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Glossary
Terminal acronyms and technical terms.
A
Alacritty — Alacritty Terminal Emulator
GPU-accelerated minimal terminal written in Rust. Pioneered GPU rendering for terminals in 2017. → Learn more
alternate screen — Alternate Screen Buffer
A separate screen that full-screen apps (vim, less, htop) switch to. When the app exits, your previous terminal content reappears. An xterm invention, not part of any formal standard. → Learn more
alternate screen buffer — Alternate Screen Buffer
A separate screen for full-screen apps. When the app exits, previous content reappears. → Learn more
ANSI — American National Standards Institute
Published the X3.64 terminal standard in 1979, withdrawn in 1994 in favor of ISO 6429. The name persists in 'ANSI escape codes'. → Learn more
ASCII — American Standard Code for Information Interchange
7-bit character encoding (128 characters) published in 1963. The first 32 codes are control characters (C0), the rest are printable. UTF-8 is a superset — all ASCII text is valid UTF-8. → Learn more
auto-wrap — Auto-Wrap Mode (DECAWM)
When text reaches the right edge of the terminal, automatically continue on the next line. Almost always enabled — disabling it causes text to overwrite the last column. → Learn more
B
baud rate — Baud Rate
The data transmission speed of a serial connection, measured in symbols per second. Physical terminals ran at 300-19200 baud. Modern pseudo-terminals ignore baud rate but the field still exists in the termios struct. → Learn more
BEL — Bell Character
ASCII character 0x07. Originally rang a physical bell. In modern terminals, may flash the title bar, play a sound, or trigger a notification. Also used as the string terminator in some OSC sequences (alternative to ST). → Learn more
BOM — Byte Order Mark
The Unicode character U+FEFF placed at the start of a file to signal encoding and byte order. Useful for UTF-16/UTF-32 but unnecessary and discouraged for UTF-8. Can cause problems when piped to terminals. → Learn more
bracketed paste — Bracketed Paste Mode
A safety feature: the terminal wraps pasted text in special markers so the shell knows it's pasted, not typed. Prevents accidental command execution from pasting text containing newlines. → Learn more
bracketed paste mode — Bracketed Paste Mode
Terminal wraps pasted text in markers so the shell knows it is pasted, not typed. Prevents accidental command execution. → Learn more
BS — Backspace
ASCII character 0x08. Moves the cursor one column left without erasing. In canonical mode the line discipline handles destructive backspace (BS + Space + BS). In raw mode the application must handle it. → Learn more
C
C0 — C0 Control Characters
The 33 non-printable ASCII characters in the 0x00–0x1F range plus DEL (0x7F). Includes ESC, BS, TAB, LF, CR, and BEL. Predates escape sequences — these are single-byte terminal commands. → Learn more
C1 — C1 Control Codes
Single-byte control characters in the 0x80–0x9F range defined by ECMA-48. Include CSI (0x9B), OSC (0x9D), DCS (0x90). Rarely used in practice because they conflict with UTF-8 encoding — the 7-bit ESC-prefixed forms are universal instead. → Learn more
canonical mode — Canonical (Cooked) Terminal Mode
The default TTY line discipline mode where input is line-buffered (delivered on Enter), with echo and basic line editing (backspace, Ctrl+U). Also called cooked mode. → Learn more
cell — Terminal Cell
One character position in the terminal grid. Each cell holds a character, foreground/background colors, and attributes (bold, italic, etc.). Wide characters occupy two cells. The terminal screen is a grid of rows x columns of cells.
