1. Input Devices
and
Output Devices
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2. Contents
• Input-Output Devices
•Illustrating the role of I/O Devices
•Input Devices
•Output Devices
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3. Input-Output Devices
Input-output devices (abbreviated as I/O devices) provide the
capability to communicate with its external environment to a
computer system.
Input unit needs instructions to carry out the operations of
CPU.
Output unit gives us the desired result from CPU.
Input-Output Devices are the communication medium between
user and the computer.
Without I/O devices, a computer is just a dumb machine that
can't operate effectively and efficiently to perform a specific
task.
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4. The role of I/O Devices
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5. Input Devices
 An input device is any hardware component that
allows a user to enter data and instructions into a
computer.
 We classify input devices into following categories:
Keyboard Devices
Point and Draw Devices
Scanning Devices
Optical Recognition Devices
Digital Cameras
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6. Keyboard Devices
A keyboard contains keys that allows a user to enter data and
instructions into the computer.
Keyboard have a typing area that includes the letters of the alphabet,
numbers, punctuation marks, and other basic keys.
Many desktop computer keyboards also have a numeric keypad located
on the right side of the keyboard.
On notebook and many handheld computers, the keyboard is built into
the top of the system unit.
A standard computer keyboard is called a QWERTY keyboard
because of the layout of its typing area which is similar to that of a
typewriter.
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7. Keyboard
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8. Types of keys on the keyboard
Sr. No Keys Description
1 Typing Keys These keys include the letter keys (A-Z) and digit keys (0-9) which generally give
same layout as that of typewriters.
2 Numeric
Keypad
It is used to enter numeric data or cursor movement. Generally, it consists of a
set of 17 keys that are laid out in the same configuration used by most adding
machines and calculators.
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9. Cont..
3 Function Keys The twelve function keys are present on the keyboard which are arranged in a
row at the top of the keyboard. Each function key has unique meaning and is
used for some specific purpose.
4 Control keys It includes four directional arrow keys. Control keys also include Home, End,
Insert, Delete, Page Up, Page Down, Control(Ctrl), Alternate(Alt), Escape(Esc).
5 Special Purpose
Keys
Keyboard also contains some special purpose keys such as Enter, Shift, Caps Lock,
Num Lock, Space bar, Tab, and Print Screen.
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10. Advantages and Disadvantages of
Keyboard
It is not necessary to buy additional equipment because most of
the computer systems are normally supplied with keyboard.
Entering data and instructions with keyboard is generally faster
than pointing devices.
It takes a lot of time to practice in order to type quickly and
accurately.
Typing speeds are still very slow when compared with
computer speeds.
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11. Point and Draw Devices
Mouse
Trackball
Light pen
Joystick
Microphone
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12. Mouse
Mouse is the most popular pointing device with a GUI environment on
personal computers.
It is a very famous cursor-control device having a small palm size box
with a round ball at its base which senses the movement of mouse and
sends corresponding signals to CPU when the mouse buttons are pressed.
Figure-2: Mouse
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13. Cont..
Mouse can be used to control the position of cursor on screen, but it
cannot be used to enter text into the computer.
A mechanical mouse has a rubber ball on its underside to detect
movement of the mouse.
A optical mouse uses devices that emit and sense light to detect the
mouse's movement.
A cordless mouse (either mechanical or optical) transmits data using
wireless technology such as radio waves or infrared light waves.
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14. Advantages and Disadvantages of mouse
Advantages:
A mouse is user-friendly for beginners.
Using a mouse to select items or move to a
particular position on the screen is faster than using a
keyboard.
Disadvantages:
It is not easy and convenient to input text with a
mouse.
Issuing commands by using a mouse is slower than
by using a keyboard.
A mouse usually requires a flat surface to operate.
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15. Trackball
 A trackball is a stationary pointing device which
can perform the same functions as a mouse. with a
ball mechanism on its top.
 Large trackballs are sometimes seen on
computerized special-purpose workstations, such as
the radar consoles in an air-traffic control room or
sonar equipment on a ship or submarine
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16. Cont…
With a trackball, the user simply rolls the ball itself using her fingers or
thumb, while the body of the device stays in place.
Although the devices can be used for identical tasks, a trackball can
sometimes offer distinct advantages over a mouse.
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17. Light Pen
light pen is a computer input device in the form of a light-
sensitive wand used in conjunction with a computer's CRT
display.
It is a pointing device which is similar to a pen. It is used to
select a displayed menu item or draw pictures on the monitor
screen.
It allows the user to point or to display objects or draw on the
screen in a similar way to a touchscreen but with greater
positional accuracy.
When the tip of a light pen is moved over the monitor screen and
pen button is pressed, its photocell sensing element detects the
screen location and sends the corresponding signal to the CPU.
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18. Light Pen
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19. Microphone
• Microphone is an input device which is taken the input sound and
then stored in digital form.
• The microphone is used for various applications like adding sound to
a multimedia presentation or for mixing music.
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20. Joystick
A joystick is a pointing device with a vertical lever mounted on a base.
The lever usually includes buttons called triggers, which activate certain
events when pressed.
Mainly used for computer games and ultrasound scanners in hospitals
Advantage
A joystick allows fast interactions required in most games.
Disadvantage
It is difficult to use a joystick to select objects accurately on the screen.
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21. Scanning Devices
 A scanner is a light-sensing input device that converts printed text and
graphics into a digital form that can be further processed by the
computer.
Two popular types of scanners are:
Flatbed Scanner
Handheld Scanner
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22. Flatbed Scanner
• Flatbed scanners look like miniature printers with a flip-up cover
protecting the glass platen.
• Depending on its size, a flatbed scanner can fit standard or legal-sized
documents, and the flexible cover allows you to scan large items such
as books.
• These scanners are great for scanning the occasional newspaper
article, book chapter, or photograph; or for those who may need to
scan or bulky items such as the cover of a DVD.
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23. A handheld scanner
It can be manually passed over the image to be scanned.
A portable device
can use to copy an image from paper to your computer.
Hand-held scanners are ideal for capturing small images, such as
signatures and logos.
A hand-held scanner is smaller, less expensive, and more portable than a
flatbed scanner.
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24. Figure: Flatbed Scanner
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25. Optical Recognition Devices
OCR
OMR
MICR
Bar Code Reader
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26. Optical Character Recognition(OCR)
Devices
OCR is an input device used to read a printed text. OCR scans
text optically character by character, converts them into a
machine readable code and stores the text on the system
memory.
Written data and printed data can be read at the same time.
The characters converted can later be edited by word
processing software.
OCR readers often do not work well with handwritten
characters or those in unusual fonts.
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OCR Device

