At sign (symbol)

Throw according to the Arial type.

The at symbol, which is represented by the character @, is a fundamental component of email addresses, where it appears as a sign or separation mark between the username and domain name, using the format user@provider.

It is also used in various computer applications, with different functions, such as, for example, to denote a user account (@username) on Twitter, Telegram, Instagram, etc. It is also used as the quintessential Internet symbol, even as a pictogram on signage, to indicate the location of a cybercafé or a place with Internet access. Within the ASCII code, it is represented by the number 64.

The term "arroba" comes from the Arabic الربع (ar-rubʿ), which means 'a quarter' and was used in Spain to represent the unit of mass also called arroba. English reads at [æt] («a», «next to» or "in"), hence its use in computing.

History

Origin

La Taula de Ariza, possibly the oldest document where the @ symbol appears.

Its origin is not completely clear, but it is probably a ligature, first calligraphic and then typographic, which represented in the Anglo-Saxon paleographic tradition the Latin preposition ad or, according to other sources, the conjunction at; In the various varieties of Castilian Gothic cursive writing, and especially in the so-called procedural writing, it represents the digraph an.

There are different theories about the early uses of the at symbol. The newspaper The Guardian published in 2000 that the professor of history of science at La Sapienza University, Giorgio Stabile, would have found proof of the first written example of the use of this symbol and that it would represent « an amphora" (old measure of capacity). In the Mediterranean area, clay vessels were used in the XVI century for the transport and trade of all kinds of food, solids (grains, cereals,) and liquids (wine, for example). The found letter is signed by Francesco Lapiun, an Italian merchant, who sent it in 1536, from Seville to Rome. In his letter, an important historical document that describes the loading of three ships that have arrived with merchandise from America, Lapiun uses the arroba symbol to refer to "amphora"; and explain their equivalence thus:

...where a wine @, which is 1/13 of a barrel, is worth 70 or 80 ducats.

The discovery would have been made as part of research for an encyclopedic entry.

Other historians mark the beginning of the use of the at symbol in earlier times. For example, the Spanish journalist and specialist in medieval history Jorge Romance has found it in the Taula de Ariza (from 1448), in a wheat entry into the Kingdom of Aragon from Castile, which would prove its use as early as the middle of the XV century. As the author indicates, because the medieval primary sources are very fragmentary, it is very difficult to relate them adequately for his interpretation. Therefore, from his discovery it should not be concluded that it is the "first appearance" of the at symbol, but simply the earliest appearance among those that have been documented to date.

In any case, the use of the sign from the XV or XVI in different places: in Italy (Florence), in Spain (Castilla, Seville, Aragon and Catalonia), as well as in France.

As a unit of measurement in Spain, without stating the beginning of the use of the symbol, it is also clear that one arroba was equivalent to a quarter of a quintal, that is:

• 30 pounds (11,502 kg) in Castile.
• 32 pounds (10.4 kg) in Catalonia.
• 36 pounds (12.5 kg) in Aragon.

Probably^{[citation needed]} for these reasons it was considered very useful to include the symbol early on the keyboards of typewriters that at the end of the century XIX were widely distributed in the most developed parts of the world. At the time of the commercialization of the first machines, in English it was already used as a replacement for the preposition at in constructions such as "100 psi @ 2000 rpm" ('one hundred pounds per square inch « a» 2000 revolutions per minute') and, mainly, also in accounting documents with the meaning of «at the rate of» (at the rate of).

Development and use

Mathematics and Engineering

For much of the early to mid-century XX, it was a symbol used in textbooks to represent the area, especially in math and engineering books.

In the scientific and technical literature, especially in English, "@" It is used to describe the conditions under which data is valid or a measurement has been made. For example: the density of salt water might read d= 1.050 g/cm³ @ 15 °C (read "a" for "@"), the density of a gas d= 0.150 g/L @ 20 °C, 1 bar, or the noise of a car of 81 dB @ 80 km/h (speed).

Computer Science

Cartel de la calle "Arroba", in the Technological Science Park of the University of Alcalá.

Currently the best known usage is for email addresses and other online services that use the username@domain format. This relationship also derives from the fact that, in English, the symbol @ is read at («a», «next to» or «in») and therefore indicates that the user is hosted "on" the server, instead of being a local message.

