Control Sequences

A control sequence is any byte stream that the terminal interprets as a command rather than rendering as text. The terminal's parser is a small state machine that distinguishes printable bytes from control bytes and routes them differently.

The four families

Family	Introduced by	Example	More
C0	a single byte in 0x00–0x1F or 0x7F	0x0A (LF)	Control
ESC	ESC + final byte (0x30–0x7E)	ESC c (RIS)	ESC
CSI	ESC [ + params + final	ESC [ 31 m	CSI
OSC	ESC ] + payload + ST	ESC ] 0 ; title BEL	OSC

A fifth less-common family covers DCS (ESC P), APC (ESC _), and PM (ESC ^) — used by Kitty graphics, tmux passthrough, and various private protocols. See External Protocols.

Parsing rules

The state machine is the VT500-Series Parser (Paul Williams). Highlights:

• CAN (0x18) and SUB (0x1A) abort any sequence in flight.
• ESC resets the parser and starts a new sequence.
• An ESC inside an OSC or DCS payload terminates the payload (string terminator).
• Invalid sequences are silently dropped; they do not show up as text.

See also

• VT Overview
• Cursor, Screen, Colors