The document discusses the major operations performed by a computer system: input, storage, processing, output, and control. It describes how each operation works, such as entering data through input devices, storing data and instructions in storage, the central processing unit performing arithmetic and logical operations, output producing results, and the control unit coordinating all operations. It then explains the three basic functional units that control a computer's operations: the arithmetic logic unit performs calculations, the control unit determines instruction sequence and coordinates activities, and the central processing unit acts as the brain that directs functions.