The document discusses various input and output devices used in computers. It describes common input devices like the mouse, keyboard, trackball, joystick, light pen, microphone, digital camera, and scanner. It provides details on the different parts and functions of a keyboard. It also explains various output devices such as monitors, printers, plotters, disk drives, CD writers, and distinguishes between soft and hard copies.

1. INTRODUCTION TO
COMPUTER
Lecture #6

2. Input/Output Devices
Unit 3

3. Mouse
 The mouse is pointing device and it has at least
two mouse buttons.
 It is used to move a pointer on the computer
screen in order to point out the things on the
screen.
 When you press the left button, it is called a left
click.
 When you press the right button, it is called a
right click.

4. Mouse
 By default, the left button is the main mouse
button, and is used for common tasks such as
selecting objects and double-clicking.
 The right mouse button is often used to open
menus, which are pop-up menus that change
depending where you click.
 Certain programs, such as video games, may
use the right click to perform other functions,
such as firing a secondary weapon in a first-
person shooter.

5. keyboard
 A keyboard is the primary text based input
device which helps us to input textual data into a
computer.
 The standard arrangement of alphabetic keys is
known as the QWERTY keyboard.
 A standard keyboard includes 100 keys; these keys
are divided into following five different groups.
 Alphabetic Keypad, Numeric Keypad, Function
Keys, Screen navigation or cursor movement keys
and Modifier Keys

6. Alphabetic Keypad
 These keys are similar to a standard typewriter and
are used to type general information. Alpha numeric
keypad consists of;
 Alphabe t ke ypad co nsists o f ke ys Ato Z.
 Num e ric Ke ys co nsists o f ke ys fro m 0 to 9 .
 Punctuatio n ke ys, spe cialcharacte r ke ys and space
bar.

7. Numeric Keypad
 A numeric keypad is a set of keys at the
right of the keyboard similar to those on a
calculator.
 In addition to rapid entry of numeric data
these keys can also be used as an
alternative to the screen navigation and
editing keys.

8. Function Keys
 These are keys marked as F1 to F12,
located normally at the top of the
keyboard.
 These are special keys provided to a
programmer which allow him to attach
special functions to each key.
 Each of these function keys are also given
some special function in different
programs.

9. Screen navigation orcursormovement
keys and editing keys
 These keys are provided to move cursor
around the screen.
 Most keyboard includes the following Cursor
movement keys.
 Arrow Keys:
 There are four arrow keys to move cursor
around the screen; left arrow key, right arrow
key, up arrow key and down arrow key.

10. Screen navigation orcursor
movement keys and editing keys
 Home Key:
 This key moves the cursor to the beginning of the line.
 End Key:
 This key moves the cursor to the end of the line.
 Page up Key:
 This key moves the cursor to the previous page.
 Page Down keys:
 This key moves the cursor to the Next page.

11. ModifierKeys
 These keys are used in combination with
other keys in order to modify the input of
other keys.
 These are;
 SHIFT
 CTRL
 ALT

12. Additional Keys
 There are some special keys present on a keyboard that
performs some special functions;
 Delete key,
 Insert key,
 Esc key
 Print screen key.
 Pause/breakkey
 Scroll Lockkey
 Menu Key
 Windows Key

13. Trackball
 A Trackball is a pointing device almost like a turned
Upside Down Mouse.
 The user controls the cursor on the screen by rolling a
plastic ball with a fingertip or palm.
 Trackball is popular among users of laptop computers
when space is limited and may be mounted on either side
of the keyboard.
 For handicapped people who may have difficulty pressing
keys on a standard keyboard or using a mouse, the
trackball may be the answer since it does not require to
moves the entire arm to use it.

14. 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.
 Joysticks are mainly used for computer
games but they could be used for
CAD/CAM systems and in other
applications too.

15. Light pen
 Light pen is an input pointing device that contains
photo detector or light source that allows interaction
with a computer through specially designed
monitors/Display screen.
 It has a switch and a cord that connects it to
computer.
 The tip of pen contains light sensitive element which
provides a very precise pointing capability directly on
the screen.
 It is used in engineering drawing, architect design,
circuit design and other several graphics and art

16. Microphone
 A microphone abbreviated as MIC is a peripheral
device that allows computer users to input audio
into their computers.
 Microphones are becoming increasingly
important input device to record voice/speech.
 They are widely used in making calls from
computer and in video conferences.

17. Voice Recognition
 A voice recognition system compares a person’s live
speech to their stored voice pattern.
 Larger organizations sometimes use voice verification
systems as time attendance devices.
 Many companies also use this technology for access to
sensitive files and networks.
 Some financial services use voice verification systems to
secure telephone banking transactions.
 This type of software requires the computer to make a
profile of your voice, that is, you train the computer to
recognize your voice patterns.

