How Is Information Stored Magnetically on Hard Drives?

Raw Data

Data on its lowest level is represented in binary, with only 1s and 0s. This system is at the basis of all digital technology. A computer hard drive functions on the same level, serving as a platform with billions or even trillions of switches, each of which can represent 1 or 0. This system is manifested physically on the hard drive in the form of a platter. The platter is made of glass or aluminum. It is then coated with a material that can be magnetized, typically cobalt, and divided into billions of sections, each of which can be independently magnetized. Once a section has been magnetized, forming a 1, it will stay magnetized until the hard drive acts upon it again.

Actuator Arm and Head

As the platter is spun, at very high speeds, the actuator arm moves up down, mere nanometers over the surface. The arm has access to every part of the spinning platter. At the tip of the actuator arm is the head, which both detects and alters the surface beneath it. It is capable of both reading and affecting the magnetic state of the minute area immediately under the reader. Additional readers are stacked on the actuator arm depending on how many platters have been mounted on the central spindle.

Circuitry

The actuator arm is controlled by the actuator, which connects directly to the computer's CPU through a printed circuit board of its own. The computer relays instructions for accessing specific data points on the platter and receives the data as a binary output from the head on the actuator arm. There are several different architectures by which the hard drive can communicate with the computer. Power to regulate the two motors, one that spins the platter and another to control the actuator arm, is provided by the computer into which the hard drive has been installed.