D Sinha

Computer Fundamentals

Debprasad Sinha
Vidyasagar College of Optometry & Vision Science

Chapter 1
Introduction

BO 205 Chapter 01: Introduction Slide 1

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Learning Objectives
In this chapter you will learn about:

▪ Computer
▪ Data processing
▪ Characteristic features of computers
▪ Computers’ evolution to their present form
▪ Computer generations
▪ Characteristic features of each computer generation

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Computer

▪ The word computer comes from the word “compute”, which

means, “to calculate”

▪ Thereby, a computer is an electronic device that can perform

arithmetic operations at high speed

▪ A computer is also called a data processor because it can store, process,

and retrieve data whenever desired

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Some Standard Definitions of a Computer

“A device used for computing; specifically, an electronic machine which, by means of
stored instructions and information, performs rapid, often complex calculations or
compiles, correlates, and selects idea”.
- Webster’s Dictionary

“A data processor that can perform substantial computation, including numerous

arithmetic and logic operations, without intervention by a human operator during the
run”.
- International Standards Organisation (ISO)

“A device capable of solving problems by accepting data, performing described

operations on the data and supplying the results of these operations”
- U. S. Institute of Computer Sciences

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Data Processing
The activity of processing data using a computer is called
data processing

Data Input Computer Output Information

(Raw material) (Data processor) (Finished product)

Data is raw material used as input to data processing and information is

processed data obtained as output

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Characteristics of Computers
Sr.
Characteristics Description
No.

1 Automation It carries out a job normally without any human intervention

It can perform several billion (109) simple arithmetic operations per second
2 High Speed

3 Accuracy It performs every calculation with the same accuracy

4 Diligence It is free from monotony, tiredness, and lack of concentration

5 Versatility It can perform a wide variety of tasks

It can store huge amount of information and can recall anypiece of this
6 Storage
information whenever required
Capacity(Memory)
It cannot take its own decisions, and has to be instructed what to do and in
7 No I. Q.
what sequence

8 Reliability It gives very accurate results with predetermined values. Correct and modify the
parameters automatically.

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Evolution of Computers
▪ Blaise Pascal invented the first mechanical adding machine in
1642
▪ Baron Gottfried Wilhelm von Leibniz invented the first
calculator for multiplication in 1671
▪ Keyboard machines originated in the United States around
1880
▪ Around 1880, Herman Hollerith came up with the concept of punched
cards that were extensively used as input media until late 1970s

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Evolution of Computers
▪ Charles Babbage is considered to be the father of
modern digital computers

▪ He designed “Difference Engine” in 1822

▪ He designed a fully automatic analytical engine in 1842 for

performing basic arithmetic functions

▪ His efforts established a number of principles that are

fundamental to the design of any digital computer

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Some Well Known Early Computers

▪ The Mark I Computer (1937-44)
▪ The Atanasoff-Berry Computer (1939-42)
▪ The Electronic Numerical Integrator And Calculator (ENIAC) (1943-46)
▪ The Electronic Discrete Variable Automatic Computer (EDVAC)
(1946-52)
▪ The Electronic Delay Storage Automatic Calculator (EDSAC) (1947-49)
▪ Manchester Mark I (1948)
▪ The Universal Automatic Computer (UNIVAC) I (1951)
▪ IBM 701 (1952)
▪ IBM 650 (1953)

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Types of Computer
Analog Computer
Digital Computer
Purpose
Hybrid Computer

Generation
Types of Computer Development
1st, 2nd, 3rd, 4th, 5th

Micro Computer
Mini Computer
Main frame Computer
Size and Performance
Super Computer

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Computer Generations
▪ “Generation” in computer talk is a step in technology. It provides a
framework for the growth of computer industry

▪ Originally it was used to distinguish between various hardware

technologies, but now it has been extended to include both hardware and
software

▪ Till today, there are five computer generations

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Computer Generations
Key hardware Key software Key Some
Generation
representative
(Period) technologies technologies characteristics
systems

First ▪ Vacuum tubes ▪ Machine and ▪ Bulky in size ▪ ENIAC

(1942-1955) ▪ Electromagnetic assembly languages ▪ Highly unreliable ▪ EDVAC
relay memory ▪ Stored program ▪ Limited commercial use ▪ EDSAC
▪ Punched cards concept and costly ▪ UNIVAC I
secondary storage ▪ Mostly scientific ▪ Difficult commercial ▪ IBM 701
applications production
▪ Difficult to use
Second (1955- ▪ Transistors ▪ Batch operating ▪ Faster, smaller, more ▪ Honeywell 400
1964) ▪ Magnetic cores system reliable and easier to ▪ IBM 7030
memory ▪ High-level program than previous ▪ CDC 1604
▪ Magnetic tapes programming generation systems
▪ UNIVAC LARC
▪ Disks for languages(FOR ▪ Scientific computation
secondary TRAN, ▪ Commercial production
storage COBOL, was still difficult and
ALGOL, costly
SNOBOL)
▪ Scientific and
commercial
applications

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Computer Generations
Generation Key hardware Key software Key Some rep.
(Period) technologies technologies characteristics systems

Third ▪ ICs with SSI and ▪ Timesharing ▪ Faster, smaller, more ▪ IBM
(1964-1975) MSI technologies operating reliable, easier and 360/370
▪ Larger magnetic system cheaper to produce ▪ PDP-8
cores memory ▪ Standardization of ▪ Commercially, easier to ▪ PDP-11
▪ Larger capacity disks high-level use, and easier to upgrade ▪ CDC 6600
and magnetic tapes programming than previous generation
secondary storage languages systems
▪ Minicomputers; ▪ Unbundling of ▪ Scientific,
upward compatible software from commercial and
family of computers hardware interactive on-line
applications

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Computer Generations
Generation Key hardware Key software Key Some rep.
(Period) technologies technologies characteristics systems
Fourth (1975- ▪ ICs with VLSI ▪ Operating systems for ▪ Small, affordable, ▪ IBM PC
1989) technology PCs with GUI and reliable, and easy and its
▪ Microprocessors; multiple windows on a to use PCs clones
semiconductor single terminal screen ▪ More powerful and ▪ Apple II
memory ▪ Multiprocessing OS reliable mainframe ▪ TRS-80
▪ Larger capacity hard with concurrent systems and ▪ VAX 9000
disks as in-built programming supercomputers
languages ▪ CRAY-1
secondary storage ▪ Totally general
▪ CRAY-2
▪ Magnetic tapes and floppy ▪ UNIX operating purpose machines
system ▪ CRAY-
disks as portable storage ▪ Easier to
X/MP
media ▪ C and C++ produce
▪ Personal computers programming commercially
language ▪ Easier to
▪ Supercomputers based on
parallel vector processing ▪ PC, Network-based, and upgrade
and symmetric supercomputing ▪ Rapid software
multiprocessing applications development
technologies ▪ Object-oriented possible
design and
▪ Spread of high-speed programming
computer networks

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Computer Generations
Generation Key hardware Key software Key Some rep.
(Period) technologies technologies characteristics systems
Fifth ▪ ICs with ULSI ▪ World Wide Web ▪ Portable ▪ IBM notebooks
(1989- technology ▪ Multimedia, computers ▪ Pentium PCs
Present) ▪ Larger capacity Internet ▪ Powerful, cheaper, ▪ SUN
main memory, applications reliable, and easier to Workstations
hard disks with ▪ Micro-kernel, use desktop machines ▪ IBM SP/2
RAID support multithreading, ▪ Very powerful ▪ SGI Origin 2000
▪ Optical disks as multicore OS mainframes
portable read-only ▪ PARAM
▪ JAVA ▪ High uptime due to Supercomputers
storage media ▪ MPI and PVM hot-pluggable
▪ Notebooks, powerful libraries for components
desktop PCs and parallel ▪ General purpose
workstations programming machines
▪ Powerful servers, ▪ Easier to produce
supercomputers commercially
▪ Internet
▪ Cluster computing

