1. PERIPHERAL
DEVICES

2. Peripheral Devices
Computer devices that are not part of the
essential computer (i.e. the main memory,
motherboard and microprocessor) are called
peripheral device.

3. Peripheral Devices
Peripheral devices can be external such as
a mouse, keyboard, printer, monitor, external
Zip drive and scanner or internal such as a
CD-ROM drive, Disk drive or internal modem.
Internal peripheral devices are often referred
to as ‘integrated peripherals’.

4. INPUT
DEVICES

5. INPUT Devices
Input
“Any thing enters in to the computer system is
called input”.
The input is in the form of instructions given
by the user with the help of any input device.
Input Devices
“The devices that are used to enter data and
instructions into the computer system are
called input devices.”

6. INPUT Devices
Keyboard
Keyboard is the most widely used input
device. It is used to enter data and program
instructions into the computer. Now a days
keyboard has more than 100 keys. Some
types of keys are follows:

7. Alphabets: A – Z and a – z keys.
Numeric: 0 – 9 keys are present at two places on
keyboard.
Mathematical symbol: + - * / ^ % etc.
Punctuation characters: . , : ; ‘ “ etc.
Cursor movement key: Four arrow keys are used to
move the cursor on the screen.
Editing function keys: ENTER, RETURN, ESC,
CTRL, ALT. CTRL & ALT are used in combination with
other keys of keyboard to perform special functions.
Function Keys: F1 – F12 keys are used to perform
different functions.
Special purpose keys: Home, End, Page Up, Page
Down, Delete, Insert etc.
Keyboard

8. Mouse
Mouse is also an important input device. It is used
for controlling screen cursor.
Construction:
It has two or three buttons on its top and a rubber
or metal ball inside its body.
INPUT Devices

9. Working:
The ball rotates as the mouse is rolled over a flat
surface. Normally, a pad is used as a flat surface.
As the mouse is rolled over a flat surface or a
mouse pad, the mouse cursor or pointer moves on
the screen. Mouse is normally used in graphic
applications. It is also used to play games on the
computer.
Mouse

10. Digital Scanner
Digital scanner is an input device. It is also called
optical reader or simply scanner. It scans or reads
text and pictures printed on a paper and enter
them directly into the computer memory.
INPUT Devices

11. Working:
The scanner takes electronic images of text or
pictures from the paper. It breaks each image into
light and dark dots and stores them into the
computer memory in machine codes.
Advantage:
The advantage of a scanner is that the input data
need not be typed in by the user. This is fast and
accurate method for entering data into the
computer.
Digital Scanner

12. Digital Camera
Digital camera is also used as an input device. It is
used to input pictures directly into the computer.
Construction:
Like traditional cameras, digital cameras have a
lens, a shutter and an optical view-finder.
INPUT Devices

13. Working:
In digital cameras, image falls on a charge-
coupled device (CCD). A photosensitive computer
chip transforms light patterns into dots.
A high quality digital camera divides a picture into
millions of dots. After the image has been
captured, it is saved into a camera’s memory card
then to the computer memory.
Advantage:
The big advantage of digital cameras is that
making photos is inexpensive and fast because
there is no film processing.
Digital Camera

14. Trackball
It is a pointing device. Essentially, a trackball is a
mouse lying on its back. To move the pointer, you
rotate the ball with your thumb, your fingers, or the
palm of your hand. There are usually one to three
buttons next to the ball, which you use just like
mouse buttons.
INPUT Devices

15. Advantage:
The advantage of trackballs over mice is that the
trackball is stationary so it does not require much
space to use it. In addition, you can place a
trackball on any type of surface, including your lap.
For both these reasons, trackballs are popular
pointing devices for portable computers.
Trackball

16. Touch Pad
A small, touch-sensitive pad used as a pointing
device on some portable computers. By moving a
finger or other object along the pad, you can move
the pointer on the display screen. And you can
click by tapping the pad or buttons available close
to touch pad.
INPUT Devices

17. Joystick
This is an input device, which allows a user to
control the movement of objects on the screen
with the help of a small lever in any direction. It is
also provided with some buttons, which are used
to carry out different actions.
INPUT Devices

18. Light Pen
It is an input device.
Construction:
It is pen-shaped input device which is held in hand
and can detect the presence or absence of light
with help of photo-electric cell mounted at its front
end. Its other end is connected to a computer
terminal by means of a cable.
INPUT Devices

19. Microphone
It is used to enter voice into the computer system.
The sound waves are converted into digital form
and then enter into the computer system for further
processing.
INPUT Devices

