ibraries provide extra functionality for use in sketches, e.g. working with hardware or manipulating data. To use a library in a sketch, select it from Sketch > Import Library.
Standard Libraries
· EEPROM - reading and writing to "permanent" storage
· Ethernet - for connecting to the internet using the Arduino Ethernet Shield
· Firmata - for communicating with applications on the computer using a standard serial protocol.
· LiquidCrystal - for controlling liquid crystal displays (LCDs)
· SPI - for communicating with devices using the Serial Peripheral Interface (SPI) Bus
· SoftwareSerial - for serial communication on any digital pins. Version 1.0 and later of Arduino incorporate Mikal Hart's NewSoftSerial library as SoftwareSerial.