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Electronic Devices Used in Computers

of Different Generations

(a) A Vacuum tube (b) A Transistor (c) An IC chip

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Classification of Computer Based on Size

▪ Super Computer
First super computer of India was PARAM – 8000 designed by Centre
for Development of Advanced Computing (C-DAC) in 1991.
▪ Most costly
▪ Fastest (Speed Measure in Terms of: Floating Point Operation per
Second-FLOPS, BIPS-Billions of instruction per second, FPU
Floating Point Unit)
▪ Biggest in size
▪ Multi processor (connected parallel)
▪ Design for specific task (special purpose)
▪ Very large memory storage
▪ Multi operator

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Classification of Computer Based on Size

▪ Mainframe Computer
▪ Used as server or workstation (Server of Telecommunication sector,
Banking, Hospitals etc) i.e used for general purpose
▪ Big but not as super
▪ Fast but not as super (measure in MIPS-Millions of Instruction Per Second)
▪ Costly but not as super
▪ Multiprocessor
▪ Multipurpose
First mainframe computer of world is UNIVAC –First designed by IBM
(International Business Machine)

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Classification of Computer Based on Size

▪ Micro Computer
▪ Laptop (client computer), Desktop, Home PC, Tablet, Palmtop, Phablet
(phone + Tablet)
▪ First micro computer in world ALTAIR-8800 designed by IBM

▪ Mini Computer
▪ Their size and capacity are more than micro computer but less than
mainframe computer
▪ ECG machine
▪ PDP (Programmed Data Processor)- is the first mini computer of the world
designed by DEC (Digital Equipment Corporation)

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Classification of Computer based on signal

Analog Computer Digital Computer Hybrid Computer
Computer which can work on Computer which can work on It can work both analog and
continuous signal like sine or discrete signal(digital signal) digital signal simultaneously
cosine signal

Used to measure the physical Manual calculation is not Used for calculation of ECG
process with high accuracy required. Digit directly shown (Eco-cardiogram) signal,
(basically used in research) on the display weather forecasting, Satellite
monitoring and controlling etc
Thermometer, Spherometer, Super, micro, mainframe
speedometer of bike etc computer, laptop, smart
phone, digital watch, digital
thermometer etc

BO 205 Chapter 01: Introduction Slide 20

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Computer Fundamentals

Chapter 2

Basic Computer Organization

BO 205 Slide 21
Chapter 02: Basic Computer Organization
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Learning Objectives
In this chapter you will learn about:
▪ Basic operations performed by all types of computer systems
▪ Basic organization of a computer system
▪ Input unit and its functions
▪ Output unit and its functions
▪ Storage unit and its functions
▪ Types of storage used in a computer system
▪ Arithmetic Logic Unit (ALU)
▪ Control Unit (CU)
▪ Central Processing Unit (CPU)
▪ Computer as a system

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The Basic Operations of a Computer

System
▪ Inputting. The process of entering data and instructions into the computer system

▪ Storing. Saving data and instructions to make them readily available for initial or
additional processing whenever required whenever required

▪ Processing. Performing arithmetic operations (add, subtract, multiply, divide,

etc.) or logical operations (comparisons like equal to, less than, greater than, etc.)
on data to convert them into useful information

▪ Outputting. The process of producing useful information or results for the user
such as a printed report or visual display

▪ Controlling. Directing the manner and sequence in which all of the above
operations are performed

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Basic Organization of a Computer System

Storage Unit

Secondary
Storage

Program Information
Input Output (Results)
and
Unit Unit
Data Primary
Storage

Control
Unit
Indicates flow of
instructions and data
Arithmetic
Indicates the control
Logic Unit
exercised by the
control unit
Central Processing Unit (CPU)

BO 205 Chapter 02: Basic Computer Organization

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Input Unit
An input unit of a computer system performs the following
functions:

1. It accepts (or reads) instructions and data from outside world

2. It converts these instructions and data in computer acceptable
form
3. It supplies the converted instructions and data to the computer
system for further processing

BO 205 Chapter 02: Basic Computer Organization

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Output Unit
An output unit of a computer system performs the following
functions:

1. It accepts the results produced by the computer, which are in coded

form and hence, cannot be easily understood by us
2. It converts these coded results to human acceptable (readable)
form
3. It supplies the converted results to outside world

BO 205 Chapter 02: Basic Computer Organization

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Storage Unit
The storage unit of a computer system holds (or stores) the following :

1. Data and instructions required for processing (received from input

devices)
2. Intermediate results of processing
3. Final results of processing, before they are released to an output
device
The broad categories of storage are:

1. Primary storage
2. Secondary storage

BO 205 Chapter 02: Basic Computer Organization Slide 27

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Primary Storage
▪ Used to hold running program instructions
▪ Used to hold data, intermediate results, and results of
ongoing processing of job(s)
▪ Fast in operation
▪ Small Capacity
▪ Expensive
▪ Volatile (looses data on power dissipation)

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Secondary Storage
▪ Used to hold stored program instructions
▪ Used to hold data and information of stored jobs
▪ Slower than primary storage
▪ Large Capacity
▪ Lot cheaper that primary storage
▪ Retains data even without power

BO 205 Chapter 02: Basic Computer Organization

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Arithmetic Logic Unit (ALU)

Arithmetic Logic Unit of a computer system is the place where the actual
executions of instructions takes place during processing operation
It perform the four basic arithmetic operations
Add
Subtract
Multiplication
Division
Logic operations
Less than
Equal to
Greater than

BO 205 Chapter 02: Basic Computer Organization

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Control Unit (CU)

❖How does an input device of a computer system know that it is time for it to feed data to
storage device?

❖How does its ALU know what should be done with the data once it receives them?

❖How the computer sends only the results for output to an output device and not the
intermediate results?

All this is possible by the Control Unit of a computer system which manages and
coordinates the operations of all other components of the computer system

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Central Processing Unit (CPU)

Arithmetic Central
Logic Unit Control Unit = Processing
+
(ALU) (CU) Unit (CPU)

▪ It is the brain of a computer system

▪ It is responsible for controlling the operations of all other

units of a computer system

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The System Concept

A system has following three characteristics:

1. A system has more than one element

2. All elements of a system are logically related
3. All elements of a system are controlled in a manner to achieve the
system goal

A computer is a system as it comprises of integrated components (input

unit, output unit, storage unit, and CPU) that work together to perform the
steps called for in the executing program

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Computer Fundamentals

Chapter 3
Number Systems

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Chapter 03: Number Systems Slide 37
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Learning Objectives
In this chapter you will learn about:

▪ Non-positional number system

▪ Positional number system
▪ Decimal number system
▪ Binary number system
▪ Octal number system
▪ Hexadecimal number system

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Chapter 03: Number Systems Slide 35
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Learning Objectives
▪ Convert a number’s base
▪ Another base to decimal base
▪ Decimal base to another base
▪ Some base to another base
▪ Shortcut methods for converting
▪ Binary to octal number
▪ Octal to binary number
▪ Binary to hexadecimal number
▪ Hexadecimal to binary number
▪ Fractional numbers in binary number system

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Chapter 03: Number Systems
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Number Systems
Two types of number systems are:

