34

Our software uses the =/+ and -/_ keys for opposite tasks. For example, increasing or decreasing a value, or zooming in or out. No modifier keys are used.

Here is the conundrum:

  • If we refer to it as the "plus (+) key," users might think they have to hold Shift.
  • If we refer to it as the "equals (=) key," we lose the intuitive dichotomy against the "minus (-) key."

Is there:

  • Research that gives a reason to prefer one form over the other?
  • A mention of this in an authoritative style guide that establishes a convention?
  • A good example of this in the wild?

Edit: Concerns about other keyboard layouts are noted, but for the purposes of this question, I'm only asking about US keyboards.

  • 2
    You might want to look at ux.stackexchange.com/q/52156/12864 to help you think about this one. – jsejcksn Oct 18 at 10:08
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    Don't forget the dedicated + key (shift also result in + so in your notation it's +/+) and -/- key on real, full-size, non-laptop, keyboards – slebetman Oct 18 at 11:05
  • 4
    this is very locale-based, not all keyboards have + and = on the same key – njzk2 Oct 19 at 19:36
  • As a user with a non-US keymap (Norwegian), my + is unshifted and to the right of 0 (zero) in the number-row (shifted it's the ?). - is unshifted at the end of the bottom-row (B N M , . - SHIFT), and shifted it's _ (underscore). = is shifted 0 (zero). – Baard Kopperud Oct 20 at 5:08
30

Based on conventions elsewhere, it is probably best to refer to it as the plus or + key.

The +/- dichotomy is used in other apps and more likely to be encountered by your users before they use yours even if it's in a different context. And your users are not trying to type the = character, they are trying to hit a specific key. This also allows users to use the + key on the num pad if their keyboard has one.

While it is true that some users could become confused and want to hold down shift, your software should be smart enough to take that into account and look at the key that is being pressed, rather than the character that is being typed.

For two quick examples, Zoom in Chrome and Font Size in Brackets (on a Mac) refer to using Cmd + and Cmd -. Granted, this is with a modifier key, but most apps that allow text input (in some capacity) use one so that you can do the function while in the middle of typing. This is something to consider in your app if a user might need to zoom or whatever while a text input has focus.

Menu in Chrome showing Zoom In and Zoom Out keyboard shortcuts. Menu in Brackets showing Increase Font Size and Decrease Font Size.

As always, testing with your actual users is the best way to know for sure. It could be that your audience skews heavily into the financial sector and they only press the buttons on the num pad (where = and + are separate keys) or maybe they are using Caps Lock and Shift for a lot of data entry or commonly typing = right before they have to change Zoom levels.

Worst case scenario: your users type on something that's not a standard QWERTY English keyboard and the + key can be in many different places. It may no longer make sense to +/- as a pair if they are nowhere near each other. Someone with more localization experience can hopefully weigh in on if keyboard shortcuts often get changed to support different language/keyboard conventions.

  • 3
    Additionally, from the Windows perspective, they have a list of keyboard accessibility shortcuts that mention using the "plus key" for zooming. – maxathousand Oct 17 at 20:15
  • 4
    "While it is true that some users could become confused and want to hold down shift, your software should be smart enough to take that into account and look at the key that is being pressed, rather than the character that is being typed." This would not be possible if you were using the shift-modified keyboard sequence to invoke a different function. Consider, for example, a constrained zoom that would be invoked when the shift key is held down (Ctrl-Shift-+), whereas the normal Ctrl-+ would result in an unconstrained arbitrary zoom. – Cody Gray Oct 18 at 5:58
  • 1
    On a german keyboard at least, + and - are primary keys (no modifier needed), while = is shift+0. – Clashsoft Oct 18 at 7:14
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    To solve the localisation problem, you can probably advertise the key as + but accept both + and =. That would cover most bases at least. – Muzer Oct 18 at 9:42
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    @KlaymenDK the entire premise of the question was that unshifted + would be accepted, as I interpreted it. So I don't think there's any danger of the key being used for something else. My comment could better be summarised as "if you're going to accept +, make sure you actually accept +, and don't do anything that depends on people having specific keyboard layouts." – Muzer Oct 20 at 11:47
69

Uhm, sorry. You refer to a =/+ key. But there is none on my keyboard.

German Keyboard layout

I think you should add a locale tag, and make sure your users only work within that locale.

  • 13
    Good point. Most software use Ctrl - and Ctrl + for zooming in/out, but my keyboard doesn't have a + key, so I have to use Ctrl - and Ctrl Shift 1 instead. It's actually quite confusing. – Nolonar Oct 18 at 9:43
  • 4
    Based on a quick wikipedia browse, most European keyboard layouts don't have = and + in the same key. (UK/Irish keymap being the biggest and most obvious exception as it's pretty much the same as the US keymap.) – ilkkachu Oct 18 at 10:17
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    yay, I am always pissed off by keyboard shortcuts like Ctrl Shift \  when my keyboard is lacking a \  key. I found out that Ctrl Shift ű works on my layout, but expecting every user to use the same English keyboard layout is sheer arrogance. – törzsmókus Oct 18 at 10:44
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    @Jon Just FYI, even though I'm Italian and I use an Italian keyboard I mostly browse English websites and use programs with English texts. So "speaking/reading/writing English" does not imply US keyboard layout. – Bakuriu Oct 18 at 17:50
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    Even though I'm Latvian it surprises me to discover anyone is using a localized layout. There are a couple of "Latvian" layouts, but every Latvian I've seen is appalled and cursing whenever they are presented with a non-US layout. – Džuris Oct 18 at 18:12
8

If your software does not already map the + to a function, then just use both for this purpose, and only document the + in order to keep the established, familiar dichotomy. This is a great example of the robustness principle.

  • 1
    By "actual + key", do you mean the dedicated one on the numeric keypad? Or do you mean the key that types the "+" symbol when the shift key is held down? – Cody Gray Oct 18 at 5:59
  • 1
    @CodyGray They are the same glyph (U+002B), but might be produced differently on different keyboards. If you want more info, see en.wikipedia.org/wiki/Plus_and_minus_signs. Thanks for pointing out how I could improve the wording of my answer—I did so. – jsejcksn Oct 18 at 10:03
1

Say “+” and put a footnote that “=“ may work but is not guaranteed.

Rationale: (1) Gives you the freedom to add a function on “=“ in the future. (2) Avoids user confusion if they get accustomed to “=“ and then acquire an app (they do exist) that has a specific function for “=“. (3) Doesn’t bite you if you expand your market to places that DO use alternate keyboards.

  • Is this backwards? The intention is for them to press =/+ without holding Shift. – Maxpm Oct 19 at 21:17
  • Which is not good advice for the reasons I stated. – WGroleau Oct 19 at 21:19
1

Write +. But make both + and = work. Let users discover for themselves that they don't need to hold shift.

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