CSC 101 2016_2017.pptx

CSC 101: Introduction to
Computer Science
1

COURSE POLICIES
• The class will be interactive
• The course has been splitted into 4 modules/parts.
Two modules will be taken by a lecturer
• Lecture Note will be given to you by your lecturers
for each module probably in batches
• No Noise Making, Phone Calls E.T.C will be
tolerated
• Attendance is compulsory unless with a genuine
reason
• Late Attendance will not be tolerated
2

COURSE POLICIES…
• You are advice to be serious, hardworking and
of good behavior
• You may be given assignments or exercises
that may help you get a better understanding
of the course and for your exams
• Feel free to ask questions
3

COURSE OUTLINE (Module 1)
• A Brief introduction to Computers and
Computer Science
• History and generations of Computers
• Characteristics of computers
• Computer Hardware
• Functional components of computers
• Modern I/O Devices
4

• Software:
– Operating Systems
– Application Packages
• computer networks
– Definition
– Types of computer networks
– Applications of computer networks
• Introduction to OSI and TCP/IP models
5

• Introduction to databases
• Review of Database Management Systems
(DBMS)
• Applications of (DBMS)
• How to use Microsoft access DBMS software
to create databases and establish relationship
between the tables
6

• Introduction to problem solving
• Tools used for solving problems:
• Algorithm
• Definition, Xtics, sample problems
• Flowcharts
• pseudo codes
7

COURSE GRADIND
• Each Lecturer will conduct a CA Test at the end
of his section graded 20 marks. You will
therefore have a total of 2 CAs each of 20
marks making 40%.
• Exams will be graded 60%
8

WHAT IS A COMPUTER?
• A computer is an electronic machine that
takes input from the user, processes the given
input and generates output in the form of
useful information.
• Computer.. Latin word.. compute
• Calculation Machine
• A computer system includes a computer,
peripheral devices, and software
10

WHAT IS A COMPUTER?
• Accepts input, processes data, stores data, and
produces output
• Input refers to whatever is sent to a Computer
system
• Data refers to the symbols that represent facts,
objects, and ideas
• Processing is the way that a computer
manipulates data
• A computer processes data in a device called the
central processing unit (CPU)
11

WHAT IS A COMPUTER?
• Input: data, programs, user reply
Data: the raw details that need to be
processed to generate some useful
information.
Programs: the set of instructions that can be
executed by the computer in sequential or
non-sequential manner.
User reply: the input provided by the user in
response to a question asked by the computer.
12

WHAT IS A COMPUTER?
• A computer includes various devices:
Central Processing Unit (CPU)
Monitor
Keyboard and Mouse
13

WHAT IS COMPUTER SCIENCE?
• No general accepted definition of the field
however,
• Computer Science can be define as the study
of computers and computational systems.
• computer scientist deals mostly with software
and software systems; this includes their
theory, design, development, and application.
14

WHAT IS COMPUTER SCIENCE?
• Computer Science is NOT just about
learning Technologies
• It is about building Technologies
• Computer science is about logic,
problem solving, and creativity
15

HISTORY OF COMPUTERS
• Before the 1500s, in Europe,
calculations were made with an abacus
– Invented around 500BC, available in many
cultures (China, Mesopotamia, Japan,
Greece, Rome, etc.)
• In 1642, Blaise Pascal (French
mathematician, physicist, philosopher)
invented a mechanical calculator called
the Pascaline
• In 1671, Gottfried von Leibniz
(German mathematician, philosopher)
extended the Pascaline to do
multiplications, divisions, square roots:
the Stepped Reckoner
• None of these machines had memory,
and they required human intervention at
each step
16

HISTORY OF COMPUTERS
• In 1822 Charles Babbage (English
mathematician, philosopher),
sometimes called the “father of
computing” built the Difference Engine
• Machine designed to automate the
computation (tabulation) of polynomial
functions (which are known to be good
approximations of many useful
functions)
– Based on the “method of finite difference”
– Implements some storage
• In 1833 Babbage designed the
Analytical Engine, but he died before
he could build it
– It was built after his death, powered by
steam
17

