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Introduction to
Computers
©Dr Loganathan R
DEFINITION
• An electronic device that is designed to accept data,
perform the required mathematical and logical operations
at high speed, and output the result
©Dr Loganathan R
CHARACTERISTICS
OF COMPUTERS
Speed
Accuracy
Automation
Diligence
Versatile
Memory
No I.Q.
Economical
©Dr Loganathan R
STORED PROGRAM CONCEPT
• Before any data is processed, instructions are read into memory
• Instructions are stored in the computer’s memory for execution
• Instructions are stored in binary form (0s &1s)
• Processing starts with the first instruction in the program, which is
copied into a control unit circuit. The control unit executes the
instructions
• Instructions written by the users are performed sequentially until
there is a break in the current flow
• Input/Output and processing operations are performed
simultaneously. While data is being read/written, the central
processing unit (CPU) executes another program in the memory that
is ready for execution.
©Dr Loganathan R
Types of Stored Program Computers
• Shared memory for instructions and data
• Separate memories for instructions and data
Processor
Main
Memory
Address Bus - carries addresses
Data Bus - carries data and instructions
Instruction
memory
Processor
Instruction Address
Instructions
Data
Memory
Data Address
Read/Write Data
©Dr Loganathan R
HISTORY OF COMPUTERS
Timeline of Developments
1822 1890 1936 1941
1943
1944
300BC
steam-driven
Difference
Engine
Charles
Babbage
computing
anything
Turing
Machine
First digital
computers
ENIAC
for
mathematical
computations
Abacus
US 1880
census
Punched
Card
System
29 equations
simultaneously
Atanasoff–
Berry
Computer
(ABC)
©Dr Loganathan R
HISTORY OF COMPUTERS
Timeline of Developments
1947 1953 1954 1958 1969
1946
vacuum
tubes
replaced
transistor
Formula
Translation
FORTRAN
Operating
System
Unix
first
commercial
computer
UNIVAC
first
computer
language
COBOL
Chip
Integrated
Circuit
©Dr Loganathan R
HISTORY OF COMPUTERS
Timeline of Developments
• 1964: prototype of the modern computer, with a mouse and a graphical user interface (GUI)
• 1970: DRAM chip was introduced by Intel
• 1971: IBM invented the floppy disk
• 1973: Ethernet for connecting multiple computers
• 1974–1977: Personal Computers
• 1975: BASIC
• 1976: Steve Jobs and Steve Wozniak started Apple Computers
• 1977: Apple II
• 1978: WordStar, a word processor application
• 1979: VisiCalc, the first computerized spreadsheet
• 1981: The first IBM personal computer with MS-DOS OS
• 1983: The first laptop
• 1985: Microsoft Windows OS
• 1986: Compaq Deskpro 386, which was a 32-bit architecture
• 1990: Tim Berners-Lee invented World Wide Web with HTML
• 1993: The Pentium microprocessor
• 1994: PC games
• 1996: Sergey Brin and Larry Page developed the Google
• 1999: Wi-Fi started connecting to the Internet without wires.
©Dr Loganathan R
HISTORY OF COMPUTERS
Generations of Computers(evolution)
Examples
ENIAC
EDVAC
EDSACUNIVAC I
IBM 701
Memory
Primary:
Electromagnetic
relay
Secondary:
punched cards
Hardware
Technolog
y
Vacuum tubes which
is made of fragile
glass
Software
Technolog
y
Programming was
done in machine or
assembly language.
Used for
Scientific
applications
Highlights
Bulky
Vacuum tubes emitted
heat and burned
Costly
Difficult to use
Constant maintenance
First
Generation
(1942–
1955)
©Dr Loganathan R
HISTORY OF COMPUTERS
Generations of Computers(evolution)
Examples
Honeywell 400
IBM 7030
CDC 1604
UNIVAC LARC
Memory
Primary: Magnetic
core
Secondary: Magne
tic tapes and disks
Hardware
Technology
Transistors: reliable
, powerful,
cheaper, smaller &
cooler .
Software
Technology
Programming was
done in High Level
programming
languages
Used for
Scientific and
commercial
applications
Highlights
Bulky
less heat than 1st Gen
Faster than 1st Gen
Costly
Difficult to use
Consumed 1/10 than
1st Gen
Second
Generation
(1955–
1964)
©Dr Loganathan R
HISTORY OF COMPUTERS
Generations of Computers(evolution)
Examples
IBM 360/370
PDP-8 & PADP-11,
CDC6600
Memory
Primary: Large
Magnetic core
Secondary:
Large Magnetic
tapes & disks
Hardware
Technology
integrated chips
(ICs):
SSI and MSI
technology
Software
Technology
Programming was
done in High Level
Language
Time sharing OS
Used for
Scientific,
Commercial &
Interactive
online applications
Highlights
Bulky
less heat than 2nd Gen
Faster than 2nd Gen
Costly
Difficult to use
Consumed less
power than 2nd Gen
Third
Generation
(1964–
1975)
©Dr Loganathan R
HISTORY OF COMPUTERS
Generations of Computers(evolution)
Examples
IBM PC, Apple II, TRS-
80, VAX 9000, CRAY- 1,
CRAY-2, CRAY-X/MP
Memory
Primary:
Semiconductor
Secondary:
Large Magnetic
tapes, disks & Floppy
Hardware
Technology
integrated chips
(ICs):
LSI and VLSI
LAN & WAN
Software
Technology
Programming was
done in High Level
Language - 'C'
GUI-OS
Used for
Scientific,
Commercial, Interac
tive online &
Network
applications
Highlights
Faster, smaller,
cheaper, powerful,
reliable, and easier
Fourth
Generation
(1975–
1989)
©Dr Loganathan R
HISTORY OF COMPUTERS
Generations of Computers(evolution)
Examples
IBM notebooks,
Pentium PCs,
SUN workstations, IBM
SP/2, Param
supercomputer
Memory
Primary:
Semiconductor
Secondary:
Large Magnetic
tapes, disks & USB
Drives
Hardware
Technology
integrated chips
(ICs): ULSI
Internet
Software
Technology
Programming was
done in HLL– Java,
Python
GUI-OS
Used for
Scientific,
Commercial, Interac
tive online,
Multimedia & N/W
applications
Highlights
Faster, smaller,
cheaper, powerful,
reliable, easier &
more Speed
Fifth
Generation
(1989–
Present)
©Dr Loganathan R
CLASSIFICATION
OF COMPUTERS
• Four categories
(speed, amount of data
processing & price)
Supercomputers
• Dumb terminals
• Intelligent terminals
Mainframe computers
Minicomputers
• Desktop PCs
• Workstations
• Laptops
• N/W Computers
• Handheld devices
Microcomputers
14
©Dr Loganathan R
©Dr Loganathan R
CLASSIFICATION OF COMPUTERS
• Supercomputers
• Fastest(one trillion calculations/s), most powerful, and most expensive, parallel
processing(thousands of concurrent users) , weather forecasting, nuclear energy research,
aircraft design, CRAY-1, CRAY-2, Control Data CYBER 205, and ETA A-10.
