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Today, you need the @ character in many places, most notably in email addresses, but I suspect that when the syntax for an email address was defined, the sign was already supported in character sets and on keyboards, so it was easy to use for addresses.

Typewriters do not have an @ sign, so when and why was the @ sign added to computers before it became important in various types of user handles on the Internet?

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    Wrong! The @ key was on typewriters in the 1940s.
    – Chenmunka ♦
    Jun 13 at 12:31
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    Fun fact: In Hebrew, it is colloquially known as שְׁטְרוּדֶל (shtrúdel), due to the visual resemblance to a cross-section cut of a strudel cake (wikipedia ref)
    – Jonathan
    Jun 14 at 10:27
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    "Typewriters do not have an @ sign" I'm frankly confused as to why you would have believed this to be the case, or generalize it so bluntly as if it didn't require comment. A bit of searching easily finds me images of typewriters with keys to produce an @ symbol, e.g.. Granted, they don't generally use shift-2.
    – Karl Knechtel
    Jun 14 at 15:12
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    @KarlKnechtel "Granted, they don't generally use shift-2." - Funnily enough, the @'s on those example typewriters are in the exact same place they are on my ISO BrE keyboard.
    – Nick is tired
    Jun 14 at 15:24
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    All the typewriters I've ever used since the early 60s had an @ sign. They didn't all have a 1 or 0 but they had an @ sign.
    – cup
    Jun 14 at 18:15

3 Answers 3

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The @ symbol was present on typewriters a long time before computers were invented, see for example this 1889 Hammond typewriter. In English-writing countries, the symbol was already used in commercial settings for prices: “3 apples @ $1”. Some other languages also used it, with different meanings.

Closer to computers, @ was commonly present in International Telegraph Alphabet 2 implementations (see also Gil Smith’s Teletypewriter Communication Codes), so teleprinter keyboards typically supported it too. The symbol is also part of EBCDIC and ASCII, among many other early character codes, and thus supported on any device supporting one of those. See Coded Character Sets, History and Development for details; @ was included in ASCII-63 as a “commercial usage” symbol, in position 0x40 just before the alphabetic characters because it was intended for replacement by “à” in countries such as France and Italy. It was moved to 0x60 in ASCII-65 and back again in ASCII-67.

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    Yes, as a kid many years ago, using @ was the way we were taught to write prices of groceries and other things. Read as "at", yes. :)
    – paul garrett
    Jun 14 at 16:40
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    What I always wondered was why we needed a symbol to abbreviate a word that's only 2 letters to begin with - like how much harder was it to write "3 apples at $1"? But that's a better question for Linguistics, as it long predates computers.
    – Darrel Hoffman
    Jun 14 at 18:13
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    @DarrelHoffman Your comment made me think of '&' which is a ligature of 2 letters, 'et'. Both @ and & are probably just faster to write by hand and so they became the norm.
    – Hans Kilian
    Jun 15 at 7:03
  • Notably, the cited Wp article shows that @ is in the expected place in ASCI-63 but not in ASCII-65. Apart from that there are a few 6-bit character sets which omit it, e.g. referring to Wp's "Six-bit" and "BCD_(character_encoding)" articles some from CDC.
    – Mark Morgan Lloyd
    Jun 15 at 11:01
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    Interesting. None of the typewriters I've seen (what are not that many models, though) had an @ sign, but probably it is a question of for which kind of business a certain model is built.
    – allo
    Jun 15 at 16:06
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The AT-symbol is a US development in use at least since the early 1800s, denoting single unit prices in commercial texts (*1). It was as much used, that early typewriters of the 1880s added it as distinct glyph (*2).

In telecommunication it was present in US variants (US TTY) of the International Teletype Alphabet Number 2 (ITA2) since the late 1920s, where it replaced the Ampersand/et (&).

In Computing it's present at least since the 1950s with the FIELDATA code (*3), itself one of the predecessors of ASCII and in turn now prevalent UNICODE.

*1 - Itself possibly a derivation of the French à used in the same context

*2 - While we like to foremost think of typewriters as tools for authors or at least letters, their most important early usage was in commercial bookkeeping. New technology was always and will always be first used where the money is to buy it - no matter how much more visible other applications are to the common eye.

*3 - Which now offered both, @ and &.

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    A couple of details that are probably not coincidental: (1) The @ sign was often used to serve a "bulky blob" glyph when printing large banners; (2) The Apple I used a blinking @ sign as a cursor; (3) Some Hazelton terminals which didn't support lowercase implemented character code 64 as a solid rectangle, which they in turn used as a cursor (perhaps they were designed to use a blinking @, but someone thought a blinking rectangle would look better)?
    – supercat
    Jun 13 at 15:12
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    Hazelton? Hazeltine
    – manassehkatz-Moving 2 Codidact
    Jun 13 at 15:56
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    Not just a US development. See my Answer. I concur with most of what you wrote, though.
    – RichF
    Jun 13 at 18:20
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    @supercat the @ as cursor comes simply from being the glyph produced by the character generator at codepoint 00.
    – Raffzahn
    Jun 13 at 19:29
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    @manassehkatz-Moving2Codidact what a coincidence - I was just reminiscing on another question about a terminal that used core memory, and it was a Hazeltine. Today I live about a mile from Lake Hazeltine, and I've always wondered if that's where the name originated.
    – Mark Ransom
    Jun 15 at 4:07
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By coincidence I just happened to watch a YouTube video yesterday:

I found it very informative. It dates the symbol back to over 2000 years ago.

I second what others have said about @ being on typewriters for a very long time. American ones, anyway. I don't know about typewriters in other countries. It could be like the # symbol, which we used to pronounce as "pound" or "sharp". British typewriters replaced it with their pound symbol, though, £. I guess by the time people started thinking of # as "hashtag", typewriters were already passé.

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    Wasn't ‘#’ called ‘hash’ long before Twitter et al? (I assumed that the term ‘hashtag’ was coined for a tag indicated by a hash symbol.)
    – gidds
    Jun 13 at 22:15
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    @gidds: The # symbol has gone by a wide variety of names. My favourites are probably "octothorpe" and "pigpen".
    – Greg Hewgill
    Jun 13 at 22:21
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    @gidds yes, among many other things (and arguably ♯, sharp, is not the same as #, hash — any more than ♭, flat is the same as b)
    – hobbs
    Jun 14 at 5:31
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    @JeremyP : it's true that some symbols are different, like ♯ and #, or ♭, and b, but in the time of mechanical typewriters they often saved on the number of keys and gears by omitting similar symbols. Many typewriters don't even have a distinct 1 and l (lower-case L).
    – vsz
    Jun 14 at 9:44
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    …Compare, for example, the Latin small letter O o, the Greek small letter omicron ο, the Cyrillic small letter O о, the Latin letter small capital O ᴏ, the ring operator ∘, the degree sign °, the masculine ordinal indicator º, the ring above ˚, the Hebrew mark Masora circle ֯, the ring point ⸰… Are they all ‘clearly the same symbol’?
    – gidds
    Jun 14 at 9:53

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