The hard drive has one or more platters that look like disks and can spin up to 10,000 rotations per minute. An arm with heads are able to read, write or wipe the drive. The heads are the small needles that are capable of writing in binary on the platters. The platters have tracks that are similar to the ones on a vinyl record. Identical tracks on either side of one platter are called cylinders. The tracks are organized into sectors. All information is written to the top of the platter sector by sector. A sector is 512 bytes in size. Sector numbering starts at 1.
Cylinder X Heads X Sectors X 512 = The capacity of the drive. (How ever many gigabytes it is)
The size of the drive is always less than the actual size drive. It is rounded down.
How does a hard drive work?
