Escape character

In computing and telecommunication, an escape character is a character which invokes an alternative interpretation on subsequent characters in a character sequence. An escape character is a particular case of metacharacters. Generally, the judgment of whether something is an escape character or not depends on context.

Escape characters are part of the syntax for many programming languages, data formats, and communication protocols. For a given alphabet an escape character's purpose is to start character sequences (so named escape sequences), which have to be interpreted differently from the same characters occurring without the prefixed escape character. An escape character may not have its own meaning, so all escape sequences are of two or more characters.

There are usually two functions of escape sequences. The first is to encode a syntactic entity, such as device commands or special data, which cannot be directly represented by the alphabet. The second use, referred to as character quoting, is to represent characters, which cannot be typed in current context, or would have an undesired interpretation. In the latter case an escape sequence is a digraph consisting of an escape character itself and a "quoted" character.

Generally, an escape character is not a particular case of (device) control characters, nor vice versa. If we define control characters as non-graphic, or as having a special meaning for an output device (e.g. printer or text terminal) then any escape character for this device is a control one. But escape characters used in programming (such as the backslash, "\") are graphic, hence are not control characters. Conversely most (but not all) of the ASCII "control characters" have some control function in isolation, therefore are not escape characters.

In many programming languages, an escape character also forms some escape sequences which are referred to control characters. For example, line break has an escape sequence of \n.

...
Wikipedia