27. OMR Devices
• Optical mark recognition (OMR) device can sense hand-
drawn marks such as small circles or rectangles made on
pre-printed forms in certain places.
• OMR readers are often used for marking multiple choice answer
sheets, capturing data from questionnaires, enrolment forms,
and lottery tickets.
• OMR has a better recognition rate than OCR because fewer
mistakes are made by machines to read marks than by reading
handwritten characters.
• Large volumes of data can be collected quickly and easily
without the need for specially trained staff.
• The OMR reader needs to be reprogrammed for each new
document design and relatively slow.
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OMR Devices

28. Magnetic Ink Character Recognition(MICR)
• MICR is an input device which is generally used in banks
because of a large number of cheques to be processed every
day.
• The bank's code number and cheque number are printed on
the cheques with a special type of ink that contains particles of
magnetic material that are machine readable.
• The main advantages of MICR is that it is fast and less error
prone.
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MICR Device

29. Bar Code Reader
• Bar Code Reader is a device used for reading bar coded data (data in
form of light and dark lines).
• Bar coded data is generally used in labeling goods, numbering the
books etc. It may be a hand held scanner or may be embedded in a
stationary scanner.
• Bar Code Reader scans a bar code image, converts it into an
alphanumeric value which is then fed to the computer to which bar
code reader is connected.
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Bar Code Reader

