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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):

1234567890

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...

marked as duplicate by msp, Charles Wesley, Mervin Johnsingh, Ben Brocka Apr 22 '15 at 16:30

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • 3
    Historical and UX designed are not mutually exclusive. – gerrit Apr 17 '15 at 17:02
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    I asked this about two years ago here: Keyboard number row ordering – Bobson Apr 17 '15 at 20:26
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    @SepehrM Almost all, but not quite all. Classical Dvorak has the 0 between 9 and 2. The Hungarian keyboard linked by Szabolcs has 0 next to 1. – gerrit Apr 22 '15 at 14:05
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    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. – Liggliluff Apr 18 at 11:00
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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".

  • 2
    In Vietnamese typewriters I've learned, there's neither 1 nor 0 key and you must type by uppercase i or o – phuclv Apr 17 '15 at 6:02
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    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. – DA01 Apr 17 '15 at 7:52
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    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. – KRyan Apr 17 '15 at 12:27
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    @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 Apr 17 '15 at 15:12
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    @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. – DA01 Apr 17 '15 at 16:38
57

supercat and BowlOfRed's answers are right on the track, but I feel like there are some missing info that I can add.

Note: Since OP mentions "On almost all keyboard layouts I have ever seen", I assume OP is talking about QWERTY layout, which "is the most common modern-day keyboard layout for Latin script."

Let's take a look at the history of keyboard layout:

History

Keyboard layouts have evolved over time, usually alongside major technology changes. Particularly influential have been: the Sholes and Glidden typewriter [...] which introduced QWERTY; its successor, the Remington No. 2 (1878), which introduced the shift key ; the IBM Selectric (1961), a very influential electric typewriter, which was imitated by computer keyboards; and the IBM PC (1981), namely the Model M (1985), which is the basis for many modern keyboard layouts.

(Emphasis mine)

Basically, we can safely say that most computer keyboards that we're using now is based on Sholes and Glidden typewriter with its QWERTY layout. So, we have to take a look at a particular characteristic of it: The Sholes and Glidden could print only upper-case letters.

Sholes and Glidden typeface

(Image courtesy of http://site.xavier.edu/polt/typewriters/sholesandglidden.html)

As it has been mentioned on previous answers, 1 and 0 didn't exist before the final iteration of QWERTY, since "1" and "0" are identical to "I" and "O".

The third iteration of QWERTY has layout like this:

  2 3 4 5 6 7 8 9 - ,
  Q W E . T Y I U O P
  Z S D F G H J K L M
A X & C V B N ? ; R

sholes and glidden keyboard

(Image courtesy of Wikimedia Commons)

The final iteration of QWERTY (as we've been using) has layout like this:

1 2 3 4 5 6 7 8 9 0 - =
Q W E R T Y U I O P [ ] \
A S D F G H J K L ; '
Z X C V B N M , . /

But before that, some keyboards still omitted 1, just like BowlOfRed mentioned, "The 0 key was added and standardized in its modern position early in the history of the typewriter, but the 1 and exclamation point were left off some typewriter keyboards into the 1970s", and it was placed after 9 because it looks better logically than having 0 before 2. And thus, 1 was placed before 2, the only place left without changing the overall layout.

qwerty without 1

(Image courtesy of BedahTekno (in Bahasa Indonesia))

  • The order of the numbers is the same on QWERTZ, AZERTY, ANSI Dvorak, Colemak... that's what I meant by almost all keyboard layouts I have seen. The only exception being classical Dvorak. – gerrit Apr 17 '15 at 4:00
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    I'm not convinced that that "Sholes and Glidden" example is at all accurate. For one, it's not monospace...which would be very odd for an early typewriter. Possible, but unlikely. – DA01 Apr 17 '15 at 6:10
  • @DA01 I admit I can't prove if that's the typeface used on real "Sholes and Glidden", but searching "sholes glidden typeface" returned similar images to that, which is indeed not a monospace. The footnote on this publication (PDF file) mention the same thing "Note: The typeface used to highlight text in this document is a replication of the font of the 1873 Sholes & Glidden type writer, based on a letter typed by Mark Twain. Courtesy of Richard Polt of the classic typewriter website." – Andrew T. Apr 17 '15 at 6:30
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    @DA01 My guess would be that the font uses the same letter-forms as the typewriter but kerns them to be variable-width rather than monospace. – David Richerby Apr 17 '15 at 10:27
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    @DavidRicherby possibly. It's just a horrible example all around. It looks like a horrible auto-trace of a bad photocopy of a microfiche scan. :) – DA01 Apr 19 '15 at 2:55
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It should not be next to the 9

...but it remains there, much like the inefficient QWERTY keyboard layout itself, because it's a legacy problem (aka people are used to it and there are high switching costs). This wikipedia entry and This book excerpt provides some interesting background on the QWERTY keyboard issue and history.


Reasons

  • 0 is one of the most commonly keyed digits. This is the reason numerical keypads often super-size the 0 key, to provide improved access:

    enter image description here

  • Benford's law shows that the lower digits are much more frequently used than higher digits. There isn't a direct mapping between Benford's law and typing, but it should be clear that the frequency of typed lower digits is likely to be significantly higher than the frequency of higher digits:

    enter image description here

  • The use of zeros is generally increasing, as this post shows.

