One difference is that the command-line and DOS applications didn't require more CPU and memory resources. Another difference is that the mouse didn't remove th

One difference is that the command-line and DOS applications didn't require more CPU and memory resources. Another difference is that the mouse didn't remove the main input device for the command line - the keyboard. Yet another difference is that extending the command-line into GUI didn't coincide with a switch to an entirely different system architecture. The argument is not that personal computer OSes and mobile device OSes won't be converging down the road. Actually that's the big thing with Lion, isn't it. And I'm sure it will be a similar thing with iOS 5. The argument, though, is that they will never meld completely because it is impossible (or at the very least very, very unlikely) to have both full backwards compatibility and full and proper casual computer, or tablet if you will, experience.