18. Digital Video Camera
 A digital camera is a handheld portable input
device.
 Normal cameras capture pictures on special
coated films; while digital camera captures
images and stores them digitally without the
need of film.
 Digital cameras use different media to store
images, which include flash memory card, floppy
disk and compact disc.
 Hence, Pictures captured by Digital Camera can

19. Disc Drive
 A disk drive is a peripheral device that read or
writes the disks those stores information.
 The term disc drive can broadly be used for optical
drives, floppy drives and hard disk drives.
 The disc drive contains a motor and read/write
heads inside it.
 The motor rotates the disc at a constant rate and
read/write reads or writes the information on the
discs.
 The disc drives are used to input extremely large

20. Scanner
 Scanner is an input device.
 It is also called Optical Reader or Digital Scanner.
 It scans or reads text and pictures and converts
them into electrical signals, which can be directly
entered into the computer memory.
 The scanner takes electronic images or text from
the paper and stores them into the computer
memory.
 Scanned text can be edited by OCR software.

21. Handheld Scanner
 A scanner that is held in the hand and
passed across the image to be scanned is
termed as handheld scanner.
 This scanner is very small in size.
 It is less expensive, but, requires a steady
hand to get a clear image.
 These scanners are easy to use but, they
are limited to scan a wide picture.

22. Flatbed Scanner
 This type of scanner has a flat piece of
glass. The document is placed on the
glass upside down and the lid of scanner is
closed to scan it.
 The machine operated head moves
beneath the glass to scan the document.
 These are most reliable and widely used
scanners.

23. Sheet-fed Scanner
 A scanner that feeds each sheet of paper
across a nonmoving scan head is known as
Sheet-fed Scanner.
 This scanner cannot be used to scan pages in
books or magazines.

24. Output Devices
 An output device is any piece of computer
hardware capable of representing information
from a computer readable form into human-
readable form.
 An output device can be used to display or
print the intermediate or final results performed
by computer.
 Some examples of output devices are:
Monitors, Printers, Plotters and Speakers etc.

25. Monitors and its types
 A monitor also knows as video display unit, is a
device that displays texts and graphics
generated by a computer.
 The monitor can be of various kinds, depending
on the type of application.
 The basic two types of monitors are;
 CRT monitors
 LCD monitors

26. CRT (Cathode RAY Tube)
Monitors
 These are big and heavy and use a lot of
desk space and electricity.
 It is the oldest technology used by monitors
and is based on the cathode ray tube
technology that was developed for television.
 Monitors are made with better parts which
give a higher display resolution and picture
sharpness than a television.
 This type of monitor is no longer popular.

27. LCDflat panel display
Monitors
 The LCD monitor, the most common kind of flat
panel display. It is a newer technology than
CRT.
 LCD monitors use much less desk space, are
lightweight and use less electricity than CRT.
 They have been used for many years in the
screens of laptop and notebook computers.
 They also work as touch screens in tablet
computers, mobile phones, and other handheld
technologies.

28. Monochrome Monitors:
 Monochrome monitors are black and white
monitors that actually display two colors;
one for the background and one for the
foreground.
 These colors can be black and white,
green and black or amber and black.

29. ColorMonitors
 Color monitors can display images and text in multiple
colors. These monitors are classified by their image
producing technology.
 A Color Graphics Adapter (CGA), displays four colors at a
resolution of 320 by 200 pixels.
 An Extended Graphics Adapter (EGA) produces images up
to 16 different colors at a high resolution of 640 by 480
pixels.
 A Video Graphic Array (VGA) displays 256 color shades at a
resolution up to 720 by 400 pixels.
 A Super Video Graphic Array (S-VGA) displays color shades
at a resolution ranging from 800 by 600 pixels to 1280 by

30. Characteristics that determine
quality of Monitors
 Following are the different characteristics that
determine the quality of Monitors:
 Resolution: It indicates how densely packed the
pixels are.
 Bandwidth: The amount of data that can be carried
from one point to another in a given time.
 Refreshrate: How many times per second the
screen is refreshed. The normal refresh rate is 72
hertz.
 Dot pitch: The amount of space between two pixels.

31. PrinterExplain its
classification
 A printer is a device that accepts text and
graphics output form a computer and
transfers the information to a paper.
 Printer can be categorized in several ways
the most common are impact and non-
impact printers.

32. Impact Printers
 Impact printers include all printers that work by
striking an ink ribbon which presses the
characters image into paper.
 The hammer strikes the paper and presses it
into the ribbon and characters are created
hence, these printers produce noise while
printing.
 These printers include: Daisy wheel, Dot matrix,
Line printers, Chain printers, drum printers and
band printers.

