Hard Disk: Hard disk is most important part of the computer system. Hard disk is a storage device it is used to storing information and data. Hardisk is a secondary storage device it is also called secondary memory. In the hard disk have tow metal plates data is stored on these plates, tow or more lens attached with these plates for writing and reading. On hardisk box a electronic plate is fixed, this plate is called card of hard disk. This electronic pale send a receive signal to lens and control all the working of the computer memory. This card is attached with a data cable and power cable and connect through these cables.
