We have seen lots of concepts related to not only time in this chapter, but also some hardware and programming concepts.

Mainly, we have learned about the different time functions the Arduino library gives us to use in our sketches and the difference between waiting with delay() and delayMicroseconds() and accounting with millis() and micros().

From the hardware point of view, we have connected a speaker to Arduino in two different ways: directly and through a transistor.

To use a speaker, we saw the use of the tone() and noTone() functions and their features.

Talking about programming, we learned to divide our code into different files and into different functions inside a file, which is a very common technique that will help you construct modular code.

We even met the while control structure, a new kind of conditional loop that evaluates a condition before executing the corresponding instructions.

Perhaps, you think that there can't be much more to learn from such a small board, but in the next chapter, I'll show you one of the most used facilities in the Arduino board, its Universal Asynchronous Receiver-Transmitter (UART), which allows Arduino to communicate with a wide number of devices, including your own computer.

Let's go ahead and open a door that will lead you to a brand new level and that will enable you to create projects that speak to others.