fundamental of computer computer what about computer works in today world

Computer Fundamentals : Pradeep K. Sinha & Priti Sinha
Chapter 01: Introduction Slide 1/17
Chapter 1
Introduction
Computer Fundamentals
Pradeep K. Sinha
Priti Sinha

Slide 2/17
Chapter 01: Introduction
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

 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
Computer
Ref. Page 01 Chapter 01: Introduction Slide 3/17

Data Processing
The activity of processing data using a computer is called
data processing
Data is raw material used as input to data processing and
information is processed data obtained as output
Data
(Raw material)
Information
(Finished product)
Computer
(Data processor)
Input
Output

Characteristics of Computers
Sr.
No.
Characteristics Description
1 Automatic It carries out a job normally without any human intervention
2 Speed
It can perform several billion (109) simple arithmetic operations
per second
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
6 Memory
It can store huge amount of information and can recall any piece
of this information whenever required
7 No I. Q.
It cannot take its own decisions, and has to be instructed what
to do and in what sequence
8 No Feelings It cannot make judgments based on feelings and instincts

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
(Continued on next slide)

 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

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)

Computer Generations

Slide 11/17
 “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
Ref. Page 04

/17
Generation
(Period)
Key hardware
technologies
Key software
technologies
Key
characteristics
Some
representative
systems
First
(1942-1955)
• Vacuum tubes
•Electromagnetic
relay memory
• Punched cards
secondary storage
Machine and
assembly
languages
 Stored program
concept
Mostly scientific
applications
 Bulky in size
 Highly unreliable
Limited commercial
use commercial
production difficult and
costly
 Difficult to use
 ENIAC
 EDVAC
 EDSAC
 UNIVAC I
 IBM 701
Second
(1955-1964)
 Transistors
Magnetic core
memory
 Magnetic tapes
Disks secondary
storage
Batch operating
system
High-level
programming
languages
Scientific and
commercial
applications
Faster, smaller, more
reliable and easier to
program than previous
generation systems
Commercial production
was still difficult and
costly
 Honeywell 400
 IBM 7030
 CDC 1604
 UNIVAC LARC

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

Generation
(Period)
Key hardware
technologies
Key software
technologies
Key
Characteristics
Some
representative
systems
Fourth
(1975-1989)
 ICs with VLSI
technology
Microprocessors;
semiconductor
memory
Larger capacity
hard disks as in-
built secondary
storage
Magnetic tapes
and floppy disks as
portable storage
media
 Personal
computers
Spread of high-
speed computer
networks
Operating systems for
PCs with GUI and Multiple
windows on a single
terminal screen
Multiprocessor operating
systems and concurrent
programming languages
 UNIX operating system
C and C++
PC-based applications;
network-based
applications
 Object-oriented software
design
Small,
affordable,
reliable, and easy
to use PCs
More powerful
and reliable
mainframe
systems
 General purpose
machines
Easier to
produce
commercially
(Con
 IBM PC and its
clones
 Apple II
 TRS-80
 VAX 9000
 CRAY-1
 CRAY-2
 CRAY-X/MP
tinued on next slide)

Generation
(Period)
Key hardware
technologies
Key software
technologies
Key
Characteristics
Some
representative
systems
Fifth
(1989-
Present)
ICs with ULSI
technology
 Multicore processor
chips
Larger capacity main
memory and hard disks
Optical disks as
portable read-only
storage media
 Solid state disks
 Notebook computers
Powerful desktop PCs
and workstations
Very powerful
mainframes
 Supercomputers based
on parallel processing
 Internet
World Wide
Web
Multimedia,
Internet-based
applications
Microkernel,
multithreading,
multicore OS
JAVA, Python
and other
programming
languages
MPI and PVM
libraries for
parallel
programming
 Portable computers
 Hand-held mobile
smart devices
More powerful,
cheaper, reliable, and
easier to use desktop
machines
Very powerful
mainframes
Very high uptime
due to hot-pluggable
components
General purpose
machines
Easier to produce
commercially
 iPhone
 iPad
 IBM notebooks
 Pentium PCs
 Windows PC
 Apple PC
 SUN
Workstations
 IBM SP/2
 SGI Origin 2000
PARAM
supercomputers

Electronic Devices Used in Computers of Different
Generations
(c) An IC chip
(b) A Transistor
(a) A Vacuum tube

Key Words/Phrases
 Computer
 Computer generations
 Computer Supported Cooperative
Working (CSCW)
 Data
 Data processing
 Data processor
 First-generation computers
 Second-generation computers
 Third-generation computers
 Fourth-generation computers
 Fifth-generation computers
 Garbage-in-garbage-out (GIGO)
 Graphical User Interface (GUI)
 Groupware
 Information
 Integrated Circuit (IC)
 Large Scale Integration (VLSI)
 Medium Scale Integration (MSI)
 Microprocessor
 Personal Computer (PC)
 Second-generation computers
 Small Scale Integration (SSI)
 Stored program concept
 Third-generation computers
 Transistor
 Ultra Large Scale Integration (ULSI)
 Vacuum tubes

