Who Invented the Arrow Keys
Possibly SAIL Keyboard 1970.
The ADM-3A Terminal year 1976 is probably also a big influence.
The first to have dedicated arrows is maybe Space Cadet Keyboard (year ~1980) It has thumb keys 👍 👎 👈 👉 But these keys are not documented in manual. Not used by default.
Arrow Keys Arrangement
first inverted T arrangement is probably DEC LK201 keyboard, 1983.
left down up right
First is probably ADM-3A terminal, 1976
up down left right
left right down up
Efficiency of Arrow Keys Arrangement
Arrow Keys Efficiency: vim HJKL vs IJKL
[history of the inverted T arrow key arrangement on keyboard By Jim Burrows. At http://www.eldacur.com/~brons/NerdCorner/InverseT-History.html ]
2018-07 thanks to Marcin Wichary
2018-07-12 to read [The Keys To Success. A lot of early video game consoles secretly wanted to be home computers, too: Their makers either sold keyboard add-ons or failed miserably in the process. By Ernie Smith. At https://tedium.co/2017/04/27/video-games-keyboards-intellivision/ ]