CHA — Cursor Horizontal Absolute
Move cursor to column N on the current row. → Learn more
charset designation — Character Set Designation (G0-G3)
The ECMA-35/VT mechanism for switching between character sets using escape sequences. G0-G3 are four slots that can be loaded with different charsets (ASCII, DEC Special Graphics, etc.). Largely obsolete — replaced by UTF-8. → Learn more
CJK — Chinese, Japanese, Korean
The three East Asian writing systems whose characters are 'fullwidth' — they occupy two terminal columns each. Correct width calculation is essential for TUI layout. → Learn more
CNL — Cursor Next Line
Move cursor to the beginning of the line N rows down. → Learn more
code point — Unicode Code Point
A number assigned to a character in the Unicode standard, written as U+XXXX (e.g. U+0041 is 'A'). Unicode defines over 149,000 code points. A single visible character (grapheme cluster) may consist of multiple code points. → Learn more
combining character — Combining Character
A Unicode character that attaches to the preceding base character without advancing the cursor. Diacritical marks (accents, umlauts) and some emoji modifiers are combining characters. Terminals must render them in the same cell as the base character. → Learn more
control character — Control Character
Non-printable characters in the 0x00-0x1F (C0) and 0x80-0x9F (C1) ranges. Includes ESC (0x1B), BEL (0x07), BS (0x08), TAB (0x09), LF (0x0A), and CR (0x0D). Terminals interpret these as commands rather than displayable text. → Learn more
Core TUI baseline — Core TUI Baseline
Every terminal should support these → Learn more
CPL — Cursor Previous Line
Move cursor to the beginning of the line N rows up. The counterpart to CNL (Cursor Next Line). → Learn more
CR — Carriage Return
ASCII character 0x0D. Moves the cursor to the beginning of the current line without advancing to the next line. Named after the typewriter carriage that physically returned to the left margin. → Learn more
CRLF — Carriage Return + Line Feed
The two-byte sequence CR (0x0D) followed by LF (0x0A). The standard line ending for terminal protocols and Windows text files. Terminals expect CRLF — the line discipline converts bare LF to CRLF on output. → Learn more
CSI — Control Sequence Introducer
The ESC [ prefix that starts most terminal escape sequences. Defined in ECMA-48. → Learn more
CSI u — CSI u Keyboard Protocol
A keyboard reporting format proposed by Leonerd (Paul Evans) in the fixterms specification. Uses CSI ... u sequences for unambiguous key reporting. Influenced the Kitty keyboard protocol, which extended and formalized the approach. → Learn more
CUB — Cursor Back
Move cursor left N columns. → Learn more
CUD — Cursor Down
Move cursor down N rows. → Learn more
CUF — Cursor Forward
Move cursor right N columns. → Learn more
CUP — Cursor Position
CSI row ; col H — move cursor to absolute position. The most fundamental cursor command. → Learn more
cursor — Text Cursor
The blinking indicator showing where the next character will appear. Terminals support block, underline, and bar shapes (DECSCUSR), can show/hide it (DECTCEM), and report its position (DSR 6). TUI apps rely on precise cursor control. → Learn more
CUU — Cursor Up
Move cursor up N rows. → Learn more
D
DA1 — Primary Device Attributes
Query the terminal for its type and supported features. The terminal responds with its capability flags. → Learn more
DA2 — Secondary Device Attributes
Query for the terminal type, firmware version, and hardware options. Sent as CSI > c. Unlike DA1 (capability flags), DA2 identifies the specific terminal product and version. → Learn more
DCH — Delete Character
Delete characters at cursor position, shifting remaining characters left. → Learn more
DCS — Device Control String
Escape sequences for device-specific data (Sixel graphics, DECRQSS queries). → Learn more
DEC — Digital Equipment Corporation
The company that created the VT100 terminal series. Their private mode sequences (DECSET/DECRST) are still the primary mechanism for terminal feature negotiation. → Learn more
DEC Special Graphics — DEC Special Graphics Character Set
A character set that maps ASCII printable characters to line-drawing symbols (box corners, horizontal/vertical lines, etc.). Activated via ESC ( 0. Used by ncurses for borders. Predates Unicode box-drawing characters. → Learn more
DECALN — DEC Screen Alignment Test
Fill the entire screen with the letter 'E'. Originally used to test CRT screen alignment. Now useful for debugging — it instantly shows the screen dimensions and clears all content. → Learn more
DECAWM — DEC Auto Wrap Mode
DEC private mode ?7 — automatically wrap text at the right margin. → Learn more
