C1 controls — 8-bit single-byte equivalents of ESC sequences (0x80–0x9F)

Byte forms

Every common string-literal form so you can paste-and-search either direction.

Description

The **C1 control set** occupies bytes `0x80`..`0x9F` and provides single-byte alternatives to the most common `ESC <letter>` sequences. The full set: `IND` (0x84, ESC D — line feed without CR), `NEL` (0x85, ESC E — CR+LF), `HTS` (0x88, ESC H — set tab stop at cursor column), `RI` (0x8D, ESC M — reverse line feed, scroll if at top), `SS2` (0x8E, ESC N — single-shift G2 charset for the next char), `SS3` (0x8F, ESC O — single-shift G3), `DCS` (0x90, ESC P — Device Control String introducer), `CSI` (0x9B, ESC [ — Control Sequence Introducer, the most common one), `ST` (0x9C, ESC \\ — String Terminator for DCS / OSC / APC / PM / SOS), `OSC` (0x9D, ESC ] — Operating System Command introducer), `PM` (0x9E, ESC ^ — Privacy Message), `APC` (0x9F, ESC _ — Application Program Command, used by Kitty's graphics protocol). **Avoid the 8-bit forms on modern terminals**: every byte in `0x80..0x9F` is a UTF-8 *continuation byte* (the first bits are `10xxxxxx`), so a stray `0x9B` in a UTF-8 stream is either consumed as part of an invalid sequence or silently dropped. Always emit the 7-bit `ESC <letter>` form (`\x1b[`, `\x1b]`, `\x1b\\`, etc.) — it is unambiguous in UTF-8, ASCII, and Latin-1, and every terminal recognises it. The 8-bit C1 set is relevant mainly to legacy contexts (DEC VT220 in S8C1T mode, ISO 8859-1 stream archives, old VT100 firmware test vectors).

Spec citation: ECMA-48 §5.2 (C1 set) / ISO 6429

Parameters

Examples

# 7-bit (preferred — UTF-8 safe):\nprintf '\033[31mred\033[0m'\nprintf '\033]0;new window title\033\\\\'\n# 8-bit C1 (legacy — breaks under UTF-8):\nprintf '\x9b31mred\x9b0m'   # only works if terminal is in 8-bit mode + Latin-1

# Prefer 7-bit ESC form:\nimport sys; sys.stdout.write('\x1b[31mred\x1b[0m')\n# 8-bit C1 — fails on UTF-8 stdouts:\n# sys.stdout.buffer.write(b'\x9b31mred\x9b0m')

// 7-bit ESC form (UTF-8 safe):\nfmt.Print("\x1b[31mred\x1b[0m")\n// 8-bit C1 — emits two UTF-8 continuation bytes interpreted as garbage:\n// os.Stdout.Write([]byte{0x9b, '3','1','m'})

process.stdout.write('\x1b[31mred\x1b[0m');\n// process.stdout.write(Buffer.from([0x9b, 0x33, 0x31, 0x6d]))  // breaks UTF-8

/* 7-bit ESC form: */\nprintf("\x1b[31mred\x1b[0m");\n/* 8-bit C1 — only safe on Latin-1 / explicit 8-bit terminals: */\n/* fputc(0x9b, stdout); fputs("31m", stdout); */

Terminal support

xterm

partial

Linux console (fbcon)

no

macOS Terminal.app

no

iTerm2

no

Windows Terminal

no

cmd.exe / ConPTY

no

kitty

no

alacritty

no

WezTerm

no

Ghostty

no

GNOME Terminal

no

Konsole

no

tmux

no

GNU screen

no

Related sequences

• C0 controls — BS, HT, LF, CR, BEL (single-byte codes)
• HTS — Horizontal Tab Set (ESC H)
• DECSTR — Soft terminal reset
• RIS — Reset to Initial State (full terminal reset)

In the family cookbook

↗ESC cookbook · 5. Locking shifts + the 8-bit C1 bridge — `\x1bn` / `\x1bo` / `\x1b|` and `\x80-\x9F`