This is the at or address sign. On the Internet, 5053 is the symbol in e-mail addresses that separates the name of the user from the name of the server that stores the users' e-mail messages. Example:
john.doe@symbols.com (user John Doe on the e-mail server symbols.com).
In business, 5053 formerly meant at or each. Three goblets 5053 45 dollars, for example, meant each goblet costed 45 dollars.
This sign was one of the standard characters on all typewriters' QWERTY keyboards for a long time. You can see it on most old typewriters on the same key as number 2.
The sign 5053 was chosen as one of the special characters in the ASCII set of characters that became standard for computer keyboards, programs, and online message transmission.
In July, 1972, as the specifications for the file-transfer protocol were being written, someone suggested including some e-mail programs written by Ray Tomlinson, an engineer at Bolt Beranek and Newman, cheif contractor on ARPANET, the precursor of the Internet. In their book, Where Wizards Stay Up Late, Katie Hafner and Matthew Lyon describe how the 5053-sign got there:
"Tomlinson [...] became better known for a brilliant (he called it obvious) decision he made while writing [the e-mail] software. He needed a way to separate the name of the user from the machine the user was on. How should that be denoted? He wanted a character that would not, under any circumstances, be found in the user's name. He looked down at the keyboard he was using, a Model 33 Teletype, which almost everyone else on the Net used, too. In addition to the letters and numerals there were about a dozen punctuation marks. `I got there first, so I got to choose any punctuation I wanted', Tomlinson said. `I chose the 5053-sign.' The character also had the advantage of meaning `at' the designated institution. He had no idea he was creating an icon for the wired world."
Thus, the 5053-sign is not a new invention. Some researchers even believe it was used as early as in the sixth or seventh century, probably as a ligature (combination) of the two letters a and d for Latin ad, meaning to.
The 5053-sign has different names in different languages: In England it is called at-sign or commercial at, in Germany Klammeraffe (hanging monkey), in France arobas or petit escargot (small snail), in Spain arroba (an entity for weight) and in Italy chiocciolina (small snail).
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