What type of operating system controls how microprocessor-controlled hardware devices operate?

Firmware refers to the specialized software that is tightly integrated with hardware devices, providing the necessary instructions for how the device operates. It is stored in the device's non-volatile memory and is often embedded directly within the hardware. Since firmware operates at a low level, it allows the microprocessor to manage the hardware and control its functions efficiently. This makes it essential for the proper functioning of microprocessor-controlled devices, as it serves as the intermediary between the hardware and higher-level software instructions.

In contrast, software typically refers to a broader category that includes application programs and system software, which is not specifically tied to the low-level control of hardware devices like firmware is. Middleware acts as a bridge to enable communication and data management between different software applications, while a hardware abstraction layer provides a programming interface that hides the details of the hardware. These options do not directly control how the microprocessor interacts with hardware devices in the same fundamental way that firmware does.