30. Output Devices
Output is any data or instructions which is taken from the memory
of a computer.
Output are two types:
1. Soft-copy Output
2. Hard-copy Output
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31. Hardcopy vs. Softcopy
Touchable Soft copy is not Touchable Hard copy is touchable.
Software Requirements Soft Copy needs specific Software
Hard Copy doesn’t need any
Software.
Power Requirement Power is needed. Power is not needed.
Type Soft Copy is Virtual Hard Copy is Physical
Picture
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32. Output Devices
An Output device is any hardware component that allows a user to
accept data and instructions from a computer.
We classify Output devices into following categories:
Monitors
Printers
Plotters
Screen Image Projector
Voice Response System
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33. Monitor
• Monitors are the main output device of a computer which
commonly called as Visual Display Unit (VDU).
• It forms images from tiny dots, called pixels that are arranged
in a rectangular form. The sharpness of the image depends
upon the number of pixels.
There are two kinds of viewing screen used for monitors:
• Cathode-Ray Tube (CRT) Monitor
• Flat Panel Display Monitor
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34. Cathode-Ray Tube (CRT) Monitor
• The CRT display is made up of small picture elements
called pixels. The smaller the pixels, the better the
resolution.
• It contains an empty glass tube with a phosphor coated
screen and a source of electrons known as electron gun.
• Large in Size
• High power consumption
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CRT Display Monitor

35. Flat-Panel Display Monitor
• The flat-panel display refers to a class of video devices that have
reduced volume, weight and power requirement in comparison to the
CRT.
The flat-panel display is divided into two categories:
• Emissive Displays - The emissive displays are devices that convert
electrical energy into light. Example are plasma panel and
LED(Light-Emitting Diodes).
• Non-Emissive Displays - The Non-emissive displays use optical
effects to convert sunlight or light from some other source into
graphics patterns. Example is LCD(Liquid-Crystal Device)
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Flat-Panel Display Monitor

36. Printer
• Printer is an output device, which is used to print information or
document on paper.
There are two types of printers:
• Impact Printers: The impact printers print the characters by
striking them on the ribbon which is then pressed on the paper.
• Non-Impact Printers: Non-impact printers print the characters
without using ribbon. These printers print a complete page at a
time so they are also called as Page Printers.
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37. Impact Printers
Characteristics of Impact Printers:
• Very low consumable costs
• Very noisy
• Useful for bulk printing due to low cost
• There is physical contact with the paper to produce an image
These printers are of two types:
• Character printers
• Line printers
Some of the most popular impact printer as follows:
• Dot Matrix Printer(DMP)
• Daisy Wheel
• Drum Printers
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38. Non-impact printers
Characteristics of Non-impact Printers:
• Faster than impact printers.
• They are not noisy.
• High quality.
• Support many fonts and different character size.
These printers are of two types:
• Laser Printers
• Inkjet Printers
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39. Laser Printer
The Laser Printers are non-impact page printers. They use
laser lights to produce the dots needed to form the characters
to be printed on a page.
Features:
• Very high speed
• Very high quality output
• Give good graphics quality
• Support many fonts and different character size
• Expensive.
• The fastest laser Printer can print up to 200 pages per
minutes in monochrome (black and white) and up to 100
per minutes in Color.
• It is extremely fast and quiet.
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40. Inkjet printers
Inkjet printers are non-impact character printers based on a relatively
new technology. They print characters by spraying small drops of ink
onto paper.
Features:
• They make less noise because no hammering is done and these have
many styles of printing modes available.
• Color printing is also possible.
• Some models of Inkjet printers can produce multiple copies of
printing also.
• High quality printing
• More reliable
• Expensive as cost per page is high
• Slow as compared to laser printer
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41. 41
Inkjet printers
Laser printers

42. Plotters
 A plotter is a special kind of output device like a printer that
produces image on paper but does so in a different way.
 Plotters are designed to produce large drawings or image, such
as construction plan for building or blueprints for mechanical
object.
 A plotter can be connected to the port normally used by a
printer.
There are two types of designs:
• 1) Flat bed: Plotters of small size to be kept on table with
restriction of paper size.
• 2) Drum: These plotter are of big size using rolls of paper of
unlimited length.
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43. Drum Plotter And Flat-bed Plotter
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44. Speaker
• Speaker are another types of output device, which allows you
to listen to voice like music, and conversation with people.
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45. Screen Image Projector
•Screen image projector is an output device, which is
used to project information from a computer onto a
large screen, so that it can be simultaneously viewed
by a large group of people.
•This output device is very useful for making
presentations to a group of people with the direct use
of a computer
•Screen image projectors have become a common
presentation equipment today.
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46. Cont..
 They are commonly used with portable notebook
computers to quickly setup a modern presentation
facility at any place.
Screen image projectors are three types:
Ultra-light portable projector
Conference room projector
Fixed Installation projector
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47. Thank you
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