QWERTY
History
Sholes struggled for the next five years to perfect his invention, making many trial-and-error rearrangements of the original machine's alphabetical key arrangement. The study of bigram (letter-pair) frequency by educator Amos Densmore, brother of the financial backer James Densmore, is believed to have influenced the array of letters, but the contribution was later called into question. Others suggest instead that the letter groupings evolved from telegraph operators' feedback.
QWERTY-6