Escape Sequences

Escape sequences are initiated by the presence of the escape control code ControlCode.ESC (0x1b) in the input stream, followed by a character in the range 0x20...0x7e. There are several different types of escape sequences, indentified by the specific character code following the escape control code:

<escape-sequence> ::= <nf-sequence> | <fp-sequence> | <fe-sequence> | <fs-sequence>

<nf-sequence>     ::= <ESC> (0x20...0x2f)+ 0x30...0x7e
<fp-sequence>     ::= <ESC> 0x30...0x3f
<fe-sequence>     ::= <ESC> (0x40...0x4f | 0x51...0x57 | 0x59...0x5a | 0x5c)
<fs-sequence>     ::= <ESC> 0x60...0x7e

<ESC>             ::= 0x1b

Fe Escape Sequences

The <fe-sequence> type was defined in order to allow 7-bit character codes to access the C1 control codes in the range 0x80...0x9f, which normally require an 8-bit code. Each <fe-sequence> maps to a C1 control code by taking its second character code and adding 64 (hexadecimal 0x40). For example, the sequence 0x1b 0x40 invokes the same function as the 0x80 control code, the sequence 0x1b 0x41 invokes the same function as the 0x81 control code, etc.

The following escape sequences map to "introducers" rather than to solitary control codes:

Escape Sequence	Introduced Element
0x1b 0x50	Control String or Control String Initiator (Device Control String)
0x1b 0x58	Control String or Control String Initiator (Start of String)
0x1b 0x5b	Control Sequence
0x1b 0x5d	Control String or Control String Initiator (Operating System Command)
0x1b 0x5e	Control String or Control String Initiator (Privacy Message)
0x1b 0x5f	Control String or Control String Initiator (Application Program Command)