A program embedded in some hardware …

The firmware is the deeply embedded, low-level software that provides an interface between the hardware and the application/operating system level software. It resides in the ROM and executes when power is applied to the embedded hardware system. Firmware can remain active after system initialization and supports basic system operations. The choice of which firmware to use for a particular ARM-based system depends upon the specific application, which can range from loading and executing a sophisticated operating system to simply relinquishing control to a small microkernel. Consequently, requirements can vary greatly from one firmware implementation to another. For example, a small system may require just minimal firmware support to boot a small operating system. One of the main purposes of firmware is to provide a stable mechanism to load and boot an operating system. The bootloader is a small application that installs the operating system or application onto a hardware target. The bootloader only exists up to the point that the operating system or application is executing, and it is commonly incorporated into the firmware.