DECCOLM — DEC Column Mode
DEC private mode ?3 — switch between 80 and 132 column mode. Originally for wide printouts on DEC terminals. Modern terminals typically resize the window instead. → Learn more
DECOM — DEC Origin Mode
DEC private mode ?6 — when set, cursor positions are relative to the scroll region instead of the full screen. Affects CUP and other absolute positioning commands. → Learn more
DECRC — DEC Restore Cursor
Restore cursor position and attributes previously saved with DECSC. Together DECSC/DECRC are used by TUI apps to preserve cursor state across screen updates. → Learn more
DECRPM — DEC Private Mode Report
Response sequence reporting whether a DEC private mode is set, reset, or unrecognized. → Learn more
DECRQM — DEC Request Mode
Query whether a specific DEC private mode is currently set, reset, or unrecognized. The terminal responds with DECRPM. Essential for feature detection without side effects. → Learn more
DECRQSS — DEC Request Status String
Query the terminal for current settings (SGR attributes, scroll region, etc.). → Learn more
DECRST — DEC Private Mode Reset
CSI ? Pm l — disable a DEC private mode. → Learn more
DECSC — DEC Save Cursor
Save cursor position and attributes for later restoration with DECRC. → Learn more
DECSCA — DEC Select Character Attributes
Mark characters as protected or unprotected. Protected characters are not affected by selective erase operations (DECSED, DECSEL). Rarely used. → Learn more
DECSCNM — DEC Screen Mode (Reverse Video)
DEC private mode ?5 — swap foreground and background colors for the entire screen. Used for light-on-dark vs dark-on-light display. → Learn more
DECSCUSR — DEC Set Cursor Style
Set cursor shape: block, underline, or bar; blinking or steady. → Learn more
DECSET — DEC Private Mode Set
CSI ? Pm h — enable a DEC private mode (alt screen, mouse tracking, bracketed paste, etc.). → Learn more
DECSTBM — DEC Set Top and Bottom Margins
Define the scroll region — lines between top and bottom margins scroll independently. → Learn more
DECTCEM — DEC Text Cursor Enable Mode
DEC private mode ?25 — show/hide the text cursor. → Learn more
DEL — Delete
ASCII character 0x7F. Originally punched all 7 holes in paper tape to 'delete' a character. In modern terminals, often sent by the Backspace key. Not part of the C0 range despite being a control character. → Learn more
DL — Delete Lines
Delete N lines at cursor position, pulling lines up from below. → Learn more
DSR — Device Status Report
Query the terminal for status information, most commonly cursor position (DSR 6). → Learn more
E
ECH — Erase Character
Erase N characters at cursor position without moving the cursor. → Learn more
echo — Terminal Echo
The line discipline's automatic display of typed characters. In canonical mode, the kernel echoes input. In raw mode, echo is disabled and the application decides what to display. Controlled via stty echo/stty -echo. → Learn more
ECMA-35 — European Computer Manufacturers Association standard 35
Standard for coded character set structure and extension techniques. Defines the G0-G3 character set designation and invocation mechanism used by VT terminals. Largely obsolete — replaced by UTF-8. → Learn more
ECMA-48 — European Computer Manufacturers Association standard 48
The foundational standard for terminal control sequences, first published in 1976. Also known as ISO 6429 and (formerly) ANSI X3.64. → Learn more
ED — Erase in Display
Clear part of the screen (below cursor, above cursor, or entire screen). → Learn more
EL — Erase in Line
Clear part of the current line (right of cursor, left of cursor, or entire line). → Learn more
ESC — Escape
ASCII character 0x1B. The byte that begins all escape sequences. Followed by [ for CSI, ] for OSC, P for DCS, or other characters for simpler sequences. Named because it 'escapes' from normal text interpretation. → Learn more
escape sequence — Escape Sequence
A special byte pattern starting with ESC (0x1B) that tells the terminal to do something other than display text — like change colors, move the cursor, or switch modes. → Learn more
F
focus events — Focus Reporting (Mode 1004)
Terminal sends escape sequences when the window gains or loses keyboard focus. Lets TUI apps pause rendering when not visible and refresh when refocused. → Learn more
focus reporting — Focus Reporting
Terminal notifies the app when the window gains or loses focus. Enables apps to pause/resume rendering. → Learn more
font fallback — Font Fallback
When a character is missing from the primary font, the terminal searches a chain of fallback fonts for a glyph. Critical for emoji and CJK rendering. Poor fallback causes tofu (missing glyph rectangles).
