Flash memory is a long-lived non-volatile memory, and the data deletion is not in a single byte but in a fixed block. The block size is generally 256KB to 20MB. Block flash is electronic can erase read-only memory (EEPROM) variant, block flash and EEPROM, EEPROM can be deleted at the byte level and rewrite instead of the entire chip to wipe, and most of the flash memory chip need block erasure. Flash memory is often used to save Settings, such as storing data in a computer's BIOS, PDA, and digital camera, because it can still save data when it is out of power.