Introduction to Computer
Lecture # 5
Course Instructor : Sehrish Rafiq
Govt. Girls Degree College Maneri Swabi
Higher Education Department KP

LectureOverview
• Computer Hardware
• Organization of a computer system
• Input Devices

ComputerHardware
• The physical components of a computer system are known as
hardware.
• Hardware refers to machines in computer system.
• Those components of a computer system which can be seen,
touched and felt are known as hardware.
• The mechanical and electrical components of a computer system are
known as hardware.

Organizationof a ComputerSystem
• Every digital computer is made of four basic units.
 Input Unit
 Central Processing Unit
 Storage Unit
 Output Unit

Responsibilitiesof Input Unit
• It accepts or reads instructions or data from outside world.
• It converts these instructions and data in computer acceptable
form(machine language).
• It supplies the converted instructions and data to the computer
system memory for further processing.

Responsibilitiesof ProcessingUnit
• Execution of program instructions
• Control other units of computer

Responsibilitiesof Output Unit
• It accepts the results produced by the computer which are in coded
form (machine language) and hence cannot be easily understood by
humans.
• It converts these coded results in to human understandable form.
• It supplies the converted results to outside world.

Responsibilitiesof StorageUnit
• Store data and instructions required for processing (received from
input devices).
• Store intermediate results of processing.
• Store final results of processing before they are released to an
output device.

Input Devices

Commonlyused input devices
• Keyboard devices
• Point and draw devices
• Data scanning devices
• Digitizer
• Electronic cards based devices
• Microphones
• Webcams
• Speech recognition devices
• Vision based devices

KeyboardDevices
• Allow entry in to a computer by pressing a set of keys (labeled
buttons) neatly mounted on a board connected to a computer
system.
• 101-keys QWERTY keyboard is most popular.
• In laptops the keyboard buttons are mounted in the machine and
are not on a separate board, therefore it is called keypad.

KeyboardDevices

Point & DrawDevices
• Used to rapidly point to and select a graphical icon or menu item from
multiple options displayed on the screen.
• Used to create graphic elements on screen such as lines, curves and
freehand shapes
• Examples:
Mouse
Track ball
Joy stick
Light pen
Touchpad
Touch screen

Mouse
• It is a hand-held pointing device that detects two-
dimensional motion relative to a surface.
• This motion is typically translated into the motion of a pointer on
a display, which allows a smooth control of the graphical user
interface.
• Types of mouse
Mechanical mouse
Optical mouse

TrackBall
• It is a pointing device which consists of a ball held by a socket containing
sensors to detect a rotation of the ball about two axes.
• It is like an upside-down mouse with a ball that sticks out.
• The user rolls the ball with the thumb, fingers or the palm of the hand
to move a cursor.
• Applications
 General Purpose Computers
 Radar consoles in an air-traffic control room
 Sonar equipment on a ship or submarine

Joy Stick
• A joystick is an input device consisting of a stick that pivots on a base
and reports its angle or direction to the device it is controlling.
• Joysticks are often used to control video games, and usually have
one or more push-buttons whose state can also be read by the
computer.
• It performs the same function to the arrow keys in the keyboard but
they provide eight direction movement.
• Applications
Video games
Controlling flight of an aircraft
controlling cranes, trucks, underwater unmanned vehicles

Light Pen
• A light pen is an input device which looks like an ordinary pen but its
tip is a contains light sensitive detector.
• It is used in conjunction with a computer's CRT display.
• When its tip touches the screen, the computer locates its position in
the form of X-Y coordinates.
•
• It allows the user to directly point to displayed objects or draw on
the screen in a similar way to a touchscreen but with greater
positional accuracy.

Touch pad
• A touchpad is also known as a track pad.
• It is a pointing device which contains a tactile sensor.
• It is a specialized surface which can translate the motion and
position of a user's fingers to a relative position on screen.
• It is a common feature of laptops and is used as a substitute for a
mouse where desk space is scarce.
• Because they vary in size, they can also be found on personal digital
assistants (PDAs) and some portable media players.
• Wireless touchpads are also available as detached accessories.

Touch Screen
• A touchscreen is a computer screen that can be used by touching it
with a finger or a stylus pen.
• It enables the user to interact directly with what is displayed.
• It can be described as a touchpad with a screen built-in to it.
• Today, all kinds of devices, both big and small, make use of
touchscreens.
• However, tablet computers and smartphones have made them
popular and are the most widely known and used products that use
touchscreens.

