Read-only memory (ROM) is used to store data that controls the most basic computer functionality, such as starting up, detecting peripherals and operating the computer fan. As the name suggests, the data cannot be edited by the system or users and, unlike RAM, the data stays recorded even when the computer is off. Like hard drives and flash memory, ROM is an example of non-volatile memory -- meaning that it remains in place when the power is off -- while RAM is considered volatile memory.