Why do even the simplest calculators feature a square root key?

[Vtile]

... But it had a reason to be there at the first place, so the relative monetary value doesn't matter in that example. Another point is that if you only have general x^a function and when you do need sqrt(9) you must you need to type: [9][^][0][.][5][accept] or something on those lines, while if you have dedicated square root in a key then that procedure contains two and much more economical calculation.

Lets take an example. I will calculate sqrt(9) in HP50g in RPN mode, I do how ever write the unnecessary zero at the front of decimal point.

Case 1 - No dedicated square root is used.

Key Travel No.Press
[9] 0 mm 1
[Ent] 35mm 2
[0] 77mm 3
[.] 91mm 4
[5] 113mm 5
[y^x] 155mm 6


Case 2 - Dedicated square root is used.

Key Travel No.Press
[9] 0 mm 1
[y^x] 45mm 2


The case shows ~70% reduction in finger travel and ~66.5% reduction in key presses. I would say that is pretty significant. This also underlines the importance of the real estate analysis of the keyboard map when engineering such as a calculator keyboard.