GENERATION OF COMPUTERS
• Generation 0: Mechanical Calculators
• Generation 1: Vacuum Tube Computers
• Generation 2: Transistor Computers
• Generation 3: Integrated Circuits
• Generation 4: Microprocessors
18

FIRST GENERATION COMPUTERS
• Employed during the
period 1940-1956
•Used the vacuum tubes
technology for
calculation and control
as well as magnetic
drum for storage
purpose.
19

•Advantages:
(1) Fastest computing devices of their time;
(2) These computers were able to execute
complex mathematical problems in an
efficient manner
20

•Disadvantages:
(1) The functioning of these computers depended on the
machine language.
(2) They were generally designed as special-purpose
computers.
(3) The use of vacuum tube technology make these
computers very large and bulky.
(4) They were not easily transferable from one place to
another due to their huge size and also required to be
placed in cool places.
(5) They were single tasking because they could execute
only one program at a time.
(6) They generate huge amount of heat and hence were
prone to hardware faults.
21

o Electronic Numerical
Integrator and Computer
(ENIAC)
o By Presper Eckert and John
Mauchly
o 18,000 vacuum tubes.
o Occupied a 30 by 50 foot
room
o Programming by plugging
wires into a patch panel.
Very difficult to do, because
this style programming
requires intimate knowledge
of the computer.
22

SECOND GENERATION COMPUTERS
•Employed during
the period 1956-
1963
•Use transistors in
place of vacuum
tubes in building
the basic logic
circuits.
23

• Advantages:
• (1) Fastest computing devices of their time;
• (2) Easy to program because of the use assembly
language;
• (3) Could be transferred from one place to other
very easily because they were small and light;
• (4) Require very less power in carrying out their
operations;
• (5) More reliable, did not require maintenance at
regular intervals of time.
24

•Disadvantages:
(1)The input and output media were not
improved to a considerable extent
(2) Required to be placed in air-conditioned
places
(3) The cost of these computers was very high
and they were beyond the reach of home users
(4) Special-purpose computers and could
execute only specific applications
25

• Transistors replaced
vacuum tubes for circuitry
and magnetic drum by
magnetic core for
memory.
• Smaller, faster and more
reliable.
• Used assembly language.
COBOL and FORTRAN
were developed at this
time too.
• Second generation
computers still relied on
punched cards for inputs
and printouts for outputs.
• IBM 7094, CDC 3600
computers are examples
of second generation
computers.
26

THIRD GENERATION COMPUTERS
•Employed during
the period 1964-
1975
•Use of Integrated
Circuits
27

• Advantages:
• (1) Fastest computing devices at that time
• (2) Very productive
• (3) Easily transportable from one place to another
because of their small size
• (4) Use high-level languages
• (5) Could be installed very easily and required
less space
• (6) Can execute any type of application.
• (7) More reliable and require less frequent
maintenance schedules.
28

• Disadvantages:
(1)The storage capacity of these computers was
still very small;
(2) The performance of these computers
degraded while executing large applications,
involving complex computations because of the
small storage capacity;
(3) The cost of these computers was very high;
(4) They were still required to be placed in air-
conditioned places.
29

FOURTH GENERATION COMPUTERS
•Employed during 1975-
1989
•Use of Large Scale
Integration (LSI)
technology and Very
Large Scale Integration
(VLSI) technology
•The term Personal
Computer (PC) became
known to the people
during this era.
31

Advantages:
(1) Very powerful in terms of their processing speed
and access time;
(2) Storage capacity was very large and faster;
(3) Highly reliable and required very less
maintenance;
(4) User-friendly environment;
(5) Programs written on these computers were
highly portable;
(6) Versatile and suitable for every type of
applications;
(7) Require very less power to operate.
32

Disadvantages:
(1) The soldering of LSI and VLSI chips on the
wiring board was not an easy task and required
complicated technologies to bind these chips on
the wiring board;
(2) The working of these computers is still
dependent on the instructions given by the
programmer.
33

