We're living in a digital world, and we have a few tech CEOs to thank for the movement — Mark Zuckerberg, Steve Jobs, Steve Ballmer, and Jeff Bezos have all played a big role in our lives as they lead Facebook, Apple, Microsoft, and Amazon (respectively) into the future. We may know the products they've helped to produce inside and out, but how much do you know about the men behind the companies? Find out when you take my "Know a CEO" quiz!