Touch ScreenDevices

• Input devices that enable direct data entry in to a computer from
source document are known as data scanning devices.
• They eliminate the need to key in text data in to computer.
• Due to reduced human effort in data entry, these devices improve
data accuracy and increase the timeliness of information processed.
• They demand high quality of input documents.
• Some of them are capable of recognizing marks or characters.
• Examples:
• Image Scanner
• Optical mark Reader
• Bar Code Reader
• Magnetic Ink Character Reader
DataScanning devices

• Scanner translates paper documents in to electronic format for storage
in computer.
• Electronic format of a scanned image is its bitmap.
• Stored image can be altered or manipulated using image processing
software.
ImageScanner

• It is a scanner equipped with a character recognition software.
• It photo-scans text character-by-character, analyzes the scanned-in
image, and translates it into character codes.
• It utilizes light beams to read alpha numeric characters of both hand
written or typed text.
• It is extremely complex because it is difficult to make computer recognize
an unlimited number of fonts.
• They are used for large volume processing applications such as scanning
of utility bills of customers etc.
OpticalCharacterRecognition(OCR)
Device

• It is a scanner capable of recognizing a pre-specified type of mark by
pencil or pen.
• It can capture human-marked data from document forms such as
surveys and tests.
• They are used to read questionnaires, multiple choice examination
paper in the form of shaded areas.
OpticalmarkReader

• A bar code reader is an electronic device that can read data in the
form of bars/lines known as Universal Product Code (UPC) in to the
computer.
• UPC contains the detailed product information and is used for
labeling goods and stock in a shop.
• After detecting the code, it transmits the product data in to
computer which locates item price, updates the stock and prints the
receipt for the customer.
Bar Code Reader

• MICR is a device capable of recognizing characters written with special ink
and in specific font.
• It is mostly used by banks for faster processing of large volume of
cheques.
• Numbers and characters (consisting of check number and account
number) are printed using Magnetic Ink on bottom of cheques.
• MICR provides a secure, high-speed method of scanning and processing
information.
• MICR supports only 14 symbols.
MagneticInk CharacterReader
(MICR)

Magnetic Ink Character Reader

• Digitizer is an input device used for producing pictorial images.
• It enables the user to write/draw something on the tablet like
surface using stylus.
• The tablet senses where the stylus touched it and sends the x-y
coordinates of each point to the computer.
• It is mostly used by architects and engineers to design cars,
buildings, medical devices, robots etc.
• It is also used for digitizing maps available in paper form.
Digitizer

• Electronic cards are small plastic cards having encoded data
appropriate for the application for which they are used.
• Electronic card reader is used to read data encoded on an electronic
card and transfer it to the computer for further processing.
• Used together as a means of direct data entry in to a computer
system.
• Used by banks for use in Automated Teller Machines (ATM’s) and
organizations for controlling access of employees to physically
secured areas.
ElectronicCard Reader

Microphone
• Microphone is an input device to input sound that is then stored in a
digital form.
• The microphone is used for various applications such as adding sound
to a multimedia presentation or for mixing music.

Webcam
• A webcam is a video camera that is used for capturing snaps or
videos.
• When "captured" by the computer, the videos/ pictures may be
saved, viewed or sent on to other networks using internet or can be
e-mailed as an attachment.
• When sent to a remote location, the videos/ pictures may be saved,
viewed or on sent there.
• A webcam is generally connected by a USB cable or built into
computer hardware, such as laptops.

SpeechRecognitionDevices
• Input device that allows a person to input data to a computer by
speaking to it is known as speech recognition device.
• Today speech recognition devices are limited to accepting few words
within a relatively small domain and can be used to enter only
limited kinds and quantities of data.
• Types of speech recognition devices
• Single word
Recognize a single word
Speaker independent
• Continuous speech recognition systems
 Recognize sentences
Speaker dependent

Usesof speechrecognitionsystems
• For inputting data to a computer by user in situations where their
hands are busy or their eyes must be fixed on a measuring
instrument or some other object.
• For data input by dictation of long text or passage for later editing
and review.
• For authentication of a user by a computer system based on voice
input.
• For limited use of computers by individuals with physical disabilities.

Vision-Input Systems
• Allow computer to accept input just by seeing an object.
• Input data is normally an object’s shape and features in the form of
an image.
• Mainly used today in factories for designing industrial robots that
are used for quality-control and assembly processes.