iPhone keyboard versus Treo

July 24, 2007

Tactile

The Treo has a physical keyboard which provides tactile feedback. The iPhone's virtual keyboard does not provide tactile feedback. Thus, this is an advantage of the Treo's keyboard over the iPhone's keyboard.

Usability

In usability, there are two empirical laws which affect a discussion of physical versus virtual keyboards. Succintly, they are:

1. It takes less time to hit a larger target.
2. The time it takes to distinguish targets goes up as the number of targets increases.

These laws match common sense (for once) and are each backed by numerous experiments.

What does this mean for physical and virtual keyboards?

Given two devices (phones) that are roughly the same size, then for the same number of buttons, the virtual keyboard can have larger keys. A smartphone with a physical keyboard will split its surface area between a screen and the buttons. The screen is likely to be at least half of the size of the device, so the keys will occupy at most half the real estate.

With a virtual keyboard, the keyboard can take up the vast majority of the screen, with a small area at the top reserved for displaying the text as it is being typed. Thus, the buttons on a virtual keyboard can be much larger.

For restricted text entry (like entering the digits of a phone number), the virtual keyboard can display only the appropriate buttons. Instead of displaying a full keyboard, the virtual keyboard can display the typical 12 phone buttons that we're familiar with. Thus, the virtual keyboard has the advantage of a smaller number of choices (law #2), and each key is individually much larger than the corresponding key on the physical keyboard, so hitting each key is faster (law #1).

Scott MacHaffie

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