I am designing a Point of Pay, as in a Point of Sales, pretty much the same functionality.

Someone comes with a payment slip containing a barcode and the cashier will scan it, and the system can derive from the barcode what the payment is about and start the procedure filling information where appropriate, and ask for the user's review.

The other way is for the user to start the procedure manually and choose the type of payment before entering the details of it.

The barcode reader will be a simple keyboard wedge and the application will be the same across many environments.

So what I am thinking is a home page with buttons for the different payment options for the manual entry and dedicate a separate area that the keystrokes will be placed and when they satisfy a validation, start the payment procedure for the matching type.


download bmml source – Wireframes created with Balsamiq Mockups

That way I make the assumption that all keyboard strokes are for the barcode, and actually I don't expect anyone to write anything else in that page, other than a barcode.

Is that a good practice or is it violating any design rule?

  • When you ask if "it's" a good practice, what part or functionality of your design are you specifically referring? Commented Nov 27, 2014 at 16:16
  • I am referring to the fact that I am taking over the keyboard strokes and regarding them only as parts of the barcode.
    – andreadi
    Commented Nov 27, 2014 at 19:58

1 Answer 1


What that sounds like is a mode sensitive interface i.e. keyboard works differently depending on the application mode.

That is not bad or good UX per se. It can have advantage of simplicity and guidance, by making a multi-purpose device act more like a task specific device. However it is quite easy to design a bad mode driven UI as it is not a natural human behaviour. Alan Cooper addresses some of this in "The Inmates Are Running the Asylum" book.

Three things are critical for good mode driven UI. User has to be able to easily

  1. understand what each mode is
  2. easily navigate between the modes
  3. see what mode the system is in

THe UX heuristics to note when designing this part of your UI are "Match between system and the real world" and "Recognition rather than recall"

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