Starting with the digital output pins

We'll use the digital output pins for our first mission. This will show us the basics of preparing a sketch—an Arduino program. We'll download it to an Arduino and watch it work.

The Arduino language is vaguely like Python, with some extraneous punctuation. The language is quite a bit simpler and is statically compiled into hardware-level instructions that are downloaded to the processor.

An Arduino sketch must define two functions: setup() and loop(). The setup() function will run just once when the board is reset. The loop() will be evaluated repeatedly—as often as possible—by the Arduino processor. The exact timing will vary depending on what additional tasks the processor has to engage in to manage memory and deal with the various devices. It's almost is if the Arduino has an overall piece of code that looks like this:

main() {
   setup();
   while(true) { loop(); }
}

We don't need to actually write code like this; our sketch is written as if this processing...