Why is the 0 next to 9, not next to 1?
On almost all keyboard layouts I have ever seen, the 0 is to the right of the 9, rather than to the left of the 1 (the original Dvorak layout is the only exception I can think of; it has 0 between 9 and 2):
Why is the 0 to the right of 9 rather than to the left of 1 — the latter seems more logical, as it means all digits are in increasing order?
The modern answer is, of course, because people are used to it. So the real answer must lie in history...
"real answer must lie in history..." Indeed. Alas, that's a history question--not UX.
@Bobson I was about to say that this is not general, because my Hungarian keyboard has the 0 before the 1, but your linked question made me realize that actually we are the only ones who do this O.o
@gerrit technically, UX as a field of practice wasn't around in the typewriter era. :) But that said, this likely wasn't UX related at all. A lot of things ended up the way they are not by design as much as by engineering, random opinions, or by accident. There may be a UX tangent here, but it's slim, at best.
There is a detail that was not mentioned before; The Zero number was invented AFTER all the other nine digits, which by extrapolation was been put AFTER. And in most situations people normally need it at the RIGHT of another digit, so why not put it at the right of everything else?
On the Hungarian keyboard, 0 has been moved to the left of 1 to make room for the letters Ö Ü Ó on the top row. The additional 8 keys are: Ő Ú É Á Ű , . - and Í is placed to the left of Z. So to avoid having Ö to the left of 1, 0 was moved there and Ö placed to the right of 9. – I have so far not seen any other keyboard do this.
The current layout makes it easier (for right handed people) to type binary code as you must use symmetric pinkies of both hands. Also "1" is the most frequent first digit of daily-usage numbers (see Benford's law), and it is more likely to start typing with the left pinky rather than the left one (only "P" is used to start). These are surely not the reasons for the layout, but (probably) happy accidents. Of course to gather evidence for this would be challenging as we wouldn't have access to the alternatives.
Many early typewriter keyboards did not have any key to the left of the "2", since a typist who needed to type the digit below that could use an uppercase "I" [for machines without "shift" keys] or lowercase "l" [for machines with them] for the purpose. Typewriter keyboards which used a shift key for uppercase did generally include a "0", however, since typing an uppercase "O" as an alternative would require using the shift key. Putting the zero to the right of the nine meant that it could be in the same place on keyboards which include a "1" as on keys which do not.
Another possible factor influencing the design is a telephone dial. On a rotary telephone in many (though not all) countries, dialing a "1" will briefly interrupt the line current once; dialing a "2" will briefly interrupt the line current twice. Having "0" interrupt the line current zero times would be rather difficult to detect, so instead it interrupts the line current ten times. As a consequence, the amount of rotation necessary to dial "0" is much closer to the amount required to dial "9" than the amount to dial "1", thus causing the numbers on the dial to be arranged "1234567890".
It'd be nice to know the timeline. The introduction of dial phones is pretty easy to determine, but I found it difficult to learn when the "0" became common on keyboards.
In Vietnamese typewriters I've learned, there's neither 1 nor 0 key and you must type by uppercase i or o
I don't know that there is a strong correlation between a rotary phone dial and a typewriter. There could be, but there's also so many differences that it seems unlikely.
Plausible speculation is **not** an answer. Just because these things **could** be why this decision was made doesn't mean either of them **are**, and that is the question you were asked to provide an answer to.
@DA01: The existence of early typewriters with keys 2-9 in their present locations and no "1" anywhere is historical fact, as is the fact that "0" became commonplace before it was normal to have two keys to the left of the "2". That would necessitate "0" being located somewhere else. My mention of rotary phones was to suggest that typewriters are not the only thing that uses "1234567890", and should not be considered particularly unusual in that regard.
@supercat which is fine. I'm not a fan of this question to begin with, and that we really *can't* answer the question only emphasizes that. We can come up with lots of great theories and guesses, but that's all they are...just theories and guesses--and none are really related to UX Design.