Steve Jobs is currently on stage at D8 being interviewed. And according to him, the iPhone OS started on a tablet. Though the iPhone was long in the making the iPad was an idea in Job’s mind long before that. Still, Apple’s phone came first.
When asked why he built the iPhone OS on a phone before building on a tablet, Jobs answered that the idea for a tablet computer came before the idea for a phone. However, he loved the UI and the screen so much that he stopped and thought that a phone would be a brilliant idea at the time. What would one day become the iPad was put on the backburner for a a while, and Apple to work on the iPhone.
Read his full quote below: