It’s pretty big. A recent article in Wired highlights how big Google actually is, at least in terms of code. All of Google’s services (Search, Mail, Maps, etc.) encompass 2 billion lines of code stored in one place and shared by 25,000 developers. The graph below illustrates just how big 2 billion lines of code is:
Microsoft Windows, “one of the most complex software tools ever built for a single computer, a project under development since the 1980s” is significantly smaller than the massiveness of Google.
Although Google’s repository is not open source, it is shared between roughly 25,000 developers who can add and modify code collaboratively. For now Google is an extreme case, but in the future more companies may need to handle gargantuan amounts of code. Facebook and Google are working together on an open source version control system to allow other companies to safely and cleanly house, modify, and create code on a large scale.