▪ Non-positional number systems

▪ Positional number systems

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Non-positional Number Systems

▪ Characteristics
▪ Use symbols such as I for 1, II for 2, III for 3, IIII for 4, IIIII
for 5, etc
▪ Each symbol represents the same value regardless of its
position in the number
▪ The symbols are simply added to find out the value of a
particular number

▪ Difficulty
▪ It is difficult to perform arithmetic with such a number
system

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Positional Number Systems

▪ Characteristics

▪ Use only a few symbols called digits

▪ These symbols represent different values depending on the
position they occupy in the number

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Positional Number Systems

▪ The value of each digit is determined by:
1. The digit itself
2. The position of the digit in the number
3. The base of the number system

(base = total number of digits in the number system)

▪ The maximum value of a single digit is always equal to one less than
the value of the base

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Decimal Number System

Characteristics
▪ A positional number system
▪ Has 10 symbols or digits (0, 1, 2, 3, 4, 5, 6, 7, 8,
9). Hence, its base = 10
▪ The maximum value of a single digit is 9 (one less than the
value of the base)
▪ Each position of a digit represents a specific power of the base
(10)
▪ We use this number system in our day-to-day life

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Binary Number System

Characteristics
▪ A positional number system
▪ Has only 2 symbols or digits (0 and 1). base = 2.
Hence its base is 2
▪ The maximum value of a single digit is 1 (one less than the
value of the base)
▪ Each position of a digit represents a specific power of the base
(2)
▪ This number system is used in computers

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Octal Number System

Characteristics
▪ A positional number system
▪ Has total 8 symbols or digits (0, 1, 2, 3, 4, 5, 6, 7). Hence, its
base = 8
▪ The maximum value of a single digit is 7 (one less than the
value of the base
▪ Each position of a digit represents a specific power of the base (8)

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Hexadecimal Number System

Characteristics
▪ A positional number system
▪ Has total 16 symbols or digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D,
E, F). Hence its base = 16
▪ The symbols A, B, C, D, E and F represent the decimal
values 10, 11, 12, 13, 14 and 15 respectively
▪ The maximum value of a single digit is 15 (one less than the value
of the base)

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Decimal Number System

Example

258610 = (2 × 103) + (5 × 102) + (8 × 101) + (6 × 100)

= 2000 + 500 + 80 + 6

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Converting a Decimal Number to a Number of

Another Base
Division-Remainder Method
▪Step 1:Divide the decimal number to be converted by the value of the new base
▪Step 2:Record the remainder from Step 1 as the rightmost digit (least significant digit)
of the new base number

▪Step 3:Divide the quotient of the previous divide by the new base

▪Step 4:Record the remainder from Step 3 as the next digit (to the left) of the new base
number
▪Repeat Steps 3 and 4, recording remainders from right to left, until the quotient
becomes zero in Step 3

❑Note that the last remainder thus obtained will be the most significant digit (MSD) of
the new base number

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Decimal to Binary Conversion

Example
5310 = ?2

Solution:

2 53 General Remainder
26 1
13 0
6 1
3 0
1 1
0 1

Answer = (110101)2

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Decimal to Octal Conversion

Example
95210 = ?8

Solution:

8 952 Remainders
119 0
14 7
1 6
0 1

Hence, 95210 = 16708

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Decimal to Hexadecimal Conversion

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Decimal to Hexadecimal Conversion

Example
23510 = ?16

Solution:

General Remainder
16 235
14 11 B
0 14 E

Answer = (EB)16

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Binary Number System

Characteristics
▪ A positional number system
▪ Has only 2 symbols or digits (0 and 1). base = 2.
Hence its base is 2
▪ The maximum value of a single digit is 1 (one less than the
value of the base)
▪ Each position of a digit represents a specific power of the base
(2)
▪ This number system is used in computers

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Bit
▪ Bit stands for binary digit
▪ A bit in computer terminology means either a 0 or a 1
▪ A binary number consisting of n bits is called ann-bit
number

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Binary to Decimal Conversion

Example

101012 = (1 x 24) + (0 x 23) + (1 x 22) + (0 x 21) x (1 x 20)

= 16 + 0 + 4 + 0 + 1
= 2110

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Binary to Octal Conversion

Example
11010102 = ?8

Step 1: Divide the binary digits into groups of 3 starting from right

001 101 010

Convert each group into one octal digit

Step 2:

0012 = 0 x 22 + 0 x 21 + 1 x 20 = 1
1012 = 1 x 22 + 0 x 21 + 1 x 20 = 5
0102 = 0 x 22 + 1 x 21 + 0 x 20 = 2

Hence, 11010102 = 1528

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Binary to Hexadecimal Conversion

Example

1111012 = ?16

Step 1: Divide the binary digits into groups of four starting

from the right

0011 1101

Step 2: Convert each group into a hexadecimal digit

00112 = 0 x 23 + 0 x 22 + 1 x 21 + 1 x 20 = 310 = 316
11012 = 1 x 23 + 1 x 22 + 0 x 21 + 1 x 20 = 310 = D16

Hence, 1111012 = 3D16

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Binary over Decimal (Why Binary?)

▪ Information is handled in a computer by electronic/ electrical
components
▪ Electronic components operate in binary mode (can only indicate two
states – on (1) or off (0)
▪ Binary number system has only two digits (0 and 1), and is suitable
for expressing two possible states
▪ In binary system, computer circuits only have to handle two binary
digits rather than ten decimal digits causing:
▪ Simpler internal circuit design
▪ Less expensive
▪ More reliable circuits
▪ Arithmetic rules/processes possible with binary numbers

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Octal Number System

Characteristics
▪ A positional number system
▪ Has total 8 symbols or digits (0, 1, 2, 3, 4, 5, 6, 7). Hence, its
base = 8
▪ The maximum value of a single digit is 7 (one less than the
value of the base
▪ Each position of a digit represents a specific power of the base (8)

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Octal to Decimal Conversion

▪ Since there are only 8 digits, 3 bits (23 = 8) are sufficient to represent
any octal number in binary

Example

20578 = (2 x 83) + (0 x 82) + (5 x 81) + (7 x 80)

= 1024 + 0 + 40 + 7

= 107110

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Octal to Decimal Conversion

Example
47068 = ?10
Common
values
multiplied
47068 = 4 x 83 + 7 x 82 + 0 x 81 + 6 x 80 by the
corresponding
= 4 x 512 + 7 x 64 + 0 + 6 x 1 digits
= 2048 + 448 + 0 + 6 Sum of these
products
= 250210

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Octal to Binary Conversion

Example
5628 = ?2
Step 1: Convert each octal digit to 3 binary digits 58 = 1012,
68 = 1102, 28 = 0102

Step 2: Combine the binary groups

5628 = 101 110 010
5 6 2

Hence, 5628 = 1011100102

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Octal to Hexadecimal Conversion

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Hexadecimal Number System

Characteristics
▪ A positional number system
▪ Has total 16 symbols or digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D,
E, F). Hence its base = 16
▪ The symbols A, B, C, D, E and F represent the decimal
values 10, 11, 12, 13, 14 and 15 respectively
▪ The maximum value of a single digit is 15 (one less than the value
of the base)

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Hexadecimal to Decimal Conversion

▪ Each position of a digit represents a specific power of the base
(16)
▪ Since there are only 16 digits, 4 bits (24 = 16) are sufficient to
represent any hexadecimal number in binary

Example

1AF16 = (1 x 162) + (A x 161) + (F x 160)

