Arduino programs can be divided in three main parts: structure, values (variables and constants), and functions.
An Arduino program run in two parts:
setup() is preparation, and loop() is execution. In the setup section, always at the top of your program, you woiuld set pinMode, initialize serial communication, etc. The loop section is the code to be executed -- reading inputs, triggering outputs, etc.
Variables are expressions that you can use in programs to store values, like e.g. sensor reading from an analog pin. They can have various types, which are described below.
Constants are labels for certain values which are preset in the Arduino compiler. You do not need to define or initialize constants. Arduino includes the following pre-defined constants.
These functions allow you to trigger a function when the input to a pin changes value.
Used for communication between the Arduino board and a computer or other devices. This communication happens via the Arduino board's serial or USB connection and on digital pins 0 (RX) and 1 (TX). Thus, if you use these functions, you cannot also use pins 0 and 1 for digital i/o.
Corrections, suggestions, and new documentation should be posted to the Forum.
The text of the Arduino reference is licensed under a Creative Commons Attribution-ShareAlike 3.0 License. Code samples in the reference are released into the public domain.