34

FIFTH GENERATION COMPUTERS
• Fifth Generation (Present and Beyond)
• The different types of modern digital computers come under
this category.
• Uses Ultra Large Scale Integration technology that allows
almost ten million electronic components to be fabricated on
one small chip.
• Fifth generation computing devices are based on artificial
intelligence and are still in development, though there are
some applications, such as voice recognition, that are being
used today. The use of parallel processing and
superconductors is helping to make artificial intelligence a
reality.
• Quantum computation and molecular and nanotechnology
will radically change the face of computers in years to come.
• The goal of fifth-generation computing is to develop devices
that respond to natural language input and are capable of
learning and self-organization.
35

FIFTH GENERATION COMPUTERS
Advantages:
(1) Fastest and powerful computers till date;
(2) Being able to execute a large number of
applications at the same time and that too at a very
high speed;
(3) Decreasing the size of these computers to a
large extent;
(4)The users of these computers find it very
comfortable to use them because of the several
additional multimedia features;
(5) They are versatile for communications and
resource sharing.
36

CLASSIFICATION OF COMPUTERS
• We can classify the computers according to
the following three criteria:
(1) Based on operating principles
(2) Based on applications
(3) Based on size and capability
38

(1) Based on operating principles:
Analog computers: represent data in the form of
continuous electrical signals having a specific
magnitude
Digital computers: store and process data in the digital
form.
Hybrid computers: a combination of analog computer
and digital computer because it encompasses the best
features of both.
39

(2) Based on applications:
General purpose computers: can work in all
environments.
Special purpose computers: can perform only a
specified task.
40

(3) Based on size and capability
Microcomputers: Designed to be used by individuals.
Mini Computers: Can handle more data and more input
and output than micro computers.
Mainframe Computers: A very large computer
Super Computers: The fastest type of computer that
can perform complex operations at a very high speed.
41

CHARACTERISTICS OF MODERN
COMPUTERS
• The unique capabilities and characteristics of a
computer:
Speed
Storage capacity
Accuracy
Reliability
Versatility
Diligence
42

COMPUTERS
• SPEED
– Computers operate at extremely high speeds
– Their speed is measured in millions of instructions
per second (MIPS).
43

COMPUTERS
• ACCURACY
– The computer’s accuracy is consistently high.
– Almost without exception, the errors in computing
are due to human rather than technological
weakness i.e. due to vague thinking by the
programmer, inaccurate data, user instructions or
hardware problems.
44

COMPUTERS
• AUTOMATIC (SPONTANEOUS)
– The computers are automatic. They do not need
any supervision in order to perform programs
when instructed or execute the work assigned.
45

COMPUTERS
• DILIGENCE (ENDURANCE)
– Computers have the ability to perform the same
task over for long time without getting tired. This
is because a computer is a machine, and so does
not have human behaviors of tiredness and lack of
concentration
46

COMPUTERS
• versatility
– Modern Computers can perform different kind of
tasks simultaneously (doing many tasks at the
same time). For example you can play music while
typing a document at the same time. This is also
known as multi-tasking.
47

COMPUTERS
• Adaptability
– Modern Computers can comply with different
settings. For example, they can be used as
personal computers, for home use, banking,
communication, entertainment, weather
forecasting, space explorations, teaching, railways,
medicine etc.
48

COMPUTERS
• Artificial intelligence
– Computers are artificially intelligent. i.e. They
can be programmed to assume capabilities
such as learning, reasoning, adaptation, and
self-correction. For example computers can
respond as if they were thinking by playing
chess, recognize handwriting and speech.
However, the computers themselves cannot
think. The artificial intelligence is only
supported by the power of the programs
installed in them.
49

COMPUTERS
• storage
– For a computer to be able to work, it must have
some form of work space where data is stored
before being processed. All information is stored
on a hard disk or in the memory, for example on a
RAM.
50

COMPUTERS
• Need user Input
– Computers cannot initiate themselves and make
the decisions. They need instructions from users
to enhance the process. After all, a computer is
only a machine.
51

