Pictured: the actuator, spindle, and platters.

A lot of people don’t realize how glorious and complex computers really are. I mean, I’m sure they know they’re complicated, to a point, after all they’re pretty complicated machines to master, but it never really occurs to them just how complex they really are. Today, we’re going to delve into that complexity a bit- we’re going to look at the ‘cogs and gears’ of one of the most vital parts of your computer system- the Hard Drive. For now, we’re just going to look at Hard Disc Drives- Solid State Drives are a whole different can of worms, and a topic for another time.

HDDs consist of three to eight magnetic discs (or “platters”) attached to a spindle and stacked on top of one another. These discs are quite thin, and can vary quite wildly in size, depending on the system they’re being used in, though the average size is usually somewhere in the area of two inches. Believe it or not, data capacity actually isn’t determined by the size of the platters- that’s determined by the efficiency of the write process and the materials used in the platters, as well as how compact they can make ‘micromagnetic’ segments that are polarized to store data- more on that in a moment.

As a result of their size, most hard drives are actually pretty fragile- jostling them too much can knock the discs off center, damage the actuator arm, or even crack one of the discs. Also, opening a hard drive and removing the discs from their metal casing will very likely ruin the disc, and water can wreak havoc with the HDDs circuitry.

So, yeah. Don’t do any of that.

Anyway, the platters are magnetically coated, and it’s through magnetism that the actuator arm of the drive writes data to the disc, transmitting an electromagnetic charge of sorts which changes the polarity of segments of the platter. To read data, the actuator will look for a particular pattern in the polarity which indicates where a particular section of data is stored. The spindle to which the platters are connected itself connects to a motor, which spins when the drive is being read or written to.

When a request is sent to the hard drive by another part of the computer, the controller (the circuitry on the underside of the HDD) springs to action, searching the registry data (also stored on a section of the hard drive) for the file’s location. The controller moves the necessary disc heads into place, and the motor starts to spin the discs. The arm then begins writing.

Data is transmitted to and from the HDD to the rest of the computer via the IDE or SATA connector towards the bottom of the hard drive. This connector is attached to a data cable which plugs in to the system’s motherboard. IDE hard drives use a ribbon cable, while newer SATA drives use wiring.  Finally, next to the data cable is the hard drive’s power cable, which provides the drive with electricity when it’s turned on.

And there you have it- the basics of how a hard disc works. Next time, we’ll take a look at Solid State drives.