A 3.5-inch Floppy Drive is the most common unit to store data that has to be movable. How does it works? Here is a step-by-step description:

1. When you insert a 3.5-inch floppy disk into the floppy drive, it presses against a  system of levers. One lever opens the shutter to open the cookie. The cookie is  nothing you can eat. It is the mylar disk coated on each side with a magnetic  material that can store your data. 

2. Other levels and gears move two read/write heads until they almost touch the  cookie on either side. These heads are tiny electromagnets and use magnetic  pulses to change the polarity of metallic particles embedded in the disk's coating. 

3. The drive's circuit board receives signals, including data and instructions for  writing that data to disk, from the floppy drive's controller board. The circuit board  then translates the instructions into signals that control the movement of the disk  and the read/write heads. 

4. If the floppy disk you have inserted into the floppy drive is write protected a small  beam can't pass through the floppy drive it don't write on your floppy drive. 

5. A motor is located beneath the disk. It spins a shaft that engages a notch on the  hub of the disk, causing the disk to spin.

 6. A stepper motor connected to a shaft that has a spiral groove cut into it. An arm  attached to the read/write heads rests inside the shaft's groove. When the shaft  turns, the arm moves back and forth, positioning the read/write heads over the  disk.

7. When the heads have moved to the correct position, electrical pulses create a  magnetic field in one of the heads to write data to either the top or bottom surface  of the disk. When the heads are reading data, they react to magnetic fields  generated by the metallic particles on the disk.