What is the main function of the central processing unit (CPU) in a computer?

The central processing unit (CPU) is often referred to as the brain of the computer, and its main function revolves around processing information. It accomplishes this by fetching instructions from memory, decoding them, and subsequently executing the specified operations. This execution sequence allows the CPU to perform calculations, manipulate data, and control the flow of information throughout the computing system.

The fetch-execute cycle, which is fundamental to CPU operations, illustrates how the CPU continually retrieves instructions, interprets their meaning, and carries out the required processes, thus driving all functionalities within a computer. This skill in managing and executing instructions is why option C accurately describes the essential role of the CPU.

The other options, while related to computer operation, do not encapsulate the primary responsibility of the CPU. For example, storing data permanently is a function of secondary storage devices like hard drives and SSDs, whereas connecting hardware components is primarily the function of the motherboard and various ports. User interfaces are managed by software running on the CPU, but this does not encompass the CPU's core function of instruction execution.