As you may have observed, the complexity of our code grows exponentially from chapter to chapter, it would be a pity to lose or break any code due to the incident. Of course, for any real-world business or service, this would be a disaster. That's why organizations make sure the code is kept safe via version control. Any time we need, we can revert the code to any of the previous versions—or even keep multiple versions of the same code, in parallel. Historically, there were a few technological solutions that allowed this, the most popular being mercurial, subversion, and Git systems. Currently, however, Git is by far the most popular – it is open source, fast, and distributed. You don't have to have the main server for the team to cooperate, but even for a single user, Git could be a life-saver!

In the following section, we will briefly discuss how Git works and where GitHub fits into this equation. We will also perform a small practical exercise.