LIMITATIONS OF A COMPUTER
Garbage-In, Garbage-Out
Dumb machine
52

THE COMPUTER SYSTEM
• Hardware
• Software
• Data
• People
53

1-55
HARDWARE AND SOFTWARE
• Hardware
– the physical, tangible parts of a computer
– keyboard, monitor, disks, wires, chips, etc.
• Software
– programs and data
– a program is a series of instructions that tells the computer
to perform a specific task
• A computer requires both hardware and software
• Each is essentially useless without the other

COMPUTER ORGANIZATION AND
ARCHITECTURE
• Computer architecture: the definition of basic
attributes of hardware components and their
interconnections, in order to achieve certain
specified goals in terms of functions and
performance.
• Computer organisation: the design and physical
arrangement of various hardware units to work in
tandem, in an orderly manner, in order to achieve
the goals specified in the architecture.
56

CENTRAL PROCESSING UNIT(CPU)
•The main operations of the CPU include four phases:
(1) Fetching instructions from the memory
(2) Decoding the instructions to decide what operations
to be performed
(3) Executing the instructions
(4) Storing the results back in the memory
57

1-58
THE CENTRAL PROCESSING UNIT
• A CPU is on a chip called a microprocessor
• It continuously follows the fetch-decode-execute
cycle:
fetch
Retrieve an instruction from main memory
decode
Determine what the
instruction is
execute
Carry out the
instruction

COMPONENTS OF A CPU
• Registers
• Arithmetic Unit
• Logic Unit
• Control Unit
60

1-61
COMPONENTS OF A CPU
• The CPU contains:
Arithmetic / Logic Unit
Registers
Control Unit
Small storage
areas
Performs calculations
and makes decisions
Coordinates
processing steps

ARITHMETIC UNIT
• Arithmetic Unit is the part of the CPU that
performs arithmetic operations on data. The
arithmetic operations can be addition,
subtraction, multiplication or division.
62

LOGIC UNIT
• Logic Unit is the part of the CPU that performs
logical operations on the data.
63

CONTROL UNIT
• Control Unit is an important component of
CPU that controls the flow of data and
information. It maintains the sequence of
operations being performed by the CPU.
64

REGISTERS
• CPU contains a few special purpose,
temporary storage units known as registers.
They are high-speed memory locations used
for holding instructions, data and
intermediate results that are currently being
processed.
65

INTERNAL COMMUNICATIONS IN CPU
• The internal communication of a processor in
the computer system can be divided into two
major categories:
(1) Processor to memory communication
(2) Processor to I/O devices communication
66

1-67
INTERNAL COMMUNICATIONS IN CPU
Central
Processing
Unit
Main
Memory
Floppy Disk
Hard Disk
Monitor
Keyboard
I/O devices facilitate
user interaction
Monitor screen
Keyboard
Mouse
Joystick
Bar code scanner
Touch screen

PROCESSOR TO MEMORY
COMMUNICATION
• The direct communication between the processor
and memory of the computer system is implemented
with the help of two registers:
(1) Memory Address Register
(2) Memory Buffer Register
The reading and writing operations performed by the
processor are called memory read and memory write
operations.
68

PROCESSOR TO I/O DEVICES
COMMUNICATION
• The communication between I/O devices and
processor of the computer system is
implemented using an interface unit. The
interface unit acts as an intermediary between
the processor and the device controllers of
various peripheral devices in the computer
system.
69

MACHINE CYCLE
• The cycle during which a machine language
instruction is executed by the processor of the
computer system is known as machine cycle.
70

INSTRUCTION CYCLE
• Fetching: The CPU retrieves the instruction
from the main memory of the computer
system.
• Decoding: Breaking down the instruction
into different parts, so that it can be easily
understood before being processed by the
CPU.
71

EXECUTION CYCLE
• Executing: The decoded instruction is
executed by the ALU of the CPU.
• Storing: The result computed in the
execution phase is either sent to the
memory or to an output device.
72

