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2

What is a Computer? 

C ommonly O  perated M achine P recisely U sed

for T raining, E ducation and R esearch.

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3

 A computer is an electronic machine that can be programmed to accept

data (input ), process it into useful information (output ), and store it in a

storage  media for future use

System Unit

Block Diagram of Computer

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Input Output Devices

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INPUT Any data and instructions you enter  into the memory of a

computer  

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INPUT• Data

Collection of unorganized fact - words, numbers, pictures,

sounds and videos  information

• Instructions

 Program

a series of instructions that tells a computer how to perform

the tasks

 Command

an instruction given to a computer by typing or pressing keys

on the keyboard or clicking a mouse button  User Response

an instruction you issue to the computer by replying to a

question posed by a computer program

E.g. : Do you want to Exit this program?

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INPUT DEVICE Any hardware component used to enter data and

instruction into a computer  

Type of

InputDevice 

Example 

Keyboard

InputKeyboard (QWERTY) 

PointingDevices

Mouse, Trackball, Joysticks, Touchpad,Light Pen

Source Data

Entry

Scanner, Optical Recognition, Voice Recognition,

 Audio and video input, Biometric device

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KEYBOARDinput device that contains keys users press toenter data and instructions into a computer

status light

numeric keypad

function keys

typing area

arrow keys

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KEYBOARD• QWERTY keyboard

 – designed for typewriter  

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KEYBOARD• Wireless or cordless keyboard

 – Transmits data using wireless technology

 – Communicate with a receiver attached to a port on the

system unit

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KEYBOARDAlternative forms for command

• Many programs allow you to use key combination, menu,or button to obtain same result

Key Menu |

Command Combination Command Button

Copy Shift+F2 or Edit | Copy

Ctrl+C

Open Ctrl+F12 File | Open

Paste Ctrl+V Edit | Paste

Key Menu |Command Combination Command Button

Copy Shift+F2 or Edit | Copy

Ctrl+C

Open Ctrl+O File | Open

Paste Ctrl+V Edit | Paste

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POINTING DEVICE

 A pointing device can be used to :

move the insertion point;

select text, graphics and other objects;

click buttons, icons, links and menu commands.

input device that allows a user to control

a pointer  on the screen

I-beam Block

arrow

Pointing

hand

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POINTING DEVICEMouse

 – pointing device that fits under the palm of your hand

Mechanical mouseHas a rubber ball underneath - electronic circuits in themouse translate the movement of the mouse into signals thecomputer can process

mouse buttons

wheelbutton

mouse pad

ball

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POINTING DEVICETouchpads

a small, flat, rectangularpointing device that is

sensitive to pressure andmotion 

Touch Screens

a touch sensitive

display device.

Users can interact

with these devices by

touching areas of the

screen

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POINTING DEVICELight pen  A pen-like device connected to the computer terminal device that

can detect the presence of light.

Uses pressure to write text or draw  press the light pen against thescreen and press a button on the pen

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SOURCE DATA ENTRY• Do not require keystroke   data is entered withoutrequiring humans to type in.

• It collects data at the source and send it directly to thecomputer.

•  Advantages : Reduces the number of possible errors.

 M ICR Readers

 Voice I nput

 Digital Cameras Video Input  

 Biometr ics

 Scanner

 Optical Readers

 Barcode Readers RFID Readers

 Magnetic Str ipe Card Readers

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SOURCE DATA ENTRYScannerConvert text and picture into recognizable form  optical recognition

The quality of a scanner is measured in no of pixels per inch(resolution)

 – determines the sharpness and clearness of the resulting image

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SOURCE DATA ENTRY

Flatbed 

Sheet-fed 

Pen or Handheld 

Drum 

Types of scanner

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SOURCE DATA ENTRYOptical Readers a device that uses a light source to

read characters, marks and codes  converts them into digital data.

Optical Mark Recognition (OMR)

read hand-drawn marks suchas small circles or rectangle

e.g. for MCQ exam 

Optical Character Recognition(OCR)

Read typewritten,computer-printed or hand-printed characters fromordinary documents

digital code 

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SOURCE DATA ENTRYBar Code Readersan optical reader that uses laser

beams to read bar codes 

(identification code that consists

of a set of vertical lines andspaces of different widths) RFID Readers

• Radio Frequency Identification  -uses radio signals to communicate

with a tag placed in or attached toan object, animal or person

• RFID tags a memory chip and anantenna.

• Does not required direct contact

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SOURCE DATA ENTRYMagnetic Stripe Card Readers Reads the magnetic stripe on the

back of credit cards, bank cardsand other similar cards.

Contains information - your name,account number, card’s expirationdate, country code, etc.

MICR Readers Convert MICR characters a form

the computer can process

MICR device - reads text printedwith magnetized ink.

Used by the banking industry -cheque processing

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SOURCE DATA ENTRYVoice Input the process of entering input by speaking

Voice or speech recognition converts a person's speech intodigital code

comparing the electrical patterns produced by the speaker'svoice with a set of prerecorded patterns stored in the computer

01

Digital voiceWave formvoice

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SOURCE DATA ENTRYDigital Camera

allows users to take pictures and store

the photographed imaged digitally

Transfer the image by downloading or

using storage media

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SOURCE DATA ENTRYVideo Input the process of capturing

full-motion images and

storing them on a

computer’s storagemedium

Videoconferencing 

Web Cams PC videocamera 

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SOURCE DATA ENTRYBiometrics the technology of authentication a person’s identity by verifying a

personal characteristic

Biometric device

translates a personal characteristic (the input)

into a digital code that is compared with a digital code stored in

the computer .