• Mainframe computers: large-scale computers, very expensive, servers(www), banks, airline
companies & universities
• Dumb terminals: a monitor and a keyboard, No CPU and memory
• Intelligent terminals: Own processor, No Memory, PCs are used to data access & services
• Minicomputers: smaller, cheaper, slower, business, as servers in a network, education, hospitals
, single/multiple users, DEC, IBM(AS/400)
• Microcomputers: IBM-PC in 1981, Apple, DOS, Windows, Mac OS, Linux,
• Desktop PCs: homes and offices
• Workstations: processing speed matches with minicomputer, Scientist, engineers, architects
• Laptops: Similar to Desktop PCs with Mobility
• N/W Computers: as terminals in a network, to access data, NetPCs
• Handheld devices: Smartphones, Tablet PCs, iOS, Android, 15
©Dr Loganathan R
©Dr Loganathan R
APPLICATIONS OF COMPUTERS
• Word processing
• Internet
• Digital audio & video composition
• Desktop publishing
• Multimedia and Animation
• Legal System
• Retail Business
• Sports
• Travel and Tourism
• Simulation
• Astronomy
• Education
• Industry and Engineering
• Robotics
• Decision Support Systems
• Expert Systems
• e-Business
• Business-to-consumer or B2C
• Business-to-business or B2B
• Consumer-to-consumer or C2C
• Electronic banking
• Bioinformatics
• biological and genetic information
• gene-based drug discovery
and development
• Health care
• Storing records
• Surgical procedures
• Diagnosis and Treatment
• Geographic Information System
and Remote Sensing
• Monitoring deforestation
• Study features of glaciers
• Analysing the depth of coastal
and ocean
• Meteorology
• Weather forecasting
• Aviation meteorology
• Agricultural meteorology
• Nuclear meteorology
• Maritime meteorology
©Dr Loganathan R
BASIC ORGANIZATION OF A COMPUTER
Block diagram of a computer
Interaction between the different
units of a computer system
©Dr Loganathan R
BASIC ORGANIZATION OF A COMPUTER
A computer performs five major operations:
Input:
• Accepting data or instructions : keyboard, mouse, scanner, and trackball
Strorage:
• Primary storage: very expensive and limited capacity
• Secondary storage: cheaper and non-volatile
Processing (ALU):
• Performing operations on the data as per the instructions(by ALU)
Output :
• Displaying result of data processing to the outside world
Control (CU):
• Controlling and coordinating all operations and Components of a computer(Control Unit)
©Dr Loganathan R
INSIDE THE COMPUTER
©Dr Loganathan R
INSIDE THE COMPUTER
CPU
RAM
HDD
Video
card
Sound
card
Modem
Network
card
Fans
Cables
©Dr Loganathan R
MOTHERBOARD
©Dr Loganathan R
MOTHERBOARD
I/O connectors
©Dr Loganathan R
MOTHERBOARD
Characteristics of a Motherboard
Form factor
• Geometry, dimensions, arrangement and electrical requirements
Integrated components
• Chipset, CMOS clock and battery, BIOS, System bus, Expansion
bus, processor, cache memory, RAM
Chipset
• Coordinates data transfers between the different components
CMOS clock and battery
• Real-Time Clock (RTC) circuit synchronize the computer’s
signals, CMOS chip is powered by a battery
Basic Input/Output System (BIOS)
• Interface between the OS & Motherboard, stored in the read-only
memory (ROM)
Processor socket
• Processor inserted very gently and easily
in Zero Insertion Force (ZIF) sockets
RAM connectors
• RAM modules are plugged into
motherboard connectors
Expansion slots
• Expansion cards can be inserted,
Example AGP (Accelerated Graphic Port)
I/O connectors
• Serial port, Parallel port, USB
ports, RJ45(LAN or Ethernet
por), VGA, Audio plugs
©Dr Loganathan R
INPUT DEVICES
©Dr Loganathan R
INPUT DEVICES
To feed data and instructions into a computer
Categories
©Dr Loganathan R
Input Devices
Keyboard Pointing devices
Mouse
Trackball
Trackpad
Handheld devices
Pen
Touchscreen
Joystick
Optical devices
Barcode reader
Scanners
OCR
OMR
MICR
Audio/Visual devices
INPUT DEVICES 1.1 Keyboard
©Dr Loganathan R
INPUT DEVICES 1.1 Keyboard
©Dr Loganathan R
• Main input device for computers
Typing keys
• The letters of the alphabet and the layout of the keyboard is known as
QWERTY
Numeric keys
• Num Lock key is set to ON to type numbers, dot, or input the symbols /,
*, - and +.
Function keys • Used by applications and OS to input specific commands.
Control keys
• To handle control of the cursor and the screen, Arrow (←,↑,→,↓) keys,
Home, End, Page Up, Page Down, Insert, Delete, Control (Ctrl), Alternate
(Alt), Escape (Esc), Print Screen, Pause, Windows or Start
Inside the Keyboard
• It has its own processor and circuitry to carry information to and from
that processor
Advantage • The keyboard is easy to use and inexpensive.
Disadvantages
• The keyboard cannot be used to draw figures.
• The process of moving the cursor to another position is very slow.
INPUT DEVICES 1.2 Pointing Devices
©Dr Loganathan R
• Enables the users to easily control the movement of the pointer to select items on a screen, commands
from commands menu, to draw graphics, etc
Mouse
• The mouse was invented by Douglas Engelbart in 1963, used in a graphical user interface (GUI)
• Point: Placing the pointer over the word or the object is termed as pointing
• Click: Pressing the left or the right button
• Drag: Pointing to a desired location while pressing the left button
• Scroll: The scroll wheel is used to vertically scroll.
• Mechanical mouse: This type of mouse has a rubber or metal ball at its bottom
• Optical mouse: The movement is detected using laser technology using optical sensors.
• Cordless mouse: A cordless or wireless mouse is connected using radio waves or infrared light waves.
• Advantages
• The mouse is easy to use and quickly place the cursor anywhere on the screen.
• It also helps to quickly and easily draw figures.
• It is inexpensive.
• Disadvantages
• Its point-and-click capabilities make it unnecessary to remember and type in commands.
• The mouse needs extra desk space to be placed and moved easily.
• The ball in the mechanical mouse must be cleaned to remove dust from it.
INPUT DEVICES 1.2 Pointing Devices
©Dr Loganathan R
Trackball on keyboard
Trackball used like a mouse
Trackball
• Used to control the position of the cursor on the screen.
• Used in notebook and laptop computers where it is placed on the keyboard
• An upside-down mouse that rotates in place within a socket.
• The user rolls the ball to position the cursor at an appropriate position on the
screen and then clicks one of the buttons to select objects or position the cursor
for text entry
Advantages
• Trackball provides better resolution
• Occupies less space
• Easier to use as compared to mouse
Disadvantages • The trackball chamber is often covered with dust, so it must be cleaned regularly
INPUT DEVICES 1.2 Pointing Devices
©Dr Loganathan R
• A small, flat, rectangular stationary pointing device with a sensitive surface of 1.5-2 square
inches
• Slide fingertips across the surface of the pad to point to a specific object on the screen.
