Two reasons are usually given for the QWERTY layout of typewriter and computer keyboards.
One claim is that the layout was deliberately chosen to slow down typists because early typewriter mechanisms jammed if the typing was too fast.
The other common story is that the layout was designed to make it easy for salesmen to demonstrate by having all of the letters of the word “typewriter” in the top row.
In fact, the QWERTY layout evolved among the earliest users of keyboards who were telegraph operators who used them to quickly interpret morse code telegraph signals. The layout was designed to place groups of letters whose code could easily be mistaken, as the morse signal arrived, close together.