The world of open-source and free software is a large and fascinating ecosystem, devoted to the idea that fundamental computing tools should be a) freely available for download, use, and redistribution; b) provide “source code” – the programming instructions – that is open for study and modification by other programmers and c) supported by the community of users and for-profit enterprises alike. You may not realize it, but you are using open-source and free software every day, because it helps operate the Internet’s essential services. Android, the mobile operating system, is open source as well – though the carriers restrict it, as we’ll learn in another chapter – and there are thousands of programs that can replace the ones you use today on the Mac and Windows.

Sidebar: Richard Stallman, founder of the Free Software Foundation

Sidebar: Christine Peterson, who coined the expression “open source”