On April 4, 1975, a Harvard dropout named Bill Gates co-founded a tiny little startup called Microsoft, which ended up doing pretty well in the technology space. That was understatement, of course. But as Microsoft hits its 40th anniversary, it’s worth taking a moment to reflect on just how much its software has changed the world. (Free software advocates would argue that, by making software a licensed commodity, Microsoft also did a lot of damage to the technology sector, but that’s a story for another day.) While it would be a full decade before Microsoft introduced Windows, its flagship product—Windows 1.0 made its debut in November 1985—the company's focus was on operating systems from virtually the beginning, building MS-DOS for IBM PCs. From operating systems, Microsoft expanded into productivity software (Office), server software, gaming (via the Xbox), the cloud (Azure and associated platforms), and mobile (Windows Mobile, followed by Windows Phone). The company’s success made Bill Gates the world’s richest man for a number of years, and billionaires and millionaires out of its earliest employees. After dominating the personal-computing realm in the 1990s, Microsoft has struggled over the past decade to compete against Apple in mobile devices and Google in the cloud. The company’s newest CEO, Satya Nadella, is betting big on cloud services to elevate Microsoft to its former prominence—and at least in the short term, a lot will depend on the success (or failure) of Windows 10, due later this year. Image: Asif Islam/Shutterstock.com