What is commonly referred to as the "brain" of a computer?

The microprocessor is commonly referred to as the "brain" of a computer because it carries out instructions from computer programs by performing basic arithmetic, logical, and control operations. It interprets and executes commands from the software, effectively making it the central component that dictates the overall behavior and performance of the computer. The microprocessor processes data and controls other components, much like how the brain when we think and regulate bodily functions.

In contrast, the motherboard is a crucial component, serving as the main circuit board that connects the microprocessor with other parts of the computer, such as memory and storage, but it does not perform computations. The hard drive is primarily responsible for data storage, holding files and programs, while the power supply unit provides the necessary electrical power to the computer's components. None of these play the same critical role in processing information as the microprocessor does.