But this is right question. It should be easy to replace part of the binary, it should be easy to run several programs at the same time, it should be easy to ty

But this is right question. It should be easy to replace part of the binary, it should be easy to run several programs at the same time, it should be easy to type on keyboard so computer executes commands. These are insanely hard problems yet they are solved because someone asked and someone tried.