With my old smartphone (Nokia N9) I could reach anywhere with my thumb as the screen was so small. No surprise that my new "phablet" is much harder to use as I constantly have to change grip, and hit stuff by accident.
Before the N9 I had a Windows Mobile 2003? And even though it had touch support, it was designed to be used with a stylus.
With a stylus you need two hands, or a table, but you can reach anywhere on the screen, and the pen is very accurate, so you can have higher information density. Android nor iOS is designed to be used with a stylus though. Modern phones have the same screen resolution as desktop monitors, so in theory using a stylus/pen (and sharp eye-sight) you could have the same user interface on the mobile as on the PC.
Also writing on a virtual keyboard using the stylus is not that bad, although not as fast as typing on a keyboard, but faster then typing by touch.
Before the N9 I had a Windows Mobile 2003? And even though it had touch support, it was designed to be used with a stylus. With a stylus you need two hands, or a table, but you can reach anywhere on the screen, and the pen is very accurate, so you can have higher information density. Android nor iOS is designed to be used with a stylus though. Modern phones have the same screen resolution as desktop monitors, so in theory using a stylus/pen (and sharp eye-sight) you could have the same user interface on the mobile as on the PC. Also writing on a virtual keyboard using the stylus is not that bad, although not as fast as typing on a keyboard, but faster then typing by touch.