This document discusses the components and operation of hard disk drives. It describes how hard disks store data using longitudinal or perpendicular magnetic recording. The key components of a hard disk drive are platters, read/write heads, cylinders, and a spindle. Platters are coated disks that store data magnetically. Read/write heads barely touch the platter surface to read and write data. Cylinders refer to vertical sections of tracks that pass through all platters. The spindle holds the platters and rotates them at high speeds during operation.

2. By Mirza Danial Masood
BS(IT) Department, U.O.S M.B.Din

3. Hard Disk
 It is a storage device that used magnetically
platters to store data, instruction and
information.
 The Desktop and notebook computer
contains 1 or more hard disks.
It have storage capacity from 40 GB to 1.5 TB
and more.
A Hard Disk that is mounted inside the system
unit sometimes is called fixed-disk.

4. Hard Disk
A Hard Disk which can remove the medium
from one computer and carry it to another
computer is called Portable-disk.
 Hard Disk store data by two ways:
 Longitudinal Recording .
 Perpendicular Recording .

5. Longitudinal Recording
 Hard disks stored data using, longitudinal
recording , which aligned the magnetic
particles horizontally around the surface of
the disk.

6. Perpendicular Recording
 Hard disks stored data using, perpendicular
recording , which aligned the magnetic
particles vertically or perpendicular around
the surface of the disk .

7. Components of Hard Disk
These are some components of hard disk :
 Platters .
 Disk case.
 Read/Write Head .
 Cylinder .
 Spindle .
 Disk cache .

8. Components of Hard Disk
 Platter : It is a circular, metal disk that is
mounted inside a hard disk drive. It is made of
aluminum, glass, or ceramic and is coated
with an alloy material that allows items to be
recorded magnetically on its surface.
 Before writing data , the hard disk must be
formatted .

9. Components of Hard Disk
The process of dividing the disk into tracks
and sectors , so that the operating system can
store and locate data and information on the
disk is called Formatting .
 A narrow recording band that forms a full
circle on the surface of the disk is called Track.
 The disk’s storage locations consist of pie-
shaped sections, which break the racks into
small arcs called sectors .

10. Components of Hard Disk
 The smallest unit of disk space that stores
data and information is called Cluster .

11. Components of Hard Disk
 Disk Case : The rectangular shaped disk case
holds all of the components of a hard disk drive .
 Read/Write Head : A read/write head
is the mechanism that reads items and writes
items in the drive as it barely touches the
disk’s recording surface .

12. Components of Hard Disk
 Cylinder :A cylinder is the vertical section
of a track that passes through all platters .

13. Components of Hard Disk

14. Components of Hard Disk
Spindle : The spindle holds the platters
together and the motor rotates the platters
at their designated speed, which is measured
in RPM.
The platters in the hard disk rotate at a high
rate of speed. This spinning, which usually is
5,400 to 15,000 revolutions per minute (rpm) .

15. Components of Hard Disk
 Disk cache : sometimes called a buffer,
consists of a memory chip(s) on a hard disk
that stores frequently accessed items such as
data, instructions, and information .

16. Head Crash
A head crash occurs when a read/write head
touches the surface of a platter, usually
resulting in a loss of data or sometimes loss of
the entire disk. Dirt, hair, dust, smoke, and
other particles could cause the hard disk to
have a head crash .