Computer Fundamentals: Pradeep K. Sinha & Priti Sinha
Chapter 02: Basic Computer Organization Slide 1/19
Pradeep K. Sinha
Priti Sinha
Chapter 2
Basic Computer
Organization

 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
Learning Objectives

 Arithmetic Logic Unit (ALU)
 Control Unit (CU)
 Central Processing Unit (CPU)
 Computer as a system
Learning Objectives

 Inputting. The process of entering data and instructions
into the computer system
 Storing. Saving data
readily available for
whenever required
and instructions to make them
initial or additional processing
 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
The Five Basic Operations of a
Computer System
Ref. Page 18 Chapter 02: Basic Computer Organization Slide 4/19

 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
The Five Basic Operations of a
Computer System

Central Processing Unit (CPU)
Storage Unit
Secondary
Storage
Primary
Storage
Control
Unit
Arithmetic
Logic Unit
Input
Unit
Output
Unit
Program
and
Data
Information
(Results)
Indicates flow of
instructions and data
Indicates the control
exercised by the
control unit
Basic Organization of a Computer System

Main Units and
Their Functions

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
Input 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
Output 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
Storage Unit

The broad categories of storage are:
1. Primary storage
2. Secondary storage
Types of 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)
Primary 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
Secondary Storage

Arithmetic Logic Unit of a computer system is the place
where the actual executions of instructions takes place during
processing operation
Arithmetic Logic Unit (ALU)

Control Unit of a computer system manages and coordinates
the operations of all other components of the computer
system
Control Unit (CU)

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

The System Concept

/19
Chapter 02: Basic Computer Organization
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
The System Concept
Ref. Page 21

/19
Chapter 02: Basic Computer Organization
 Auxiliary storage
 Computer system
 Controlling
 Input interface
 Input unit
 Inputting
 Main memory
 Output interface
 Output unit
 Outputting
 Primate storage
 Processing
 Secondary storage
 Storage unit
 Storing
 System
Key Words/Phrases

Chapter 03: Number Systems Slide 1/43
Chapter 3
Number Systems
Pradeep K. Sinha
Priti Sinha

 Non-positional number system
 Positional number system
 Decimal number system
 Binary number system
 Octal number system
 Hexadecimal number system
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
Learning Objectives

Two types of number systems are:
 Non-positional number systems
 Positional number systems
Number Systems
Ref. Page 23 Chapter 03: Number Systems Slide 4/43

Basics and Few Popular
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
Non-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
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
Positional Number Systems

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
Decimal Number System

Example
258610 = (2 x 103) + (5 x 102) + (8 x 101) + (6 x 100)
= 2000 + 500 + 80 + 6
Decimal Number System

Characteristics
 Has only 2 symbols or digits (0 and 1).
base = 2
Hence its
of the base (2)
 This number system is used in computers
Binary Number System

Example
101012 = (1 x 24) + (0 x 23) + (1 x 22) + (0 x 21) x (1 x 20)
= 16 + 0 + 4 + 0 + 1
= 2110
Binary Number System

In order to be specific about which number system we
are referring to, it is a common practice to indicate the
base as a subscript. Thus, we write:
101012 = 2110
Representing Numbers in Different
Number Systems

 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 an n-bit
number
Bit

Characteristics
 Has total 8 symbols or digits (0, 1, 2, 3, 4, 5, 6, 7).
Hence, its base = 8
than the value of the base
 Each position of a digit represents a specific power of
the base (8)
Octal Number System

 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
Octal Number System

Characteristics
 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
Hexadecimal Number System

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
Hexadecimal Number System

Converting from One
Number System to Another

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
Converting a Number of Another Base to a
Decimal Number

47068 = 4 x 83 + 7 x 82 + 0 x 81 + 6 x 80
= 4 x 512 + 7 x 64 + 0 + 6 x 1
= 2048 + 448 + 0 + 6
= 250210
Example
47068 = ?10
Column values
multiplied
by the
corresponding
digits
Sum of these
products
Converting a Number of Another Base to a
Decimal Number

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
Divide the quotient of the previous divide by the
new base
Step 3:
Converting a Decimal Number to a Number
of Another 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
of Another Base

Example
95210 = ?8
Solution:
0
8 952 Remainders
119 0
14 7
1 6
1
Hence, 95210 = 16708
of Another Base

Method
Step 1: Convert the original number to a decimal
number (base 10)
Step 2: Convert the decimal number so obtained to
the new base number
Converting from a Base Other Than 10 to
Another Base Other Than 10

Example
5456 = ?4
Solution:
Step 1: Convert from base 6 to base 10
5456 = 5 x 62 + 4 x 61 + 5 x 60
= 5 x 36 + 4 x 6 + 5 x 1
= 180 + 24 + 5
= 20910

