Editing Escape sequence (section)

==Control sequences==
When directed, this series of [[character (computing)|characters]] is used to change the [[State (computer science)|state]] of [[computer]]s and their attached [[peripheral]] devices, rather than to be displayed or printed as regular [[Data (computing)|data]] bytes would be, these are also known as '''control sequences''', reflecting their use in device control, beginning with the '''Control Sequence Initiator''' - originally the "escape character" ASCII code - character 27 (decimal) - often written "Esc" on [[keycap]]s.

With the introduction of ANSI terminals most escape sequences began with the ''two'' characters "ESC" then "[" or a specially-allocated '''CSI''' character with a code 155 (decimal).

Not all control sequences used an escape character; for example:
* modem control sequences used by AT/[[Hayes command set|Hayes-compatible]] modems<ref name="Hayes"/><ref name="CISCO"/>

* [[Data General]] terminal control sequences,<ref name="Data_General_Terminals"/><ref name="Kermit"/><ref name="DG210"/> but they often were still called escape sequences, and the very common use of "escaping" special characters in programming languages and command-line parameters today often use the "backslash" character to begin the sequence.

Escape sequences in communications are commonly used when a computer and a peripheral have only a single channel through which to send information back and forth (so escape sequences are an example of [[in-band signaling]]).<ref name="Dict"/><ref name="Terminal_Handbook"/> They were common when most [[dumb terminals]] used [[ASCII]] with 7 data bits for communication, and sometimes would be used to switch to a different character set for "foreign" or graphics characters that would otherwise been restricted by the 128 codes available in 7 data bits. Even relatively "dumb" terminals responded to some escape sequences, including the original mechanical Teletype printers (on which "glass Teletypes" or VDUs were based) responded to characters 27 and 31 to alternate between letters and figures modes.