I've been studying how quickly we can get energy out to the poor countries - a lot of which are in Africa - and how little progress we've made there. There's no more electricity today in sub-Saharan Africa per person than there was 20 years ago.

When the PC was launched, people knew it was important.

It was really phenomenal [Warren Buffett donation]. It grew out of the friendship that we had and the fact that his plan to have his wife run the foundation and give things away changed when she tragically died.

So we do software for watches, for phones, for TV sets, for cars. And some of these take a long time to catch on.

I considered law and math. My Dad was a lawyer. I think though I would have ended up in physics if I didn't end up in computer science.

Microsoft does not dominate the software industry by any stretch of the imagination. We have lots of very able competitors who keep us constantly vigilant, and sometimes they beat us to the punch. Microsoft's success to date is based solely on the fact that people like Microsoft software.

Intermittency [in availability for wind and solar] changes the economics, particularly this requirement that the power company at all times be able to require power. That's large.