DOS and Windows

A huge blow to the popularity of the sequences was that the IBM PC, introduced in 1983, did not support them for local programs (this was common for "all in one" home computers, but rare for machines of this complexity). Only a few control characters (BEL, CR, LF, BS) were interpreted by the underlying BIOS, making it almost^{[lower-alpha 1]} impossible to do any kind of full-screen application. Any display effects had to be done with BIOS calls, which were notoriously slow, or by directly manipulating the IBM PC hardware. This made any interesting software non-portable and led to the need to duplicate details of the display hardware in PC Clones.

DOS 2.0 introduced the ability to add a device driver for the ANSI escape sequences: ANSI.SYS. Slowness, and the fact that it was not installed by default, made software rarely take advantage of it; instead, applications continued to directly manipulate the hardware to get the text display needed. ANSI.SYS and similar drivers continued to work in Windows 9x up to Windows Me, and in NT-derived systems for 16-bit legacy programs executing under the NTVDM.

Many clones of DOS were able to interpret the sequences and do not require a separate ANSI driver to be loaded. PTS-DOS^[7][8] as well as Concurrent DOS, Multiuser DOS^[9] and REAL/32 have built-in support (plus a number of extensions). OS/2 had an ANSI command that enabled the sequences.

The Windows Console did not support ANSI escape sequences, nor did Microsoft provide any method to enable them. Some replacements or additions for the console window such as JP Software's TCC (formerly 4NT), Michael J. Mefford's ANSI.COM, Jason Hood's ANSICON^[10] and Maximus5's ConEmu interpreted ANSI escape sequences printed by programs. A Python package named colorama^[11] internally interprets ANSI escape sequences in text being printed, translating them to win32 calls to modify the state of the terminal, to make it easier to port Python code using ANSI to Windows. Cygwin performs similar translation to all output written to the console using Cygwin file descriptors, the filtering is done by the output functions of cygwin1.dll, to allow porting of POSIX C code to Windows.

In 2016, Microsoft released the Windows 10 version 1511 update which unexpectedly implemented support for ANSI escape sequences, over two decades after the debut of Windows NT.^[12] This was done alongside Windows Subsystem for Linux, allowing Unix-like terminal-based software to use the sequences in Windows Console. This defaults to off, but Windows PowerShell 5.1 enabled it. PowerShell 6 made it possible to embed the necessary ESC character into a string with `e.^[13]

Windows Terminal, introduced in 2019, supports the sequences by default, and Microsoft intends to replace the Windows Console with Windows Terminal.^[14]

C0 control codes

Almost all users assume some functions of some single-byte characters. Initially defined as part of ASCII, the default C0 control code set is now defined in ISO 6429 (ECMA-48), making it part of the same standard as the C1 set invoked by the ANSI escape sequences (although ISO 2022 allows the ISO 6429 C0 set to be used without the ISO 6429 C1 set, and vice versa, provided that 0x1B is always ESC). This is used to shorten the amount of data transmitted, or to perform some functions that are unavailable from escape sequences:

Escape sequences vary in length. The general format for an ANSI-compliant escape sequence is defined by ANSI X3.41 (equivalent to ECMA-35 or ISO/IEC 2022).^[15]: 13.1 The escape sequences consist only of bytes in the range 0x20—0x7F (all the non-control ASCII characters), and can be parsed without looking ahead. The behavior when a control character, a byte with the high bit set, or a byte that is not part of any valid sequence, is encountered before the end is undefined.

Fe Escape sequences

If the ESC is followed by a byte in the range 0x40 to 0x5F, the escape sequence is of type Fe. Its interpretation is delegated to the applicable C1 control code standard.^{[15]: 13.2.1} Accordingly, all escape sequences corresponding to C1 control codes from ANSI X3.64 / ECMA-48 follow this format.^[5]: 5.3.a

The standard says that, in 8-bit environments, the control functions corresponding to type Fe escape sequences (those from the set of C1 control codes) can be represented as single bytes in the 0x80–0x9F range.^[5]: 5.3.b This is possible in character encodings conforming to the provisions for an 8-bit code made in ISO 2022, such as the ISO 8859 series. However, in character encodings used on modern devices such as UTF-8 or CP-1252, those codes are often used for other purposes, so only the 2-byte sequence is typically used. In the case of UTF-8, representing a C1 control code via the C1 Controls and Latin-1 Supplement block results in a different two-byte code (e.g. 0xC2,0x8E for U+008E), but no space is saved this way.

