How to store variables in EEPROM and use them for permanent storage

Syntax#

EEPROM.write(address, value); //(Store variables in EEPROM in a particular address)
EEPROM.read(address); //(Retrieve values from EEPROM and read data stored in EEPROM)

Parameters#

Parameters of EEPROM.write	Detail
address	The address where value is to be stored in EEPROM
value	Main variable to store in EEPROM. Note that this is a `uint_8` (single byte)—you must split multiple-byte data types into single bytes yourself. Or you can use `EEPROM.put` to store floats or other data types.
Parameters of EEPROM.Read	Detail
address	The address from which the variable is to be read
## Remarks#
The allowable addresses vary by hardware.

ATMega328 (Uno, Pro Mini, etc.): 0–1023
ATMega168: 0-511
ATMega1280: 0-4095
ATMega2560: 0-4095

source

Store a variable in EEPROM and then retrieve it and print to screen

First, add a reference to <EEPROM.h> at the start of your sketch:

#include <EEPROM.h>

Then your other code:

// Stores value in a particular address in EEPROM. There are almost 512 addresses present.

    // Store value 24 to Address 0 in EEPROM
    int addr = 0;
    int val = 24;
    EEPROM.write(addr, val);     // Writes 24 to address 0
    
    // ---------
    // Retrieves value from a particular address in EEPROM
    // Retrieve value from address 0 in EEPROM
    int retrievedVal = EEPROM.read(0);    // Retrieves value stored in 0 address in
                                          // EEPROM

    // *[NOTE: put Serial.begin(9600); at void setup()]*
    Serial.println(retrievedVal);        // Prints value stored in EEPROM Address 0 to 
                                         // Serial (screen)