Step 2: Convert 20910 to base 4
Hence, 20910 = 31014
So, 5456 = 20910 = 31014
Thus, 5456 = 31014
Remainders
1
0
1
3
209
52
13
3
0
4

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
Shortcut Method for Converting a Binary
Number to its Equivalent Octal Number

Example
11010102 = ?8
Step 1: Divide the binary digits into groups of 3 starting
from right
001 101 010
Step 2: Convert each group into one octal digit
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
Number to its Equivalent Octal 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)
binary
single
groups
binary
(of 3 digits
Step 2: Combine all the resulting
each) into a
number
Shortcut Method for Converting an Octal
Number to Its Equivalent Binary Number

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
Shortcut Method for Converting an Octal
Number to Its Equivalent Binary Number

Method
Step 1:
Divide the binary digits into groups of four
starting from the right
Combine each group of four binary digits to
one hexadecimal digit
Step 2:
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
Number to its Equivalent Hexadecimal 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
Shortcut Method for Converting a Hexadecimal
Number to its Equivalent Binary Number

Example
2AB16 = ?2
Step 1: Convert each hexadecimal digit to a 4 digit
binary number
216 = 210 = 00102
A16 = 1010 = 10102
B16 = 1110 = 10112

Step 2: Combine the binary groups
2AB16 = 0010 1010 1011
2 A B
Hence, 2AB16 = 0010101010112

Fractional Numbers

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

Formation of Fractional Numbers in
Binary Number System (Example)
Position
Position Value
4 3 2 1 0 . -1 -2 -3 -4
24 23 22 21 20 2-1 2-2 2-3 2-4
Quantity
Represented
16 8 4 2 1 1/2
1/4
1/8
1/16
Binary Point

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
Binary Number System (Example)

Position 3 2 1 0 . -1 -2 -3
Position Value 83 82 81 80 8-1 8-2 8-3
Quantity
Represented
512 64 8 1 1/8
1/64
1/512
Octal Point
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
Octal Number System (Example)

Key Words/Phrases
 Base
 Binary number system
 Binary point
 Bit
 Decimal number system
 Division-Remainder technique
 Fractional numbers
 Hexadecimal number system
 Least Significant Digit (LSD)
 Memory dump
 Most Significant Digit (MSD)
 Non-positional number
system
 Number system
 Octal number system
 Positional number system

Chapter 04: Computer Codes Slide 1/36
Chapter 4
Computer Codes
Pradeep K. Sinha
Priti Sinha

Slide 2/36
Chapter 04: Computer Codes
 Computer data
 Computer codes: representation of data in binary
 Most commonly used computer codes
 Collating sequence
Learning Objectives

Data Types and Their
Binary Representation

 Numeric Data consists of only numbers 0, 1, 2, …, 9
 Alphabetic Data consists of only the letters A, B, C,
…, Z, in both uppercase and lowercase, and blank
character
 Alphanumeric Data is a string of symbols where a
symbol may be one of the letters A, B, C, …, Z, in
either uppercase or lowercase, or one of the digits 0,
1, 2, …, 9, or a special character, such as + - * / , . (
) = etc.
Data Types
Ref. Page 38 Chapter 04: Computer Codes Slide 4/36

 Computer codes are used for internal representation of
data in computers
 As computers use binary
representation, computer
schemes
numbers for internal data
codes use binary coding
 In binary coding, every symbol that appears in the data
is represented by a group of bits
 The group of bits used to represent a symbol is called a
byte
Computer Codes

 As most modern coding schemes use 8 bits to represent
a symbol, the term byte is often used to mean a group
of 8 bits
 Commonly used computer codes are BCD, EBCDIC, and
ASCII
Computer Codes

BCD

 BCD stands for Binary Coded Decimal
 It is one of the early computer codes
 It uses 6 bits to represent a symbol
 It can represent 64 (26) different characters
BCD

Char
BCD Code
Octal
Zone Digit
A 11 0001 61
B 11 0010 62
C 11 0011 63
D 11 0100 64
E 11 0101 65
F 11 0110 66
G 11 0111 67
H 11 1000 70
I 11 1001 71
J 10 0001 41
K 10 0010 42
L 10 0011 43
M 10 0100 44
Char
BCD Code
Octal
Zone Digit
N 10 0101 45
O 10 0110 46
P 10 0111 47
Q 10 1000 50
R 10 1001 51
S 01 0010 22
T 01 0011 23
U 01 0100 24
V 01 0101 25
W 01 0110 26
X 01 0111 27
Y 01 1000 30
Z 01 1001 31
Coding of Alphabetic and Numeric
Characters in BCD

Character
BCD Code Octal
Equivalent
Zone Digit
1 00 0001 01
2 00 0010 02
3 00 0011 03
4 00 0100 04
5 00 0101 05
6 00 0110 06
7 00 0111 07
8 00 1000 10
9 00 1001 11
0 00 0000 00
Characters in BCD