CSI (Control Sequence Introducer) sequences

For Control Sequence Introducer, or CSI, commands, the ESC [ (written as \e[ or \033[ in several programming languages) is followed by any number (including none) of "parameter bytes" in the range 0x30–0x3F (ASCII 0–9:;<=>?), then by any number of "intermediate bytes" in the range 0x20–0x2F (ASCII space and !"#$%&'()*+,-./), then finally by a single "final byte" in the range 0x40–0x7E (ASCII @A–Z[\]^_`a–z{|}~).^[5]: 5.4

All common sequences just use the parameters as a series of semicolon-separated numbers such as 1;2;3. Missing numbers are treated as 0 (1;;3 acts like the middle number is 0, and no parameters at all in ESC[m acts like a 0 reset code). Some sequences (such as CUU) treat 0 as 1 in order to make missing parameters useful.^[5]: F.4.2

A subset of arrangements was declared "private" so that terminal manufacturers could insert their own sequences without conflicting with the standard. Sequences containing the parameter bytes <=>? or the final bytes 0x70–0x7E (p–z{|}~) are private.

The behavior of the terminal is undefined in the case where a CSI sequence contains any character outside of the range 0x20–0x7E. These illegal characters are either C0 control characters (the range 0–0x1F), DEL (0x7F), or bytes with the high bit set. Possible responses are to ignore the byte, to process it immediately, and furthermore whether to continue with the CSI sequence, to abort it immediately, or to ignore the rest of it.

SGR (Select Graphic Rendition) parameters

The control sequence CSI n m, named Select Graphic Rendition (SGR), sets display attributes. Several attributes can be set in the same sequence, separated by semicolons.^[24] Each display attribute remains in effect until a following occurrence of SGR resets it.^[5] If no codes are given, CSI m is treated as CSI 0 m (reset / normal).

ESC[38;5;⟨n⟩m Select foreground color      where n is a number from the table below
ESC[48;5;⟨n⟩m Select background color
  0-  7:  standard colors (as in ESC [ 30–37 m)
  8- 15:  high intensity colors (as in ESC [ 90–97 m)
 16-231:  6 × 6 × 6 cube (216 colors): 16 + 36 × r + 6 × g + b (0 ≤ r, g, b ≤ 5)
232-255:  grayscale from dark to light in 24 steps

ESC[38:5:⟨n⟩m Select foreground color      where n is a number from the table below
ESC[48:5:⟨n⟩m Select background color

ESC[38;2;⟨r⟩;⟨g⟩;⟨b⟩ m Select RGB foreground color
ESC[48;2;⟨r⟩;⟨g⟩;⟨b⟩ m Select RGB background color

ESC[38:2:⟨Color-Space-ID⟩:⟨r⟩:⟨g⟩:⟨b⟩:⟨unused⟩:⟨CS tolerance⟩:⟨Color-Space associated with tolerance: 0 for "CIELUV"; 1 for "CIELAB"⟩ m Select RGB foreground color
ESC[48:2:⟨Color-Space-ID⟩:⟨r⟩:⟨g⟩:⟨b⟩:⟨unused⟩:⟨CS tolerance⟩:⟨Color-Space associated with tolerance: 0 for "CIELUV"; 1 for "CIELAB"⟩ m Select RGB background color

OSC (Operating System Command) sequences

Most Operating System Command sequences were defined by Xterm, but many are also supported by other terminal emulators. For historical reasons, Xterm can end the command with BEL (0x07) as well as the standard ST (0x9C or 0x1B 0x5C).^[16] For example, Xterm allows the window title to be set by ESC ]0;this is the window title BEL.

A non-xterm extension is the hyperlink, ESC ]8;;link ST from 2017, used by VTE,^[44] iTerm2,^[44] and mintty,^[45] among others.^[46]

The Linux console uses ESC ] P n rr gg bb to change the palette, which, if hard-coded into an application, may hang other terminals.^[47] However, appending ST will be ignored by Linux and form a proper, ignorable sequence for other terminals.