G
Ghostty — Ghostty Terminal Emulator
GPU-accelerated terminal by Mitchell Hashimoto, written in Zig with excellent standards compliance. → Learn more
glyph — Glyph
The visual representation of a character as rendered by a font. A single code point may have multiple glyphs (ligatures, contextual forms), and multiple code points may produce one glyph (grapheme clusters).
GNU Screen — GNU Screen Terminal Multiplexer
The original terminal multiplexer (1987). Session persistence and detach/reattach for remote work. → Learn more
grapheme — Grapheme
The smallest unit of a writing system that a user perceives as a single character. In Unicode, a grapheme cluster may span multiple code points — an accented letter, a flag emoji, or a family emoji are each one grapheme. → Learn more
grapheme cluster — Grapheme Cluster
What humans perceive as a single character — which may be multiple Unicode codepoints. The family emoji is 7 codepoints but one grapheme cluster occupying 2 terminal columns. → Learn more
H
headless — Headless Terminal
A terminal emulator library running without a visible window — used for automated testing. It parses escape sequences but doesn't render pixels. → Learn more
HTS — Horizontal Tab Set
Set a tab stop at the current cursor column. Used with TBC (tab clear) to customize tab stop positions beyond the default every-8-columns. → Learn more
I
ICH — Insert Character
Insert blank characters at cursor position, shifting existing characters right. → Learn more
IL — Insert Lines
Insert N blank lines at cursor position, pushing existing lines down. → Learn more
IRM — Insert/Replace Mode
ECMA-48 mode 4. When set (SM 4), typed characters push existing text right instead of overwriting. When reset (RM 4), characters overwrite. Most terminals default to replace mode. → Learn more
ISO 6429 — ISO 6429
The ISO version of ECMA-48 — the foundational terminal control sequence standard. Published alongside ANSI X3.64 (now withdrawn). When someone says 'ANSI escape codes' they mean ISO 6429 / ECMA-48 sequences. → Learn more
ISO 8859-1 — ISO 8859-1 (Latin-1)
8-bit extension of ASCII adding 96 Western European characters (accented letters, symbols). Was the default encoding before UTF-8 took over. The first 256 Unicode code points match Latin-1 exactly. → Learn more
iTerm2 inline images — iTerm2 Inline Image Protocol
Protocol for displaying images inline in terminal output using base64-encoded data in OSC 1337 sequences. Adopted by several terminals beyond iTerm2 including WezTerm and mintty. → Learn more
J
job control — Job Control
Shell feature for managing foreground/background processes. Ctrl+Z suspends (SIGTSTP), fg resumes in foreground, bg resumes in background. Relies on the kernel's process group and TTY subsystem. → Learn more
K
Kitty — Kitty Terminal Emulator
GPU-accelerated terminal by Kovid Goyal. Pioneer of the Kitty keyboard and graphics protocols. → Learn more
Kitty graphics protocol — Kitty Graphics Protocol
Inline image display via chunked base64 transfer. More capable than Sixel but less widely supported. → Learn more
Kitty keyboard protocol — Kitty Keyboard Protocol
Unambiguous key reporting with modifiers and release events. Solves Ctrl+I/Tab ambiguity. Adopted by Ghostty, WezTerm, foot. → Learn more
L
LF — Line Feed
ASCII character 0x0A. Moves the cursor down one line. In terminals, the line discipline typically translates LF to CR+LF on output (the onlcr setting). Unix convention uses LF alone as the line ending. → Learn more
ligature — Ligature
Two or more characters rendered as a single combined glyph. Programming ligatures (-> becomes an arrow, != becomes not-equal) are popular in coding fonts like Fira Code and JetBrains Mono. Not all terminals support ligature rendering.
