Zune (easiest)

Sholes consulted with an educator who helped him analyze the most common pairings of letters in the English language. He then split up those letters so that their type bars were farther apart and less likely to jam. That in turn dictated the layout of the keyboard - known as QWERTY, for the first five letters in the upper row. In a manner of speaking, he slowed down the typists to prevent jamming, and thus speed up the typing.