• Buttons around the edge of the pad that work like mouse buttons
Touchpad
• Easier to use as compared to mouse as its use involves less hands and arms movements
• It is built-in the keyboard, so no need to carry an extra device separately
• Occupies less space
Advantages
INPUT DEVICES 1.3 Handheld Devices
©Dr Loganathan R
Joystick
• Cursor control device widely used in computer games and CAD/CAM applications
• Consists of a hand-held lever that pivots on one end and transmits its coordinates to a computer
• Has one or more push-buttons, called switches, whose position can also be read by the computer
Stylus
• Pen-shaped input device used to enter information or write on the touch screen of a phone.
• Used to draw lines on a surface as input to a computer, choose an option from a menu, move the
cursor to another location on the screen, take notes and create short messages.
• The stylus usually slides into a slot built into the smart phone for that purpose.
Touch screen
• Display screen which can identify the occurrence and position of a touch inside the display region
• The user can touch the screen either by his finger or by using a stylus
• These displays can be connected to computers, laptops, PDAs, cell phones
INPUT DEVICES 1.4 Optical Devices
©Dr Loganathan R
Barcode Reader
• To capture and read information stored in a barcode
• A barcode reader works by directing a beam of light across the barcode
• Used in: supermarkets, retail stores, library, manufacturing and shipping,
Advantages
• Barcode readers are inexpensive.
• They are portable.
• They are handy and easy to use
Disadvantages
• To be handled with care
• can interpret information using a limited series of thin and wide bars
INPUT DEVICES 1.4 Optical Devices
©Dr Loganathan R
Image Scanner
• Captures images, printed text, handwriting from different sources and converts it into a
digital image for computer editing and display
• Types: hand-held, feed-in, and flatbed
• Scanning either colour images, black-and-white images, or both
Advantages
• Any printed or handwritten document can be scanned and stored in a computer
• The scanned and stored document will never deteriorate in quality with time.
• There is no fear of loss of documents.
Disadvantages
• Costlier than other input devices
• Scanned and stored as images have a higher size
INPUT DEVICES 1.4 Optical Devices
©Dr Loganathan R
Optical Character Recognition (OCR) Device
• Converting printed materials into text or word processing files that can be easily edited and stored
• Scanning the text character by character
• Analysing the scanned image to translate the character images into character code
Advantages
• Printed documents can be converted into text files.
• Advanced OCR can recognize handwritten text and convert it into computer-readable texts.
Disadvantages
• OCR cannot recognize all types of fonts.
• Documents that are poorly typed or have strikeover cannot be recognized.
• Very old documents when passed through OCR may not convert into the text file
Uses:
• Digitize and preserve documents in libraries
• Process checks and credit card slips
• Sort letters for speeding up mail delivery
Printed
Documents
OCR
Technology
Computer
readable Text
files of size 2-
3KB per page
Scans the documents
and makes a bitmap of
size 50-150KB per page
INPUT DEVICES 1.4 Optical Devices
©Dr Loganathan R
Optical Mark Recognition (OMR) Device
• Electronically extracting data from marked fields, such as checkboxes and fill-in fields, on printed forms
• Pen or pencil marks in pre-defined positions to indicate each selected response
• Detect the presence of a mark by measuring the reflected light levels
Advantages
• Optical mark readers work at very high speeds. They can read up to 9000 forms per hour.
Disadvantages
• It is difficult to gather large amounts of information using an OMR.
• Some data may be missing in the scanned document.
• It is a sensitive device that rejects the OMR sheet if it is folded. torn or crushed.
INPUT DEVICES 1.4 Optical Devices
©Dr Loganathan R
Magnetic Ink Character Reader
• To verify the legitimacy of paper documents, especially bank checks.
• MICR characters are usually printed in E-13B or CMC-7 fonts.
• MICR consists of magnetic ink printed characters which can be recognized by high speed magnetic
recognition devices
Advantages
• Enhances security
• Speeds up the sorting of document
• minimize the exposure to check frauds
INPUT DEVICES 1.5 Audio-visual Input Devices
©Dr Loganathan R
Either capture or create sound
Audio Devices
• Enable computers to accept music, speech, or sound effects for recording and/or editing
• A microphone feeds audio input to the computer
• The sound card is a hardware unit that converts analog signals generated through the microphone into
digital data
Capture video from the outside world into the computer
Video Input Devices
• Video cards to convert analog video signals to digital data to store
• Digital camera and web camera are popular examples of video input devices
Advantages
• Audio devices can be used by people who are visually impaired.
• Users want to avoid input through keyboard or mouse.
• Video input devices are very useful for applications such as videoconferencing.
• Record memorable moments in one's life.
• Used for security purposes.
Disadvantages
• Audio input devices are not effective in noisy places.
• With audio i/p devices, it is difficult to distinguish between 2 similar sounding words such as 'sea' and 'see'.
• Videos and images captured using video input devices have very big file sizes, and they must be compressed
©Dr Loganathan R
OUTPUT DEVICES
©Dr Loganathan R
• Any device that outputs/gives information from a computer is called an output device
• Electromechanical devices that accept data from the computer and convert them into
human understandable form
2.1 Soft Copy Devices
• Produce an electronic version of an output
Output
Devices
Soft Copy
Devices
Monitor
Projector
Speaker
Hard Copy
Devices
Printer
Plotter
• Features
• The output can be viewed only when the
computer is on.
• The user can easily edit soft copy output
• Soft copy cannot be used by people who do not
have a computer.
• Searching for data in a soft copy is easy and fast.
• Electronic distribution of material as soft copy is
cheaper and can be done easily and quickly.
OUTPUT DEVICES
©Dr Loganathan R
2.1 Soft Copy Devices
• Displays video and graphics information generated by the computer through the
video card.
• Similar to television screens but they display information at a much higher
quality.
• The monitor is connected to either the VGA or the digital video interface (DVI).
Monitors
• Cathode Ray Tube (CRT), Liquid Crystal Display (LCD) and Plasma
Three variants
OUTPUT DEVICES
©Dr Loganathan R
2.1 Soft Copy Devices
CRT Monitor Work by firing charged electrons at a phosphorus film
When electrons hit the phosphor-coated screen, they glow, thereby enabling the user to see
the output.
Advantages CRT monitors provide images of good quality
CRT monitors are cheapest when compared to LCD and plasma monitors
The images are clear even when you try to view it from an angle.
Disadvantages CRT monitors occupy a large space on the desk.
They are bigger in size and weight, so difficult to move from one place to another
Power consumption is higher than the other monitors.
OUTPUT DEVICES
©Dr Loganathan R
2.1 Soft Copy Devices
LCD Monitor A thin, flat, electronic visual display, uses the light modulating properties of liquid crystals,
which do not emit light directly
LCD screens are more compact, lightweight, portable, more reliable, easier on the eyes, energy
efficient and offer safer disposal than CRTs
Most LCD displays use active matrix technology in which a thin film transistor (TFT) arranges
tiny transistors and capacitors in a matrix on the glass of the display
Advantages Very compact and lightweight consume less power.
They do not suffer from geometric distortion and Little or no flicker of images
Made in almost any size or shape and cause less eye fatigue
More reliable than CRTs
Disadvantages Images are not very clear when tried to view from an angle
Expensive than CRTs.