line discipline — TTY Line Discipline
A kernel-level module that sits between the PTY and the application. Handles echo, line editing, signal generation (Ctrl+C → SIGINT), and newline translation. Controlled via stty. → Learn more
M
Mode 1049 — Alternate Screen with Cursor Save
Switch to alternate screen buffer and save/restore cursor position. → Learn more
Mode 2004 — Bracketed Paste Mode
Terminal wraps pasted text in markers so the shell knows it is pasted, not typed. → Learn more
Mode 2026 — Synchronized Output
Buffer all output between start/end markers and paint as one frame. Eliminates flicker. → Learn more
Modern TUI baseline — Modern TUI Baseline
Expected by modern TUI frameworks → Learn more
modifyOtherKeys — Xterm Modify Other Keys
An xterm mode that reports modifier keys for non-special characters. Predates the Kitty keyboard protocol. Enabled via CSI > 4 ; 2 m. Less comprehensive than Kitty's protocol but more widely supported in older terminals. → Learn more
monospace — Monospace Font
A font where every character occupies the same horizontal width. Essential for terminal rendering since the character grid assumes uniform cell widths. Wide (CJK/emoji) characters occupy exactly two cells.
mouse tracking — Mouse Tracking
Terminal reports mouse clicks, movement, and scroll wheel events to the application. → Learn more
N
ncurses — New Curses
Free reimplementation of the Unix curses TUI library, maintained by Thomas Dickey since 1996. The most widely used TUI library on Unix systems. Uses terminfo for terminal capability lookup. → Learn more
O
OSC — Operating System Command
Escape sequences for application-to-terminal communication: window title, clipboard, hyperlinks. → Learn more
OSC 0 — Window Icon and Title
Set the terminal window title and icon name. → Learn more
OSC 10 — Foreground Color Query
Query the terminal default foreground color. Response is an X11 color string. → Learn more
OSC 11 — Background Color Query
Query the terminal default background color. Used for light/dark mode detection. → Learn more
OSC 133 — Semantic Prompt Markers
Invisible markers for shell prompt, command, and output boundaries. Enables click-to-navigate between commands. → Learn more
OSC 1337 — iTerm2 Protocol
iTerm2 proprietary extensions including inline images, shell integration, and capability reporting. → Learn more
OSC 2 — Window Title
Set the terminal window title. → Learn more
OSC 4 — Color Palette
Query or set entries in the terminal 256-color palette. → Learn more
OSC 52 — Operating System Command 52
Escape sequence for reading/writing the system clipboard. Allows terminal applications to access the clipboard over SSH without X11 forwarding. Some terminals disable read access for security. → Learn more
OSC 633 — VS Code Shell Integration
VS Code extension of OSC 133 with additional markers for command detection and shell state. → Learn more
OSC 7 — Current Working Directory
Report the shell current directory to the terminal. Used for tab titles and new-tab-in-same-directory. → Learn more
OSC 8 — Operating System Command 8
Escape sequence for clickable hyperlinks in terminal output. Text between OSC 8 start and end markers becomes a link. Supported by most modern terminals. → Learn more
P
POSIX — Portable Operating System Interface
IEEE standard defining the Unix API, including terminal I/O (termios), job control, and process groups. The termios API (tcgetattr/tcsetattr) is how programs configure raw mode, echo, and signal handling. → Learn more
