Hardware in data processing refers to the mechanical and physical components of a computer system such as the central processing unit (CPU), input/output devices, storage devices, and other components that make up the physical structure of the computer. These are the tangible, physical parts of the computer system that can be seen, touched, and manipulated. The hardware of a computer system enables it to receive, process, store, and output data or information. Therefore, the correct option is "mechanical components of the computer."