Reference Language (extended) | Libraries | Comparison
To use an existing library in a sketch, go to the Sketch menu, choose "Import Library", and pick from the libraries available. This will insert one or more #include statements at the top of the sketch and allow it to use the library.
Because libraries are uploaded to the board with your sketch, they increase the amount of space it takes up. If a sketch no longer needs a library, simply delete its #include statements from the top of your code.
These are the "official" libraries that are included in the Arduino distribution.
These libraries are compatible Wiring versions, and the links below point to the (excellent) Wiring documentation.
These are not (yet) included with the Arduino distribution and may change.
To install, unzip the library to a sub-directory of the hardware/libraries sub-directory of the Arduino application directory. Then launch the Arduino environment; you should see the library in the Import Library menu.
For a guide to writing your own libraries, see this tutorial.
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.