Example
Show the binary digits used to record the word BASE in BCD
Solution:
B = 110010 in BCD binary notation
A = 110001 in BCD binary notation
S = 010010 in BCD binary notation
E = 110101 in BCD binary notation
So the binary digits
110010 110001 010010 110101
B A S E
will record the word BASE in BCD
BCD Coding Scheme (Example 1)

Example
Using octal notation, show BCD coding for the word DIGIT
Solution:
D = 64 in BCD octal notation
I = 71 in BCD octal notation
G = 67 in BCD octal notation
I = 71 in BCD octal notation
T = 23 in BCD octal notation
Hence, BCD coding for the word DIGIT in octal notation will be
64 71 67 71 23
D I G I T
BCD Coding Scheme (Example 2)

EBCDIC

 EBCDIC stands for Extended Binary Coded Decimal
Interchange Code
 It uses 8 bits to represent a symbol
 It can represent 256 (28) different characters
EBCDIC

Char
EBCDIC Code
Hex
Digit Zone
A 1100 0001 C1
B 1100 0010 C2
C 1100 0011 C3
D 1100 0100 C4
E 1100 0101 C5
F 1100 0110 C6
G 1100 0111 C7
H 1100 1000 C8
I 1100 1001 C9
J 1101 0001 D1
K 1101 0010 D2
L 1101 0011 D3
M 1101 0100 D4
Char
EBCDIC Code
Hex
Digit Zone
N 1101 0101 D5
O 1101 0110 D6
P 1101 0111 D7
Q 1101 1000 D8
R 1101 1001 D9
S 1110 0010 E2
T 1110 0011 E3
U 1110 0100 E4
V 1110 0101 E5
W 1110 0110 E6
X 1110 0111 E7
Y 1110 1000 E8
Z 1110 1001 E9
Characters in EBCDIC

Character
EBCDIC Code Hexadecimal
Equivalent
Digit Zone
0 1111 0000 F0
1 1111 0001 F1
2 1111 0010 F2
3 1111 0011 F3
4 1111 0100 F4
5 1111 0101 F5
6 1111 0110 F6
7 1111 0111 F7
8 1111 1000 F8
9 1111 1001 F9
Characters in EBCDIC

 Zoned decimal numbers are used to represent numeric
values (positive, negative, or unsigned) in EBCDIC
 A sign indicator (C for plus, D for minus, and F for
unsigned) is used in the zone position of the rightmost
digit
 Zones for all other digits remain as F
, the zone value for
numeric characters in EBCDIC
 In zoned format, there is only one digit per byte
Zoned Decimal Numbers

Numeric Value EBCDIC Sign Indicator
345 F3F4F5 F for unsigned
+345 F3F4C5 C for positive
-345 F3F4D5 D for negative
Examples Zoned Decimal Numbers

 Packed decimal numbers are formed from zoned decimal
numbers in the following manner:
Step 1: The zone half and the digit half of
the rightmost byte are reversed
Step 2: All remaining zones are dropped out
 Packed decimal format requires fewer number of bytes
than zoned decimal format for representing a number
 Numbers represented in packed decimal format can be
used for arithmetic operations
Packed Decimal Numbers

Numeric Value EBCDIC Sign Indicator
345 F3F4F5 345F
+345 F3F4C5 345C
-345 F3F4D5 345D
3456 F3F4F5F6 03456F
Examples of Conversion of Zoned
Decimal Numbers to Packed Decimal Format

Example
Using binary notation, write EBCDIC coding for the word BIT
. How
many bytes are required for this representation?
Solution:
B = 1100 0010 in EBCDIC binary notation
I = 1100 1001 in EBCDIC binary notation
T = 1110 0011 in EBCDIC binary notation
Hence, EBCDIC coding for the word BIT in binary notation will be
11000010 11001001 11100011
B I T
3 bytes will be required for this representation because each letter
requires 1 byte (or 8 bits)
EBCDIC Coding Scheme

ASCII

 ASCII stands for American Standard Code for
Information Interchange.
 ASCII is of two types – ASCII-7 and ASCII-8
 ASCII-7 uses 7 bits to represent a symbol and can
represent 128 (27) different characters
 ASCII-8 uses 8 bits to represent a symbol and can
represent 256 (28) different characters
 First 128 characters in ASCII-7 and ASCII-8 are same
ASCII

Character
ASCII-7 / ASCII-8 Hexadecimal
Equivalent
Zone Digit
0 0011 0000 30
1 0011 0001 31
2 0011 0010 32
3 0011 0011 33
4 0011 0100 34
5 0011 0101 35
6 0011 0110 36
7 0011 0111 37
8 0011 1000 38
9 0011 1001 39
Coding of Numeric and
Alphabetic Characters in ASCII

Character
Equivalent
Zone Digit
A 0100 0001 41
B 0100 0010 42
C 0100 0011 43
D 0100 0100 44
E 0100 0101 45
F 0100 0110 46
G 0100 0111 47
H 0100 1000 48
I 0100 1001 49
J 0100 1010 4A
K 0100 1011 4B
L 0100 1100 4C
M 0100 1101 4D

