The document discusses hardware components of computers including input devices like keyboards and mice, the central processing unit (CPU), internal memory like RAM and ROM, external storage devices, and output devices like monitors and printers. It then classifies computers into major categories such as supercomputers, mainframes, midrange computers, and microcomputers. Finally, it lists considerations for purchasing hardware such as power, expandability, ports, ergonomics, compatibility, footprint, support, warranty, and cost.