  • The 0 key is very inconveniently located on a keyboard. It is often next to punctuation or the Delete keys. Given the prevalence of 0 and 1, 2, 3.. low digits, it means users have to position both hands on the numberline to type many numbers.

  • If the 0 key were next to the 1 key, many numbers (Benford's law) would be faster to type with just one hand. For these numbers, users would only have to position the left hand rather than spend time positioning both hands.

    • Fitt's Law and the KLM-GOMS model provide some background theory around the congitive load and timing for positioning hands on a keyboard.
  • It's for this reason that dedicated numerical keypads place the 0, 1, 2 and 3 keys in close proximity: users can rest their fingers on these most-frequently-used digits and enter data more quickly.


Unfortunately, because of legacy issues, this is unlikely to change anytime soon....

  • 12
    Hmm I think the downvoters are right here because my answer doesn't actually address the question! – tohster Apr 16 '15 at 21:57
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    Nevertheless interesting, so I upvoted the answer. More info supporting your answer at quora.com/… – Devin Apr 17 '15 at 1:30
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    You're making a wrong (but extremely common) assumption here. Placing commonly paired keys together doesn't speed typing up, but slows it down - because your fingers get in each other's way. Type "encyclopedia" and then "stewardesses". They have the same number of letters, but alternating hands (encyclopedia) speeds you up, while "stewardesses" is a very unpleasant word to type. That's also one of the reasons that people believe that QWERTY is bad. AFAIK there is no conclusive evidence that Dvorak is better, especially when you consider that there are many parameters in this, not just speed. – Vitaly Mijiritsky Apr 17 '15 at 7:46
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    Vitaly I'm familiar with the controversy over QWERTY vs Dvorak but my point about key collocation was something slightly different: by collocating the frequent keys, there is a greater chance that users will only need use one hand instead of two to type out numbers, which reduces the slow and cognitively disruptive process of repositioning fingers between the alphabetic keyboard and the number line. – tohster Apr 17 '15 at 7:59
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    Benford's law is not relevant. It only talks about the first digit in a number, which is never 0. – Taemyr Apr 17 '15 at 9:41
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At least part of the answer must be that it couldn't be placed next to the 1 because... there was usually no 1 (mentioned in this Wikipedia article).

The original keyboards were quite simple and did not have a separate key for either 0 or 1 (as they could be rendered with O and l). The 0 key appears to have become popular on layouts before the 1 key was. Indeed I remember using my family's typewriter in the 1970's (age unknown) and it didn't have a 1 key.

If I had to add 0 to a layout that includes 2-9, I'd probably always add it next to the 9.

3

The simple answer is that you are more likely to type '0' alongside another number.

A slightly more complicated answer is that it marks the decade and more represents the 10 than a number lower than one

  • I don't see how your first point relates to the position of the key. For example, the letter G is more likely to be typed alongside another letter, but it's right in the middle of the keyboard. – David Richerby Apr 17 '15 at 10:29
  • Sorry I should have clarified that: There are two things going on there. One is the dissociation (put it at the end away from all the others) the other is when typing with two hands it's much easier to type if the hands are not close together and there was (at the time the keyboard layout was designed) a stronger likelyhood of zero being used in conjunction with the lower numbers. But if the point you were trying to make was that there were much better answers here then, yes, I agree! – Andrew Martin Apr 17 '15 at 11:33
3

1. Most people start counting from 1

The top row of keys is more likely to be used when creating a shopping list than doing calculation. When entering a list of items on the keyboard a 0 is more likely to get in the way if it were over by the 1. Since zeros are more likely to be used at the end of a number it seems more natural to type 1 on the left and then 00 on the right for 100 instead of the other way around.

Many computer languages are zero based (start counting from 0) but most people who use keyboards don't use them to write computer code.

2. Many keyboards also have a 10-key pad

A special type of keyboard can be used when entering lots of numbers. Many keyboards have a special 10-key pad off to the side where the 0 is so important that it is larger and has a dedicated thumb for pressing it often. Numerical entry from an accountant can be done there instead.

  • 4
    I fail to see what point 3 has to do with keyboards – Mooing Duck Apr 16 '15 at 21:49
  • I agree and decided to add point 3 about binary digits onto the end of point 1. – DaveAlger Apr 16 '15 at 23:16
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    I don't think people number their shopping lists. However, I do like the theory that zeros usually FOLLOW a number, rather than precede it. Though I think that's just a theoretical reason for the placement. – DA01 Apr 17 '15 at 7:55
0

I will try to explain this from my perspective. To use the right half of my keyboard, I usually take my right hand. When you use zeroes it usually goes with larger numbers so if I am using a zero, I will take both of my hands anyways. While if it would be on the left side, next to one. It would push another number to the right side and would make me take my right hand which is one the mouse in order to just type a single-digit number.

Question of efficiency for me.

  • "when you use zeros it usually goes with larger numbers"...can you explain why you believe this? I believe 1 is the most frequent number preceding a zero. – tohster Apr 17 '15 at 22:25
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    @tohster I mean that when you use zeroes it will most likely be composed of multiple digits. So you would take both of your hands to type it quicker (at least for me that is). – Slava Knyazev Apr 18 '15 at 0:08

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