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
QWERTY through the key. On Macintosh computers, the "Norwegian" and "Norwegian extended" keyboard layouts have a slightly different placement for some of the symbols obtained with the help of the or keys. Notably, the "$" sign is accessed with and "¢" with . Furthermore, the frequently used "@" is placed between and . Most typewriters use a QWERTZ keyboard with Polish letters (with diacritical marks) accessed directly (officially approved as "Typist's keyboard", , Polish Standard PN-87), which is mainly ignored in Poland as impractical (except custom-made, e.g., in public sector and some Apple computers); the "Polish programmer's" () layout has become