Esc key

For other uses, seeESC.

Not to be confused withEscape character.

Oncomputer keyboards,theEsc keyEsc(namedEscape keyin the international standard seriesISO/IEC 9995) is a key used to generate theescape character(which can be represented asASCIIcode 27 in decimal,UnicodeU+001B, orCtrl+[). The escape character, when sent from the keyboard to a computer, often is interpreted by software as "stop", "cancel" or "exit", and when sent from the computer to an external device (including many printers since the 1980s,computer terminalsandLinux consoles,for example) marks the beginning of anescape sequenceto specify operating modes or characteristics generally.

A computer keyboard with the Esc key in the top-left corner

IBM 83-key keyboard (1981), with Esc in the top-left corner of the Alpha numeric section

It is now generally placed at the top left corner of the keyboard, a convention dating at least to the originalIBM PC keyboard,though the key itself originated decades earlier withteletypewriters.

Symbol

ISO keyboard symbol for "Escape"

The keyboard symbol for the ESC key (which may be used when the usual Latin lettering "Esc" is not preferred for labelling the key) is standardized inISO/IEC 9995-7 as symbol 29, and in ISO 7000"Graphical symbols for use on equipment"as symbol ISO-7000-2029. This symbol is encoded inUnicodeas U+238Bbroken circle with northwest arrow(⎋).

Origins

The name of the equivalent key on some earlyTeletype Model 33keyboards was labeledAlt Mode..., the alternative mode of operation causing the escapement to treat the following one character in a special way. Much later printers andcomputer terminalsthat would useescape sequencesoften would take more than one following byte as part of a special sequence.

Uses

As most computer users are no longer concerned with the details of controlling their computer'speripherals,the task for which the escape sequences were originally designed, the escape key was appropriated byapplicationprogrammers, most often to meanStop.This use continues today inMicrosoft Windows's method of escape as a shortcut in dialog boxes forNo,Quit,Exit,Cancel,orAbort,as well as a common shortcut key for theStopbutton in manyweb browsers,and to canceldrag and dropoperations.

On machines runningMicrosoft Windows,prior to the implementation of theWindows keyon keyboards, the typical practice for invoking the "start" button was to hold down theControl keyand press escape. This key combination still works as of Windows 10.

Microsoft Windows makes use of "Esc" for many key shortcuts.Many of these shortcuts have been present sinceWindows 3.0,throughWindows XPand later.

In macOS, "Esc" usually closes or cancels a dialog box or sheet. The⌘ Command+⌥ Option+⎋ Esccombination opens theForce Quitdialog box, allowing users to end non-responsive applications. Another use for the Esc key, in combination with the Command key, is switching toFront Row,if installed.

In most computer games, the escape key is used as a pause button and/or as a way to bring up the in-game menu, usually containing ways to exit the program. This is despite the existence of a separatePause/Break key.

ADM-3Akeyboard layout used in vi development, with escape in what is now the tab position

In thevifamily of text editors, escape is used to switch modes. This usage is due to escape being conveniently placed in what is now the tab position on theADM-3Aterminal keyboard used to develop vi, though it is now inconveniently placed. This is similar to how the extensive modifier keys inEmacswere easily used on the original keyboard (thespace-cadet keyboard), being placed together, but these keys have now been spread around the keyboard, becoming more difficult to use.

TheTECOeditor uses ESCape as a delimiter when used once, and as anexecutekey when used twice in a row.

Escape sequences on KSR terminals

Old keyboard Send/Receive (KSR) printers, andvisual display units(VDUs), would normally be controlled byescape sequencessent by the computer to the peripheral device, but there were situations where these devices could be used "off-line" with the keyboard effectively connected to the output device, and so the need could arise to type escape sequences "by hand" to control the peripheral. Although such devices are long out of use, standard processingofANSI Escape sequencesvery similar to the 1970sVT100,is implemented in bothANSI.SYSand other more modern pseudo-terminal interfaces used inUnix-likeenvironments, one example beingLinux consoles,meaning newer, higher-level abstractions haven't changed the fact that typing the escape key followed by something like the six characters[32;1maffects subsequently text in output, in this case turning it green.

References

IBM PC keyboard(Windows,ANSIUS layout)
Esc		F1	F2	F3	F4		F5	F6	F7	F8		F9	F10	F11	F12		PrtScn/ SysRq	Scroll Lock	Pause/ Break
																	Insert	Home	PgUp		Num Lock	∕	∗	−
																	Delete	End	PgDn		7	8	9	+
																					4	5	6
																		↑			1	2	3	Enter
																	←	↓	→		0 Ins		. Del