I recently purchased an HP50G (waiting for it to arrive). I know this topic has been beaten to death, and I am aware of some of the reasons for the ENTER key being placed where it is include:
- the need to be able to enter in letters and press the arrow keys simultaneously (K, P, Q, and R on the HP48 series were tied to the arrows keys); having a larger ENTER key meant losing one of the regular keys
- similarity to other graphic calculators (e.g. TI has its ENTER key in the same position)
While the second reason seems silly to me, I have to wonder why they made the keys on rows 4 through 6 slightly wider than the first 3 rows. The HP48 calculators only had "large" keys for the numbers, shifts, and four basic operations +, -, *, and /. The other keys were all smaller width. It seems to me that had rows 4 through 6 on the HP50 used keys with the same widths as rows 1 through 3, they could have fit 3 more buttons per row. Or this could translate to 2 more new keys and a large ENTER.
I wonder if the design was limited by the number of address lines connected to the CPU...