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.
PCalc, a calculator with functions aimed at programmers, began as a desktop application for Macintosh in 1992. Over the years, PCalc for Mac blossomed into a full-featured scientific calculator to manage all the math you can muster including hexadecimal, octal, and binary functions; programmable functions; unit conversions; and a library of scientific constants. It's a brainy calculator for math mavens.
When the iPhone arrived, PCalc developer James Thomson thought his application and its familiar interface would translate easily to the handheld device. He soon ran headlong, however, into the limitations of the iPhone's tiny screen, wrestling with button sizes and working out creative ways to preserve features in limited screen space. James shared his experiences exploring the constraints and opportunities of a virtual keypad and what it means to design a tap-intensive app for fingertips instead of a mouse and keyboard.