= 1 x 256 + 10 x 16 + 15 x 1
= 256 + 160 + 15
= 43110

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Hexadecimal to Binary Conversion

Example

2AB16 = ?2

Step 1: Convert each hexadecimal digit to a 4 digit binary

number

216 =210 = 00102

A16 = 1010 = 10102
B16 = 1110 = 10112

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Converting a Number of Another Base to a

Decimal Number
Method

Step 1: Determine the column (positional) value of each digit

Step 2: Multiply the obtained column values by the digits in

the corresponding columns

Step 3: Calculate the sum of these products

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Shortcut Method for Converting a Binary

Number to its Equivalent Octal Number
Method
Step 1: Divide the digits into groups of three starting from the
right

Step 2: Convert each group of three binary digits to one octal digit
using the method of binary to decimal conversion

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Shortcut Method for Converting an Octal

Number to Its Equivalent Binary Number
Method
Step 1:
Convert each octal digit to a 3 digit binary number (the octal digits may be treated
as decimal for this conversion)
Step 2:
Combine all together resulting binary groups (of 3 digits each) into a single binary
number

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Shortcut Method for Converting a Binary

Number to its Equivalent Hexadecimal Number
Method

Step 1: Divide the binary digits into groups of four starting

from the right

Step 2: Combine each group of four binary digits to one

hexadecimal digit

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Shortcut Method for Converting a Binary

Number to its Equivalent Hexadecimal Number
Example

1111012 = ?16

Step 1: Divide the binary digits into groups of four starting

from the right

0011 1101

Step 2: Convert each group into a hexadecimal digit

00112 = 0 x 23 + 0 x 22 + 1 x 21 + 1 x 20 = 310 = 316
11012 = 1 x 23 + 1 x 22 + 0 x 21 + 1 x 20 = 310 = D16

Hence, 1111012 = 3D16

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Shortcut Method for Converting a Hexadecimal

Number to its Equivalent Binary Number
Method
Step 1: Convert the decimal equivalent of each hexadecimal digit to a 4
digit binary number

Step 2: Combine all the resulting binary groups (of 4 digits each) in a single
binary number

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Shortcut Method for Converting a Hexadecimal

Number to its Equivalent Binary Number

Step 2: Combine the binary groups

2AB16 = 0010 1010 1011
2 A B

Hence, 2AB16 = 0010101010112

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Fractional Numbers
Fractional numbers are formed same way as decimal
number system
In general, a number in a number system with base b
would be written as:
an an-1… a0 . a-1 a-2 … a-m

And would be interpreted to mean:

an x bn + an-1 x bn-1 + … + a0 x b0 + a-1 x b-1 + a-2 x b-2 +
… + a-m x b-m

The symbols an, an-1, …, a-m in above representation

should be one of the b symbols allowed in the number
system

BO 205 Slide 72
Chapter 03: Number Systems
D Sinha

Formation of Fractional Numbers in Binary

Number System (Example)

Binary Point

Position 4 3 2 1 0 . -1 -2 -3 -4

Position Value 24 23 22 21 20 2-1 2-2 2-3 2-4

Quantity 16 8 4 2 1 1/ 1/ 1/ 1/
2 4 8 16
Represented

BO 205 Slide 73
Chapter 03: Number Systems
D Sinha

Formation of Fractional Numbers in Binary

Number System (Example)

Example

110.1012 = 1 x 22 + 1 x 21 + 0 x 20 + 1 x 2-1 + 0 x 2-2 + 1 x 2-3

= 4 + 2 + 0 + 0.5 + 0 + 0.125
= 6.62510

BO 205 Slide 74
Chapter 03: Number Systems
D Sinha

Formation of Fractional Numbers in Octal

Number System (Example)

Octal Point

Position 3 2 1 0 . -1 -2 -3

Position Value 83 82 81 80 8-1 8-2 8-3

Quantity 512 64 8 1 1/ 1/ 1/
8 64 512
Represented

BO 205 Slide 75
Chapter 03: Number Systems
D Sinha

Formation of Fractional Numbers in Octal

Number System (Example)
Example

127.548 = 1 x 82 + 2 x 81 + 7 x 80 + 5 x 8-1 + 4 x 8-2

= 64 + 16 + 7 + 5/8 + 4/64
= 87 + 0.625 + 0.0625
= 87.687510

BO 205 Slide 76
Chapter 03: Number Systems
D Sinha

Computer Fundamentals

Chapter 7
Processor and Memory

BO 205 Chapter 07: Processor and Memory Slide 77

D Sinha

Learning Objectives
In this chapter you will learn about:

▪ Internal structure of processor

▪ Memory structure
▪ Determining the speed of a processor
▪ Different types of processors available
▪ Determining the capacity of a memory
▪ Different types of memory available
▪ Several other terms related to the processor and
main memory of a computer system

BO 205 Chapter 07: Processor and Memory Slide 78

D Sinha

Basic Processor & Memory Architecture of

a Computer System
ROM PROM EPROM
Main memory (RAM)

Cache memory

S
E
Accumulator
C Decoder register
O I/O
N D Program Control General-purpose
D register register D
E
A E
V Storage Instruction General-purpose I/O
R register register V
I interfaces interfaces
Y I
C
S Memory address C
E register
T E
S
O Memory buffer S
A register
G
I/O
E register

General-purpose General-purpose
register register

Control Unit Arithmetic Logic Unit

Central Processing Unit

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D Sinha

Central Processing Unit (CPU)

▪ The brain of a computer system
▪ Performs all major calculations and comparisons
▪ Activates and controls the operations of other units of a computer
system
▪ Two basic components are
▪ Control Unit (CU)
▪ Arithmetic Logic Unit (ALU)

▪ No other single component of a computer determines

its overall performance as much as the CPU

BO 205 Chapter 07: Processor and Memory Slide 80

D Sinha

Control Unit (CU)

▪ One of the two basic components of CPU
▪ Acts as the central nervous system of a computer system
▪ Selects and interprets program instructions, and coordinates execution
▪ Has some special purpose registers and a decoder to perform these
activities

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Slide 81
D Sinha

Arithmetic Logic Unit (ALU)

▪ One of the two basic components of CPU.
▪ Actual execution of instructions takes place in ALU
▪ Has some special purpose registers
▪ Has necessary circuitry to carry out all the arithmetic and logic
operations included in the CPU instruction set

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Slide 82
D Sinha

Instruction Set
▪ CPU has built-in ability to execute a particular set of machine instructions,
called its instruction set
▪ Most CPUs have 200 or more instructions (such as add, subtract, compare,
etc.) in their instruction set
▪ CPUs made by different manufacturers have different instruction sets
▪ Manufacturers tend to group their CPUs into “families” having similar
instruction sets
▪ New CPU whose instruction set includes instruction set of its predecessor
CPU is said to be backward compatible with its predecessor

BO 205 Chapter 07: Processor and Memory

Slide 83
D Sinha

Registers

▪ Special memory units, called registers, are used to hold information

on a temporary basis as the instructions are interpreted and executed
by the CPU
▪ Registers are part of the CPU (not main memory) of a computer
▪ The length of a register, sometimes called its word size, equals the
number of bits it can store
▪ With all other parameters being the same, a CPU with 32-bit
registers can process data twice larger than one with 16-bit registers

BO 205 Chapter 07: Processor and Memory

Slide 84
D Sinha

Functions of Commonly Used Registers

Sr. No. Name of register Function

Holds address of the active memory
1 Memory Address (MAR)
location
Holds information on its way to and from memory
2 Memory Buffer (MBR)