Character
Equivalent
Zone Digit
N 0100 1110 4E
O 0100 1111 4F
P 0101 0000 50
Q 0101 0001 51
R 0101 0010 52
S 0101 0011 53
T 0101 0100 54
U 0101 0101 55
V 0101 0110 56
W 0101 0111 57
X 0101 1000 58
Y 0101 1001 59
Z 0101 1010 5A

1000010 1001111 1011001
B O Y
Since each character in ASCII-7 requires one byte for its representation and
there are 3 characters in the word BOY, 3 bytes will be required for this
representation
ASCII-7 Coding Scheme
Example
Write binary coding for the word BOY in ASCII-7. How many bytes are required
for this representation?
Solution:
B = 1000010 in ASCII-7 binary notation
O = 1001111 in ASCII-7 binary notation
Y = 1011001 in ASCII-7 binary notation
Hence, binary coding for the word BOY in ASCII-7 will be

ASCII-8 Coding Scheme
Example
Write binary coding for the word SKY in ASCII-8. How many bytes are
required for this representation?
Solution:
S = 01010011 in ASCII-8 binary notation
K = 01001011 in ASCII-8 binary notation
Y = 01011001 in ASCII-8 binary notation
Hence, binary coding for the word SKY in ASCII-8 will be
01010011 01001011 01011001
S K Y
Since each character in ASCII-8 requires one byte for its representation
and there are 3 characters in the word SKY, 3 bytes will be required for
this representation

Unicode

 Why Unicode:
 No single encoding system supports all languages
 Different encoding systems conflict
 Unicode features:
 Provides a consistent way of encoding multilingual
plain text
 Defines codes for characters used in all major
languages of the world
 Defines codes for special characters, mathematical
symbols, technical symbols, and diacritics
Unicode

 Unicode features (continued):
 Capacity to encode as many as a million characters
 Assigns each character a unique numeric value and
name
 Reserves a part of the code space for private use
 Affords simplicity and consistency of ASCII, even
corresponding characters have same code
 Specifies an algorithm for the presentation of text
with bi-directional behavior
 Encoding Forms
 UTF-8, UTF-16, UTF-32
Unicode

Collating Sequence

 Collating sequence defines the assigned ordering
among the characters used by a computer
 Collating sequence may vary, depending on the type
of computer code used by a particular computer
 In most computers, collating sequences follow the
following rules:
1. Letters are considered in alphabetic order
(A < B < C … < Z)
2. Digits are considered in numeric order
(0 < 1 < 2 … < 9)
Collating Sequence

Example
Suppose a computer uses EBCDIC as its
representation of characters. In which order
internal
will this
computer sort the strings 23, A1, 1A?
Solution:
In EBCDIC, numeric characters are treated to be greater
than alphabetic characters. Hence, in the said computer,
numeric characters will be placed after alphabetic
characters and the given string will be treated as:
A1 < 1A < 23
Therefore, the sorted sequence will be: A1, 1A, 23.
Sorting in EBCDIC

Example
Suppose a computer uses ASCII for its internal representation of
characters. In which order will this computer sort the strings 23, A1,
1A, a2, 2a, aA, and Aa?
Solution:
In ASCII, numeric characters are treated to be less than alphabetic
characters. Hence, in the said computer, numeric characters will be
placed before alphabetic characters and the given string will be
treated as:
1A < 23 < 2a < A1 < Aa < a2 < aA
Therefore, the sorted sequence will be: 1A, 23, 2a, A1, Aa, a2, and
aA
Sorting in ASCII

 Alphabetic data
 Alphanumeric data
 American Standard Code for Information Interchange (ASCII)
 Binary Coded Decimal (BCD) code
 Byte
 Collating sequence
 Computer codes
 Control characters
 Extended Binary-Coded Decimal Interchange Code (EBCDIC)
 Hexadecimal equivalent
 Numeric data
 Octal equivalent
 Packed decimal numbers
 Unicode
 Zoned decimal numbers
Key Words/Phrases

Chapter 05: Computer Arithmetic Slide 1/31
Pradeep K. Sinha
Priti Sinha
Chapter 5
Computer
Arithmetic

Slide 2/31
Chapter 05: Computer Arithmetic
 Reasons for using binary instead of decimal
numbers
 Basic arithmetic operations using binary numbers
 Addition (+)
 Subtraction (-)
 Multiplication (*)
 Division (/)
Learning Objectives

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
Binary over Decimal
Ref. Page 51 Slide 4/31

Binary
State
On (1) Off (0)
Bulb
Switch
Circuit
Pulse
Examples of a Few Devices that work in
Binary Mode

Binary Arithmetic

 Binary arithmetic is simple to learn as binary number
system has only two digits – 0 and 1
 Following slides show rules and example for the four
basic arithmetic operations using binary numbers
Binary Arithmetic