20. OUTPUT
DEVICES

21. Output
“The information or results, we receive from
computer system are called output”.
Output Devices
“The devices that are used to receive
information from computer and give it to user
are called output devices”.
OUTPUT Devices

22. Monitor
The monitor or Visual Display Unit (VDU) is
the most commonly used output device. It is
like a TV screen. It can display alphanumeric
characters, special characters and graphics.
The output provided by monitor is called ‘soft
copy’.
OUTPUT Devices

23. Types of Monitor
CRT Monitors
It is like a TV screen. The monitor contains a
large Vacuum tube called Cathode Ray Tube
(CRT). Due to CRT, they are also called CRT
monitor. A CRT consists of three ‘Electron
Guns’ of three colors Red, Green, Blue. Every
picture is formed with combination of these
three colors.
OUTPUT Devices

24. LCD Monitors
LCD stands for Liquid Crystal Display.
A monitor that uses LCD technologies rather
than the conventional CRT technologies is
called LCD monitor.
Advantage
The main advantage of LCD monitors
is that they take up less desk space
and are lighter in weight.
OUTPUT Devices

25. Printer
Printers are used to produce output in the form
of text and graphics on paper. The output on a
paper is called ‘hardcopy’.
OUTPUT Devices

26. Impact Printers:
Impact printers print on the paper with the
strikes of hammer or pins on a ribbon. These
printers work like a typewriter. They are mostly
used with personal computers.
E.g. Dot Matrix Printers
OUTPUT Devices

27. Dot matrix printer is an impact printer. It makes
a hardcopy by printing one character at a time.
It uses 100 to 300 dots per inch (DPI) to print
output on the paper. Dot matrix printers are
also used to create character shape of
alphabets of other languages such as Urdu,
Arabic, Chinese and Hindi etc. They are less
expensive printers.
OUTPUT Devices

28. Working:
The output from the CPU in digital signals
makes the pins pressed forward by a magnetic
device and the required character is printed.
Speed:
The printing speed of dot matrix varies from
200 to 1000 or more characters per minute.
OUTPUT Devices

29. Non-Impact Printers:
Non-Impact printers use thermal, electrostatic,
laser and inkjet technologies for printing.
These printers are faster and produce high
quality output as compared to the impact
printers. E.g. Laser Printers, Inkjet Printers etc.
OUTPUT Devices

30. Laser Printers:
Laser stands for Light Amplification by
Stimulated Emission of Radiation. Laser
printer is a non-impact printer. It uses 300 to
2000 dots per inch (DPI). Laser printer print
one page at a time that’s why these are also
called page printers. Laser printer produces a
very high quality text and graphics.
OUTPUT Devices

31. Working:
In these printers, a full page is assembled in
the printer buffer and a laser beam prints
image of characters and pictures on the paper.
Speed:
They have very printing speed. The printing
speed of these printers ranges from 5 to 300
pages per minute.
OUTPUT Devices

32. Inkjet printers:
Inkjet printer is a non-impact printer. It is a
character printer its print quality is higher than
that of the dot matrix printer.
OUTPUT Devices

33. Working:
It creates output on paper by a spray of ink
from a fine jet. An electric field controls the
spraying jet that forms characters or graphs on
the paper.
Speed:
It is a character printer and produces
one character at a time.
The printing speed of these
printers varies from 1 page to
8 pages per minute.
OUTPUT Devices

34. Speaker
To hear voice from computer we can attach
speaker with the computer as an output
device.
OUTPUT Devices

35. STORAGE
DEVICES

36. Computer Storage
Permanent Secondary Temporary
ROM
RAM Cache
Optical Flash Magnetic Magnetic
Disk Memory Tape Disk
C.D DVD H.D F.D ZIP
STORAGE Devices

37. Secondary Storage
It is not possible to store large amount of data
for future use in primary memory of computer
because its size is small and it cannot store
data on permanent basis. So it is necessary to
use some extra media to store large amount of
data. That kind of memory is called secondary
storage, auxiliary storage, additional storage,
external storage or semi-permanent storage.
Storage Devices

38. Magnetic Tape
Magnetic tape is one of the oldest & popular
device used for storing data permanently. As
its name suggests, this device stores
information on a magnetic tape that is made of
plastic(Mylar) that is coated with magnetic
material. Date is stored on the magnetic tape
in the form of magnetic spots.
Storage Devices

39. Size
The tape ribbon itself is stored in reels of 50 to
2400 feet or a small cartridge or cassette.
Quality
It is similar to the tape used on a tape recorder
except that it is of higher quality and more durable.
Non-Volatile Nature
By nature it is a non-volatile memory. Like recorder
tape computer tape can be erased and reused
indefinitely. Old data on a tape are automatically
erased as new data are recorded in the same
area.
Storage Devices

