1. History of hard disk drive
By the early 1980s hard disk had becomes an important part of a personal computers, which helps the operating system to be further development.The very first production of the hard disk drive was IBM305 Ramac. Ramac(random access method of accounting and control)

2. IBM305 Ramac was invented in 1956,sept13 by Ted Hoff
IBM305 Ramac was invented in 1956,sept13 by Ted Hoff. Which having capacity only 5mb on 50 disk platter. Each platter having a diameter of 24” and rotating at about 1200rpm( revolution per minute). The hard disk drive holds an operating system that boot the system which stores the multimegabite application and files that are used by the user.

3. COMPONENTS OF HARD DISK DRIVE
PLATTER
READ/ WRITE HEAD
HEAD ACTUATOR/HEAD ASSEMBLY
SPINDLE MOTOR
STEPPER MOTOR
LOGIC CARD
INTER FACE

4. PLATTER
The platters are the actual disk in side the drive that stores the magnetized data. Traditionally platters are made made up of a light aluminum alloy and coated with a magnetically material such as a ferrite compound that is applied in liquid form across the platter or thin metal film plating that is applied to the platter through electro platting. Newer technology uses glass or ceramic platters because they can be made thinner magnetization that are oriented to store information that is transferred through the read/write head. Most drives have at least two platter. Which makes the larger storage capacity of the drives. Each platter is magnetised on each side, so a drive with two platter has 4 sides to store data. The speed of hard disk depends upon the rotation of platter. The ceramic platters rotates at about 7,200rpm to 10,000rpm, where as the alluminium platter rotates at about 3,600 to 5,400rpm.

5. STEPPER MOTOR
This motor is responsible for moving the read/write head.
As the name suggests this stepper motor works in step wise manner, it rotate in a fixed angle of rotation. Each steps of this stepper motor defined a track on the platters.

6. THE READ/WRITE HEAD
The read /write heads read and writes data to the platters. There is typically one head per platter side, and each head is attached to a single actuator shaft so that all the heads moves in unison. When one head is on a track, all the other heads are at the same location over their respective surfaces. Typically, only one of the heads is active at a time, that is reading and writing data. When not in used, the heads rests on the stationary platter.

7. But when in motion the spinning of the platter create an air pressure that helps the read/write head lifts off the platter. The space between the platter and the read/write head is very less. So that even an dust particle or finger print could disable the spinning of platter. This necessitates that hard drive assembly be done in a clean room. When the platters cease spinning the heads come to rest or park at a predefined position on the heads is called as the “LANDING ZONE”

8. THE SPINDLE AND SPINDLE MOTOR
The platter in a hard disk drives are separated by disk spacers and are clamped to a rotating spindle that turns all the platters in unison. The spindle motor is built in to the spindle or mounted bellow it and spins the platters at a constant speed rate ranging from rpm the main function of the spindle motor is it responsible for rotating of the platters

9. THE HEAD ACTUATOR
All the heads are attached to a single head actuator, or actuator arms, that moves the heads around the platters. Older hard drives used a stepper motor actuator, which moves the heads based on a motor reacting to stepper pulses. Each pulse moved the actuator over the platter in predefined steps. The movements of the head actuator or actuator arm is controlled by the stepper motor.
The platters, spindle, spindle motor, head actuator and the read/write head are all contained in a chamber called the hard disk assembly. Outside of the Hard disk a logic card is connected and that logic card controls the movements of the internal parts and controls the movement of data into and out of the drive.

11. sector
TRACKS
cluster
TRACKS, SECTORS, CLUSTERS OF A PLATTER

12. TOP OF A PLATTER
CYLINDERS
BUTTOM OF A PLATTER

13. Number of tracks present on the top surface of a platter are equal to the number of tracks present on the buttom of the platters. So by connecting any points of a track present on the top of the platters to the same track in the buttom surface, then cylinder is created.

14. LOGIC CARD
Logic card is presents on the back side of a hard disk and this card is responsible for give supply to every components present in side of hard disk and D/A and A/D converter also present with the hard disk logic card.

15. Interface
Through which port data will send to hard disk from microprocessor and from hard disk to the microprocessor is known as “Interface” and that interface is further divided into two type.
1-SATA-Serial Advanced Technology Attachment
Only PIV 865,915,945,965)
2-PATA-Parallel Advanced Technology Attachment
( (PI,PII,PIII,PIV 845,865)
SATA-7 pins
PATA-39/40 pins
SCSI-Small Computer System Interface(mainframe comp.)
SCSI pins

16. MANUFACTURER OF HDD Seagate Maxtor Seagate Generic Quantum Samsung
Fujistu
Hitachi
Seagate
Plane
(5400rpm)
Baracuda
(7200rpm)
Chitta
(10000rpm)

17. TRACKS LANDING ZONE SECTORS
Platters of Hard disk consists of concentric circles called tracks. A typical platter physically contains of many thousands of tracks. Out of these tracks two tracks are kept reserve for Track 0 (T0) is other wise called as Toc (Table Of Contents) which is the outermost tracks of the platter.
LANDING ZONE
The track on which the R/W head take rest when hard disk is off condition is known as “Landing zone”.
SECTORS
The tracks are further divided into small small segments called “Sectors”. A sectors holds 512bytes of data and normally each track is divided into 63 numbers of sectors.

18. CLUSTERS
The combination of sectors is called as “Cluster”. The clusters are the logical units of data storage.
CYLINDER
Tracks of the same number on all platters of the drive from a cylinder. Cylinders are the set of tracks that lies at the same distance from the spindle motor from all sides of the platter.

19. FUNCTION OF HDD
The user gives digital signal to the hard disk by the help off keyboard. First the signal goes to the logic card. In logic card A/D and D/A converter is there which converts the digital signal to analog signal. This analog signal is given to R/W head with the help of data cable. The R/W head read and write data from the tracks by the help of Toc. So it first read write data from T0. At last it is resting on landing zone when power is off.