Rule for binary addition is as follows:
0 + 0 = 0
0 + 1 = 1
1 + 0 = 1
1 + 1 = 0 plus a carry of 1 to next higher column
Binary Addition

10011 19
+100
1
+
9
11100 28
Example
Add binary numbers 10011 and 1001 in both decimal and
binary form
Solution
Binary
carry 11
Decimal
In this example, carry are generated for first and second columns
carry 1
Binary Addition (Example 1)

Example
Add binary numbers 100111 and 11011 in both decimal
and binary form
Solution
Binary Decimal
carry 11111 carry 1
100111 39
+11011 +27
1000010 66
The addition of three 1s
can be broken up into two
steps. First, we add only
two 1s giving 10 (1 + 1 =
10). The third 1 is now
added to this result to
obtain 11 (a 1 sum with a 1
carry). Hence, 1 + 1 + 1 =
1, plus a carry of 1 to next
higher column.
Binary Addition (Example 2)

Rule for binary subtraction is as follows:
0 - 0 = 0
0 - 1 = 1 with a borrow from the next column
1 - 0 = 1
1 - 1 = 0
Binary Subtraction

Example
Subtract 011102 from 101012
Solution
12
0202
10101
-01110
00111
Note: Go through explanation given in the book
Binary Subtraction (Example)

Complement
of the number
Base of the
number
C = Bn - 1 - N
Number of digits
in the number
The number
Complement of a Number

Example
Find the complement of 3710
Solution
Since the number has 2 digits and the value of
base is 10,
(Base)n - 1 = 102 - 1 = 99
Now 99 - 37 = 62
Hence, complement of 3710 = 6210
Complement of a Number (Example 1)

Example
Find the complement of 68
Solution
Since the number has 1 digit and the value of
base is 8,
(Base)n - 1 = 81 - 1 = 710 = 78
Now 78 - 68 = 18
Hence, complement of 68 = 18
Complement of a Number (Example 2)

Complement of a binary number can be obtained by
transforming all its 0’s to 1’s and all its 1’s to 0’s
Example
Complement of 1 0 1 1 0 1 0 is
0 1 0 0 1 0 1
Note: Verify by conventional complement
Complement of a Binary Number

Involves following 3 steps:
Step 1: Find the complement of
are subtracting (subtrahend)
Step 2: Add this to the number
are taking away (minuend)
the number you
from which you
Step 3: If there is a carry of 1, add it to obtain
the result; if there is no carry, recomplement the
sum and attach a negative sign
Complementary subtraction is an additive approach of subtraction
Complementary Method of Subtraction

Example:
Subtract 5610 from 9210 using complementary method.
Solution
Step 1: Complement of 5610
= 102 - 1 - 56 = 99 – 56 = 4310
Step 2: 92 + 43 (complement of 56)
= 135 (note 1 as carry)
Step 3: 35 + 1 (add 1 carry to sum)
Result = 36
The result may be
verified using the
method of normal
subtraction:
92 - 56 = 36
Complementary Subtraction (Example 1)

Example
Subtract 3510 from 1810 using complementary method.
Solution
Step 1: Complement of 3510
= 102 - 1 - 35
= 99 - 35
= 6410
18
Step 2:
+ 64 (complement
of 35)
82
Step 3: Since there is no carry,
re-complement the sum and
attach a negative sign to
obtain the result.
Result = -(99 - 82)
= -17
The result may be verified using normal
subtraction:
18 - 35 = -17
Complementary Subtraction (Example 2)

Example
Subtract 01110002 (5610) from 10111002 (9210) using
complementary method.
Solution
1011100
+1000111 (complement of 0111000)
10100011
1 (add the carry of 1)
0100100
Result = 01001002 = 3610
Binary Subtraction Using Complementary
Method (Example 1)

Example
Subtract 1000112 (3510) from 0100102 (1810) using
complementary method.
Solution
010010
+011100 (complement of 100011)
101110
Since there is no carry, we have to complement the sum and
attach a negative sign to it. Hence,
Result = -0100012 (complement of 1011102)
= -1710
Binary Subtraction Using Complementary
Method (Example 2)

Table for binary multiplication is as follows:
0 x 0 = 0
0 x 1 = 0
1 x 0 = 0
1 x 1 = 1
Binary Multiplication

Example
Multiply the binary numbers 1010 and 1001
Solution
1010
x1001
Multiplicand
Multiplier
101
0
Partial Product
0000 Partial Product
1011010 Final Product
Binary Multiplication (Example 1)

(S = left shift)
1010
1010SS
1011010
Whenever a 0 appears in the multiplier, a separate partial
product consisting of a string of zeros need not be generated
(only a shift will do). Hence,
1010
x1001
Binary Multiplication (Example 2)

Table for binary division is as follows:
1  0 = Divide by zero error
0  1 = 0
1 0 = Divide by zero error
1  1 = 1
As in the decimal number system (or in any other number
system), division by zero is meaningless
The computer deals with this problem by raising an error
condition called ‘Divide by zero’ error
Binary Division

