HAMDARD UNIVERSITY

KARACHI

HAMDARD INSTITUTE OF MANAGEMENT

SCIENCES.
INFORMATION TECHNOLOGY
INPUT AND OUTPUT DEVICES OF COMPUTER

SUBMITTED BY ::LIAYAZ AHMED

SUBMITTED TO::Miss SHARAFAT BIBI
Computer Input Devices
An input device for a computer is anything that sends information to the CPU to perform a specific function.
A computer has the ability to use many different types of input devices to provide a unique experience to
each user.
Computer input devices include many types of hardware such as a keyboard, mouse, webcam, scanner as
well as a microphone.

Keyboard
 The keyboard is one of the most common types of input devices that is used with a computer. A keyboard
consists of letters, numbers and other types of keys that perform different types of functions when used
with a computer system. A keyboard can connect to the computer through a cord as well through a wireless
connection.

Trackpoint
  

Touch pad of a PC laptop

Some sub-notebook computers (such as the IBM ThinkPad), which lack room for even a touch pad,
incorporate a trackpoint, a small rubber projection embedded between the keys of the keyboard. The
trackpoint acts like a little joystick that can be used to control the position of the on-screen cursor.

Trackball
  
Joysticks and other game controllers can also be connected to a computer as pointing devices. They are
generally used for playing games, and not for controlling the on-screen cursor in productivity software.

Feature
Trackball is another pointing device that resembles a ball nestled in a square cradle and serves as an
alternative to a mouse. Like a mouse, a trackball is also used to control cursor movements and the actions
on a computer screen. 

Trackpoint
The trackball is sort of like an upside-down mouse, with the ball located on top. You use your fingers to roll
the trackball, and internal rollers (similar to what’s inside a mouse) sense the motion which is transmitted to
the computer. Trackballs have the advantage over mice in that the body of the trackball remains stationary
on your desk, so you don’t need as much room to use the trackball. Early laptop computers often used
trackballs (before superior touch pads came along).

Trackballs have traditionally had the same problem as mice: dirty rollers can make their cursor control
jumpy and unsmooth. But there are modern optical trackballs that don’t have this problem because their
designs eliminate the rollers.

A keyboard is the most commonly used input device. It has keys to type alphabets, digits and some other
special characters.

(i)                Its letters are arranged in the universal QWERTY layout.

(ii)              The digits are arranged above the alphabets.

(iii)            Function keys are aligned horizontally at the top.

(iv)            Special keys such as windows key, control key, Alt etc. are arranged in a particular way.
Joysticks and feature
  

Joystick is a device that moves in all directions and controls the movement of the cursor. The joystick offers
three types of control: digital, glide, and direct. Digital control allows movement in a limited numbers of
directions such as up, down, left, and right.
A joystick is generally used to control the velocity of the screen cursor movement rather than its absolute
position. 

Mouse
The mouse pointing device sits on your work surface and is moved with your hand. In older mice, a ball in
the bottom of the mouse rolls on the surface as you move the mouse, and internal rollers sense the ball
movement and transmit the information to the computer via the cord of the mouse.

The newer optical mouse does not use a rolling ball, but instead uses a light and a small optical sensor to
detect the motion of the mouse by tracking a tiny image of the desk surface. Optical mice avoid the problem
of a dirty mouse ball, which causes regular mice to roll unsmoothly if the mouse ball and internal rollers are
not cleaned frequently.

A cordless or wireless mouse communicates with the computer via radio waves (often using BlueTooth
hardware and protocol) so that a cord is not needed (but such mice need internal batteries).

A mouse also includes one or more buttons (and possibly a scroll wheel) to allow users to interact with the
GUI. The traditional PC mouse has two buttons, while the traditional Macintosh mouse has one button. On
either type of computer you can also use mice with three or more buttons and a small scroll wheel (which
can also usually be clicked like a button).
Two-button mouse with scroll wheel

Wireless Macintosh mouse

Mouse  is  a  small  hand-held  pointing  devices , which  is  rectangular-shaped  with  a  rubber 
ball  embedded  at  its  lower  side  and  buttons  on  the  top . The  Mouse  may  be  classified 
as  a  mechanical  mouse  or  an  optical  mouse , based  on  technology  it  uses .
A  mouse  allows  us  to  create  graphic  element  on  the  screen , such  as  lines , curves ,and 
freehand  shapes . It  is  much  easier  and  convenient  to  work  as  compared  to  the  keyboard.

MIDI Devices
MIDI (Musical Instrument Digital Interface) is a system designed to transmit information between electronic
musical instruments. A MIDI musical keyboard can be attached to a computer and allow a performer to play
music that is captured by the computer system as a sequence of notes with the associated timing (instead
of recording digitized sound waves).

  

Graphics tablet.
Webcam
 A webcam is a device that acts as a video camera and sends a video signal into the computer that can be
viewed over the Internet. A webcam can be used for various types of activities such as online chatting as
well as video conferencing. A webcam can also be used to record video that can be saved to the hard disk
or burned to a DVD.

Scanner
 A scanner is a device that is used to copy an image or document and convert it into a digital file that is
used with a computer system. Scanners can be used to create digital images of family photos as well as
create digital images of important documents. A scanner is available as a flatbed device or a sheet fed
device that can come bundled with many printers and fax machines.

Scanner is a device used to make a soft copy of document or photo. It is just like a camera which takes
snap of your document or photo and feed to computor.

Microphone
 A microphone is an input device that can be used in a computer for many different applications. One way
to use a microphone is to record audio or video tutorials. Another use for a microphone is for performances
such as karaoke or professional audio recording. A microphone is available as a hand-held model as well
as a headset.