THE BUS
• A bus is a set of wires that is used to connect the different
internal components of the computer system for the purpose
of transferring data as well addresses amongst them.
• Data bus: used to transfer data amongst the different internal
components. Modern computer systems use 32-bit data
buses for data transfer.
• Address bus: transfers the memory addresses for read and
write memory operations.
73

MEMORY AND STORAGE SYSTEMS
• Primary Memory: Store the data that are
being currently handled by the CPU; generally
known as “memory” , main memory or RAM;
• Secondary Memory: Store the results and the
data for future use; generally known as
“storage”;
• Internal Process Memory: Placed either inside
the CPU or near the CPU such as Cache
memory and Registers.
75

MEMORY REPRESENTATION
• In the memory, values are represented by sequences
of binary digits, know as bits. Most computers use a
group of eight bits, known as a byte, to represent a
character.
• Memory is a “bunch” of bytes or cells into which we
can place data. Each cell, known as a data item, is
assigned a unique number known as “address”. The
CPU can identify each cell by its address.
76

1-77
Main memory is divided
into many memory
locations (or cells)
9278
9279
9280
9281
9282
9283
9284
9285
9286
Each memory cell has a
numeric address, which
uniquely identifies it

1-78
9278
9279
9280
9281
9282
9283
9284
9285
9286
Large values are
stored in consecutive
memory locations
10011010
Each memory cell stores a
set number of bits (usually 8
bits, or one byte)

• The byte is defined as the “smallest addressable unit” of
memory. Most computers use groups of bytes, usually 2 or 4,
known as “words” to represent information.
• Computer memories are often rated in terms of their capacity
to store information. Typically, capacities are described using
the unit of byte as follows:
(1) 1 KB (Kilobyte)=1,024 bytes
(2) 1 MB (Megabyte)=1,048,576 bytes
(3) 1 GB (Gigabyte)=1,073,741,824 bytes
(4) 1 TB (Terabyte)=1,099,511,627,776 bytes
79

RANDOM ACCESS MEMORY(RAM)
• Random Access Memory (RAM) is a volatile memory
and loses all its data when the power is switched off.
• It is the main memory of the computer system that
stores the data temporarily and allows the data to be
accessed in any order.
• RAM can be categorised into two main types, namely,
Static RAM and Dynamic RAM.
80

RANDOM ACCESS MEMORY(RAM)
• Static RAM: is a type of RAM in which data is stored till the
power of the computer system is switched on. SRAM uses a
number of transistors to store a single bit of digital
information.
• Dynamic RAM: is the RAM in which data is stored in a storage
cell, consisting of a transistor and a capacitor. The DRAM
needs to be continuously refreshed with power supply
because the capacitor has the tendency to get discharged.
DRAM retains the data for a very short span of time, even
after the power supply is switched off.
81

READ ONLY MEMORY(ROM)
• ROM is the memory that stores the data
permanently.
• The data can be easily read from this type of memory
but cannot be changed.
• ROM is most commonly used in devices such as
calculators, laser printers, etc.
• ROM does not allow the random access of data, and
allows sequential access of data.
83

READ ONLY MEMORY(ROM)
ROM is divided into four types:
(1) Programmable ROM: a memory chip on which the write operation of
data can be performed only once. PROM is reliable and stores the data
permanently without making any change in it. It is mostly used in video
games and electronic dictionaries.
(2) Erasable PROM: a type of ROM in which data can be erased or
destroyed using Ultraviolet Light.
(3) Electrically Erasable PROM: a type of ROM in which data can be
erased or destroyed by exposing it to an electric charge.
(4) Flash ROM: a type of EEPROM that stores the information using
floating-gate transistors, which can store electric charge for a longer
period of time as compared to the normal transistors. This memory is
mainly used in the memory cards of mobile phones, digital cameras and
iPods for storing data. Flash ROM has faster speed of reading data, as
compared to any other type of ROM.
84

SECONDARY STORAGE SYSTEMS
• Storage systems are the devices used for data
storage. The main objective of the storage system is
to permanently store data. The storage systems can
be classified as follows:
(1) Magnetic
(2) Optical
(3) Solid state
(4) Magneto Optical
88

