This is the last chapter of this book and is the most advanced, but not the most complex. You will learn about C code optimization through several typical examples that will bring you a bit further and make you more capable for your future projects using Arduino. I am going to talk about libraries and how they can improve the reusability of your code to save time in the future. I will describe some tips to improve the performance of your code by using bit-shifting instead of the usual operators, and by using some memory management techniques. Then, I will talk about reprogramming the Arduino chip itself and debugging our code using an external hardware programmer.