(also embedded software, embedded system)
Firmware is a type of software that provides low-level control over the hardware it is embedded into. All digital devices have firmware. For complex devices, firmware may only contain basic functions and loading instructions. For simple devices, firmware may act as the entire operating system.
Firmware is installed in a special memory space within the hardware itself during the manufacturing process. Manufacturers typically do not allow end users to alter or delete firmware — doing so may void the device’s warranty and leave it inoperable. Nevertheless, a process called “flashing” lets users overwrite firmware in certain cases.
BIOS: The Basic Input/Output System (BIOS) is PC firmware that is installed on a chip in the computer’s motherboard. BIOS holds the computer’s startup instructions and checks its hardware components during the boot sequence. BIOS also lets the operating system interact with peripherals.