I believe innovation is the most powerful force for change in the world. People who are pessimistic about the future tend to extrapolate from the present in a straight line. But innovation fundamentally shifts the trajectory of development.

When you write a piece of software you assume a certain type of hardware. If you assume hardware that's too powerful then you can't sell many copies cause very few people have that machine. If you assume hardware that's too simple your product can't do as much.

Never before in history has innovation offered promise of so much to so many in so short a time.

Melinda [Gates] has been my partner in raising the kids and I went from before I met her, intentionally having an unbalanced life, to having a more balanced life with all sorts of fun things that she and I do together.

It's OK for China to invent cancer drugs that cure patients in the United States. We want them to catch up. But as the leader, we want to keep setting a very, very high standard. We don't want them to catch up because we're slowing down or, even worse, going into reverse.

Even when I wrote Basic myself the day before I burned it into a computer I wasn't making design changes. I didn't have a testing team. I did all the testing myself. And there was no project methodology or schedule that, there was the notion of coming to a close means testing a lot at the end and making very few changes.

So we can simulate Richter-10 earthquakes. We simulate 70-foot waves coming into these things. Very cool. We basically say no human should ever be required to do anything, because if you judge by Chernobyl and Fukushima, the human element is not on your side.