3.5. First Person: James Thomson and PCalc

Since its introduction in the 1970s as the first mobile computer, the pocket calculator hasn't changed its essential form. The calculator's familiar key layout remains a remarkably stable handheld interface, one that Apple faithfully reproduced in the built-in Calculator app for iPhone. In fact, the reliable ergonomics of handheld calculators would seem to make it a no-brainer for developing an iPhone version. Just clone the key layout as-is on the iPhone screen, and you've got a proven, intuitive, and well-proportioned interface, right? Turns out it's not quite so simple, especially if your calculator happens to offer a complex collection of features.