In 1971, Ray Tomlinson, the American computer programmer who implemented the first email system, was looking for a symbol to separate a person's name from where they were. Due to its commercial use, some of the first typewriters, developed after 1885, already included this sign (this is the case of the Underwood, 1885 or the Lambert, 1902, both made in the United States). The at sign was also on the keyboard of the ASR-33 teletype (Teletype Corporation Model-33). His idea was to use a symbol that was on all keyboards but that did not appear in the proper names of people or companies or servers. The @ was on the keyboards but it was useless, so it didn't conflict with anything previously stated. Tomlinson sent the first email message to himself, as a test, from his PDP-10 computer to another machine that was physically immediately next to his. He used the at symbol, because it was the way he devised to differentiate local messages from remote ones. Thus, between the identification of the user (sender or recipient) and the server host, a sign was needed to separate them. Tomlinson also chose at because it was already used in English with the meaning of at, but rather with the meaning of a or por (as in the case of prices: "10 units @ $1.95".

This was the first e-mail addresses in history as we know them now:

tomlinson@bbn-tenexa

The @ symbol is also used in many programming languages, albeit with various functions:

• In ALGOL 68 the @ symbol is an abbreviated form of the keyword at, whose function is to change the lower limit of a matrix. For example, arrayx[@88] refers to a matrix beginning in index 88.
• In ActionScript it is used in XML analysis as a text string prefix to identify attributes in contrast to child elements.
• In C# it points out "literal chains" in which no escape characters were used and in which two rowed double quotes represent a double quote. As a prefix it also allows keywords to be used as identifiers.
• In Forth is a word that returns the contents of the memory address found at the top of the data stack.

Other uses in computing have been:

• Indicate the position of the screen in which you will write (in some dialects of BASIC, PRINT @line,columnin Clipper, @line,column SAY).
• In Lotus 1-2-3, the rice was the prefix of mathematical functions (e.g., "@MOD" was the equivalent of the "MOD" of Excel).
• In DOS and in the Windows command console, prefixed instructions with an arroba (typically, "@ECHO OFF") are not displayed on screen).
• In bash, the character @ is treated as a wild symbol that expands in a special way.
• On Twitter and other social networks, rice is the prefix (rather than suffix) of a user's name.

Construction and technical drawing

Also used in construction and some well-known drafting and design systems, such as AutoCAD, where it denotes relative coordinates (Cartesian or polar).

Indication of both genders

In recent years, due to the rise in the use of gender language, the custom —unnecessary, according to the Royal Spanish Academy— of making explicit allusions to both sexes when using animated nouns or adjectives is spreading:

The students and students of this class won the beauty contest.

With the aim of saving said use of language, the use of the at sign (@) has begun to spread as a graphic resource to integrate the masculine and feminine forms of the noun in a single word, since this sign would include in his stroke the vowels a and o:

L@s alumn@s of this class won the beauty contest.

The use of the at sign to integrate the masculine and feminine forms of the noun in a single word is very frequent in the publications of organizations committed to equal rights between men and women (left-wing political parties, associative movements, youth press) and has even been used in some institutional campaigns. Its extension by political parties is also implied by wanting to take on an air of modernity and progressivism. Likewise, the letter x has begun to be used instead of the @, since it is considered that human sexuality does not only include the masculine and feminine options, but a great variety of options (see, for example, the articles transsexuality and transgender).

The Royal Spanish Academy does not admit any of these options for various reasons:

• In the nouns that designate animated beings, the grammatical male is not only used to refer to male individuals, but also to designate all individuals of the species, without distinction of sex. Such use of the male grammar does not denote any discriminatory intention, but the application of the language law of the expressive economy.

• The use of both genders is only required when the gender opposition is a relevant factor in the context:

The proportion of students in universities has been invested in recent years.

Pan-Hispanic dictionary of doubts

• Forced and unnatural expressions such as 'the citizens' are also not admitted.
• Likewise, the use of "@" (such as "x") prevents correct reading in screen readers for people with visual impairments.
• It is impossible to read since the rice has no pronunciation beyond its name.

How to type the @ symbol on the keyboard

On a computer keyboard the symbol is not fully accessible, mainly because when keyboards were designed, this symbol was very unusual (unlike today, which is an extremely common symbol).

The way to get the symbol depends on the language settings and the operating system.

Windows

Ubuntu 12.04/14.04

Mac