MAGNETIC STORAGE SYSTEMS
• Magnetic storage systems can be defined as the
storage systems that store the data on a magnetised
medium, with the help of magnetised particles.
Magnetic tapes, magnetic disks, hard disks, floppy
disks are examples of magnetic storage systems.
• Can store any type of data, such as text, audio, video,
image
89

MAGNETIC STORAGE SYSTEMS
• Magnetic tapes: The plastic tapes with magnetic coating that
are used for storing the data. They are similar to the normal
recording tapes. The data stored on the magnetic tapes can
be accessed using the sequential access method.
• Magnetic Disks: A flat disk that is covered with magnetic
coating for holding information. It is used to store digital
information in the form of small and magnetized needles.
These needles help in encoding a single bit of information by
getting polarized in one direction represented by 1, and
opposite direction represented by 0. It allows the random
access of data and provides the facility of erasing and re-
recording the data as many times as required.
90

OPTICAL STORAGE SYSTEMS
• The optical storage systems use the laser light
as the optical medium to retrieve as well as
record data.
• The optical storage devices are either read-
only or writable.
92

SOLID-STATE STORAGE DEVICES
• Solid-state Storage Devices were developed in 1978
by Storage Tek Company.
• Do not use magnetic and optical medium to store
data. Instead, use the semiconductor devices.
• Contains all the properties of hard disk drives to
store the data and use solid-state memory, which has
no moving parts.
• The examples of SSD are flash memory cards and
Universal Serial Bus (USB) devices.
93

CACHE MEMORY
• Cache memory is a small, fast and expensive
memory that stores the copies of data that
needs to be accessed frequently from the
main memory.
94

STORAGE EVALUATION CRITERIA
• Access Mode: random access mode, sequential access mode,
direct access mode
• Access Time: the time taken by the processor in completing
the requests made by the user for performing the read and
write operations.
• Storage Capacity: the size of the memory available for storing
the data, and measured in terms of bytes.
• Storage Type: Temporary and permanent memory.
• Cost: the cost of the storage device used in the computer
system for holding the data.
95

INPUT DEVICES
• Input devices are electromechanical devices that are
used to provide data to a computer for storing and
further processing, if necessary.
• We can provide the input to a computer in two ways:
(1) Manually through devices such as keyboard and
mouse; (2) Directly from documents using devices
such as scanners.
96

INPUT DEVICES
Depending upon the type or method of input, the input
device may belong to one of the following categories:
(1) Keyboard
(2) Pointing devices
(3) Scanning devices
(4) Optical recognition devices
(5) Digital camera
(6) Voice recognition devices
(7) Media input devices
97

Keyboard
Keyboard is the most commonly used input device. We can use a keyboard to
type data and text and execute commands. A standard keyboard consists of
the following groups of keys:
(1) Alphanumeric keys: The alphanumeric keys include the number keys and
alphabet keys. These keys are arranged in the same style as in the normal
typewriters, popularly known as QWERTY layout;
(2) Function keys: Arranged in a row on the top of the keyboard. Help
perform specific tasks, such as searching a file or refreshing a web page;
(3) Central keys: Used for controlling the movement of cursor and screen
display. Include arrow keys, modifier keys such as SHIFT, ALT, CTRL;
(4) Numeric keypad: Located on the right side of the keyboard. This looks like
a calculator’s keypad;
(5) Special purpose keys: Escape, Insert, Delete, Print Screen, Pause, Tab,
Spacebar;
99

Pointing Devices
Pointing devices are the input devices that are generally used for
moving the cursor to a particular location to point an object on
the screen. With the help of pointing devices, we can easily
select the icons, menus, windows, etc on the Graphical User
Interface. Some of the commonly used pointing devices are:
(1) Mouse
(2) Trackball
(3) Light pen
(4) Joystick
(5) Touchscreen
100

Mouse
A small hand-held pointing device that basically
controls the two-dimensional movement of the
cursor on the displayed screen. The most
commonly used types of mouse are:
(1) Mechanical mouse
(2) Optical mouse
101