OUTPUT DEVICES
©Dr Loganathan R
2.1 Soft Copy Devices
Plasma monitor Thin and flat monitors used in TVs and computers and two glass plates that have tiny cells filled
with xenon and neon gas
The display electrode is covered by a magnesium oxide protective layer and arranged in
horizontal rows along the screen while the address electrodes are arranged in vertical columns
The electrodes that intersect at that cell are charged, current flow through the gas which creates a
rapid flow of charged particles to stimulate the gas atoms to release Ultra-Violet photons
Advantages The technology used in plasma monitors allows producing a very wide screen using extremely
thin materials
Very bright images are formed which look good from almost every angle
These monitors are not heavy and are thus easily portable
Disadvantages Very expensive and High power consumption.
The images are phosphor-based, at times, they may suffer from flicker
OUTPUT DEVICES
©Dr Loganathan R
2.1 Soft Copy Devices
• Takes an image from a video source and projects it onto a
screen or other surface.
• Used for many applications varying from home theater systems
to organizations for projecting information and presentations
onto screens large enough for rooms
• LCD projector: Use their own light to display the image
• Digital Light Processing (DLP) projector: Use a number of
mirrors to reflect the light.
Projector
• Different types of speakers to enable users to enjoy music, movie or a
game and the voice will be spread through the entire room
• A headphone is used to enjoy loud music without disturbing the
people
• Headsets allow the users to talk and listen at the same time, using the
same device
Speakers
OUTPUT DEVICES 2.2 Hard Copy Devices
©Dr Loganathan R
• Hard copy output devices are those that produce a physical form of output.
• The features of hard copy output
• A computer is not needed to see the output.
• Editing and incorporating the edits in the hard copy is difficult.
• Hard copy output can be easily distributed to people who do not have a
computer.
• Searching for data in a hard copy is a tiring and difficult job.
• Distribution of hard copy is not only costly but slower as well
Printers
• Takes the text and graphics information from a computer and prints it on a
paper
• Available in the market in various sizes, speeds, sophistication, and costs
• The qualities of printers that are of interest to users include: Colour, Resolution,
Speed and Memory.
OUTPUT DEVICES 2.2 Hard Copy Devices
©Dr Loganathan R
• Color: Colored printouts are needed for presentations or maps and other pages
where color is part of the information. They are more expensive,
• Memory: Most printers have a small amount of memory that can be expanded
by the user. Having more memory makes enhances the speed of printing
• Resolution: The resolution of a printer means the sharpness of text and images
on paper. It is usually expressed in dots per inch (dpi). Even the least
inexpensive printer provides sufficient resolution for most purposes at 600 dpi.
• Speed: Speed means number of pages that are printed in one minute. While
high speed printers are a little expensive, the inexpensive printers on the other
hand can print only about 3 to 6 sheets per minute. Color printing is even
slower.
• Printers can be broadly classified into two groups:
• Impact printers
• Non-impact printers
OUTPUT DEVICES 2.2 Hard Copy Devices
©Dr Loganathan R
Printers
Impact
primers
Dot Matrix Daisy wheel Line
Non-Impact
printers
Inkjet Laser
OUTPUT DEVICES 2.2 Hard Copy Devices
©Dr Loganathan R
Impact
Printer
• Print characters by striking an inked ribbon against
the paper
• Examples: dot matrix printers, daisy wheel printers
and line printers.
Advantages
• Enables the user to produce carbon copies.
• They are cheap
Disadvantages
• Impact printers are slow.
• Poor print quality, especially in the case of graphics
• Extremely noisy
• Print only the standard font
OUTPUT DEVICES 2.2 Hard Copy Devices
©Dr Loganathan R
Non-impact
printer
• Less noisy since printing heads do not strike the paper
• Better print quality, faster printing and sophisticated
graphics
• Use either solid or liquid cartridge-based ink which is
either sprayed, dripped or electro statically drawn
• Types are: inkjet, printer, laser printer and thermal
printer.
Advantages
• Produce pnnts of good quality and render graphics.
• Noiseless and fast.
• Pnnt text in different fonts.
Disadvantages
• Eexpensive.
• Ink cartridges used by them are also costly.
OUTPUT DEVICES 2.2 Hard Copy Devices
©Dr Loganathan R
Dot matrix printer
• A dot matrix printer prints characters and images of all types as a
pattern of dots
• It has a print head (or hammer) that consists of pins representing
the character or image
• The print head runs back and forth/up and down motion, prints by
striking an ink-soaked cloth ribbon against the paper.
Advantages
• Can produce carbon copies and the lowest printing cost per page.
• used for bulk printing where the quality of he print is not of importance.
• Inexpensive
• When the ink is about to be exhausted, the print gradually fades rather than suddenly stopping
• Can use continuous paper rather than individual sheet, making them useful for data logging.
Disadvantages
• Creates a lot of noise when head strike the ribbon against the paper.
• Print lower resolution graphics, with limilud quality.
• Very slow and
• Poor print quality.
OUTPUT DEVICES 2.2 Hard Copy Devices
©Dr Loganathan R
Daisy wheel printer
• The print head is a circular wheel, 3 inches in diameter with arms or spokes, the characters are
embossed at the outer end of the arms
• The wheel is rotated in such a way that the character to be printed is positioned just in front of the
printer ribbon
• The spoke containing the required character is then hit by a hammer thereby striking the ribbon to
leave an impression on the paper
• Print quality is high as the exact shape of the character hits the ribbon and 3 times faster Dot matrix
printer
OUTPUT DEVICES 2.2 Hard Copy Devices
©Dr Loganathan R
Line printer
• Line printer is a high speed impact printer in which one typed line is printed at a time
• The speed of a line printer usually varies from 600 to 1200 lines-per-minute or approximately 10 to 20
pages per minute
• They are widely used in datacenters and in industrial environments
• Band printer is a commonly used variant of line printers
OUTPUT DEVICES 2.2 Hard Copy Devices
©Dr Loganathan R
Band Printer
• The set of characters are permanently embossed on the band and this set cannot be changed unless
the band is replaced
• The band itself revolves around hammers that push the paper against the ribbon, allowing the desired
character to be produced on the paper
• The advantage is its high speed, can print 2000 lines per minute, perfect for high volume printing in
businesses, schools, and other organizations
• It cannot be used for any graphics printing as the characters are predetermined and cannot be
changed unless the band is changed
OUTPUT DEVICES 2.2 Hard Copy Devices
©Dr Loganathan R
Inkjet printer
• The print head has several tiny nozzles, also called jets.
• As the paper moves past the print head, the nozzles spray ink onto it, forming the characters and
images.
• The dots are extremely small (50 and 60 microns) and are positioned very precisely, with resolutions of
up to 1440x720 dots per inch (dpi).
• One black ink cartridge and color cartridge containing ink in primary pigments (cyan, magenta, and
yellow).
• Cheaper than laser printers, but expensive to maintain
• Not well-suited for high-volume print jobs
OUTPUT DEVICES 2.2 Hard Copy Devices
©Dr Loganathan R
Laser printer
• A laser beam 'draws' the document on a drum (which is coated with a photo-conductive material)
using electrical charges.
• After the drum is charged, it is rolled in a toner (a dry powder type of ink).
• The toner sticks to the charged image on the drum.
• The toner is transferred onto a piece of paper and fused to the paper with heat and pressure.
• After print, the electrical charge is removed from the drum and the excess toner is collected.
