A form of Memory called NVRAM keeps data even when the electricity to the host device is shut off. The two most popular varieties of NVRAM are SRAM and EEPROM.

SRAM, which is spelled "s-ram," preserves data by using a backup power source, such as a battery. SRAM is frequently used to keep computer hardware configurations that must be kept when the computer is turned off. Examples include the PRAM options on MacOS systems or the UEFI settings on Windows machines. The data saved in the SRAM will be destroyed if the battery expires or is removed because SRAM usually requires a battery to maintain memory. Therefore, if BIOS or PRAM settings are lost after a computer restarts, it is probable that the computer's battery needs to be changed because it has lost its charge.

EEPROM (pronounced "e-e-p-rom") stores data using electrical charges that maintain their state without electrical power. Therefore, EEPROM does not need a battery or other power source to retain data. The most common type of EEPROM is flash memory, which is used for USB keychain drives and other portable electronic devices.