In 1977, a 21-year-old Steve Jobs unveiled something the world had never seen before: a ready-to-program personal computer. After powering the machine up, proud Apple II owners were confronted with a cryptic blinking cursor, awaiting instructions.

The Apple II was a clean slate, a device built – boldly – with no specific tasks in mind. Yet, despite the cursor, you did not have to know how to write programs. Instead, with a few keystrokes you could run software acquired from anyone, anywhere. The Apple II was generative. After the launch, Apple had no clue what would happen next, which meant that what happened was not limited by Mr Jobs' hunches. Within two years, Dan Bricklin and Bob Frankston had released VisiCalc, the first digital spreadsheet, which ran on the Apple II. Suddenly businesses around the world craved machines previously marketed only to hobbyists. Apple IIs flew off the shelves. The company had to conduct research to figure out why.

Thirty years later Apple gave us the iPhone. It was easy to use, elegant and cool – and had lots of applications right out of the box. But the company quietly dropped a fundamental feature, one signalled by the dropping of “Computer” from Apple Computer's name: the iPhone could not be programmed by outsiders. “We define everything that is on the phone,” said Mr Jobs. “You don't want your phone to be like a PC. The last thing you want is to have loaded three apps on your phone and then you go to make a call and it doesn't work any more.”