Q: And why aren't the letters in alphabetical order? Curiosity! XD
A: Christopher Sholes in 1874 invented the arrangement as typewriters had the tendency of the typebars to clash and jam if struck in rapid succession. This was a particularly serious problem, in that the mishap would only be discovered when the typist raised the carriage to inspect what had been typed. This is why the keys aren't in order. The keyboard layout is known as QWERTY layout based on the first 6 letters of the keyboard.