The physical components of a computer system are called hardware. Such items may be electronic, electrical, magnetic, mechanical or optical component. Examples of components are microprocessors, ICs, hard disk, floppy disks, optical disks, cathode ray tube (CRT), keyboard, printer, plotter etc. A computer system is composed of different hardware such as Central Processing Unit (CPU) , Video Display Unit (VDU) and different input devices such as a keyboard, a mouse, a modem etc. Or Hardware is a general term that refers to the physical artifacts of a technology. The term artifact means an object produced or shaped by human craft, especially a tool, weapon, or ornament of archaeological or historical interest. A PC (Personal Computer) contains in a desktop or tower case the following parts: Motherboard which holds the CPU, main memory and other parts, and has slots for expansion cards, power supply – a case that holds a transformer, voltage control and fan storage controllers, of IDE (Integrated Drive Electronics), SCSI or other type, that control hard disk , floppy disk, CD-ROM (Compact Disk Read Only Memory) and other drives; the controllers sit directly on the motherboard (on-board) or on expansion cards, graphics controller that produces the output for the monitor,the hard disk, floppy disk and other drives for mass storage,interface controllers (parallel, serial, USB) to connect the computer to external peripheral devices such as printers or scanners.