A hard disk drive contains rigid, disk-shaped platters, usually constructed of aluminum or glass
Unlike floppy disks, the platters cannot bend or flex—hence the term hard disk. The hard disk comprises of a set of platters which are coated with magnetized particles on both sides of each platter.
In most hard disk drives, cannot remove the platters and they are electro-mechanical device, so they are sometimes called fixed disk drives.
Removable hard disk drives are also available. this means the entire drive unit (that is, the disk and the drive)
The platters are connected at the center to a spindle (which rotates the platters). Data is read in a random-access manner, meaning individual blocks of data can be stored or retrieved in any order.