40. Advantages of Magnetic Tape
Unlimited storage
The storage capacity of a magnetic tape is virtually
unlimited because we can use as many tapes as
required for recording our data.
High data density
A typical 10.5 inch reel of magnetic tape is 2400
feet long and is able to hold 800, 1600 or 6250
characters per inch of this length.
Low Cost
It is very low cost storage media.
Portability
A reel of tape is also a convenient way of carrying
information from one place to another.
Storage Devices

41. Limitations of Magnetic Tape
No direct access
Magnetic tape is a sequential access device
and hence data recorded on tape cannot be
addressed directly. That’s why data access
speed is quite slow.
Environmental problems
Dust, uncontrolled humidity or temperature
levels can cause tape-reading errors.
Storage Devices

42. Magnetic Disk
A magnetic disk is a thin, circular metal plate
coated on both sides with a magnetic material.
Like the magnetic tape, it is also used to
store data permanently in the form of magnetic
spots. Now a days most computers use
magnetic disk as a secondary storage.
Storage Devices

43. Storage of Information
Before storing data or programs on the disk,
the disk is prepared. The preparation of a disk
for data storage is known as ‘formatting.’
Formatting is done with the help of a special
program in the operating system.
Formatting divides the disk into concentric
circles called tracks.
Each track is further subdivided into sectors.
The operating system labels each sector of
each track with an address.
Storage Devices

44. The data is stored in sectors. In one sector,
512 bytes are stored. The computer directly
goes to the specified sector and reads or write
data.
Floppy Disk
Floppy disk is also called simply a diskette or
disk. It is a small flexible plastic disk that is
coated with magnetic material.
Storage Devices

45. Uses of Floppy disk
Usually floppy disks were used to transfer
small amount of data from one computer to
another computer.
Storage Devices

46. Hard Disk
It is a popular secondary storage medium uses
now a days that no PC is assembled without it.
It exists in almost every computer system that
is used. It is also called fixed disk.
Storage Devices

47. Storage of information
In a disk pack, information is stored on both the
surfaces of each disk plate except the upper
surface of the top plate and the lower surface of
the bottom plate, which are not used. As shown in
fig(a) each disk consists of number of invisible
concentric circles called tracks. A set of
corresponding tracks in all the surfaces is called a
cylinder fig(b). Thus a disk pack having 10 disk
plates will have 18 recording surfaces and hence it
will have 18 tracks per cylinder. Each track is
further subdivided into sectors fig(c).
Storage Devices

48. Track Sector Upper surface
(Not used) Central shaft
Surface 0
Surface 1
Cylinder
Surface 2
Surface 3
Lower
Surface
(Not
used)
Storage Devices

49. Speed
The hardness of hard disk allows it to spin
much faster, typically more than ten times
faster than a floppy disk, a hard disk spins
between 3600 RPM and 7200 RPM. Where
RPM stands for Revolution Per Minute.
Storage Devices

50. ZIP Disk
Zip disk is a removable magnetic disk. It is like
a floppy disk. It has a large storage capacity.
One zip disk can store 100 –1000 MB of data.
Zip drive is used to read/write data on Zip disk.
Storage Devices

51. Optical Disk
An optical disk storage system consists of
rotating disk, which is coated with a thin metal
or other material that is highly reflective. Data
recording is done by focusing a laser beam o
the surface of the spinning disk. The laser
beam is turned on and off at a varying rate
because of which tiny holes are burnt into
metal coating of disk along its tracks.
Storage Devices

52. CD ROM
CD ROM stands for Compact Disk Read Only
Memory. It is new technology and very popular
storage media. LASER technology is used to
store data on CD.
Storage Capacity
CD is normally less than 5 inches in diameter
and yet can store 560-700 MB of data.
Storage Devices

53. DVD ROM
DVD ROM stands for Digital Video Disk Read
Only Memory. A DVD is an advanced form of
CD ROM. The difference between a CD ROM
and DVD ROM is the amount of data stored by
them. A CD ROM can store about 560-700
Million Bytes, while a DVD can store 4-10
Billion bytes per disk.
Storage Devices

54. It is interesting to know that about 1000
pages of text can be stored in one million
bytes. It means that a single DVD can store
around 10 Million Pages of text on it.
Storage Devices

55. Flash Memory
A flash memory consists of a flash memory data
storage device with a USB interface. USB flash
drives are typically removable, rewritable and
physically much smaller than Floppy, CD or DVD.
Storage Devices