Scanning Devices
• Scanning devices are the input devices that can
electronically capture text and images, and convert
them into computer readable form.
• The basic task of a scanning devices is to convert an
image or the textual data into digital data, i.e., in the
form of boxes, where each box represents either zero
or one. The resultant matrix is known as bit map and
is displayed on the screen.
102

Scanning Devices
• The scanning devices can be differentiated from each other
on the basis of the following characteristics:
• Resolution: the closeness of the pixels in the bit map, and
vary from 72 to 600 dots per inch (dpi);
• Size: the small sized scanning device can scan approximately
two to five inches of the document, whereas the large sized
one can scan approximately up to forty inches of the
document.
103

Scanning Devices
• Scanning technology: Some use Charged Coupled Device (CCD)
arrays, whereas others use Photo Multiplier Tubes (PMT)
technology. The CCD consists of a series of light receptors,
which are sensitive to the variation in the light frequency. As
the frequency of light changes, these scanning devices detect
the change and the output obtained after scanning also gets
accordingly changed. The PMT consists of a photocathode,
which is a photosensitive surface used for generating the
electrons. PMT is used for identifying the light emitted by the
weak signals.
104

Scanning Devices
• On the basis of these characteristics, the scanning devices can
be categorized as follows:
• Hand-held scanners: are suitable for scanning small images
rather than the whole page of text or pictures, and are
generally used for identifying the bar-code label of the
products.
• Flat-bed scanners: consist of a flat surface composing of glass
pane on which the documents are kept for scanning. Under
this glass pane, there is xenon light and a CCD, which consists
of an array of red, green and blue filters.
105

Scanning Devices
• Drum scanners: consist of a large drum, which is used for
scanning the documents. These scanners make use of the
PMT technology, instead of the CCD technology. The
resolution image of these scanners is very high, ranges form
8000 dpi to 11000 dpi.
• Slide scanners: are used for scanning slides as well as film
negatives. These scanners are also known as film scanners as
they can easily scan the original image of the film. The dark
areas appear light and the light areas appear dark.
106

Optical Recognition Devices
• Optical recognition devices are used for recognizing the
characters optically. The optical recognition devices
basically make use of optical scanner for inputting data.
Unlike keyboards, the optical recognition devices do not
enter the data by pressing the keys. They help the users
in saving a lot of time. Commonly used optical
recognition devices are:
 Optical Character Recognition (OCR) devices: scan a
particular document by recognizing its individual
characters and converting it into the editable form.
107

• Optical Mark Recognition (OMR) devices: help in obtaining
the data from the marked fields. These devices prove to be of
great use in recognizing characters in question sheets,
enrolment forms, registration forms, employee payroll, etc.
Most popularly, the OMR devices are used for scanning the
documents having multiple choices as in the question papers
used in schools, colleges, etc.
108

• Magnetic Ink Character Recognition (MICR) devices: special
devices used for recognizing the characters written with
magnetic ink consisting of iron oxide particles. These devices
were specially developed for the banking operations. The
details on the bank cheques, such as cheque number, bank
and branch code are written with the magnetic ink.
109

Digital Camera
• A digital camera is a handheld electronic device that is used to
capture the image of an object electronically. The digital
camera consists of a built-in computer, which helps in
recording the images electronically. The following are the
main features of the digital camera:
• Capturing and storing thousands of images on a single
memory chip
• Editing as well as deleting the images
• Recording the video clip with sound
• Showing the just recorded video clip on the camera screen
110

Digital Camera
• The image captured by a digital camera is in the digital format
and can be easily downloaded on a computer system.
• The quality of the pictures captured by a digital camera
depends on the resolution factor. The more the resolution of
a digital camera, the better is the image quality.
111

Voice Recognition System
• The voice recognition devices generally record the voice of a
person and transform it into electrical signals. The electrical
signals are then converted into the machine readable code.
• The voice recognition system only recognises the voice of the
speaking person rather than what he speaks.
• The voice recognition devices are used for various purposes
such as dictation, training air-traffic controllers, etc. These
systems allow users to communicate with computers directly
without using a keyboard or mouse.
112

