Read-only memory

Read-only memory (ROM) is a type of memory that is used to store data that the computer needs to access quickly, but that doesn’t ever change (except for during a BIOS flash / update).

It’s called ‘read-only’ because the data stored in ROM can’t be changed by the computer - it’s ‘read-only’ data. That’s the opposite of RAM, which is ‘read-write’ memory, because the data stored in RAM can be changed by programs.

Role of ROM

ROM stores the firmware of the computer, which is the software that is built into the hardware of the computer, and that controls how the hardware works.

The main example you’ll here is the BIOS (Basic Input/Output System), which is the firmware that controls the basic functions of the computer, and it’s needed to boot up the computer. BIOS is stored in ROM.

In reality, modern computers use a more advanced type of firmware called UEFI, but the concept is the same - it’s still stored in ROM, and it still controls the basic functions of the computer.

Volatility

ROM is non-volatile - that means that, when we cut the power to the computer, the data stored in ROM is not lost. It wouldn’t be great if we lost the BIOS every time we shut down the computer…