The hard drive consists of several hard platters> which are coated with metal oxide much like its cousin, the floppy disk. These platters are usually made of aluminum, but can be made from glass or ceramic materials.

Generally, the hard drive contains a read/write head> for each hard platter surface. These heads move in between the platters reading and writing information.

The platters and read/write heads are contained in an airtight case. Why? The read/write heads are only 10 millionths of an inch above the surface of the platters. If any particle of dust, smoke, or other debris comes between the read/write heads and the platters, it would cause a head crash> destroying data, the platter, and the read/write heads. Sealing the hard drive preserves the "clean" environment within the hard drive preventing such problems.

Like the floppy disk, the hard drive platters are divided up into tracks, sectors, and clusters. Cluster size is important in determining the overall storage efficiency of your hard drive. The smaller the cluster size, the more efficient your hard drive stores information.