Continuing our examination of the components of a standard personal computer, over the next 2 articles, we take a close look at what a hard-drive is, how it works, why its important.

A Hard-drive, in a standard PC, measures approximately 5? x 3? x 1?; its underside is a printed circuit, and its top is usually a virtually impenetrable, steel, casing.

If you ever managed to break your hard-drive open, you would find inside, several ?platters? ? single magnetic discs, mounted one above the other, equidistant from each other. You would also find the ?head?, a device, not unlike the stylus of a gramophone in operation, that swings out across the platters and either reads, or writes information to each individual platter.

This kind of device is a magnetic storage device, to understand what this means, we must first understand, that in computer terms, everything boils down to binary data - either zero or one: Everything. Storing data, in its simplest form, can be described as representing these zeroes and ones, in any way useable.

As magnetic devices, therefore, hard-drives utilise the north and south polarity, that we all remember from tenth-grade science, and store all our data as either north or south polarity ?marks? on the surface of the platters.

Hard-drives are measured in two ways: Capacity and RPM. The capacity represents the amount of data it can store, and is measured in Gigabytes(GB), (one gigabyte is one million bytes).

Storage of your data has never been cheaper, and will continue to drop in price.

Today, it is difficult to get any hard-drive less than about 40GB. With the prevalence of multi-media material (that?s sound, pictures, movies, presentations etc), all of which require vast amounts of storage capacity, you should look to procure a minimum of about 80GB if you can afford it, and most home users will find it difficult to run out of space with such storage available.

RPM, stands for revolutions per minute, as with vinyl records, the obvious implication here is that faster drives mean faster access to data.

This kind of measure is really only useful to those seeking optimum performance, where every millisecond of delay makes a huge difference, such as business users. For us ordinary folk, its probably something we can dismiss.

Your hard-drive is your long term storage, and, you should ensure that access to data is of optimum performance. You do this by defragmentation: When you write a file to a disk, the processor will attempt to write it as one big ?lump?.

Lets assume its 10MB in size; Next you write a 5MB file, right after it on the disc. Later, you delete the 10MB file. I

f you then wish to create a 15MB file, the processor cannot write it as one ?lump?, because it would collide with the 5MB file, which starts 10MB into the disc.

What the processor does, therefore, is write the first 10MB of the file, plant a ?signpost? for us to follow, that indicates that the next part of the file can be found a further 5MB into the disc, then it leaps the 5MB file, and continues to write the remainder beyond it. Over time, with many file creations and deletions, you can imagine that files will be spread into smaller ?lumps? or fragments, and distributed to available space wherever it can be found on the disc. Now, when you read the file into memory, the disc has to work tremendously hard to find a fragment, read a signpost, direct the read-head to that part of the disc, read another fragment, read another signpost, and so on.

This can be incredibly time consuming, and cause delays to us, the user. Disk defragmenter reorganises these fragments, into contiguous, complete files. It does this by intelligently utilising current empty space to shuffle everything around and thereby improve the efficiency of file access. Defragmenter can be found on every MS Windows PC.

Next, we?ll take a second look at hard-drives, examining different types of drive and their access mechanisms.