Here’s a nice write up about how the iPhone keyboard was designed. It’s hard to imagine these days, but typing on touch screens back then was simply impossible. Touch screens were essentially merely more than left-click input devices, multi touch was unsupported, and the touch screens back then were really bad at handling hit zones close to one another.

I am wondering what were the reasons to not explore T9 like input systems more. T9 was well established back then, and you could achieve insane typing speeds with it. I’d guess that this would also hold true on touch screens since the buttons can be much bigger, and there are far less rows/columns to account for than on a QWERTY keyboard.

The article mentions a similar approach and its main drawback - the fact that when you pause in the middle of a word, you have to memorize where you left off and are confronted with a word that might be very far off from what you’d intended to type. However, I have the feeling that this limitation alone could have been overcome with software alone.