A microphone can be attached to a computer to record sound (usually through a sound card input or
circuitry built into the motherboard). The sound is digitized—turned into numbers that represent the original
analog sound waves—and stored in the computer to later processing and playback.

MPORTANCE  OF INPUT  DEVICES

Input devices play a major role in the processing of any data via the computer system because the output
of the computer is always based on the given input. Generally, data, which is given to the input devices, is
row. Therefore, it is the function of the input devices to manipulate the raw data and then send it for further
processing. The preparation of input is the initial step in the creation of useful information.

Output Devices of Computer

Output Device
An output device is any piece of computer hardware equipment used to communicate the results of data
processing carried out by an information processing system (such as a computer) to the outside world.

Or

Output devices are things we use to get information OUT of a computer.

Some Important output devices are listed below.

CRT Monitor
   

The traditional output device of a personal computer has been the CRT (Cathode Ray Tube) monitor. Just
like a television set (an older one, anyway) the CRT monitor contains a large cathode ray tube that uses an
electron beam of varying strength to “paint” a picture onto the color phosphorescent dots on the inside of
the screen. CRT monitors are heavy and use more electrical power than flat panel displays, but they are
preferred by some graphic artists for their accurate color rendition, and preferred by some gamers for faster
response to rapidly changing graphics.

Monitor screen size is measured diagonally across the screen, in inches. Not all of the screen area may be
usable for image display, so the viewable area is also specified. The resolution of the monitor is the
maximum number of pixels it can display horizontally and vertically (such as 800 x 600, or 1024 x 768, or
1600 x 1200). Most monitors can display several resolutions below its maximum setting. Pixels (short for
picture elements) are the small dots that make of the image displayed on the screen. The spacing of the
screen’s tiny phosphor dots is called the dot pitch (dp), typically .28 or .26 (measured in millimeters). A
screen with a smaller dot pitch produces sharper images.

Your computer must produce a video signal that a monitor can display. This may be handled by circuitry on
the motherboard, but is usually handled by a video card in one of the computer’s expansion slots; often the
slot is a special one dedicated to video use, such as an AGP slot (Accelerated Graphics Port). Video cards
are also called video display adapters, and graphics cards. Many video cards contain separate processors
and dedicated video memory for generating complex graphics quickly without burdening the CPU. These
accelerated graphics cards are loved by gamers.

Flat Panel Monitor

  

CRT monitor

A flat panel display usually uses an LCD (Liquid Crystal Display) screen to display output from the
computer. The LCD consists of several thin layers that polarize the light passing through them. The
polarization of one layer, containing long thin molecules called liquid crystals, can be controlled
electronically at each pixel, blocking varying amounts of the light to make a pixel lighter or darker. Other
types of flat panel technology exist (such as plasma displays) but LCDs are most commonly used in
computers, especially laptops.

Older LCDs had slow response times and low contrast, but active matrix LCD screens have a transparent
thin film transistor (TFT) controlling each pixel, so response, contrast, and viewing angle are much
improved.

Flat panel displays are much lighter and less bulky than CRT monitors, and they consume much less
power. They have been more expensive than CRTs in the past, but the price gap is narrowing. You will see
many more flat panels in the future.

As with CRTs, the display size of a flat panel is expressed in inches, and the resolution is the number of
pixels horizontally and vertically on the display.

Ink Jet Printer

  
Flat panel display (LCD)

For hardcopy (printed) output, you need some kind of printer attached to your computer (or available over a
network). The most common type of printer for home systems is the color ink jet printer. These printers
form the image on the page by spraying tiny droplets of ink from the print head. The printer needs several
colors of ink (cyan, yellow, magenta, and black) to make color images. Some photo-quality ink jet printers
have more colors of ink.

Ink jet printers are inexpensive, but the cost of consumables (ink cartridges and special paper) make them
costly to operate in the long run for many purposes.

Laser Printer
  

Inkjet Printer

A laser printer produces good quality images by the same technology that photocopiers use. A drum coated
with photosensitive material is charged, then an image is written onto it by a laser (or LEDs) which makes
those areas lose the charge. The drum then rolls through toner (tiny plastic particles of pigment) that are
attracted to the charged areas of the drum. The toner is then deposited onto the paper, and then fused into
the paper with heat.

Most laser printers are monochrome (one color only, usually black), but more expensive laser printers with
multiple color toner cartridges can produce color output.

Laser printers are faster than ink jet printers. Their speed is rated in pages per minute (ppm). Laser printers
are more expensive than ink jets, but they are cheaper to run in the long term if you just need good quality
black & white pages.
Other Printers

  

Laser Printer

Multi-function printers are available that not only operate as a computer printer, but also include the
hardware needed to be a scanner, photocopier, and FAX machine as well.

Dot matrix printers use small electromagnetically activated pins in the print head, and an inked ribbon, to
produce images by impact. These printers are slow and noisy, and are not commonly used for personal
computers anymore (but they can print multi-layer forms, which neither ink jet or laser printers can).

Sound Output
   

Computers also produce sound output, ranging from simple beeps alerting the user, to impressive game
sound effects, to concert quality music. The circuitry to produce sound may be included on the
motherboard, but high quality audio output from a PC usually requires a sound card in one of the expansion
slots, connected to a set of good quality external speakers or headphones.

Multimedia is a term describing computer output that includes sound, text, graphics, movies, and animation.
A sound card is an example of a multimedia output device (as is a monitor that can display graphics).

Refrences
http://www.buzzle.com/articles/computer-output-devices.html

http://www.computerhope.com/jargon/m/monitor.htm