Hard Drive.

Hard Drive.

1 - A totally sealed metal housing protects internal components from dust particles that could penetrate
in the tiny space between the heads read / write and dishes, and cause damage to the magnetic coating of
dishes.

2 - In the lower part of the unit, one printed circuit board, also known as logic board receives commands
Controller, which in turn is controlled by the operating system. The logic board converts these commands into
voltage fluctuations that force the actuator to move the heads to read / write on the plate surfaces. The plate
also causes the rotational speed of the plates is constant and informs the drive heads when reading and when
record on the disc. In an IDE disk (Intcgrated Drive Electronics), the controller incorporates the logic board.

3 - A spindle connected to an electric motor rotates eight magnetically coated plates at a rate of thousands of
revolutions per minute. The number of plates of magnetic coating composition and determine the capacity of the unit.
Currently, the use dishes are almost always covered by an alloy of about 3 millionths of an inch thick.

4 - The actuator pushes and pulls the arm head group of read / write across the surface of the plates with precision
critical. It aligns the heads with tracks arranged in concentric circles from the surface of the dishes.

5 - The heads read / write connected to the ends of the movable arms sliding over the surface synchronized
the disk platters spinning. Heads record the data from the controller by aligning the magnetic particles in
surface of the plates, and then read the data to detect the polarity of the particles that were already aligned.

6 - When you or your program asks the operating system to read or write a file, the system prompts the
parent move their heads read / write to the file allocation table (FAT). The operating system
reads the FAT to determine which disk clusters that file is located or that disk parts are still available
to store a new file.

7 - A single file can be segmented into clusters positioned in hundreds of different dishes. The operating system
Guard the top of the file in the first block available that find the FAT. The FAT keeps track of chained
clusters occupied by the file, and each link leads to the next block that contains more pieces of the file.
Once the data from FAT have passed through the electronic part of the unit and the disk controller and returned to
operating system, this instructs the unit to skip their heads read / write on the surface of the plates,
reading or writing clusters on plates that are spinning in their heads.
After the operating system writes a new file on disk, the heads read / write FAT to return to
record the list of all clusters of the file.

Source: Evolution of Computers