1. Start from the left of the dividend
2. Perform a series of subtractions in which the divisor is
subtracted from the dividend
3. If subtraction is possible, put a 1 in the quotient and
subtract the divisor from the corresponding digits of
dividend
4. If subtraction is not possible (divisor greater than
remainder), record a 0 in the quotient
5. Bring down the next digit to add to the remainder
digits. Proceed as before in a manner similar to long
division
Rules for Binary Division

Example
Divide 1000012 by 1102
Sol ution 0101 (Quotient)
11
0
100001 (Dividend)
110
110 1 Divisor greater than 100, so put 0 in quotient
1000 2 Add digit from dividend to group used above
110 3 Subtraction possible, so put 1 in quotient
100 4 Remainder from subtraction plus digit from dividend
5
1001 6
110 7
11
Divisor greater, so put 0 in quotient
Add digit from dividend to group
Subtraction possible, so put 1 in quotient
Remainder
Binary Division (Example 1)

Most computers use the additive method for performing
multiplication and division operations because it simplifies
the internal circuit design of computer systems
Example
4 x 8 = 8 + 8 + 8 + 8 = 32
Additive Method of Multiplication
and Division

 Subtract the divisor repeatedly from the dividend until
the result of subtraction becomes less than or equal to
zero
 If result of subtraction is zero, then:
 quotient = total number of times subtraction was
performed
 remainder = 0
 If result of subtraction is less than zero, then:
 quotient = total number of times subtraction was
performed minus 1
 remainder = result of the subtraction previous to
the last subtraction
Rules for Additive Method of Division

Example
Divide 3310 by 610 using the method of addition
Solution:
33 - 6 = 27
27 - 6 = 21
21 - 6 = 15
15 - 6 = 9
9 - 6 = 3
3 - 6 = -3
Total subtractions = 6
Since the result of the last
subtraction is less than zero,
Quotient = 6 - 1 (ignore last
subtraction) = 5
Remainder = 3 (result of previous
subtraction)
Additive Method of Division (Example)

Slide 31/31
 Additive method of division
 Additive method of multiplication
 Additive method of subtraction
 Binary addition
 Binary arithmetic
 Binary division
 Binary multiplication
 Binary subtraction
 Complement
 Complementary subtraction
 Computer arithmetic
Key Words/Phrases

Chapter 06: Boolean Algebra and Logic Circuits Slide 1/86
Pradeep K. Sinha
Priti Sinha
Chapter 6
Boolean Algebra
and Logic Circuits

Slide 2/86
Chapter 06: Boolean Algebra and Logic Circuits
 Boolean algebra
 Fundamental concepts and basic laws of Boolean
algebra
 Boolean function and minimization
 Logic gates
 Logic circuits and Boolean expressions
 Combinational circuits and their design
Learning Objectives

Boolean Algebra

 An algebra that deals with binary number system
 George Boole (1815-1864), an English mathematician,
developed it for:
 Simplifying representation
 Manipulation of propositional logic
 In 1938, Claude E. Shannon proposed using Boolean
algebra in design of relay switching circuits
 Provides economical and straightforward approach
 Used extensively in designing electronic circuits used in
computers
Boolean Algebra
Ref. Page 63 Chapter 06: Boolean Algebra and Logic Circuits Slide 4/86

Fundamental Concepts of Boolean Algebra
 Use of binary digit
 Variables used in Boolean equations can have either of
two possible values, 0 or 1
 Logical addition
 Symbol ‘+’, also known as ‘OR’ operator, is used for
logical addition. It follows law of binary addition
 Logical multiplication
 Symbol ‘.’, also known as ‘AND’ operator, is used for
logical multiplication. It follows law of binary
multiplication
 Complementation
 Symbol ‘-’, also known as ‘NOT’ operator, is used for
complementation. It follows law of binary complement

Inputs Output
A  B = C
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A  B = C
0 0 0
0 1 0
1 0 0
1 1 1
Input Output
A A
0 1
1 0
Truth Table for OR (+) Truth Table for AND (.) Truth Table for NOT (-)
Truth Tables for Boolean Operators

 Each operator has a precedence level
 Higher the operator’s precedence level, earlier it is evaluated
 Expression is scanned from left to right
 First, expressions enclosed within parentheses are evaluated
 Then, all complement (NOT) operations are performed
 Then, all ‘’ (AND) operations are performed
 Finally, all ‘’ (OR) operations are performed
Operator Precedence

Operator Precedence
Y
X   Z
1st
2nd
3rd

Postulate 1:
(a) A = 0, if and only if, A is not equal to 1
(b) A = 1, if and only if, A is not equal to 0
Postulate 2:
(a) x  0 = x
(b) x  1 = x
Postulate 3: Commutative Law
(a) x  y = y  x
(b) x  y = y  x
Postulates of Boolean Algebra

