control character

Control-Z

In computing, control-Z is a control character in ASCII code, also known as the substitute (SUB) character. It is generated by pressing the key while holding down the key on a computer keyboard.

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-Z can be used to undo the last cut-and-paste operation performed by the user. Some software programs also provide a keystroke that functions as the opposite redo operation, which re-applies the last editing operation, generally activated by a control-Y or control-shift-Z. Control-Z 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-Z (or Apple-Z).

In some operating systems, control-Z is used to signal an end-of-file when typing at a terminal, terminal emulator, MS-DOS command line, or Win32 console. Early DEC operating systems used this convention, which was borrowed by CP/M, and was later in turn borrowed and continued in the MS-DOS and Microsoft Windows operating systems.

On Unix-like systems, control-Z is the most common default keyboard mapping for the key sequence that suspends a process. When entered by a user at their computer terminal, the currently running foreground process is sent a SIGTSTP signal, which generally causes the process to suspend its execution. The user can later continue the process execution or run the process in background mode.

Representation

  • ASCII and Unicode representation of "substitute":
  • : Octal code: 32
  • : Decimal code: 26
  • : Hexadecimal code: 1A, U+001A
  • : Mnemonic symbol: SUB

See also

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