Editing Escape sequence (section)

==Keyboard==
An escape character is usually assigned to the [[Esc key]] on a [[computer keyboard]], and can be sent in other ways than as part of an escape sequence.  For example, the Esc key may be used as an input character in editors such as [[Vi (text editor)|vi]],<ref name="VI"/> or for backing up one level in a menu in some applications.<ref name="PCWorld_2009"/> The Hewlett Packard [[HP 2640]] terminals had a key for a "display functions" mode which would display graphics for all control characters, including Esc, to aid in [[debugging]] applications.

If the Esc key and other keys that send escape sequences are both supposed to be meaningful to an application, an ambiguity arises if a [[character terminal]] is in use. When the application receives the [[ASCII]] escape character, it is not clear whether that character is the result of the user pressing the Esc key or whether it is the initial character of an escape sequence (e.g., resulting from an arrow key press).  The traditional method of resolving the ambiguity is to observe whether or not another character quickly follows the escape character. If not, it is assumed not to be part of an escape sequence. This [[heuristic]] can fail under some circumstances, especially without fast modern communication speeds.

Escape sequences date back at least to the 1874 [[Baudot code]].<ref name="Economist_2013"/><ref name="Baudot"/><ref name="TC304"/>