Post on 02-Jun-2018
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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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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