primary DA — Primary Device Attributes (DA1)
The most fundamental terminal query — CSI c. The terminal responds with capability flags indicating what features it supports. Also used for terminal detection since different terminals report different values. → Learn more
process group — Process Group
A set of processes that receive signals together. The foreground process group gets keyboard signals (SIGINT, SIGTSTP). Background groups are stopped if they try to read from the terminal. → Learn more
PTY — Pseudo-Terminal
A virtual terminal device that allows a process to interact with a terminal emulator as if it were a real serial terminal. → Learn more
R
raw mode — Raw Terminal Mode
A TTY line discipline setting where every byte is delivered to the application immediately — no echo, no line editing, no signal generation. What TUI apps use. Opposite of canonical mode. → Learn more
REP — Repeat Preceding Character
CSI Pn b — repeat the last printed character N times. A bandwidth optimization that avoids sending the same character repeatedly. Supported by most modern terminals. → Learn more
reverse index — Reverse Index (RI)
Move the cursor up one line. If already at the top of the scroll region, scroll the content down instead. The opposite of a newline. → Learn more
RGB — Red, Green, Blue
Color model using three values (0-255 each) to specify any of 16.7 million colors. Used by truecolor escape sequences. → Learn more
Rich TUI baseline — Rich TUI Baseline
Advanced features for cutting-edge TUIs → Learn more
RIS — Reset to Initial State
Full terminal reset — cursor, modes, scroll regions, character sets, colors all reset. → Learn more
RM — Reset Mode
CSI Pm l — disable an ECMA-48 standard mode. The counterpart to SM. Distinct from DECRST (CSI ? Pm l) for DEC private modes. → Learn more
S
scroll region — Scroll Region (DECSTBM)
Define a range of lines that scroll independently. Used by TUIs for status bars, headers. → Learn more
scrollback — Scrollback Buffer
The history of text that has scrolled off the top of the terminal screen. You scroll up to see it. Size varies by terminal (typically 1,000–100,000 lines). → Learn more
SD — Scroll Down
Scroll the display down N lines. New blank lines appear at the top. → Learn more
semantic prompts — Semantic Prompt Markers (OSC 133)
Invisible markers that tell the terminal where each shell prompt, command, and output starts and ends. Enables click-to-navigate between commands and red/green indicators for success/failure. → Learn more
SGR — Select Graphic Rendition
Escape sequences for text styling: bold, italic, underline, colors, etc. → Learn more
SGR 38 — Set Foreground Color
Extended foreground color: SGR 38;5;N for 256-color, SGR 38;2;R;G;B for truecolor. → Learn more
SGR 48 — Set Background Color
Extended background color: SGR 48;5;N for 256-color, SGR 48;2;R;G;B for truecolor. → Learn more
SGR mouse — SGR Mouse Tracking (Mode 1006)
Extended mouse reporting format using CSI < sequences with semicolon-delimited parameters. Supports coordinates beyond column 223 (the limit of X10 encoding). The modern standard for mouse tracking in terminals. → Learn more
shell — Shell
The command interpreter (bash, zsh, fish) that runs inside a terminal emulator. The shell handles commands; the terminal handles display. → Learn more
Sixel — Six-Pixel Graphics
