x1B

x1B, also written 0x1B, is the hexadecimal notation for the byte value 1B (27 in decimal) in the ASCII and Unicode character sets. This value corresponds to the Escape character, a non-printable control character used mainly to introduce escape sequences in text terminals and various communication protocols.

In early and modern terminals, the Escape character begins control sequences. The most common form is an Escape followed by a left bracket, ESC [, which starts an ANSI escape code (CSI) used for cursor movement, color and text formatting, and screen control. Examples: ESC [ 2 J clears the screen; ESC [ 31 m sets foreground color to red; ESC [ 0 m resets attributes. Other sequences use ESC P to start, ESC \ to terminate, for device control strings (DCS).

In programming, the value is often embedded in strings as \x1B in languages like C and C++, or as \u001B in Unicode escapes. It is treated as a control code rather than a printable character.

In Unicode, ESC is U+001B. Its usage spans terminal emulators, printers, and some network protocols; the interpretation of the sequence depends on the context.

Note that the Escape key on keyboards may generate different codes depending on platform and software; it frequently maps to the Escape character, but not guaranteed.