Holds address of the next instruction to be executed

3 Program Control (PC)

Accumulates results and data to be

4 Accumulator (A)
operated upon
Holds an instruction while it is being
5 Instruction (I)
executed

6 Input/Output (I/O) Communicates with I/O devices

BO 205 Chapter 07: Processor and Memory

Slide 85
D Sinha

Execution of Instructions
▪ Control unit takes address of the next program instruction to be executed
from program control register and reads the instruction from
corresponding memory address into the instruction register
▪ Control unit then sends the operation and address parts of the instruction
to the decoder and memory address register
▪ Decoder interprets the instruction and accordingly the control unit sends
command signals to the appropriate unit for carrying out the task
specified in the instruction
▪ As each instruction is executed, address of next instruction is loaded and
steps are repeated

BO 205 Chapter 07: Processor and Memory

Slide 86
D Sinha

Processor Speed
▪ Computer has a built-in system clock that emits millions of regularly spaced
electric pulses per second (known as clock cycles)
▪ It takes one cycle to perform a basic operation, such as moving a byte of data
from one memory location to another
▪ Normally, several clock cycles are required to fetch, decode, and execute a
single program instruction
▪ Hence, shorter the clock cycle, faster the processor
▪ Clock speed (number of clock cycles per second) is measured in Megahertz
(106 cycles/sec) or Gigahertz (109 cycles/sec)

BO 205 Chapter 07: Processor and Memory Slide 87

D Sinha

Types of Processor
Type of
Features Usage
Architecture
▪ Large instruction set
CISC (Complex ▪ Variable-length instructions Mostly used in
Instruction Set ▪ Variety of addressing modes personal
Computer) ▪ Complex & expensive to computers
produce
▪ Small instruction set
RISC (Reduced
▪ Fixed-length instructions Mostly used in
Instruction Set
▪ Reduced references to memory to workstations
Computer)
retrieve operands

BO 205 Chapter 07: Processor and Memory Slide 88

D Sinha

Types of Processor
Type of
Features Usage
Architecture
▪ Allows software to communicate
explicitly to the processor when
operations are parallel
▪ Uses tighter coupling between the
EPIC (Explicitly compiler and the processor Mostly used in high-
Parallel
▪ Enables compiler to extract end servers and
Instruction
maximum parallelism in the workstations
Computing)
original code, and explicitly
describe it to the processor

BO 205 Chapter 07: Processor and Memory

Slide 89
D Sinha

Types of Processor
Type of
Features Usage
Architecture
▪ Processor chip has multiple cooler-
running, more energy- efficient
processing cores
▪ Improve overall performance by
handling more work in parallel Mostly used in
Multi-Core
high-end servers and
Processor ▪ can share architectural components,
workstations
such as memory elements and
memory management

BO 205 Chapter 07: Processor and Memory

Slide 90
D Sinha

Power-Efficient Processors
▪ Manufacturers of computing systems have made attempts to reduce
power consumption of systems
▪ New processor architectures to reduce power consumption right at
processor level
▪ latest processor offers a technology called Demand Based Switching
(DBS) for reduced power consumption
▪ Processors based on DBS technology are designed to run at multiple
frequency and voltage settings
▪ processors automatically switch to and operate at the lowest setting that
is consistent with optimal application performance

BO 205 Chapter 07: Processor and Memory Slide 91

D Sinha

Main Memory
▪ Every computer has a temporary storage built into the computer
hardware
▪ It stores instructions and data of a program mainly when the
program is being executed by the CPU
▪ This temporary storage is known as main memory, primary storage,
or simply memory
▪ Physically, it consists of some chips either on the motherboard or
on a small circuit board attached to the motherboard of a computer
▪ It has random access property
▪ It is volatile

BO 205 Chapter 07: Processor and Memory Slide 92

D Sinha

Storage Evaluation Criteria

Primary Secondary
Property Desirable
storage storage
Storage
Large storage capacity Small Large
capacity

Access Time Fast access time Fast Slow

Cost per bit of
Lower cost per bit High Low
storage
Volatility Non-volatile Volatile Non-volatile
Pseudo-
random
Random
Access Random access access or
access
sequential
access

BO 205 Chapter 07: Processor and Memory Slide 93

D Sinha

Main Memory Organization

0
1
2
3
Addresses of a 4
Words of a
memory 5
memory

N-2
N-1
Each word contains
Bit 1 Bit 2 the same number of
bits = word length

BO 205 Chapter 07: Processor and Memory Slide 94

D Sinha

Main Memory Organization

▪ Machines having smaller word-length are slower in
operation than machines having larger word-length

▪ A write to a memory location is destructive to its previous contents

▪ A read from a memory location is non-destructive to its previous

contents

BO 205 Chapter 07: Processor and Memory Slide 95

D Sinha

Fixed Word-length Memory

Word
0501 B O M B A Y
0502 D E L H I
Address
0503
Numbers

1024

▪ Storage space is always allocated in multiples of word-length

▪ Faster in speed of calculation than variable word-length memory
▪ Normally used in large scientific computers for gaining speed of calculation

BO 205 Chapter 07: Processor and Memory Slide 96

D Sinha

Variable Word-length Memory

0025 B 0051 D ▪ Each memory location can
store only a single
0026 O
0052 E character
0027 M L
0053 ▪ Slower in speed of
0028 B 0054 H calculation than fixed
world-length memory
Address 0029 A Address I
0055
Numbers Numbers ▪ Used in small business
0030 Y
0056 computers for optimizing
0031 the use of storage space

4096 4096

Note: With memory becoming cheaper and larger day-by-day, most modern computers
employ fixed-word-length memory organization

BO 205 Chapter 07: Processor and Memory Slide 97

D Sinha

Memory Capacity
▪ Memory capacity of a computer is equal to the number of bytes that
can be stored in its primary storage

▪ Its units are:

Kilobytes (KB) : 1024 (210) bytes

Megabytes (MB) : 1,048,576 (220) bytes

Gigabytes (GB) : 1,073,741824 (230) bytes

BO 205 Chapter 07: Processor and Memory

Slide 98
D Sinha

Types of Memory Chips

Memory chips

Volatile and writable Non-volatile and read-only

Static Dynamic Manufacturer- User-programmed

(SRAM) (DRAM) programmed
(ROM)

PROM EPROM

UVEPROM EEPROM

BO 205 Chapter 07: Processor and Memory Slide 99

D Sinha

Random Access Memory (RAM)

▪ Primary storage of a computer is often referred to as RAM because of its
random access capability
▪ RAM chips are volatile memory.
▪ A computer’s motherboard is designed in a manner that the memory
capacity can be enhanced by adding more memory chips
▪ The additional RAM chips, which plug into special sockets on the
motherboard, are known as single-in-line memory modules (SIMMs)

BO 205 Chapter 07: Processor and Memory Slide 100

D Sinha

Read Only Memory (ROM)

▪ ROM a non-volatile memory chip
▪ Data stored in a ROM can only be read and used – they cannot be
changed
▪ ROMs are mainly used to store programs and data, which do not change
and are frequently used. For example, system boot program

BO 205
Chapter 07: Processor and Memory Slide 101
D Sinha

Types of ROMs
Type Usage
Data is burnt by the manufacturer of
Manufacturer-
the electronic equipment in which it
programmed ROM
is used.