33. Dot-Matrix Printer
 A dot-matrix printer uses print heads containing
from 9 to 24 pins.
 These pins strike an ink ribbon that produce
patterns of dots on the paper to form the
individual characters.
 The more pins a dot matrix printer has, the
clearer would be the letters on the paper.
 Dot-matrix printers are inexpensive and typically
print at speeds of 100-600 characters per
second.

34. Daisy wheel
 It is called daisy-wheel printer because the print
mechanism looks like a daisy; at the end of each
“Petal” is a fully formed character which produces
solid-line print.
 A hammer strikes a “petal” containing a character
against the ribbon, and the character prints on the
paper.
 Its speed is slow typically 25-55 characters per
second.
 Daisy wheel printer produces letter quality print but
cannot print graphics.

35. Line printer
 Line printers use special mechanism that
can print a whole line at once; they can
typically print the range of 1,200 to 6,000
lines per minute.
 They are high speed printers but produce
low quality print.
 Types of line printers include chain
printers, band printers and Drum, printers.

36. Non Impact Printers
 Non-impact printers do not use a striking
device to produce characters on the paper;
hence they are much quieter.
 Following are some non-impacted printers.
 The most popular non-impact printers are
thermal printer, ink-jet printer and laser
printer.

37. LaserPrinter
 A laser printer works like a photocopy machine.
 Laser printers produce images by passing a laser
beam which duplicates image on a rotating drum
and forms a charge image ion it.
 The drum has a special coating on it to which toner
(an ink powder) sticks and the image is transformed
on a paper that passes the drum.
 Laser printers use buffers that store an entire page
at a time.

38. LaserPrinter
 The speed of laser printers is high and
they print quietly without producing much
noise.
 Many laser printers can print eight pages
per minute, but faster and print
approximately 21,000 lines per minute, or
437 pages per minute if each page
contains 48 lines.

39. Thermal Printer
 It is a kind of non-impact printer.
 In electro-thermal printing, characters are
burned on to a special paper by heated
rods on a print heat.
 They transfer ink from a wax-based ribbon
onto plain paper. This printer can support
high quality graphic.

40. Inkjet Printer
 Ink-jet printers work in the same fashion as dot-
matrix printers, except that inkjet printers have
fine nozzles instead of tiny pins in print head.
 Ink-jet printers form characters on paper by
spraying ink from tiny nozzles through an
electrical field that arranges the charged ink
particles into characters at the rate of
approximately 250 characters per second.
 The ink is absorbed into the paper and dries
instantly. Various colors of ink can also be used.

41. Plotterand its classification
 Plotter is a special output device, which is
used to produce high quality hard copy
output.
 Plotters are designed to produce large
drawings or images such as construction
plans for buildings or blue prints for
mechanical devices.
 Plotters have been used in automotive and
aircraft design, other similar complex drafting

42. Drumplotter
 A drum plotter is also known as Roller Plotter.
 It consists of a drum or roller on which a paper is
placed and the drum rotates back and forth to
produce the graph on the paper.
 It also consists of Robotic Drawing Arm that holds a
set of colored ink pens or pencils.
 Drum plotters are used to produce continuous
output, such as plotting earthquake activity, or for
long graphic output, such as structural view of a
skyscraper.

43. Flatbed Plotter
 A flatbed plotter is also known as Table Plotter.
 It plots on paper that is spread and fixed over a rectangular
flatbed table.
 The flatbed plotter uses two robotic drawing arms, each of
which holds a set of colored ink pens or pencils.
 The plot size may be 20- by-50 feet.
 It is used in the design of cars, ships, aircrafts, buildings,
highways etc.
 It is very slow in drawing or printing graphs.
 The main reason of the slow printing is due to the movement
mechanical devices.

44. DiskDrive
 A disk drive is a peripheral device that reads or
writes the disks (hard disks, floppy disks, etc) that
store information.
 Disk drives are called “Storage Device” because
they store information.
 The drive contains a motor to rotate the disk at a
constant rate and one or more read/write heads,
which are positioned over the desired track.
 These devices are dual purpose devices as they
can be used for both input and output devices.

45. CD-WRITER
 A CD writer is a device connected to your computer
which can write on CD-WR and CD-R discs.
 CD-WR discs may be written, erased and rewritten,
while CD-R discs may be written only once.
 CD writer performances is measured in X unit, where IX
=150 kilobytes/sec.
 This allows user to master a CD-ROM or audio CD for
publishing CD-R devices can also read CD-ROMs and
play audio CDs.
 The CD writer is also called a CD-R drive (short for
Compact Disc – Recordable Drive)

46. soft copyandhardcopy
 In compute, the term hard copy is used for
computer’s output that has been printed on
some surface like paper.
 In compute, the term soft copy is used for
computer’s output that appears on a monitor
or LCD screen.
 In simple, the tangible output is known as
hard copy and intangible output is known as
soft copy.