A raster image format from DEC (1983) that encodes images as printable ASCII characters, each representing a 1×6 pixel column. Revived in modern terminals for inline image display. Uses DCS sequences. → Learn more
SM — Set Mode
CSI Pm h — enable an ECMA-48 standard mode (insert mode, auto-wrap). Distinct from DECSET (CSI ? Pm h) which controls DEC private modes. → Learn more
soft reset — Soft Terminal Reset (DECSTR)
CSI ! p — partial terminal reset. Resets modes, character sets, and cursor state without clearing the screen or scrollback. Less disruptive than RIS (full reset). → Learn more
SPA — Start of Protected Area
ECMA-48 sequence marking the beginning of a protected area that cannot be erased by selective erase operations. Rarely used in modern terminals. → Learn more
ST — String Terminator
The ESC \ sequence that ends OSC, DCS, and other string-type escape sequences. BEL (0x07) is accepted as an alternative terminator by most terminals. → Learn more
stty — Set Terminal Type
Unix command to configure the TTY line discipline: echo, canonical mode, signal characters (Ctrl+C, Ctrl+Z), baud rate, and newline translation. TUI apps use stty (or tcsetattr) to enter raw mode. → Learn more
SU — Scroll Up
Scroll the display up N lines. New blank lines appear at the bottom. → Learn more
synchronized output — Synchronized Output (Mode 2026)
Buffer all output between start/end markers and paint as one frame. Eliminates flicker. → Learn more
T
TAB — Horizontal Tab
ASCII character 0x09. Advances the cursor to the next tab stop (default every 8 columns). Tab stops can be set and cleared with the HTS and TBC sequences. → Learn more
TBC — Tab Clear
Clear tab stops. TBC 0 clears the stop at the current column; TBC 3 clears all tab stops. → Learn more
TEA — The Elm Architecture
A functional UI pattern: Model → Update → View. Used by Bubbletea (Go) and Silvery's optional app framework. → Learn more
termcap — Terminal Capability Database
The predecessor to terminfo, created by Bill Joy in 1978 for vi. Text-based format with 2-character capability codes. Largely replaced by terminfo but still referenced in documentation. → Learn more
terminal emulator — Terminal Emulator
A program that simulates a hardware terminal. Ghostty, iTerm2, and Windows Terminal are terminal emulators — they display text and interpret escape sequences. → Learn more
terminal multiplexer — Terminal Multiplexer
Software that lets you run multiple terminal sessions inside one connection, with session persistence across disconnects. tmux and GNU Screen are terminal multiplexers. They must parse and re-emit escape sequences, which can cause feature loss. → Learn more
terminfo — Terminal Information Database
A compiled database mapping terminal names to their capabilities (colors, cursor control, key sequences). Used by ncurses and most Unix TUI libraries. Limited to capabilities known at compile time — cannot describe modern features like Kitty keyboard or OSC 8. → Learn more
text reflow — Text Reflow
When you resize the terminal window, wrapped lines re-wrap to fit the new width instead of staying broken. Not all terminals support this. → Learn more
tmux — Terminal Multiplexer
The most widely used terminal multiplexer — session persistence, window management, and pane splitting. → Learn more
tofu — Tofu (Missing Glyph)
The small rectangle displayed when a font lacks a glyph for a character. Named for its resemblance to a block of tofu. Common with emoji and rare scripts when font fallback fails.
