Bell character


Bell character

A bell code (sometimes bell character) is a device control code originally sent to ring a small electromechanical bell on tickers and other teleprinters (remote printers) and teletypewriters (such as Teletypes, abbreviated TTYs) to alert operators at the other end of the line, often of an incoming message. Though tickers punched the bell codes into their tapes,[1] printers generally do not print a character when the bell code is received. Bell codes are usually represented by the label "BEL" and have been used since 1870[citation needed] for instance in Baudot code.

To maintain backward compatibility, video display terminals (VDTs) that replaced teletypewriters included speakers or buzzers to perform the same function, as did the personal computers that followed. Modern terminal emulators often integrate the warnings to the desktop environment (for example, the Mac OS X Terminal will play the system warning sound) and also often offer a silent visual bell feature that flashes the terminal window briefly.

Contents

Representations

In ASCII and Unicode the character with the value 7 is BEL. It can be referred to as control-G or ^G in caret notation. Unicode also includes a character for the visual representation of the bell code, "symbol for bell" () at U+2407.

In the 5-bit Baudot codes (created by Émile Baudot in 1870, patented in 1874, modified by Donald Murray in 1901, and standardized by CCITT as International Telegraph Alphabet No. 2 (ITA2) in 1930), BEL is represented by the number 11 (0x0B) when in "figures" mode.

In the C programming language (created in 1972), the bell character can be placed in a string or character constant with \a ('a' stands for "alert" or "audible" and was chosen because \b was already used for backspace).

Usage

On Unix-like systems, MS-DOS or Windows, you can cause the equivalent of ringing the bell to happen by typing at the command prompt the command:

echo ^G

where the ^G is produced by holding down Ctrl and typing G. On Unix you may need to type Ctrl+V first to "quote" the ^G.

A program can get the same result by printing the BEL character to a terminal.

On modern systems this may not make a noise, it may instead make a visual indication such as flashing the screen, or do nothing at all.

See also

References

  1. ^ Baudot. [1]. Accessed Feb. 1, 2009.

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Bell character — Caractère d appel Pour les articles homonymes, voir BEL. En informatique, dans les standards de codage de caractères, le caractère d appel, abrégé BEL (de l anglais bell character), est un caractère qui, lorsqu il est envoyé à une imprimante ou à …   Wikipédia en Français

  • bell character — skambučio simbolis statusas T sritis automatika atitikmenys: angl. bel; bell character vok. Glocke, f; Klingel, f; Zeichen für Klingelzeichen, n rus. символ звонковой сигнализации, m pranc. caractère d appel, m; caractère de sonnerie, m …   Automatikos terminų žodynas

  • bell character — skambučio ženklas statusas T sritis informatika apibrėžtis Valdymo ženklas, skirtas signalizuoti skambučiu arba kitokiu garsu. ASCII kodas 07. atitikmenys: angl. bell character …   Enciklopedinis kompiuterijos žodynas

  • Bell — may refer to: Devices that produce sound * Altar bell, a bell rung during the Catholic Mass. * Bell character, a character that produces an audible signal at a terminal. * Bell effect, a musical technique similar to an arpeggio. * Bell… …   Wikipedia

  • Bell's theorem — is a theorem that shows that the predictions of quantum mechanics (QM) are not intuitive, and touches upon fundamental philosophical issues that relate to modern physics. It is the most famous legacy of the late physicist John S. Bell. Bell s… …   Wikipedia

  • Bell (surname) — Bell is a surname, and may refer to many people.Family name name=BellA* Acton Bell, pseudonym of Anne Brontë * Adrian Bell, British farmer writer, father of Martin Bell * Alexander Graham Bell (1847 1922), inventor * Alexander Melville Bell,… …   Wikipedia

  • Bell Matriculation Higher Secondary School — History Bell Matriculation Higher Secondary School was founded in 1992 by Mr. A.Chelladhurai, an eminent industrialist and entrepreneur in Southern India. The school is run by Indrani Chelladhurai Charities, a trust that was formed by the founder …   Wikipedia

  • Bell v. Lever Brothers Ltd. — Bell v Lever Brothers Ltd. [Case citation| [1931] ALL E.R. Rep. 1, [1932] A.C. 161] is a leading House of Lords decision on common mistake in contract law. Background During March 1929 the N. Company, which dealt in trade in the western African… …   Wikipedia

  • Bell System — ] The Bell System was commonly referred to by the nickname Ma Bell. History Formation under Bell patentReceiving a U.S. patent for the invention of the telephone on March 7, 1876, Alexander Graham Bell formed the Bell Telephone Company in 1877… …   Wikipedia

  • Bell (instrument) — See also: Tubular bell For the part of a wind instrument, see Wind instrument#Parts. Bell Parts of a typical bell: 1. yoke, 2. crown, 3. head, 4. shoulder, 5. waist …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.