This completes the first part of this book. I hope you have been able to absorb and enjoy these first (huge) steps. If not, you may want to take the time to review something you may not have clarity on; it's always worth it to better understand what you're doing.
We know a bit more about C and C++ programming, at least enough to lead us safely through the next two parts. We can now understand the basic tasks of Arduino, we can upload our firmware, and we can test them with the basic wiring.
Now, we'll move a step further into a territory where things are more practical, and less theoretical. Prepare yourself to explore new physical worlds, where you can make things talk, and communicate with each other, where your computer will be able to respond to how you feel and react, and without wires sometimes! Again, you may want to take a little time to review something you might still be a little hazy on; knowledge is power.
The future is now!