Fs Escape sequences

If the ESC is followed by a byte in the range 0x60—0x7E, the escape sequence is of type Fs. This type is used for control functions individually registered with the ISO-IR registry.^[48] A table of these is listed under ISO/IEC 2022.

Fp Escape sequences

If the ESC is followed by a byte in the range 0x30—0x3F, the escape sequence is of type Fp, which is set apart for up to sixteen private-use control functions.^{[15]: 6.5.3}

nF Escape sequences

If the ESC is followed by a byte in the range 0x20—0x2F, the escape sequence is of type nF. Said byte is followed by any number of additional bytes in this range, and then a byte in the range 0x30-0x7E. These escape sequences are further subcategorised by the low two bits of the first byte, e.g. "type 2F" for sequences where the first byte is 0x22; and by whether the final byte is in the range 0x30—0x3F indicating private use (e.g. "type 2Fp") or not (e.g. "type 2Ft").^{[15]: 13.2.1}

Most of the nFt sequences are for changing the current character set, and are listed in ISO/IEC 2022. Some others:

If the first byte is '#' the public sequences are reserved for additional ISO-IR registered individual control functions.^{[15]: 6.5.2} No such sequences are presently registered.^[48] Type 3Fp sequences (which includes ones starting with '#') are available for private-use control functions.^{[15]: 6.5.3}

Examples

CSI 2 J — This clears the screen and, on some devices, locates the cursor to the y,x position 1,1 (upper left corner).

CSI 32 m — This makes text green. The green may be a dark, dull green, so you may wish to enable Bold with the sequence CSI 1 m which would make it bright green, or combined as CSI 32 ; 1 m. Some implementations use the Bold state to make the character Bright.

CSI 0 ; 6 8 ; "DIR" ; 13 p — This reassigns the key F10 to send to the keyboard buffer the string "DIR" and ENTER, which in the DOS command line would display the contents of the current directory. (MS-DOS ANSI.SYS only) This was sometimes used for ANSI bombs. This is a private-use code (as indicated by the letter p), using a non-standard extension to include a string-valued parameter. Following the letter of the standard would consider the sequence to end at the letter D.

CSI s — This saves the cursor position. Using the sequence CSI u will restore it to the position. Say the current cursor position is 7(y) and 10(x). The sequence CSI s will save those two numbers. Now you can move to a different cursor position, such as 20(y) and 3(x), using the sequence CSI 20 ; 3 H or CSI 20 ; 3 f. Now if you use the sequence CSI u the cursor position will return to 7(y) and 10(x). Some terminals require the DEC sequences ESC 7 / ESC 8 instead which is more widely supported.

ls --color

make 2>&1 | sed -e 's/.*\bWARN.*/\x1b[7m&\x1b[0m/i' -e 's/.*\bERR.*/\x1b[93;41m&\x1b[0m/i'

flasher () { while true; do printf \\e[?5h; sleep 0.1; printf \\e[?5l; read -s -n1 -t1 && break; done; }

printf \\033c

In C

Output of example program on Gnome Terminal

#include <stdio.h>

int main(void)
{
    int i, j, n;

    for (i = 0; i < 11; i++) {
        for (j = 0; j < 10; j++) {
            n = 10 * i + j;
            if (n > 108) break;
            printf("\033[%dm %3d\033[m", n, n);
        }
        printf("\n");
    }
    return 0;
}

Terminal input sequences

Pressing special keys on the keyboard, as well as outputting many xterm CSI, DCS, or OSC sequences, often produces a CSI, DCS, or OSC sequence, sent from the terminal to the computer as though the user typed it.

When typing input on a terminal keypresses outside the normal main alphanumeric keyboard area can be sent to the host as ANSI sequences. For keys that have an equivalent output function, such as the cursor keys, these often mirror the output sequences. However, for most keypresses there isn't an equivalent output sequence to use.

There are several encoding schemes, and unfortunately most terminals mix sequences from different schemes, so host software has to be able to deal with input sequences using any scheme. To complicate the matter, the VT terminals themselves have two schemes of input, normal mode and application mode that can be switched by the application.

