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Glossary
Terminal acronyms and technical terms.
A
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
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Published the X3.64 terminal standard in 1979, withdrawn in 1994 in favor of ISO 6429.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
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
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
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
C
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
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
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
CUP — Cursor Position
CSI row ; col H — move cursor to absolute position. The most fundamental cursor command. → 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
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
DECAWM — DEC Auto Wrap Mode
DEC private mode ?7 — automatically wrap text at the right margin. → Learn more
DECRPM — DEC Private Mode Report
Response sequence reporting whether a DEC private mode is set, reset, or unrecognized. → 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
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
DSR — Device Status Report
Query the terminal for status information, most commonly cursor position (DSR 6). → Learn more
E
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
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
G
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
I
ICH — Insert Character
Insert blank characters at cursor position, shifting existing characters right. → Learn more
M
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
mouse tracking — Mouse Tracking
Terminal mode that reports mouse clicks, movement, and scroll wheel events to the application. Enables clickable TUI interfaces. Multiple protocols exist (X10, SGR, urxvt). → 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 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 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
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
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
RIS — Reset to Initial State
Full terminal reset — cursor, modes, scroll regions, character sets, colors all reset. → Learn more
S
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
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
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
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
synchronized output — Synchronized Output (Mode 2026)
Buffers all terminal output between start/end markers and paints it as one frame. Eliminates the visible flicker when clearing and redrawing the screen. → Learn more
T
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
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
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
TUI — Text User Interface
A graphical user interface rendered in a terminal using text characters and escape sequences. → Learn more
V
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
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
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
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
XTGETTCAP — Xterm Get Terminal Capability
Query the terminal for a specific terminfo capability value via DCS. → 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