|Integer ASCII code:||27|
|Binary code:||0001 1011|
Unicode symbol: ␛, int code: 9243 (html ␛) hex code: 241B (html ␛)
Pressing the Escape key on the keyboard will make this character to be sent on most systems. It can be used in software user interfaces in the function of the exit from a screen, menu, or operating mode, or in device-control protocols (like printers and terminals). In this function it lets the person know, that what comes next is a special command sequence rather than normal text. It doesn't matter if systems based on ISO/IEC 2022 use another set of C0 control codes. This octet is necessarily required to always represent the escape character.
The escape character is widely used in computing and telecommunication. In this role an escape character is a character, which applies to a different interpretation on subsequent characters in a character sequence. In context of escape character we can talk about metacharacters. It's believed that escape can be called a kind if metacharacter. In most cases, the judgment of whether something is an escape character or not depends on context.
All escape sequences strictly have at least two characters just because an escape character may not have its own meaning.
Escape characters make a part of the syntax for lots of programming languages, data formats, and communication protocols. If we're talking about a given alphabet, here an escape character's aim is to start character sequences (so called escape sequences). The things is that they have to be interpreted in a different way from the same characters appeared without the prefixed escape character.
Commonly escape sequences have two functions. The first one is to encode a syntactic realia, for example device commands or special data, which can't be represented by the alphabet itself in the clear form. The second function (by the way, it is called character quoting) is to reflect characters, typing of which is impossible in current context, or would have an adverse, wrong interpretation. In the latter case an escape sequence is represented by a digraph, which consists of an escape character itself and a "quoted" character.
Usually an escape character is neither a special case of (device) control characters, nor vice versa. Imagine, that we determine control characters to be non-graphic, or as possessing a particular meaning for an output device (like printer or text terminal). This way, any escape character for this device is a control one, which is quite ambiguous, since escape characters used in programming (such as the backslash, '\') are graphic characters, deprived of any control function. On the contrary, most (but not all) of the ASCII "control characters" have some concealed control function, therefore are not escape characters.
Besides, an escape character forms some escape sequences in lots of programming languages. All of them are connected to control characters. For example, line break has an escape sequence of .
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