Many newcomers to computing will believe that hard drives are part and parcel of all computers and have always been so, but this simply isn't the case. Only in recent years has new manufacturing techniques and competition brought the price down to reasonable levels.

While many will be familiar with their role and function, very few will actually no their history or inner secrets. Let us go on a voyage of discovery.

The actual inventor of the device is disputed, because early computer pioneers used magnetic disk techniques to store and retrieve data since the late sixties, although they often looked more like a water tank than anything we would recognise today. Only since the mid-eighties have the devices been cheap enough for home and small business uses and many computers launched as late as the early nineties did not feature them as standard.

What has held the device back, until recent times, is the ability to produce increddible accuracy at a workable price. Infact the common measurement for mechanical movement of the drive head is "microns" or millionth of a metre. The kind of accuracy not needed when landing on another planet!

Hard drives store there data in a very different way than normal computer memory. It is stored in a state called "magnetic flux." This flux takes longer to be accessed than normal computer memory - which, at its heart, is just a collection of switches. This is an important point, because if the access speed could match that of computer memory the devices could be used as "virtual memory."

Your average hard drive has seven major parts that interest us today: The printed circuit board (which merely houses the parts and central control software) , the motor, the magnet, the platter, the base unit, the read/write head and the sealing case.

The magnet features a positioning coil that is often called the "voice unit" or "voice coil." This will position the head to one of around 2200 different tracks with only the very minimal deviation in accuracy. Some drives feature more than one set of units or platters, but let us ignore this today.

The accuracy factors have always been the toughest nut to crack and nearly all present drives feature some kind of "appraisal loop" that measures and grades the drives performance. This device saves many a hard drive from an early grave, when a crash, or other unexpected event, leaves the head "unparked."

The motor is less interesting, but with a greater demand for laptop computing the less power that is required the better. Inside most desktop computers you will find a hard drive with a three-coil DC spindle motor providing power of between +/- 12v.

The main disk is usually made from aluminum with an added coating of magnetic material. It is on this magnetic material that the all-important flux is stored. The procedure for placing this magnetic material on the plate is called "spluttering" and uses a vacuum (or semi-vacuum) process to give it the smoothest possible read/write surface.

The distance between the reading head and the disk is a very important issue. In short the lower the head can "fly" the tighter the information can be packed. With means more drive capacity. Many ideas have been put forward to lower this distance further, including tightly controlled fluids, but the key element is to get close, but never to actually touch. Any friction would be an absolute disaster.

The basic read/write process employs many of the elements of a hovercraft in that air is used to cushion the read/write head from the actual surface. When the disk starts to spin the air bearing "sliders" creates a form of wing and the head lifts. While this process is smooth it is not totally noiseless.

Here we come across another headline irony of hard drives. The faster the disk spins the higher the head will lift. However, as I explained before, the higher the head lifts the less effiency the drive will be. However the faster the drive spins the quicker the data is to read! Today running speeds vary, but 6000 rpm is about the average for a modern drive.

As air is central to the whole procedure it is a myth that they are vacuum packed. What they have instead is a sealed case containing "clean air." This is air containing next to no pollutants, such as dust or pollen. This means that manufacturing must always take place in "clean room" environments and the employees wear all-over body suits,

(The minimum requirement is 10 particles of .3 microns of dust in any 1 cubic metre of air. For obvious reasons factories are situated outside of heavily built-up areas.)

Although the main storage medium is flux the data is transferred by way of serial-form binary. This will look like this 1,1,1,0,01,1 etc. The onboard software looks only for a change in flux state so that it doesn't need to keep reading and buffering the same bit.

While we computer journalists say it all too often, the problem with all computer components is that they have an "absolute nature." They are not like cars that may cough and splutter but let you drive them to the garage - if a little slowly. In this technology it would only take only one incorrect flux state for software or data to become totally useless.

In many ways hard drives are computers answer to a timebomb, they will all "go off" eventually. The only hope is that you change to another computer before they do. If this article doesn't encourage you to regularly back-up your hard drive data nothing will!