First question.

I barely started my programming class today, and a question just popped into my mind:

• How is it that we can control machines through inputs? What makes it possible?

Edit:

 Well, looking back at it, I don't think I made the right question. More precisely, "How is it that computer can compute stuff like adding numbers and processing the truth value of a boolean statement given the truth values of its components?"

There's still stuff that I don't get like how cpus work.