User-programmed ROM
or The user can load and store “read-
only” programs and data in it
Programmable ROM
(PROM)

The user can erase information stored

in it and the chip can be
Erasable PROM (EPROM)
reprogrammed to store new
information

BO 205
Chapter 07: Processor and Memory Slide 102
D Sinha

Types of ROMs
Type Usage

A type of EPROM chip in which the

Ultra Violet EPROM stored information is erased by exposing
(UVEPROM) the chip for some time to ultra-violet light

Electrically EPROM
A type of EPROM chip in which the
(EEPROM)
stored information is erased by using high
or
voltage electric pulses
Flash memory

BO 205 Chapter 07: Processor and Memory

Slide 103
D Sinha

Cache Memory
▪ It is commonly used for minimizing the memory- processor speed
mismatch.
▪ It is an extremely fast, small memory between CPU and main
memory whose access time is closer to the processing speed of the
CPU.
▪ It is used to temporarily store very active data and instructions
during processing.

Cache is pronounced as “cash”

BO 205 Chapter 07: Processor and Memory

Slide 104
D Sinha

Computer Fundamentals

Chapter 9

Input – Output Devices

BO 205 Chapter 09: Input – Output Devices Slide 105

D Sinha

Learning Objectives
In this chapter you will learn about:
▪ Input/output (I/O) devices
▪ Commonly used input devices
▪ Commonly used output devices
▪ Other concepts related to I/O devices

BO 205 Chapter 09: Input – Output Devices Slide 106

D Sinha

I/O Devices

▪ Provide means of communication between a computer and outer world

▪ Also known as peripheral devices because they surround the CPU and
memory of a computer system
▪ Input devices are used to enter data from the outside world into primary
storage
▪ Output devices supply the results of processing form primary storage to
users

BO 205 Chapter 09: Input – Output Devices Slide 107

D Sinha

Role of I/O Devices

Results of
Input processing in
Input CPU and Output
data human
Devices Memory Devices
from acceptable
externa form
l world

Input data coded in Processed data in

internal form internal form

BO 205 Chapter 09: Input – Output Devices Slide 108

D Sinha

Commonly used input devices

▪ Keyboard devices
▪ Point-and-draw devices
▪ Data scanning devices
▪ Digitizer
▪ Electronic cards base devices
▪ Speech recognition devices
▪ Vision based devices

BO 205 Chapter 09: Input – Output Devices Slide 109

D Sinha

Keyboard devices

▪ Allow data entry into a computer system by pressing a set

of keys (labelled buttons) neatly mounted on a keyboard
connected to a computer system

▪ 101 – keys QWERTY keyboard is most popular

BO 205 Chapter 09: Input – Output Devices Slide 110

D Sinha

The Layout of Keys on a QWERTY Keyboard

BO 205 Chapter 09: Input – Output Devices Slide 111

LABELLED KEYBOARD
D Sinha

Point - and - Draw Devices

▪ Used to rapidly point to and select a graphic icon or menu item
from multiple option displayed on the Graphical user interface
(GUI) of a screen

▪ Used to create graphic elements on the screen such as lines,

curves, and freehand shapes

▪ Some commonly used point – and – draw devices are mouse,

track ball, joy stick, light pen and touch screen

BO 205 Chapter 09: Input – Output Devices Slide 113

D Sinha

Mouse

▪ Mouse is the most popular point – and – draw device

▪ Mouse is a small hand – held device that fits comfortably in user’s palm
▪ It rolls on a small bearing and has one or more button on the top
▪ When a user rolls a mouse on a flat surface, a graphics cursor moves
on the terminal screen in the direction of the mouse’s movement
▪ Different applications display the graphics cursor as different symbols
▪ Graphics cursor, irrespective of its size and shape, has a pixel – size
point that is the point of reference to decide the position of the cursor
on the screen. This point is known as hot spot

BO 205 Chapter 09: Input – Output Devices Slide 114

PARTS OF A MOUSE
D Sinha

Mouse

BO 205
Chapter 09: Input – Output Devices Slide 116
D Sinha

Types of Mouse
▪ Mechanical mouse

▪ Mechanical mouse has a ball inside it that partially projects out through an
opening in its base
▪ Ball rolls due to surface friction when the mouse is moved on a flat
surface
▪ On two sides of the ball are two small wheel that spin to match the speed
of the ball. Each wheel of the ball is connected to a sensor
▪ As the mouse ball rolls when a user moves the mouse, the sensor detect
how much each wheel spins and send this information to the computer in
the form of changes to the current position

BO 205
Chapter 09: Input – Output Devices Slide 117
D Sinha

Types of Mouse
▪ Optical mouse
▪ An optical mouse has no mechanical parts like the ball and the wheel
▪ It has a built – in photo - detector
▪ When a user moves the mouse on a special pad with gridlines, the photo –
detector sense each horizontal and vertical line on the pad, and sends this
information to the computer in the form of changes to the current position

▪ One, Two and Three Button Mouse

▪ Mouse can have one, two, or three buttons
▪ With a mouse having multiple buttons, the left most button is the main
button that allows for most mouse operation
▪ A user can configure another button as main button

BO 205
Chapter 09: Input – Output Devices Slide 118
D Sinha

Types of Mouse
▪ Serial and Bus Mouse
▪ A serial mouse plugs into a serial port
▪ A bus mouse requires a special electronic card, which provides a special
port just for connecting the mouse to the computer

▪ Wired and Cordless Mouse

▪ Wired mouse is connected to the computer with a small cord
▪ A cordless mouse operates by transmitting a low intensity radio or
infrared signal

BO 205
Chapter 09: Input – Output Devices Slide 119
D Sinha

Trackball
▪ A trackball is a pointing device similar to a mechanical mouse

▪ Roller ball is placed on the top along with the buttons

▪ We have to roll the ball with hand

▪ Trackball requires less space than a mouse for operation

▪ Trackball is a preferred device for CAD/CAM applications

BO 205
Chapter 09: Input – Output Devices Slide 120
D Sinha

Trackball

BO 205
Chapter 09: Input – Output Devices Slide 121
D Sinha

Joystick
▪ Joystick is a pointing device that works on the same principle as a
trackball
▪ To make the movements of the spherical ball easier, it is placed in a
socket with a stick mounted on it
▪ User hold the stick in her/his hand and moves it around to move the
spherical ball
▪ User can move the stick forward or backward, left or right, to move
and position the graphic cursor at a desirable position
▪ Joystick use potentiometers to sense stick and ball movements
▪ A button on top of the stick enables a user to select the option
pointed to by the cursor

BO 205 Slide 122

Chapter 09: Input – Output Devices
D Sinha

Joystick

Click button

Stick

Socket

Light
indicator

BO 205 Slide 123

Chapter 09: Input – Output Devices
D Sinha

Electronic Pen
▪ Light pen
▪ Uses a photoelectric cell and an optical lens mounted in a pen – shaped case
▪ It focuses on to it any light in its field of view
▪ It detects the light emitted from a limited field of view of the monitor’s display
▪ System transmit this electric response to a processor, which identifies the menu item or icon
that is triggering the photocell
▪ Pen has a finger operated button

▪ Writing pen with pad

▪ This type of electronic pen comes with a special type of writing pad
▪ Users write on the pad with the electronic pen whatever data he/she wants to input to the
computer
▪ The input device with hand writing recognition software is used often as an easy way to input
text and freehand drawings into computer

BO 205 Chapter 09: Input – Output Devices Slide 122

D Sinha

Touch Screen
▪ Most simple, intuitive, and easiest to learn of all input devices

▪ Enables user to choose from available options by simply touching with

their finger the desired icon or menu item displayed on the screen

▪ Most preferred human – computer interface used in information

kiosks (unattended interactive information systems such as ATM )