• Works at very high speeds and produces high-quality text and graphics
OUTPUT DEVICES 2.2 Hard Copy Devices
©Dr Loganathan R
Plotters
• A plotter is a printer that interprets commands from a computer to make line drawings on paper with
one or more automated pens
• Plotters are expensive than printers, they are used only for specialized applications like CAD, CAM and
CAE
• A drum plotter is used to draw graphics on a paper that is wrapped around a drum.
• It works by rotating the drum back and forth to produce vertical motion.
• The pen which is mounted on a carriage is moved across the width of the paper.
• The vertical movement of the paper and the horizontal movement of the pen create the required
design under the control of the computer.
OUTPUT DEVICES 2.2 Hard Copy Devices
©Dr Loganathan R
Plotters
• Flatbed plotter, the paper is spread on the flat rectangular surface of the plotter and the pen is moved
over it.
• Flatbed plotters are less expensive and used in many smaller computing systems.
• The paper is not moved rather plotting is done by moving an arm that moves a pen over paper.
©Dr Loganathan R

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M1. Introducing Computers Part A .pdf

  • 2. DEFINITION • An electronic device that is designed to accept data, perform the required mathematical and logical operations at high speed, and output the result ©Dr Loganathan R
  • 4. STORED PROGRAM CONCEPT • Before any data is processed, instructions are read into memory • Instructions are stored in the computer’s memory for execution • Instructions are stored in binary form (0s &1s) • Processing starts with the first instruction in the program, which is copied into a control unit circuit. The control unit executes the instructions • Instructions written by the users are performed sequentially until there is a break in the current flow • Input/Output and processing operations are performed simultaneously. While data is being read/written, the central processing unit (CPU) executes another program in the memory that is ready for execution. ©Dr Loganathan R
  • 5. Types of Stored Program Computers • Shared memory for instructions and data • Separate memories for instructions and data Processor Main Memory Address Bus - carries addresses Data Bus - carries data and instructions Instruction memory Processor Instruction Address Instructions Data Memory Data Address Read/Write Data ©Dr Loganathan R
  • 6. HISTORY OF COMPUTERS Timeline of Developments 1822 1890 1936 1941 1943 1944 300BC steam-driven Difference Engine Charles Babbage computing anything Turing Machine First digital computers ENIAC for mathematical computations Abacus US 1880 census Punched Card System 29 equations simultaneously Atanasoff– Berry Computer (ABC) ©Dr Loganathan R
  • 7. HISTORY OF COMPUTERS Timeline of Developments 1947 1953 1954 1958 1969 1946 vacuum tubes replaced transistor Formula Translation FORTRAN Operating System Unix first commercial computer UNIVAC first computer language COBOL Chip Integrated Circuit ©Dr Loganathan R
  • 8. HISTORY OF COMPUTERS Timeline of Developments • 1964: prototype of the modern computer, with a mouse and a graphical user interface (GUI) • 1970: DRAM chip was introduced by Intel • 1971: IBM invented the floppy disk • 1973: Ethernet for connecting multiple computers • 1974–1977: Personal Computers • 1975: BASIC • 1976: Steve Jobs and Steve Wozniak started Apple Computers • 1977: Apple II • 1978: WordStar, a word processor application • 1979: VisiCalc, the first computerized spreadsheet • 1981: The first IBM personal computer with MS-DOS OS • 1983: The first laptop • 1985: Microsoft Windows OS • 1986: Compaq Deskpro 386, which was a 32-bit architecture • 1990: Tim Berners-Lee invented World Wide Web with HTML • 1993: The Pentium microprocessor • 1994: PC games • 1996: Sergey Brin and Larry Page developed the Google • 1999: Wi-Fi started connecting to the Internet without wires. ©Dr Loganathan R
  • 9. HISTORY OF COMPUTERS Generations of Computers(evolution) Examples ENIAC EDVAC EDSACUNIVAC I IBM 701 Memory Primary: Electromagnetic relay Secondary: punched cards Hardware Technolog y Vacuum tubes which is made of fragile glass Software Technolog y Programming was done in machine or assembly language. Used for Scientific applications Highlights Bulky Vacuum tubes emitted heat and burned Costly Difficult to use Constant maintenance First Generation (1942– 1955) ©Dr Loganathan R
  • 10. HISTORY OF COMPUTERS Generations of Computers(evolution) Examples Honeywell 400 IBM 7030 CDC 1604 UNIVAC LARC Memory Primary: Magnetic core Secondary: Magne tic tapes and disks Hardware Technology Transistors: reliable , powerful, cheaper, smaller & cooler . Software Technology Programming was done in High Level programming languages Used for Scientific and commercial applications Highlights Bulky less heat than 1st Gen Faster than 1st Gen Costly Difficult to use Consumed 1/10 than 1st Gen Second Generation (1955– 1964) ©Dr Loganathan R
  • 11. HISTORY OF COMPUTERS Generations of Computers(evolution) Examples IBM 360/370 PDP-8 & PADP-11, CDC6600 Memory Primary: Large Magnetic core Secondary: Large Magnetic tapes & disks Hardware Technology integrated chips (ICs): SSI and MSI technology Software Technology Programming was done in High Level Language Time sharing OS Used for Scientific, Commercial & Interactive online applications Highlights Bulky less heat than 2nd Gen Faster than 2nd Gen Costly Difficult to use Consumed less power than 2nd Gen Third Generation (1964– 1975) ©Dr Loganathan R
  • 12. HISTORY OF COMPUTERS Generations of Computers(evolution) Examples IBM PC, Apple II, TRS- 80, VAX 9000, CRAY- 1, CRAY-2, CRAY-X/MP Memory Primary: Semiconductor Secondary: Large Magnetic tapes, disks & Floppy Hardware Technology integrated chips (ICs): LSI and VLSI LAN & WAN Software Technology Programming was done in High Level Language - 'C' GUI-OS Used for Scientific, Commercial, Interac tive online & Network applications Highlights Faster, smaller, cheaper, powerful, reliable, and easier Fourth Generation (1975– 1989) ©Dr Loganathan R
  • 13. HISTORY OF COMPUTERS Generations of Computers(evolution) Examples IBM notebooks, Pentium PCs, SUN workstations, IBM SP/2, Param supercomputer Memory Primary: Semiconductor Secondary: Large Magnetic tapes, disks & USB Drives Hardware Technology integrated chips (ICs): ULSI Internet Software Technology Programming was done in HLL– Java, Python GUI-OS Used for Scientific, Commercial, Interac tive online, Multimedia & N/W applications Highlights Faster, smaller, cheaper, powerful, reliable, easier & more Speed Fifth Generation (1989– Present) ©Dr Loganathan R
