Your Arduino has a specific type of memory called EEPROM (Electrically Erasable Programmable Read-Only Memory) that you can use to store data you need to be retained even when your Arduino is powered off (it is a non-volatile memory). The EEPROM is made of small elements called cells. Each cell has a size of 1 byte. You can access each cell from your program, but this access has some limitations:
- you can read a cell as much as you want, but you can only write in it a 100000 times max.
- reading is slow and writing is very slow, compared to SRAM memory.