What Is Inside a Hard Drive?

A hard disk allows massive amounts of data to be stored and retrieved quickly. Internal hard drives are installed within the computer's cabinet and connect directly to the motherboard. External hard drives are self-contained units that use a USB cable to connect to the computer and enable you to expand the storage capacity of your main computer.

Motors

A hard drive contains two internal motors. One of these electric motors spins the platters and the other moves the writing head into place.

Controller

The controller is responsible for coordinating all of the hard drive's parts to retrieve or store data. When a request for information is received by the controller, it determines the exact physical location of that data and signals the actuator arm to move the heads into the correct position.

Actuator Arm

The actuator arm moves the read and write heads into place over the magnetic platters according to the instructions given by the controller.

Platters

Hard drives store information on magnetic platters that spin at high speeds around a central spindle. Data is written by magnetizing specific sections of the platter. The magnetic field can then be read by the head as the platter spins past it.

Heads

There is one read and write head for each magnetic platter in a hard drive. The heads do not actually touch the surface of the platter.