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Examples of biometric technology

Voice verification system compares live

speech with stored voice pattern

Signature verification system recognizesshape of signature

Iris recognition system reads patterns in

blood vessels in back of eye

Fingerprint scanner  captures curves andindentations of fingerprint

Hand geometry system measures shape

and size of person’s hand 

SOURCE DATA ENTRY

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OUTPUT DEVICE

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OUTPUT data that has been processed into useful form  Information

4 categories of output

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• Text

Examples of text based output are

Memos/Notices

Letters

Reports

E-mail messages

OUTPUTCategories of output

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Example of audio :-

 audio clips

 live broadcasts of interview

 listen to music while working

with computer

 chat using microphone

OUTPUT

• Audio

• Video

Categories of output

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Examples of graphics :-

 logos

 chart

 drawing clip art

 photographs

OUTPUT

• Graphics

• Animation

Categories of output

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OUTPUTTwo kinds of output 

Hardcopy

printed output

Softcopy

data that are kept in

any storage media

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OUTPUT

 Any hardware component that conveys

information to one or more users.

printer speakerDisplay device

Output Devices

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COMPUTER DISPLAY TECHNOLOGY An output device that visually conveys text, graphics andvideo information - softcopy

It consists of a screen and the other components 

Types of displayCRT (Cathode Ray tube )

Flat-panel displays

CRT Flat-panel display

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COMPUTER DISPLAY TECHNOLOGYQuality of a Monitor

Resolution

the number of pixels (horizontal by vertical)

E.g. 640x480, 800x600, 1024x768

800 horizontal pixels

600 vertical

pixelsTotal of 480,000

pixels on screen

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PRINTERSDevices that produces text and graphic on a

physical medium  hardcopy/printout

• Two orientations: portrait and landscape

• Printer resolution is measured by number of

dots per inch (dpi).• Higher the resolution, the higher the image

quality

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300 dpi 1,200 dpi600 dpi

PRINTERS

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Types of printers

1. Impact

• Form character/graphics by striking a

mechanism against an inked ribbon  leavingan image on paper physically

2. Non-impact

• Place image on a page without touching the

page physically

PRINTERS

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PRINTERS• Impact

Dot Matrix Printer

• Produced images when tiny

wire pins strike an inked

ribbon.• Widely used for business

• Useful for low quality carbon

copy printing

•  Advantages:

 – Handle continuous-form

paper

 – cheapDOT MATRIX PRINTER

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PRINTERS – Line Printer

• Print an entire line at a

time

• Speed – measured by noof lines per minute

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PRINTERS• Non-impact Ink-jet Printer

• Spray tiny drop of liquid ink onto paper  using multiple jet nozzles

• Can print – black/ white and several different colors

• Resolution  – measured by dpi (dots per inch)• Speed  - measured by ppm (pages per minute)

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PRINTERSLaser Printer

• Used a laser beam and

powdered ink (toner) to transfer

images onto paper

• Prints text and graphics in very

high-quality resolution

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PRINTERSPlotter• Large printers specialized to

produce high-quality

graphics• Large-format printer createsphoto-realistic qualitycolor prints

• Print signs, posters and

other professional qualitydisplays

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Mobile Printer

• Small lightweight,

battery-powered

printer

• allows mobile user

to print from

notebook

computer, while

traveling

• Used ink-jet

PRINTERS

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OTHER OUTPUT DEVICES• Fax machine (Input as well as Output Device)

Fax machine  – a device that code and encode documents to be

transmitted over telephone lines

• Multifunction peripheral

 A device that looks like a copy machine but provide functionality – printer, scanner, copy machine and fax machine

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OTHER OUTPUT DEVICES• Data projector

 A device that displays text and image on a computer screen  

projects them on large screen – we can see the image clearly

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System Unit

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• What is the

system unit?

 – Case that containselectronic

components of the

computer used to

process data

• Sometimes called

the chassis

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The System Unit

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Common components inside the SU

Memory Adapter cards

Sound card

Modem card

Video card

Networkcard

Ports Power supply

power supply

ports

drive bays

processor

memory

sound card

video cardmodem card

network card

Processor

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CPU/Processor

Control

Unit

Arithmetic

Logic Unit (ALU)

Arithmetic

Logic Unit (ALU)

Input

Devices

Storage

Devices

Output

Devices

Interprets and

carries out basic

instructions that

operate acomputer

MemoryData Information

Instructions

Data

Information

Instructions

DataInformation

Control

Unit

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2.1 CPU or microprocessors 

Consists of two major parts which are:

Control units

Tells the rest of thecomputer systems how

to carry out a program's

instruction.

For each instruction, the

control unit repeats a set

of 4 basic operations know

as machine cycle (Fetch,

Decode, Execute, Store).

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2.0 Central Processing Unit 

Control ALU

1

2 3

4

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 ALUPerforms arithmetic operation and logical operationsand controls the speed of the operation.

 Arithmetic operation - performs four kinds of arithmeticoperations or mathematical calculations: +, -, X and /.

Logical operation - comparisons such as ==, >=, <= andothers.

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Control ALU

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System Unit

 

MotherboardThe main circuit board in the system unit which holds:

• The CPU or microprocessor .

• Electronic memory that assists the CPU, known as RAM.

• And some expansion slots where additional circuit boards,

called expansion boards may be plugged in.processor chip

adapter cards

memory chips

memory slots

motherboard

Expansion

slots for

adapter cards

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EXPANSION SLOT