QWERTZ keyboard (like the German layout). The diacritical marks contained in the common secondary group act as dead keys, i.e. they are to be entered before the base characters they apply to. This mechanism is also to be used for sequences of more than