EEPROM - Arduino Sketches: Tools and Techniques for Programming Wizardry - page 104

the ATmega328 in the Uno has 1,024 bytes. The ATmega1280 and ATmega2560
used in the different versions of the Arduino Mega both have 4 KB of EEPROM.
The EEPROM Library
The EEPROM library is a collection of routines that can access the internal
EEPROM memory, reading and writing bytes. The EEPROM library can be
imported by manually writing the include statement:
#include <EEPROM.h>
Optionally, you can add the EEPROM library using the Arduino IDE. Go to
the Sketch menu item; select the Import Library submenu, and select EEPROM.
This automatically includes the library, as shown in Figure 6-2.
Figure 6-2: Importing the EEPROM library
Reading and Writing Bytes
The entire EEPROM library consists of two functions: read() and write() .
These two functions can read and write bytes from specii c memory locations.
The read() function reads data from a specii ed address adr , expressed as
an int , and returns data as a byte .
EEPROM.read(adr);