  • 14. CLASSIFICATION OF COMPUTERS • Four categories (speed, amount of data processing & price) Supercomputers • Dumb terminals • Intelligent terminals Mainframe computers Minicomputers • Desktop PCs • Workstations • Laptops • N/W Computers • Handheld devices Microcomputers 14 ©Dr Loganathan R ©Dr Loganathan R
  • 15. CLASSIFICATION OF COMPUTERS • Supercomputers • Fastest(one trillion calculations/s), most powerful, and most expensive, parallel processing(thousands of concurrent users) , weather forecasting, nuclear energy research, aircraft design, CRAY-1, CRAY-2, Control Data CYBER 205, and ETA A-10. • Mainframe computers: large-scale computers, very expensive, servers(www), banks, airline companies & universities • Dumb terminals: a monitor and a keyboard, No CPU and memory • Intelligent terminals: Own processor, No Memory, PCs are used to data access & services • Minicomputers: smaller, cheaper, slower, business, as servers in a network, education, hospitals , single/multiple users, DEC, IBM(AS/400) • Microcomputers: IBM-PC in 1981, Apple, DOS, Windows, Mac OS, Linux, • Desktop PCs: homes and offices • Workstations: processing speed matches with minicomputer, Scientist, engineers, architects • Laptops: Similar to Desktop PCs with Mobility • N/W Computers: as terminals in a network, to access data, NetPCs • Handheld devices: Smartphones, Tablet PCs, iOS, Android, 15 ©Dr Loganathan R ©Dr Loganathan R
  • 16. APPLICATIONS OF COMPUTERS • Word processing • Internet • Digital audio & video composition • Desktop publishing • Multimedia and Animation • Legal System • Retail Business • Sports • Travel and Tourism • Simulation • Astronomy • Education • Industry and Engineering • Robotics • Decision Support Systems • Expert Systems • e-Business • Business-to-consumer or B2C • Business-to-business or B2B • Consumer-to-consumer or C2C • Electronic banking • Bioinformatics • biological and genetic information • gene-based drug discovery and development • Health care • Storing records • Surgical procedures • Diagnosis and Treatment • Geographic Information System and Remote Sensing • Monitoring deforestation • Study features of glaciers • Analysing the depth of coastal and ocean • Meteorology • Weather forecasting • Aviation meteorology • Agricultural meteorology • Nuclear meteorology • Maritime meteorology ©Dr Loganathan R
  • 17. BASIC ORGANIZATION OF A COMPUTER Block diagram of a computer Interaction between the different units of a computer system ©Dr Loganathan R
  • 18. BASIC ORGANIZATION OF A COMPUTER A computer performs five major operations: Input: • Accepting data or instructions : keyboard, mouse, scanner, and trackball Strorage: • Primary storage: very expensive and limited capacity • Secondary storage: cheaper and non-volatile Processing (ALU): • Performing operations on the data as per the instructions(by ALU) Output : • Displaying result of data processing to the outside world Control (CU): • Controlling and coordinating all operations and Components of a computer(Control Unit) ©Dr Loganathan R
  • 19. INSIDE THE COMPUTER ©Dr Loganathan R
  • 23. MOTHERBOARD Characteristics of a Motherboard Form factor • Geometry, dimensions, arrangement and electrical requirements Integrated components • Chipset, CMOS clock and battery, BIOS, System bus, Expansion bus, processor, cache memory, RAM Chipset • Coordinates data transfers between the different components CMOS clock and battery • Real-Time Clock (RTC) circuit synchronize the computer’s signals, CMOS chip is powered by a battery Basic Input/Output System (BIOS) • Interface between the OS & Motherboard, stored in the read-only memory (ROM) Processor socket • Processor inserted very gently and easily in Zero Insertion Force (ZIF) sockets RAM connectors • RAM modules are plugged into motherboard connectors Expansion slots • Expansion cards can be inserted, Example AGP (Accelerated Graphic Port) I/O connectors • Serial port, Parallel port, USB ports, RJ45(LAN or Ethernet por), VGA, Audio plugs ©Dr Loganathan R
  • 25. INPUT DEVICES To feed data and instructions into a computer Categories ©Dr Loganathan R Input Devices Keyboard Pointing devices Mouse Trackball Trackpad Handheld devices Pen Touchscreen Joystick Optical devices Barcode reader Scanners OCR OMR MICR Audio/Visual devices
  • 26. INPUT DEVICES 1.1 Keyboard ©Dr Loganathan R
  • 27. INPUT DEVICES 1.1 Keyboard ©Dr Loganathan R • Main input device for computers Typing keys • The letters of the alphabet and the layout of the keyboard is known as QWERTY Numeric keys • Num Lock key is set to ON to type numbers, dot, or input the symbols /, *, - and +. Function keys • Used by applications and OS to input specific commands. Control keys • To handle control of the cursor and the screen, Arrow (←,↑,→,↓) keys, Home, End, Page Up, Page Down, Insert, Delete, Control (Ctrl), Alternate (Alt), Escape (Esc), Print Screen, Pause, Windows or Start Inside the Keyboard • It has its own processor and circuitry to carry information to and from that processor Advantage • The keyboard is easy to use and inexpensive. Disadvantages • The keyboard cannot be used to draw figures. • The process of moving the cursor to another position is very slow.
  • 28. INPUT DEVICES 1.2 Pointing Devices ©Dr Loganathan R • Enables the users to easily control the movement of the pointer to select items on a screen, commands from commands menu, to draw graphics, etc Mouse • The mouse was invented by Douglas Engelbart in 1963, used in a graphical user interface (GUI) • Point: Placing the pointer over the word or the object is termed as pointing • Click: Pressing the left or the right button • Drag: Pointing to a desired location while pressing the left button • Scroll: The scroll wheel is used to vertically scroll. • Mechanical mouse: This type of mouse has a rubber or metal ball at its bottom • Optical mouse: The movement is detected using laser technology using optical sensors. • Cordless mouse: A cordless or wireless mouse is connected using radio waves or infrared light waves. • Advantages • The mouse is easy to use and quickly place the cursor anywhere on the screen. • It also helps to quickly and easily draw figures. • It is inexpensive. • Disadvantages • Its point-and-click capabilities make it unnecessary to remember and type in commands. • The mouse needs extra desk space to be placed and moved easily. • The ball in the mechanical mouse must be cleaned to remove dust from it.
