Picture the keypad of a telephone and calculator side by side. Can you see the subtle difference between the two without resorting to your smartphone? Don’t worry if you can’t recall the design.

A Navy technician attends to the Automatic Sequence Controlled Calculator in Cambridge, Mass., on Aug. 7, 1944. The calculator was developed by IBM.

Google search has long featured a built-in calculator function but a recent update added a fully functional 34-button scientific calculator. Previously, when a user entered, say, 2+2, ...