Data Acquisition Sensors
• Sensors are the devices that are used for detecting
and measuring the physical quantities, such as heat,
temperature, and converting them into electrical
signals. The sensors are most commonly used in data
acquisition systems.
• The data acquisition system collects the electrical
signals from various devices and converts them into
the digital signals for further assessment.
113

Media Input Devices
• The input devices, which are generally used in
media for communicating with the mass audiences,
are known as media input devices. The following
are the most popularly used media input devices:
• Microphone
• Webcam
• Graphics tablet
114

OUTPUT DEVICES
• Output devices receive the processed data (information) from the
CPU and present it to the user in a desired form. They act as an
interface between the computer and the user. The main task of an
output device is to convert the machine readable information into
human-readable form which may be in the form of text, graphics,
audio or video. Depending upon the form of output required, the
output device may belong to one of the following categories:
• Display monitors
• Printers
• Plotters
• Voice output systems
• Projectors
115

OUTPUT DEVICES
• While the printers and plotters provide the physical form of
output known as hard copy, the display monitors, voice
output systems and projectors provide temporary output
known as soft copy. Unlike hard copy, soft copy is not a
permanent form of output.
117

Display Monitors
• Earlier, the display monitors were capable of displaying the
characters only in a single font and in a single color. These
characters were arranged in a rectangular grid on the screen.
• The display screens, which are available today, support many
fonts and colors.
• Different types of display monitors use different technology
for displaying the data.
118

Display Monitors
• Cathode Ray Tube (CRT) Monitor: contain an empty glass
tube with a phosphor coated fluorescent screen and a source
of electrons known as electron gun. A CRT monitor has many
advantages, such as a high contrast ratio and color depth. It
also provides a change in the resolution without affecting the
clarity of the picture. But it is very bulky and occupies a lot of
space on the desk. It also consumes a lot of power and
produces a large amount heat.
119

Display Monitors
• Liquid Crystal Display (LCD) Monitor: Use liquid crystals
technology to display the images. An LCD monitor is small in
size and light in weight so it occupies less space on the desk.
Also, the power consumption by an LCD monitor is very less.
However, it has a weak color quality as compared to a CRT
monitor.
• Thin Film Transistor (TFT) Monitor: A TFT monitor is similar to
an LCD monitor except for one difference that it uses thin film
transistor technology along with liquid crystal technology to
improve the quality of the image.
120

Printers
• A printer is a computer hardware that generates the hard copy
of the information processed by a computer system.
• Impact Printers: there exists a mechanical contact between
print head and paper. Print head is the part of the printer that
resembles a hammer and is responsible for transferring the ink
to the paper in the form of required characters. Impact printer
contains an individual print head for each character.
• Non-Impact Printers: there exists no mechanical contact
between the print head and paper. These printers spray ink on
the paper with the help of a nozzle. The most popular ones are
ink-jet printers and laser printers.
121

Plotters
• Plotter is a device used to print high quality graphics and
images. It uses one or more pens to produce a high quality
drawing. These pens change their positions and draw
continuous lines to produce an image. The plotters were used
as a substitute to the colored printers when the printers were
very expensive and were also not capable of drawing bigger
images such as graphs.
122

Voice Output Systems
• Voice output systems record the simple messages in human
speech form and then combine all these simple messages to
form a single message. The voice response system is of two
types: (1) a reproduction of human voice and other sounds; (2)
speech synthesis.
• The basic application of a voice output system is in Interactive
Voice Response systems, which are used by the customer care
or customer support departments of an organization, such as
telecommunication companies, etc.
123

Projectors
• A projector is a device that is connected to a computer or a
video device for projecting an image from the computer or
video device onto the big white screen.
• A projector consists of an optic system, a light source and
displays, which contain the original images.
• Projectors were initially used for showing films but now they
are used on a large scale for displaying presentations in
various situations.
124

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