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48-436: ANSI escape sequences are a standard for in-band signaling to control cursor location, color, font styling, and other options on video text terminals and terminal emulators . Certain sequences of bytes , most starting with an ASCII escape character and a bracket character, are embedded into text. The terminal interprets these sequences as commands, rather than text to display verbatim. ANSI sequences were introduced in

96-446: A guard tone may be employed to prevent this. In voice over IP (VoIP), DTMF signals are transmitted in-band by two methods. When transmitted as audio tones in the voice stream, voice encoding must use a lossless coder, such as μ-law or A-law pulse-code modulation , to preserve the integrity of frequency signals. Still, this method proved often unreliable and was subject to interference from other audio sources. The standard method

144-513: A modem . In-band signaling is insecure because it exposes control signals, protocols and management systems to end users , which may result in falsing . In the 1960s and 1970s, so-called phone phreaks used blue boxes for deliberate falsing, in which the appropriate tones for routing were intentionally generated, enabling the caller to abuse functions intended for testing and administrative use and to make free long-distance calls. Modems may also interfere with in-band signaling, in which case

192-403: A land-line telephone , the telephone number is encoded and transmitted across the telephone line in form of dual-tone multi-frequency signaling (DTMF). The tones control the telephone system by instructing the telephone switch where to route the call. These control tones are sent over the same channel , the copper wire, and in the frequency range (300 Hz to 3.4 kHz) as the audio of

240-410: A runtime change of the palette, and more "proper" xterm OSC 4/10/11 sequences already exist. 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). For example, Xterm allows the window title to be set by ESC ]0;this

288-547: A similar but incompatible 88-color encoding using the same escape sequence, seen in rxvt and xterm-88color . Not much is known about the scheme besides the color codes. It uses a 4×4×4 color cube. As "true color" graphic cards with 16 to 24 bits of color became common, applications began to support 24-bit colors. Terminal emulators supporting setting 24-bit foreground and background colors with escape sequences include Xterm, KDE's Konsole , and iTerm, as well as all libvte based terminals, including GNOME Terminal . The syntax

336-423: A similar feature, invoked using ~ , DC1 and then the X and Y positions separated with a comma. While the two terminals had identical functionality in this regard, different control sequences had to be used to invoke them. As these sequences were different for different terminals, elaborate libraries such as termcap ("terminal capabilities") and utilities such as tput had to be created so programs could use

384-467: A simpler and more universal detection mechanism compared to querying the now-updated libraries. Some terminal emulators (urxvt, konsole) set $ COLORFGBG to report the color scheme of the terminal (mainly light vs. dark background). This behavior originated in S-Lang and is used by vim. Gnome-terminal refuses to add this behavior, as the syntax for the value is not agreed upon, the value cannot be changed upon

432-433: Is a Japanese Industrial Standard defining C0 and C1 control codes and control sequences . It was first established in 1986, with subsequent editions in 1991 and 1994. It defines C0 and C1 control characters for use with other JIS coded character sets , e.g. JIS X 0201 and JIS X 0208 . It is a derivative of ISO/IEC 6429 (ECMA-48); however, it doesn't feature all control functions presently listed by ISO/IEC 6429. It

480-643: Is adopted as a Japanese Industrial Standard , as JIS X 0211 . Related standards include ITU T.61 , the Teletex standard, and the ISO/IEC 8613 , the Open Document Architecture standard (mainly ISO/IEC 8613-6 or ITU T.416). The two systems share many escape codes with the ANSI system, with extensions that are not necessarily meaningful to computer terminals. Both systems quickly fell into disuse, but ECMA-48 does mark

528-440: Is defined by ANSI X3.41 (equivalent to ECMA-35 or ISO/IEC 2022). 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. If the ESC

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576-443: Is desired, is usually done by escaping the control instructions. Occasionally, however, networks are designed so that data is, to a varying degree, garbled by the signaling. Allowing data to become garbled is usually acceptable when transmitting sounds between humans, since the users rarely notice the slight degradation, but this leads to problems when sending data that has very low error tolerance, such as information transmitted using

624-408: 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. Accordingly, all escape sequences corresponding to C1 control codes from ANSI X3.64 / ECMA-48 follow this format. The standard says that, in 8-bit environments, the control functions corresponding to type Fe escape sequences (those from

672-535: Is in the range 0x30—0x3F indicating private use (e.g. "type 2Fp ") or not (e.g. "type 2Ft "). 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. No such sequences are presently registered. Type 3Fp sequences (which includes ones starting with '#') are available for private-use control functions. CSI 2 J — This clears

720-558: Is initially found in Konsole. Rather than using the color support in termcap and terminfo introduced in SVr3.2 (1987), the S-Lang library (version 0.99-32, June 1996) used a separate environment variable $ COLORTERM to indicate whether a terminal emulator could use colors at all, and later added values to indicate if it supported 24-bit color. This system, although poorly documented, became widespread enough for Fedora and RHEL to consider using it as