BO 205 Chapter 09: Input – Output Devices Slide 123

D Sinha

Data Scanning Devices

▪ Input devices that enable direct data entry into a computer from
source documents
▪ Eliminate the need to key in text data into the computer
▪ Due to reduced human effort in data entry, they improve data
accuracy and also increase the timelines of the information
processed
▪ Demand high quality of input document
▪ Some data scanning devices are also capable of recognizing marks
of characters
▪ Form design and ink specification usually becomes more critical
for accuracy

BO 205 Chapter 09: Input – Output Devices Slide 124

D Sinha

Image Scanner
▪ Input devices that translates paper documents into an electronic
format for storage in computer
▪ Electronic format of a scanned image is its bit map representation
▪ Stored image can be altered or manipulated with an image
processing software

A flatbed scanner A hand – held scanner

BO 205 Chapter 09: Input – Output Devices Slide 125

D Sinha

Optical Character Recognition(OCR) Device

▪ Scanner equipped with a character recognition software (called
OCR software) converts the bit map images of characters to
equivalent ASCII code

▪ Enables word processing of input text and also requires less

storage for storing the document as text rather than an image

▪ OCR software is extremely complex because it is difficult to

make a computer recognize an unlimited number of typefaces
and fonts

▪ Two standard OCR fonts are OCR–A (American standard) and

OCR-B (European standard)

BO 205 Chapter 09: Input – Output Devices Slide 126

D Sinha

Optical Character Recognition(OCR) Device

▪ It converts images of text into machine-readable text

▪ Converting print to digital: convert scanned documents, receipt

into editable and searchable digital file
▪ Accessibility for visual impaired: Converting the text in images
into a format that can be read aloud by screen readers

▪ Automation of data entry: It streamline data entry by automating

the process of extracting the text from images, which reduces
manual effort and the risk of errors.

BO 205 Chapter 09: Input – Output Devices Slide 126

D Sinha

Optical Mark Reader

▪ Scanner capable of recognition a pre – specified type of mark
by pencil or pen

▪ Very useful for grading tests with objective type questions, or

for any input data that is of a choice or selection nature

▪ Technique used for recognition of marks involves focussing a

light on the page being scanned and detecting the reflected
light pattern from the marks

BO 205 Chapter 09: Input – Output Devices Slide 127

D Sinha

Sample Use of OMR

For each question, four options are given out of which only one is correct. Choose
the correct option and mark your choice against the corresponding question
number in the given answer sheet by darkening the corresponding circle with a
lead pencil.

1. The binary equivalent of decimal 4 is: a) 101

b) 111
c) 001
d) 100

Indicates direction in which the

2. The full form of CPU is: sheet should be fed to the OMR
a) Cursor Positioning Unit 1.
b) Central Power Unit a b c d
c) Central Processing Unit
d) None of the above 2.
a b c d

3. Which is the largest unit of storage among the following: 3.

a) Terabyte a b c d
b) Kilobyte
c) Megabyte (b) Pre-printed answer sheet
d) Gigabyte

(a) Question sheet

A sample use of OMR for grading tests with objective type questions

BO 205 Chapter 09: Input – Output Devices Slide 128

D Sinha

Bar – code Reader

▪ Scanner used for reading (decoding) bar-code data
▪ Bar-code presents alphanumeric data by a combination of adjacent
vertical lines (bars) by varying their width and the spacing between
them
▪ Scanner uses laser beam to stroke across pattern of bar code.
Different patterns of bars reflect the beam in different ways sensed
by a light – sensitive detector
▪ Universal product code (UPC) is the most widely known bar
coding system

BO 205 Chapter 09: Input – Output Devices Slide 129

D Sinha

An Example of UPC Bar Code

Product category character 0 –

grocery products
3 – drugs and health related 0
products, etc.

21000 67520

Manufacturer/supplier
identification number Specific product code
number

BO 205 Chapter 09: Input – Output Devices Slide 130

D Sinha

Magnetic-Ink Character Recognition

(MICR)
▪ MICR is used by banking industry for faster processing of large
volume of cheques
▪ Bank’s identification code (name, branch, etc.), account number and
cheque number are pre-printed (encoded) using characters from a
special character set on all cheques
▪ Special ink is used that contains magnetizable particles of iron oxide
▪ MICR reader-sorter reads data on cheques and sorts them for
distribution to other banks or for further processing

BO 205 Chapter 09: Input – Output Devices Slide 131

D Sinha

MICR Character Set (E13B Font)

▪ It consists of numerals 0 to 9 and four special characters

▪ MICR is not adopted by other industries because it supports only 14 symbols

BO 205 Chapter 09: Input – Output Devices Slide 132

D Sinha

Digitizer
▪ Input device used for converting (digitizing) pictures,
maps and drawings into digital form for storage in
computers
▪ Commonly used in the area of Computer Aided Design
(CAD) by architects and engineers to design cars,
buildings medical devices, robots, mechanical parts, etc.
▪ Used in the area of Geographical Information System
(GIS) for digitizing maps available in paper form

BO 205 Chapter 09: Input – Output Devices Slide 133

D Sinha

Digitizer

Table top
Digitizing tablet

Cursor
Stylus

BO 205 Chapter 09: Input – Output Devices Slide 134

D Sinha

Electronic-card Reader
▪ Electronic cards are small plastic cards having encoded
data appropriate for the application for which they are
used
▪ Electronic-card reader (normally connected to a
computer) is used to read data encoded on an electronic
card and transfer it to the computer for further processing
▪ Used together as a means of direct data entry into a
computer system
▪ Used by banks for use in automatic teller machines
(ATMs) and by organizations for controlling access of
employees to physically secured areas

BO 205 Chapter 09: Input – Output Devices Slide 135

D Sinha

Speech Recognition Devices

▪ Input device that allows a person to input data to a

computer system by speaking to it
▪ Today’s speech recognition systems are limited to
accepting few words within a relatively small domain
and can be used to enter only limited kinds and
quantities of data

BO 205 Chapter 09: Input – Output Devices Slide 136

D Sinha

Types of Speech Recognition Systems

▪ Single word recognition systems can recognize only a single
spoken words, such as YES, NO, MOVE, STOP, at a time.
Speaker-independent systems are mostly of this type

▪ Continuous speech recognition systems can recognize

spoken sentences, such as MOVE TO THE NEXT BLOCK.
Such systems are normally speaker-dependent

BO 205 Chapter 09: Input – Output Devices Slide 137

D Sinha

Uses of Speech Recognition Systems

▪ For inputting data to a computer system by a person in

situations where his/her hands are busy, or his/her eyes
must be fixed on a measuring instrument or some other
object
▪ For data input by dictation of long text or passage for later
editing and review
▪ For authentication of a user by a computer system based
on voice input
▪ For limited use of computers by individuals with physical
disabilities

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D Sinha

Vision-Input Systems
▪ Allow computer to accept input just by seeing an object.

