New calculator interface

[David Hayden]

I really like the idea of grouping the functions in related concentric circles. Calculators tend to group them together, but, the groupings are somewhat awkward and unintuitive to me. I find myself scanning around the keyboard to find them.

The strangest part of the paper is that it hasn't mapped all the functions of the matrix calculator they compare to. Most importantly, I don't see the STO function. I also don't see the Quote function (Key 42 on the matrix calc using HP's common row-column format), the back arrow (key -52), comma (-54), etc.

The entire analysis in section 5 is based on travel distance for one finger. This ignores the accuracy, which I think all users would agree is more important, and the fact that many users will use multiple fingers. Regarding accuracy, placing the ON key dead center makes accidental presses easy. It's also odd to make the decimal point so small and right next to divide and zero. I'm sure I'd frequently hit divide or zero instead of decimal point. Placing the keys so close together seems to invite pressing the wrong one or pressing two keys accidentally. Finally, a "power user" undoubtedly will want to enter numbers without looking at the keyboard. I'm not sure how easy that would be with numbers arranged in a circle.

Regarding one-finger use, anyone who uses a calculator more than casually uses multiple fingers to type, and this is where the matrix design for the dgiits is most handy (pun intended).

The paper states "there is an equal chance of any of the numbers to be selected at any given position along an algebraic operation." I think Feynman showed that this isn't true. The smaller digits are appear more frequently than the larger ones.

Many of these complaints highlight the need for empirical testing of the design. it's too bad that they weren't able to construct a working model and test it out.

When AT&T designed the touch tone telephone, they did extensive research on the design, so I'm inclined to believe that the matrix is a good idea for numbers. The author's seem to assume that they're the first to study a keyboard layout.

Placing Phi on the keyboard is just a mystery to me. I've never needed it in any calculations I've ever done. I don't doubt its usefulness, I just don't think it rises to the necessity of being a key. You could always store it in a register if there were only a STO key....

The paper ignores manufacturing issues. Wouldn't it be difficult to print (gack!) the symbols onto curved keys? Would it be more difficult to place them during manufacture?