768-444: Is likely based on the ITU 's T.416 Open Document Architecture (ODA) and interchange format: Character content architectures, which was adopted as ISO/IEC 8613-6 but ended up as a commercial failure. The ODA version is more elaborate and thus incompatible: The ITU-RGB variation is supported by xterm, with the colorspace ID and tolerance parameters ignored. The simpler scheme using semicolons

816-399: Is the window title BEL . A non-xterm extension is the hyperlink, ESC ]8;;link ST from 2017, used by VTE, iTerm2, and mintty, among others. 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. However, appending ST will be ignored by Linux and form a proper, ignorable sequence for other terminals. If

864-564: Is to digitally remove DTMF tones from the audio at the source and from the Real-time Transport Protocol (RTP) voice stream and encode them separately as a digital information payload, often termed named telephone events (NTE), according to RFC 4733. Such DTMF frames are transmit in-band with all other RTP packets on the identical network path. In contrast to in-band transmission of DTMF, VoIP signaling protocols also implement out-of-band method of DTMF transmission. For example,

912-444: 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

960-468: 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. A table of these is listed under ISO/IEC 2022 . 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. If

1008-567: The Session Initiation Protocol (SIP), as well as the Media Gateway Control Protocol (MGCP) define special message types for the transmission of digits. As a method of in-band signaling, DTMF tones were also used by cable television broadcasters to indicate the start and stop times of local insertion points during station breaks for the benefit of cable companies. Until better, out-of-band signaling equipment

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1056-491: The 1970s to replace vendor-specific sequences and became widespread in the computer equipment market by the early 1980s. Although hardware text terminals have become increasingly rare in the 21st century, the relevance of the ANSI standard persists because a great majority of terminal emulators and command consoles interpret at least a portion of the ANSI standard. Almost all manufacturers of video terminals added vendor-specific escape sequences to perform operations such as placing

1104-573: The CSI sequence, to abort it immediately, or to ignore the rest of it. 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. Each display attribute remains in effect until a following occurrence of SGR resets it. If no codes are given, CSI m is treated as CSI 0 m (reset / normal). The original specification only had 8 colors, and just gave them names. The SGR parameters 30–37 selected

1152-623: The Python colorama package or Cygwin modified text in-process as it was sent to the console, extracting the ANSI Escape sequences and emulating them with Windows calls. In 2016, Microsoft released the Windows 10 version 1511 update which unexpectedly implemented support for ANSI escape sequences, over three decades after the debut of Windows. This was done alongside Windows Subsystem for Linux , apparently to allow Unix-like terminal-based software to use

1200-487: The Windows Console. Windows PowerShell 5.1 enabled this by default, and PowerShell 6 made it possible to embed the necessary ESC character into a string with `e . Windows Terminal , introduced in 2019, supports the sequences by default, and Microsoft intends to replace the Windows Console with Windows Terminal. Almost all users assume some functions of some single-byte characters. Initially defined as part of ASCII,

1248-563: The ability to directly specify the "bright" colors with 90–97 and 100–107. The chart below shows a few examples of how VGA standard and modern terminal emulators translate the 4-bit color codes into 24-bit color codes. As 256-color lookup tables became common on graphic cards, escape sequences were added to select from a pre-defined set of 256 colors: The ITU 's T.416 Information technology - Open Document Architecture (ODA) and interchange format: Character content architectures uses ":" as separator characters instead: There has also been

1296-583: The cable industry was discontinued because it was distracting to viewers, and was susceptible to interference when DTMF tones were sounded by characters in television shows. For example, a character dialing a Touch-Tone telephone in a television show could cause the cable company computers to switch away from a "hot feed" to dead air , and the cost of human-imperceptible signaling technologies decreased. In-band signaling applies only to channel-associated signaling (CAS). In common channel signaling (CCS) separate channels are used for control and data, as opposed to

1344-463: 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. 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

1392-497: The cursor at arbitrary positions on the screen. One example is the VT52 terminal, which allowed the cursor to be placed at an x,y location on the screen by sending the ESC character, a Y character, and then two characters representing numerical values equal to the x,y location plus 32 (thus starting at the ASCII space character and avoiding the control characters). The Hazeltine 1500 had

1440-609: 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

1488-499: The escape sequences worked, leading to almost all new terminals and emulator programs supporting them. In 1981, ANSI X3.64 was adopted for use in the US government by FIPS publication 86. Later, the US government stopped duplicating industry standards, so FIPS pub. 86 was withdrawn. ECMA-48 has been updated several times and is currently at its 5th edition, from 1991. It is also adopted by ISO and IEC as standard ISO/IEC 6429 . A version

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1536-714: The extensions used in them as reserved. In the early 1980s, large amounts of software directly used these sequences to update screen displays. This included everything on VMS (which assumed DEC terminals), most software designed to be portable on CP/M home computers, and even lots of Unix software as it was easier to use than the termcap libraries, such as the shell script examples below in this article. Terminal emulators for communicating with remote machines almost always implement ANSI escape codes. This includes anything written to communicate with bulletin-board systems on home and personal computers. On Unix terminal emulators such as xterm also can communicate with software running on

