Writing Data onto Hard Disk1. Read/Write Head is an electromagnet

2. Magnetic polarity of the Read/Write head can be changed by reversing the direction of the current that is made to pass thru electromagnet

3. When the Read/Write head has a north pole near the magnetic surface of the disk, a south pole is induced onto magnetic particles on the disk surface

4. When the Read/Write head has a south pole near the magnetic surface of the disk, a north pole is induced onto magnetic particles on the disk surface

5. These induced magnetic charges are used to store 1s and zeros on the disk surface, for example north pole may denote a 1 and south pole may denote a 0

Reading data from disk

1. Magnetic disk is rotated at a certain speed, in one direction only

2. Moving magnetic charges on the disk surface induce electric current in the read/write head.

3. Polarity of the moving charges determines the direction of current induced in the read/write head. For example, a moving north pole may induce current in clockwise direction and a moving south pole may induce current in anti clockwise direction

4. The direction of current is sensed to find out whether a north pole was stored or a south pole, which means whether a 1 was stored or a 0 was stored.