Microsoft

Microsoft was founded in 1975 by Bill Gates and Paul Allen, and grew by selling software for personal computers: first MS-DOS, then Windows, which became the operating system of most office and home PCs, and Office (Word, Excel, PowerPoint, Outlook). It is based in Redmond, near Seattle.

Its biggest shift was from selling software in a box to renting it by subscription. Office became Microsoft 365, paid monthly per person, and companies also pay for Teams, Outlook email and the tools that manage employees' accounts and devices. Most of its customers are businesses and governments, which is why Microsoft matters even to people who never think about it: their employer probably runs on it.

The other half is Azure, its cloud, one of the largest next to AWS: companies rent servers, databases and AI services in Microsoft's data centers. Microsoft has been a major investor in and partner of OpenAI since 2019; OpenAI's models run on Azure and power Microsoft's Copilot assistants inside Windows, Office and GitHub. It also owns GitHub, where most open source code lives, LinkedIn, and the Xbox gaming business.