  • 29. INPUT DEVICES 1.2 Pointing Devices ©Dr Loganathan R Trackball on keyboard Trackball used like a mouse Trackball • Used to control the position of the cursor on the screen. • Used in notebook and laptop computers where it is placed on the keyboard • An upside-down mouse that rotates in place within a socket. • The user rolls the ball to position the cursor at an appropriate position on the screen and then clicks one of the buttons to select objects or position the cursor for text entry Advantages • Trackball provides better resolution • Occupies less space • Easier to use as compared to mouse Disadvantages • The trackball chamber is often covered with dust, so it must be cleaned regularly
  • 30. INPUT DEVICES 1.2 Pointing Devices ©Dr Loganathan R • A small, flat, rectangular stationary pointing device with a sensitive surface of 1.5-2 square inches • Slide fingertips across the surface of the pad to point to a specific object on the screen. • Buttons around the edge of the pad that work like mouse buttons Touchpad • Easier to use as compared to mouse as its use involves less hands and arms movements • It is built-in the keyboard, so no need to carry an extra device separately • Occupies less space Advantages
  • 31. INPUT DEVICES 1.3 Handheld Devices ©Dr Loganathan R Joystick • Cursor control device widely used in computer games and CAD/CAM applications • Consists of a hand-held lever that pivots on one end and transmits its coordinates to a computer • Has one or more push-buttons, called switches, whose position can also be read by the computer Stylus • Pen-shaped input device used to enter information or write on the touch screen of a phone. • Used to draw lines on a surface as input to a computer, choose an option from a menu, move the cursor to another location on the screen, take notes and create short messages. • The stylus usually slides into a slot built into the smart phone for that purpose. Touch screen • Display screen which can identify the occurrence and position of a touch inside the display region • The user can touch the screen either by his finger or by using a stylus • These displays can be connected to computers, laptops, PDAs, cell phones
  • 32. INPUT DEVICES 1.4 Optical Devices ©Dr Loganathan R Barcode Reader • To capture and read information stored in a barcode • A barcode reader works by directing a beam of light across the barcode • Used in: supermarkets, retail stores, library, manufacturing and shipping, Advantages • Barcode readers are inexpensive. • They are portable. • They are handy and easy to use Disadvantages • To be handled with care • can interpret information using a limited series of thin and wide bars
  • 33. INPUT DEVICES 1.4 Optical Devices ©Dr Loganathan R Image Scanner • Captures images, printed text, handwriting from different sources and converts it into a digital image for computer editing and display • Types: hand-held, feed-in, and flatbed • Scanning either colour images, black-and-white images, or both Advantages • Any printed or handwritten document can be scanned and stored in a computer • The scanned and stored document will never deteriorate in quality with time. • There is no fear of loss of documents. Disadvantages • Costlier than other input devices • Scanned and stored as images have a higher size
  • 34. INPUT DEVICES 1.4 Optical Devices ©Dr Loganathan R Optical Character Recognition (OCR) Device • Converting printed materials into text or word processing files that can be easily edited and stored • Scanning the text character by character • Analysing the scanned image to translate the character images into character code Advantages • Printed documents can be converted into text files. • Advanced OCR can recognize handwritten text and convert it into computer-readable texts. Disadvantages • OCR cannot recognize all types of fonts. • Documents that are poorly typed or have strikeover cannot be recognized. • Very old documents when passed through OCR may not convert into the text file Uses: • Digitize and preserve documents in libraries • Process checks and credit card slips • Sort letters for speeding up mail delivery Printed Documents OCR Technology Computer readable Text files of size 2- 3KB per page Scans the documents and makes a bitmap of size 50-150KB per page
  • 35. INPUT DEVICES 1.4 Optical Devices ©Dr Loganathan R Optical Mark Recognition (OMR) Device • Electronically extracting data from marked fields, such as checkboxes and fill-in fields, on printed forms • Pen or pencil marks in pre-defined positions to indicate each selected response • Detect the presence of a mark by measuring the reflected light levels Advantages • Optical mark readers work at very high speeds. They can read up to 9000 forms per hour. Disadvantages • It is difficult to gather large amounts of information using an OMR. • Some data may be missing in the scanned document. • It is a sensitive device that rejects the OMR sheet if it is folded. torn or crushed.
  • 36. INPUT DEVICES 1.4 Optical Devices ©Dr Loganathan R Magnetic Ink Character Reader • To verify the legitimacy of paper documents, especially bank checks. • MICR characters are usually printed in E-13B or CMC-7 fonts. • MICR consists of magnetic ink printed characters which can be recognized by high speed magnetic recognition devices Advantages • Enhances security • Speeds up the sorting of document • minimize the exposure to check frauds
  • 37. INPUT DEVICES 1.5 Audio-visual Input Devices ©Dr Loganathan R Either capture or create sound Audio Devices • Enable computers to accept music, speech, or sound effects for recording and/or editing • A microphone feeds audio input to the computer • The sound card is a hardware unit that converts analog signals generated through the microphone into digital data Capture video from the outside world into the computer Video Input Devices • Video cards to convert analog video signals to digital data to store • Digital camera and web camera are popular examples of video input devices Advantages • Audio devices can be used by people who are visually impaired. • Users want to avoid input through keyboard or mouse. • Video input devices are very useful for applications such as videoconferencing. • Record memorable moments in one's life. • Used for security purposes. Disadvantages • Audio input devices are not effective in noisy places. • With audio i/p devices, it is difficult to distinguish between 2 similar sounding words such as 'sea' and 'see'. • Videos and images captured using video input devices have very big file sizes, and they must be compressed
  • 39. OUTPUT DEVICES ©Dr Loganathan R • Any device that outputs/gives information from a computer is called an output device • Electromechanical devices that accept data from the computer and convert them into human understandable form 2.1 Soft Copy Devices • Produce an electronic version of an output Output Devices Soft Copy Devices Monitor Projector Speaker Hard Copy Devices Printer Plotter • Features • The output can be viewed only when the computer is on. • The user can easily edit soft copy output • Soft copy cannot be used by people who do not have a computer. • Searching for data in a soft copy is easy and fast. • Electronic distribution of material as soft copy is cheaper and can be done easily and quickly.
  • 40. OUTPUT DEVICES ©Dr Loganathan R 2.1 Soft Copy Devices • Displays video and graphics information generated by the computer through the video card. • Similar to television screens but they display information at a much higher quality. • The monitor is connected to either the VGA or the digital video interface (DVI). Monitors • Cathode Ray Tube (CRT), Liquid Crystal Display (LCD) and Plasma Three variants
  • 41. OUTPUT DEVICES ©Dr Loganathan R 2.1 Soft Copy Devices CRT Monitor Work by firing charged electrons at a phosphorus film When electrons hit the phosphor-coated screen, they glow, thereby enabling the user to see the output. Advantages CRT monitors provide images of good quality CRT monitors are cheapest when compared to LCD and plasma monitors The images are clear even when you try to view it from an angle. Disadvantages CRT monitors occupy a large space on the desk. They are bigger in size and weight, so difficult to move from one place to another Power consumption is higher than the other monitors.
  • 42. OUTPUT DEVICES ©Dr Loganathan R 2.1 Soft Copy Devices LCD Monitor A thin, flat, electronic visual display, uses the light modulating properties of liquid crystals, which do not emit light directly LCD screens are more compact, lightweight, portable, more reliable, easier on the eyes, energy efficient and offer safer disposal than CRTs Most LCD displays use active matrix technology in which a thin film transistor (TFT) arranges tiny transistors and capacitors in a matrix on the glass of the display Advantages Very compact and lightweight consume less power. They do not suffer from geometric distortion and Little or no flicker of images Made in almost any size or shape and cause less eye fatigue More reliable than CRTs Disadvantages Images are not very clear when tried to view from an angle Expensive than CRTs.
