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 Z key while holding down the Ctrl key on a computer keyboard.

Control-Z was one of a handful of keyboard sequences chosen by the program designers at Xerox PARC to control text editing. It is used to undo the last cut-and-paste operation performed by the user. 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. Such usage continues today in many GUI-based operating systems (including Microsoft Windows and Mac OS (although here the Command key is used instead of the control key)) and word processing software. 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.

In some operating systems, control-Z is used to indicate the end of a file. Early DEC operating systems used this convention, which was borrowed by CP/M, and was later in turn borrowed and continued in the Microsoft DOS operating system.

On Unix and Unix-like operating 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.

Summary

• ASCII and Unicode representation of "substitute":

  Octal code: 32

  Decimal code: 26

  Hexadecimal code: 1A, U+001A

  Mnemonic symbol: SUB

See also

• Control-C
• Control-V
• Control-X
• Control-\
• C0 and C1 control codes (ISO 646)
• Cut and paste
• End-of-file
• Undo