Virtually every PC sold today has at least one hard disk drive installed inside its system case. At one time, this was also true of floppy disk drives, but PCs with floppy disk drives are beginning to disappear, giving way to Zip disks, Super disks, and other forms of removable mass storage.
The hard disk and floppy disk are types of secondary storage, with the PC's RAM providing its primary storage . Where primary storage stores data temporarily while it's in use, secondary storage holds data, programs, and other digital objects permanently. In fact, RAM is referred to as temporary storage, and the hard disk and floppy disk are considered permanent storage. The data is not permanent in the sense that it is etched in stone, but compared to the volatility of RAM, it is far more enduring. Permanent storage on a disk drive means that the data is still available even after the primary power source is removed.
HARD DISK DRIVES
The hard disk is hardly a personal computer invention. The first hard disks, which first showed up in the 1950s on mainframe computers, were 20 inches in diameter and held only a few megabytes of data. Hard disks were originally called "fixed disks" and "Winchester drives" and became known as hard disks later to differentiate them from floppy disks. However, the basic technology used in the earliest hard disks has not changed all that much over the years, although the size and capacity of the drives has.
Hard Disk Construction
There are many different types and styles of hard disks on the market, all of which have roughly the same physical components. The differences among the different drive styles and types are usually in the components the materials used and the way they are put together. But essentially one disk drive operates like all others.
Disk platters
Spindle and spindle motor
Read /write heads
Head actuators
Air filter
Logic board
Connectors and jumpers
Bezel
Of this list, only the connectors and jumpers are accessible outside of the enclosure that houses all of the other components of the disk drive. The metal case and the components it encloses from what is called the Head Disk Assembly (HDA). The HDA is a sealed unit that is never opened.