truecolor — 24-bit RGB Color
Specify any of 16.7 million colors using red/green/blue values (0-255 each). Before truecolor, terminals were limited to 256 indexed colors. → Learn more
TTY — Teletypewriter
Originally a physical printing terminal. Now refers to the kernel subsystem that manages terminal I/O — the TTY driver, line discipline, and pseudo-terminal (PTY) devices. → Learn more
TUI — Text User Interface
A graphical user interface rendered in a terminal using text characters and escape sequences. → Learn more
U
UCS-2 — Universal Character Set — 2-byte
Fixed 2-byte encoding covering the Basic Multilingual Plane (U+0000-U+FFFF). Predecessor to UTF-16. Cannot represent emoji or supplementary characters. → Learn more
Unicode — Unicode Standard
Universal character encoding standard covering over 149,000 characters from all modern writing systems plus emoji, symbols, and historic scripts. Terminal correctness requires handling width (wcwidth), grapheme clusters, and combining characters. → Learn more
Unicode baseline — Unicode Baseline
Unicode correctness — wide chars, combining, emoji → Learn more
UTF-16 — Unicode Transformation Format — 16-bit
Variable-length encoding using 2 or 4 bytes per code point. Used internally by JavaScript and Windows. Not used in terminal I/O — terminals use UTF-8 exclusively. → Learn more
UTF-32 — Unicode Transformation Format — 32-bit
Fixed-width encoding using 4 bytes per code point. Simple indexing but wasteful. Used internally by some text processing libraries but never for terminal wire format. → Learn more
UTF-8 — Unicode Transformation Format — 8-bit
Variable-length encoding (1-4 bytes) that maps every Unicode code point to a byte sequence. Backward-compatible with ASCII. The universal encoding for modern terminals, designed by Rob Pike and Ken Thompson in 1992. → Learn more
V
VPA — Vertical Line Position Absolute
CSI Pn d — move cursor to row N on the current column. The vertical counterpart to CHA (horizontal absolute). → Learn more
VS16 — Variation Selector 16
A Unicode character (U+FE0F) that forces emoji presentation of the preceding character. Without VS16, some characters display as text (1 column); with VS16, they display as emoji (2 columns). Terminal width calculation must account for this. → Learn more
VT100 — Video Terminal 100
DEC's 1978 terminal that defined the escape sequence grammar used by every modern terminal emulator. → Learn more
vt100.js — vt100.js Terminal Emulator
Lightweight pure TypeScript VT100/VT220 terminal emulator with zero dependencies. → Learn more
VT220 — Video Terminal 220
DEC's 1983 terminal that added insert/delete operations (ICH, DCH, IL, DL) and 8-bit controls. → Learn more
VT510 — Video Terminal 510
One of DEC's later VT terminals (1993). Added cursor visibility (DECTCEM), reverse video (DECSCNM), and scroll commands (SU/SD). → Learn more
VT52 — Video Terminal 52
DEC's 1975 pre-ANSI terminal with proprietary escape sequences predating ECMA-48. First DEC video terminal with cursor addressing. → Learn more
vterm.js — vterm.js Terminal Emulator
Full-featured TypeScript terminal emulator targeting 100% of the terminfo.dev feature matrix. → Learn more
W
wcwidth — Wide Character Width
A C function that returns the display width (1 or 2 columns) of a Unicode character. Based on Unicode's East Asian Width property (UAX #11). Predates emoji and doesn't handle grapheme clusters, variation selectors, or ZWJ sequences. → Learn more
WezTerm — WezTerm Terminal Emulator
Rust terminal emulator and multiplexer by Wez Furlong with Lua configuration and SSH domain support. → Learn more
wide character — Wide Character (Fullwidth)
A character that occupies two terminal columns instead of one. CJK ideographs (Chinese, Japanese, Korean) and many emoji are wide characters. → Learn more
X
xterm — X Terminal Emulator
The reference X11 terminal emulator (1984), maintained by Thomas Dickey since 1996. Defined most 'standard' terminal behavior including 256-color, truecolor, mouse tracking, and bracketed paste. → Learn more
xterm.js — xterm.js Terminal Emulator
The most widely deployed terminal emulator — powers VS Code, Cursor, and countless web terminals. → Learn more
XTGETTCAP — Xterm Get Terminal Capability
Query the terminal for a specific terminfo capability value via DCS. → Learn more
XTVERSION — Xterm Version Query
Query the terminal for its name and version string. Sent as CSI > 0 q (or DCS in some terminals). Response format varies by terminal. Useful for terminal detection. → Learn more
XTWINOPS — Xterm Window Operations
CSI t sequences for window manipulation — resize, move, minimize, report size in pixels or characters. Some operations are disabled by default for security. → Learn more
Z
ZWJ — Zero-Width Joiner
A Unicode character (U+200D) that joins adjacent characters into a single grapheme cluster. Used in emoji sequences: 👨👩👧 is three emoji joined by two ZWJs. Terminals must handle these for correct cursor positioning. → Learn more