▪ Input data is normally an object’s shape and features in the

form of an image

▪ Mainly used today in factories for designing industrial

robots that are used for quality-control and assembly
processes

BO 205 Chapter 09: Input – Output Devices Slide 139

D Sinha

Output Devices
Commonly used output devices are:
▪ Monitors
▪ Printers
▪ Screen image and projector
▪ Plotters
▪ Voice response system

BO 205 Chapter 09: Input – Output Devices Slide 140

D Sinha

Types of Output
▪ Soft-copy output
▪ Not produced on a paper or some material that can be touched and carried
for being shown to others
▪ It focuses on to it any light in its field of view
▪ It detects the light emitted from a limited field of view of the monitor’s
display
▪ System transmit this electric response to a processor, which identifies the
menu item or icon that is triggering the photocell
▪ Pen has a finger operated button
▪ Hard-copy output
▪ This type of electronic pen comes with a special type of writing pad
▪ Users write on the pad with the electronic pen whatever data he/she wants
to input to the computer
▪ The input device with hand writing recognition software is used often as
an easy way to input text and freehand drawings into computer

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D Sinha

Monitors
▪ Monitors are the most popular output devices used for
producing soft-copy output
▪ Display the output on a television like screen
▪ Monitor associated with a keyboard is called a video display
terminal (VDT). It is the most popular I/O device

BO 205 Chapter 09: Input – Output Devices Slide 142

D Sinha

Monitors

Monitor

Keyboard

A video display terminal consists of a monitor and a keyboard

BO 205 Chapter 09: Input – Output Devices Slide 143

D Sinha

Types of Monitors

▪ (CRT) Cathode Ray Tube monitors look like a television and

are normally used with non-portable computer systems
▪ LCD (Liquid Crystal Display flat-panel monitors are thinner
and lighter and are commonly used with portable computer
system like notebook computers. Now they are also used
with the non-portable desktop computer system because they
occupy less table space

BO 205 Chapter 09: Input – Output Devices Slide 144

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CRT and LCD Monitors

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Printers
Most common output devices for producing hard-copy output

These are of two types:

i. Dot-marix Printer
ii. Ink-jet Printer

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Dot-Matrix Printers
▪ Character printers that form characters and all kinds of
images as a pattern of dots
▪ Print many special characters, different sizes of print
and graphics such as charts and graphs
▪ Impact printers can be used for generating multiple
copies by using carbon paper or its equivalent
▪ Slow, with speeds usually ranging between 30 to 600
characters per second
▪ Cheap in both initial cost and cost of operation

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Formation of Characters as a pattern of dots

ABCDEFGHIJKLMNOPQRSTUVWXYZ
0123456789-.,
&/$*#%@=(+)

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Dot Matrix Printer Printing Mechanism

Inked Paper below Print head Direction of movement of
ribbon the ribbon pins print head pins

Direction of movement of
print head
Printed characters formed
of dots in a 5 x 7 matrix Print head

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Dot Matrix Printer

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Inkjet Printers
▪ Character printers that form characters and all kinds of
images by spraying small drops of ink on to the paper
▪ Print head contains up to 64 tiny nozzles that can be
selectively heated up in a few micro seconds by an
integrated circuit register
▪ To print a character, the printer selectively heats the
appropriate set of nozzles as the print head moves
horizontally
▪ Can print many special characters, different sizes of print,
and graphics such as charts and graphs

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Inkjet Printers
▪ Non-impact printers. Hence, they cannot produce
multiple copies of a document in a single printing
▪ Can be both monochrome and color
▪ Slower than dot-matrix printers with speeds usually
ranging between 40 to 300 characters per second
▪ More expensive than a dot-matrix printer

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An Inkjet Printer

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Drum Printers
▪ Line printers that print one line at a time
▪ Have a solid cylindrical drum with characters embossed on
its surface in the form of circular bands
▪ Set of hammers mounted in front of the drum in such a
manner that an inked ribbon and paper can be placed
between the hammers and the drum
▪ Can only print a pre-defined set of characters in a pre-
defined style that is embossed on the drum
▪ Impact printers and usually monochrome
▪ Typical speeds are in the range of 300 to 2000 lines per
minute
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Printing Mechanism of a Drum Printer

Hammers (one for each band)

Paper
Ribbon
WW WWW WWW WWW WWW VV
V VV V VV V VV V V V
U UU U UU U UU U UU U U
TT TTT TTT TTT TT T
S SS S SS S SS S SS S S R R R R R R R
R R R R R RR
Solid cylindrical Q Q Q Q Q Q Q Q Q Q Q Q Q Q
drum with P PP P PP P PP P PP P P O O OO O OO O
embossed O OO O OO N NN N NN N NN N NN N N

characters

Total number of bands is equal to the

maximum number of characters
(print positions) on a line. Each
band has all characters supported by
the printer.

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Chain/Band Printers
▪ Line printers that print one line at a time
▪ Consist of a metallic chain/band on which all
characters of the character set supported by the printer
are embossed
▪ Also have a set of hammers mounted in front of the
chain/band in such a manner that an inked ribbon and
paper can be placed between the hammers and the
chain/band

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Chain/Band Printers
▪ Can only print pre-defined sets of characters that are embossed
on the chain/band used with the printer
▪ Cannot print any shape of characters, different sizes of print,
and graphics such as charts and graphs
▪ Are impact printers and can be used for generating
multiple copies by using carbon paper or its equivalent
▪ Are usually monochrome
▪ Typical speeds are in the range of 400 to 3000 lines per
minute

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Printing Mechanism of a Chain/Band Printer

One section of 48 Direction of

Complete chain is characters movement of
composed of five the chain
sections of 48
characters each
Paper

Ribbon

Hammers

132 print positions

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Laser Printers
▪ Page printers that print one page at a time
▪ Consist of a laser beam source, a multi-sided mirror, a photoconductive
drum and toner (tiny particles of oppositely charged ink)
▪ To print a page, the laser beam is focused on the electro statically
charged drum by the spinning multi-sided mirror
▪ Toner sticks to the drum in the places the laser beam has charged the
drum’s surface.
▪ Toner is then permanently fused on the paper with heat and pressure to
generate the printer output
▪ Laser printers produce very high quality output having resolutions in
the range of 600 to 1200 dpi

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Laser Printers
▪ Can print many special characters, different sizes of
print, and graphics such as charts and graphs
▪ Are non-impact printers
▪ Most laser printers are monochrome, but color laser
printers are also available
▪ Low speed laser printers can print 4 to 12 pages per
minute. Very high-speed laser printers can print 500 to
1000 pages per minute
▪ More expensive than other printers

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A Laser Printer

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Plotters
Plotter are an ideal output device for architects, engineers, city
planners, and others who need to routinely generate high-precision,
hard-copy graphic output of widely varying sizes

Two commonly used types of plotters are:

Drum plotter: In which the paper on which the design
has to be placed over a drum that can rotate in both clock-
wise and anti clock-wise direction
Flatbed plotter: In which the paper on which the design
has to be made is spread and fixed over a rectangular
flatbed table

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Plotters

Paper
Design drawn
on the paper
Design drawn
on the paper

Paper

A drum plotter A flatbed plotter

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Screen Image Projector

▪ An output device that can be directly plugged to a
computer system for projecting information from a
computer on to a large screen
▪ Useful for making presentations to a group of people
with direct use of a computer
▪ Full-fledged multimedia presentation with audio, video,
image, and animation can be prepared and made using
this facility

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Screen Image Projector

Operations buttons

On/Off light indicator

Projection lens

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Voice Response Systems

▪ Voice response system enables a computer to talk to a
user
▪ Has an audio-response device that produces audio
output
▪ Such systems are of two types:
▪ Voice reproduction systems
▪ Speech synthesizers

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Voice Reproduction Systems

▪ Produce audio output by selecting an appropriate audio
output from a set of pre-recorded audio responses
▪ Applications include audio help for guiding how to
operate a system, automatic answering machines,
video games, etc.

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Speech Synthesizers
▪ Converts text information into spoken sentences
▪ Used for applications such as:
▪ Reading out text information to blind persons
▪ Allowing those persons who cannot speak to
communicate effectively
▪ Translating an entered text into spoken words in a
selected language

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