(draft section)

<char>                                         -> char
<esc> <nochar>                                 -> esc
<esc> <esc>                                    -> esc
<esc> <char>                                   -> Alt-keypress or keycode sequence
<esc> '[' <nochar>                             -> Alt-[
<esc> '[' (<modifier>) <char>                  -> keycode sequence, <modifier> is a decimal number and defaults to 1 (xterm)
<esc> '[' (<keycode>) (';'<modifier>) '~'      -> keycode sequence, <keycode> and <modifier> are decimal numbers and default to 1 (vt)

If the terminating character is '~', the first number must be present and is a keycode number, the second number is an optional modifier value. If the terminating character is a letter, the letter is the keycode value, and the optional number is the modifier value.

The modifier value defaults to 1, and after subtracting 1 is a bitmap of modifier keys being pressed: Meta+Ctrl+Alt+⇧ Shift. So, for example, <esc>[4;2~ is ⇧ Shift+End, <esc>[20~ is function key F9, <esc>[5C is Ctrl+→.

In other words, the modifier is the sum of the following numbers:

vt sequences:
<esc>[1~    - Home        <esc>[16~   -             <esc>[31~   - F17
<esc>[2~    - Insert      <esc>[17~   - F6          <esc>[32~   - F18
<esc>[3~    - Delete      <esc>[18~   - F7          <esc>[33~   - F19
<esc>[4~    - End         <esc>[19~   - F8          <esc>[34~   - F20
<esc>[5~    - PgUp        <esc>[20~   - F9          <esc>[35~   - 
<esc>[6~    - PgDn        <esc>[21~   - F10         
<esc>[7~    - Home        <esc>[22~   -             
<esc>[8~    - End         <esc>[23~   - F11         
<esc>[9~    -             <esc>[24~   - F12         
<esc>[10~   - F0          <esc>[25~   - F13         
<esc>[11~   - F1          <esc>[26~   - F14         
<esc>[12~   - F2          <esc>[27~   -             
<esc>[13~   - F3          <esc>[28~   - F15         
<esc>[14~   - F4          <esc>[29~   - F16         
<esc>[15~   - F5          <esc>[30~   -

xterm sequences:
<esc>[A     - Up          <esc>[K     -             <esc>[U     -
<esc>[B     - Down        <esc>[L     -             <esc>[V     -
<esc>[C     - Right       <esc>[M     -             <esc>[W     -
<esc>[D     - Left        <esc>[N     -             <esc>[X     -
<esc>[E     -             <esc>[O     -             <esc>[Y     -
<esc>[F     - End         <esc>[1P    - F1          <esc>[Z     -
<esc>[G     - Keypad 5    <esc>[1Q    - F2       
<esc>[H     - Home        <esc>[1R    - F3       
<esc>[I     -             <esc>[1S    - F4       
<esc>[J     -             <esc>[T     - 

<esc>[A to <esc>[D are the same as the ANSI output sequences. The <modifier> is normally omitted if no modifier keys are pressed, but most implementations always emit the <modifier> for F1–F4. (draft section)

Xterm has a comprehensive documentation page on the various function-key and mouse input sequence schemes from DEC's VT terminals and various other terminals it emulates.^[16] Thomas Dickey has added a lot of support to it over time;^[56] he also maintains a list of default keys used by other terminal emulators for comparison.^[57]

• On the Linux console, certain function keys generate sequences of the form CSI [ char. The CSI sequence should terminate on the [.
• Old versions of Terminator generate SS3 1; modifiers char when F1 – F4 are pressed with modifiers. The faulty behavior was copied from GNOME Terminal.
• xterm replies CSI row ; column R if asked for cursor position and CSI 1 ; modifiers R if the F3 key is pressed with modifiers, which collide in the case of row == 1. This can be avoided by using the ? private modifier as CSI ? 6 n, which will be reflected in the response as CSI ? row ; column R.
• many terminals prepend ESC to any character that is typed with the alt key down. This creates ambiguity for uppercase letters and symbols @[\]^_, which would form C1 codes.
• Konsole generates SS3 modifiers char when F1 – F4 are pressed with modifiers.
• iTerm2 supports reporting additional keys via an enhanced CSI u mode.^[58]