  • 43. OUTPUT DEVICES ©Dr Loganathan R 2.1 Soft Copy Devices Plasma monitor Thin and flat monitors used in TVs and computers and two glass plates that have tiny cells filled with xenon and neon gas The display electrode is covered by a magnesium oxide protective layer and arranged in horizontal rows along the screen while the address electrodes are arranged in vertical columns The electrodes that intersect at that cell are charged, current flow through the gas which creates a rapid flow of charged particles to stimulate the gas atoms to release Ultra-Violet photons Advantages The technology used in plasma monitors allows producing a very wide screen using extremely thin materials Very bright images are formed which look good from almost every angle These monitors are not heavy and are thus easily portable Disadvantages Very expensive and High power consumption. The images are phosphor-based, at times, they may suffer from flicker
  • 44. OUTPUT DEVICES ©Dr Loganathan R 2.1 Soft Copy Devices • Takes an image from a video source and projects it onto a screen or other surface. • Used for many applications varying from home theater systems to organizations for projecting information and presentations onto screens large enough for rooms • LCD projector: Use their own light to display the image • Digital Light Processing (DLP) projector: Use a number of mirrors to reflect the light. Projector • Different types of speakers to enable users to enjoy music, movie or a game and the voice will be spread through the entire room • A headphone is used to enjoy loud music without disturbing the people • Headsets allow the users to talk and listen at the same time, using the same device Speakers
  • 45. OUTPUT DEVICES 2.2 Hard Copy Devices ©Dr Loganathan R • Hard copy output devices are those that produce a physical form of output. • The features of hard copy output • A computer is not needed to see the output. • Editing and incorporating the edits in the hard copy is difficult. • Hard copy output can be easily distributed to people who do not have a computer. • Searching for data in a hard copy is a tiring and difficult job. • Distribution of hard copy is not only costly but slower as well Printers • Takes the text and graphics information from a computer and prints it on a paper • Available in the market in various sizes, speeds, sophistication, and costs • The qualities of printers that are of interest to users include: Colour, Resolution, Speed and Memory.
  • 46. OUTPUT DEVICES 2.2 Hard Copy Devices ©Dr Loganathan R • Color: Colored printouts are needed for presentations or maps and other pages where color is part of the information. They are more expensive, • Memory: Most printers have a small amount of memory that can be expanded by the user. Having more memory makes enhances the speed of printing • Resolution: The resolution of a printer means the sharpness of text and images on paper. It is usually expressed in dots per inch (dpi). Even the least inexpensive printer provides sufficient resolution for most purposes at 600 dpi. • Speed: Speed means number of pages that are printed in one minute. While high speed printers are a little expensive, the inexpensive printers on the other hand can print only about 3 to 6 sheets per minute. Color printing is even slower. • Printers can be broadly classified into two groups: • Impact printers • Non-impact printers
  • 47. OUTPUT DEVICES 2.2 Hard Copy Devices ©Dr Loganathan R Printers Impact primers Dot Matrix Daisy wheel Line Non-Impact printers Inkjet Laser
  • 48. OUTPUT DEVICES 2.2 Hard Copy Devices ©Dr Loganathan R Impact Printer • Print characters by striking an inked ribbon against the paper • Examples: dot matrix printers, daisy wheel printers and line printers. Advantages • Enables the user to produce carbon copies. • They are cheap Disadvantages • Impact printers are slow. • Poor print quality, especially in the case of graphics • Extremely noisy • Print only the standard font
  • 49. OUTPUT DEVICES 2.2 Hard Copy Devices ©Dr Loganathan R Non-impact printer • Less noisy since printing heads do not strike the paper • Better print quality, faster printing and sophisticated graphics • Use either solid or liquid cartridge-based ink which is either sprayed, dripped or electro statically drawn • Types are: inkjet, printer, laser printer and thermal printer. Advantages • Produce pnnts of good quality and render graphics. • Noiseless and fast. • Pnnt text in different fonts. Disadvantages • Eexpensive. • Ink cartridges used by them are also costly.
  • 50. OUTPUT DEVICES 2.2 Hard Copy Devices ©Dr Loganathan R Dot matrix printer • A dot matrix printer prints characters and images of all types as a pattern of dots • It has a print head (or hammer) that consists of pins representing the character or image • The print head runs back and forth/up and down motion, prints by striking an ink-soaked cloth ribbon against the paper. Advantages • Can produce carbon copies and the lowest printing cost per page. • used for bulk printing where the quality of he print is not of importance. • Inexpensive • When the ink is about to be exhausted, the print gradually fades rather than suddenly stopping • Can use continuous paper rather than individual sheet, making them useful for data logging. Disadvantages • Creates a lot of noise when head strike the ribbon against the paper. • Print lower resolution graphics, with limilud quality. • Very slow and • Poor print quality.
  • 51. OUTPUT DEVICES 2.2 Hard Copy Devices ©Dr Loganathan R Daisy wheel printer • The print head is a circular wheel, 3 inches in diameter with arms or spokes, the characters are embossed at the outer end of the arms • The wheel is rotated in such a way that the character to be printed is positioned just in front of the printer ribbon • The spoke containing the required character is then hit by a hammer thereby striking the ribbon to leave an impression on the paper • Print quality is high as the exact shape of the character hits the ribbon and 3 times faster Dot matrix printer
  • 52. OUTPUT DEVICES 2.2 Hard Copy Devices ©Dr Loganathan R Line printer • Line printer is a high speed impact printer in which one typed line is printed at a time • The speed of a line printer usually varies from 600 to 1200 lines-per-minute or approximately 10 to 20 pages per minute • They are widely used in datacenters and in industrial environments • Band printer is a commonly used variant of line printers
  • 53. OUTPUT DEVICES 2.2 Hard Copy Devices ©Dr Loganathan R Band Printer • The set of characters are permanently embossed on the band and this set cannot be changed unless the band is replaced • The band itself revolves around hammers that push the paper against the ribbon, allowing the desired character to be produced on the paper • The advantage is its high speed, can print 2000 lines per minute, perfect for high volume printing in businesses, schools, and other organizations • It cannot be used for any graphics printing as the characters are predetermined and cannot be changed unless the band is changed
  • 54. OUTPUT DEVICES 2.2 Hard Copy Devices ©Dr Loganathan R Inkjet printer • The print head has several tiny nozzles, also called jets. • As the paper moves past the print head, the nozzles spray ink onto it, forming the characters and images. • The dots are extremely small (50 and 60 microns) and are positioned very precisely, with resolutions of up to 1440x720 dots per inch (dpi). • One black ink cartridge and color cartridge containing ink in primary pigments (cyan, magenta, and yellow). • Cheaper than laser printers, but expensive to maintain • Not well-suited for high-volume print jobs
  • 55. OUTPUT DEVICES 2.2 Hard Copy Devices ©Dr Loganathan R Laser printer • A laser beam 'draws' the document on a drum (which is coated with a photo-conductive material) using electrical charges. • After the drum is charged, it is rolled in a toner (a dry powder type of ink). • The toner sticks to the charged image on the drum. • The toner is transferred onto a piece of paper and fused to the paper with heat and pressure. • After print, the electrical charge is removed from the drum and the excess toner is collected. • Works at very high speeds and produces high-quality text and graphics
  • 56. OUTPUT DEVICES 2.2 Hard Copy Devices ©Dr Loganathan R Plotters • A plotter is a printer that interprets commands from a computer to make line drawings on paper with one or more automated pens • Plotters are expensive than printers, they are used only for specialized applications like CAD, CAM and CAE • A drum plotter is used to draw graphics on a paper that is wrapped around a drum. • It works by rotating the drum back and forth to produce vertical motion. • The pen which is mounted on a carriage is moved across the width of the paper. • The vertical movement of the paper and the horizontal movement of the pen create the required design under the control of the computer.
  • 57. OUTPUT DEVICES 2.2 Hard Copy Devices ©Dr Loganathan R Plotters • Flatbed plotter, the paper is spread on the flat rectangular surface of the plotter and the pen is moved over it. • Flatbed plotters are less expensive and used in many smaller computing systems. • The paper is not moved rather plotting is done by moving an arm that moves a pen over paper.