1584-406: The fact that it was not installed by default, meant software rarely (if ever) took advantage of it. The Windows Console did not support ANSI escape sequences, nor did Microsoft provide any method to enable them. Some replacements such as JP Software's TCC (formerly 4NT), Michael J. Mefford's ANSI.COM, Jason Hood's ANSICON and Maximus5's ConEmu enabled ANSI escape sequences. Software such as

1632-487: The feeds should be switched to and away from the master control feed, to locally-broadcast commercials. The following is an example of such a sequence by a cable company that communicated the following to the cable company's broadcast equipment: SWITCH TO LOCAL NOW - SWITCH TO LOCAL NOW - PREPARE TO SWITCH BACK - PREPARE TO SWITCH BACK - SWITCH BACK TO NATIONAL NOW - SWITCH BACK TO NATIONAL NOW - "IF YOU HAVEN'T SWITCHED BACK TO NATIONAL NOW, DO SO IMMEDIATELY" DTMF signaling in

1680-417: 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

1728-613: The foreground color, while 40–47 selected the background. Quite a few terminals implemented "bold" (SGR code 1) as a brighter color rather than a different font, thus providing 8 additional foreground colors. Usually you could not get these as background colors, though sometimes inverse video (SGR code 7) would allow that. Examples: to get black letters on white background use ESC[30;47m , to get red use ESC[31m , to get bright red use ESC[1;31m . To reset colors to their defaults, use ESC[39;49m (not supported on some terminals), or reset all attributes with ESC[0m . Later terminals added

1776-756: The international standard. The first popular video terminal to support these sequences was the Digital VT100 , introduced in 1978. This model was very successful in the market, which sparked a variety of VT100 clones, among the earliest and most popular of which was the much more affordable Zenith Z-19 in 1979. Others included the Qume QVT-108, Televideo TVI-970, Wyse WY-99GT as well as optional "VT100" or "VT103" or "ANSI" modes with varying degrees of compatibility on many other brands. The popularity of these gradually led to more and more software (especially bulletin board systems and other online services ) assuming

1824-447: 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. 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

1872-424: 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{|}~ ). 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

1920-524: The same API to work with any terminal. In addition, many of these terminals required sending numbers (such as row and column) as the binary values of the characters; for some programming languages, and for systems that did not use ASCII internally, it was often difficult to turn a number into the correct character. The ANSI standard attempted to address these problems by making a command set that all terminals would use and requiring all numeric information to be transmitted as ASCII numbers. The first standard in

1968-563: The same machine, and thus software running in X11 under a terminal emulator could assume the ability to write these sequences. As computers got more powerful even built-in displays started supporting them, allowing software to be portable between CP/M systems. There were attempts to extend the escape sequences to support printers and as an early PDF-like document storage format, the Open Document Architecture . The IBM PC, introduced in 1983, did not support these or any other escape sequences for updating

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2016-472: 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. In-band signaling When dialing from

2064-568: The screen. Only a few control characters ( BEL , CR , LF , BS ) were interpreted by the underlying BIOS. 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 version 2.0 included an optional device driver named ANSI.SYS . Poor performance, and

2112-551: The series was ECMA-48, adopted in 1976. It was a continuation of a series of character coding standards, the first one being ECMA-6 from 1965, a 7-bit standard from which ISO 646 originates. The name "ANSI escape sequence" dates from 1979 when ANSI adopted ANSI X3.64. The ANSI X3L2 committee collaborated with the ECMA committee TC 1 to produce nearly identical standards. These two standards were merged into an international standard, ISO 6429. In 1994, ANSI withdrew its standard in favor of

2160-452: The set of C1 control codes ) can be represented as single bytes in the 0x80–0x9F range. 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

2208-558: The shared channel in CAS, so all control is out-of-band by definition. In computer data, the term refers to embedding any kind of metadata directly within regular data. These uses have similar tradeoffs as in telecommunications, such as opening an attack surface vs. simplifying processing. A few of many examples: When out-of-band communication is unavailable, one of two techniques may be used to preserve network transparency . JIS X 0211 JIS X 0211 , originally designated JIS C 6323

2256-462: The telephone call. In-band signaling is also used on older telephone carrier systems to provide inter-exchange information for routing calls. Examples of this kind of in-band signaling system are the Signaling System No. 5 (SS5) and its predecessors, and R2 signalling . Separating the control signals, also referred to as the control plane, from the data, if a bit-transparent connection

2304-457: Was developed in the 1990s, fast, unacknowledged, and loud DTMF tone sequences could be heard during the commercial breaks of cable channels in the United States and elsewhere. These DTMF sequences were sent by the originating cable network's equipment at the uplink satellite facility, and were decoded by equipment at local cable companies. A specific tone sequence indicated the exact time that

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