Keyboard Layout HP-41C and early models

[RMollov]

My own theory is that that: HP-41 - use your left hand to operate the keyboard and write results with your right hand. At that time intermediate results were usually written down too. That's what one of my professors in uni was teaching us. Latter either printers were more available/affordable or results were displayed on screen and saved and that was enough, approach changed. So now you operate the calculator with your right hand - hence ENTER & +-/* on the right hand side. Recently I had a chance to play with HP Prime my young colleague purchased. Absolutely loved keyboard feel and arrangement, disliked the display (far away from todays standards), hated the no-RPN/L.