Postulate 4: Associative Law
(a) x  (y  z) = (x  y)  z
(b) x  (y  z) = (x  y)  z
Postulate 5: Distributive Law
(a) x  (y  z) = (x  y)  (x  z)
(b) x  (y  z) = (x  y)  (x  z)
Postulate 6:
(a)x  x = 1
(b)x  x = 0
Postulates of Boolean Algebra

Column 1 Column 2 Column 3
Row 1 1  1 = 1 1 + 0 = 0  1 = 1 0  0 = 0
Row 2 0  0 = 0 0  1 = 1  0 = 0 1  1 = 1
There is a precise duality between the operators
(OR), and the digits 0 and 1.
. (AND) and +
For example, in the table below, the second row is obtained from
the first row and vice versa simply by interchanging ‘+’ with ‘.’
and ‘0’ with ‘1’
Therefore, if a particular theorem is proved, its dual theorem
automatically holds and need not be proved separately
The Principle of Duality

Some Important Theorems of
Boolean Algebra
Sr.
No.
Theorems/
Identities
Dual Theorems/
Identities
Name
(if any)
1 x + x = x x  x = x Idempotent Law
2 x + 1 = 1 x  0 = 0
3 x + x  y = x x  (x + y) = x Absorption Law
4 x = x Involution Law
5 x  (x + y ) = x  y x + x  y = x + y
6 xy = x  y x  y = x + y De Morgan’s Law

The theorems of Boolean algebra may be proved by using
one of the following methods:
1. By using postulates to show that L.H.S. = R.H.S
2. By Perfect Induction or Exhaustive Enumeration method
where all possible combinations of variables involved in
L.H.S. and R.H.S. are checked to yield identical results
3. By the Principle of Duality where the dual of an already
proved theorem is derived from the proof of its
corresponding pair
Methods of Proving Theorems

Theorem:
x + x · y = x
Proof:
L.H.S.
= x  x  y
= x  1  x  y
= x  (1  y)
= x  (y  1)
= x  1
= x
= R.H.S.
by postulate 2(b)
by postulate 5(a)
by postulate 3(a)
by theorem 2(a)
by postulate 2(b)
Proving a Theorem by Using Postulates
(Example)

Proving a Theorem by Perfect Induction
(Example)
x y x  y x  x  y
0 0 0 0
0 1 0 0
1 0 0 1
1 1 1 1
Theorem:
x + x · y = x
=

Theorem:
x + x = x
Proof:
L.H.S.
= x  x
= (x  x)  1 by postulate 2(b)
= (x  x)  (x +X) by postulate 6(a)
= x  x  X
= x  0
= x
= R.H.S.
by postulate 5(b)
by postulate 6(b)
by postulate 2(a)
Proving a Theorem by the
Principle of Duality (Example)

Dual Theorem:
x  x = x
Proof:
L.H.S.
= x  x
= x  x  0 by postulate 2(a)
by postulate 6(b)
by postulate 5(a)
by postulate 6(a)
by postulate 2(b)
= x  x  x  X
= x  (x + X )
= x  1
= x
= R.H.S.
Notice that each step of
the proof of the dual
theorem is derived from
the proof of its
corresponding pair in
the original theorem
Proving a Theorem by the
Principle of Duality (Example)

Boolean Functions

 A Boolean function is an expression formed with:
 Binary variables
 Operators (OR, AND, and NOT)
 Parentheses, and equal sign
 The value of a Boolean function can be either 0 or 1
 A Boolean function may be represented as:
 An algebraic expression, or
 A truth table
Boolean Functions

and Z, can also be
 The RHS of the equation is called an expression
 The symbols X, Y
, Z are the literals of the function
 For a given Boolean function, there may be more than
one algebraic expressions
W = X +Y ·Z
 Variable W is a function of X, Y
,
written as W = f (X, Y
, Z)
Representation as an Algebraic Expression

Representation as a Truth Table
X Y Z W
0 0 0 0
0 0 1 1
0 1 0 0
0 1 1 0
1 0 0 1
1 0 1 1
1 1 0 1
1 1 1 1
W = X + Y  Z

 The number of rows in the table is equal to 2n, where
n is the number of literals in the function
 The combinations of 0s and 1s for rows of this table
are obtained from the binary numbers by counting
from 0 to 2n - 1
Representation as a Truth Table

 Minimization of Boolean functions deals with
 Reduction in number of literals
 Reduction in number of terms
 Minimization is achieved through manipulating
expression to obtain equal and simpler expression(s)
(having fewer literals and/or terms)
Minimization of Boolean Functions

F 1 = x  y  z + x  y  z + x  y
F1 has 3 literals (x, y, z) and 3 terms
F 2 = x  y + x  z
F2 has 3 literals (x, y, z) and 2 terms
F2 can be realized with fewer electronic components,
resulting in a cheaper circuit

x y z F1 F2
0 0 0 0 0
0 0 1 1 1
0 1 0 0 0
0 1 1 1 1
1 0 0 1 1
1 0 1 1 1
1 1 0 0 0
1 1 1 0 0
Both F1 and F2 produce the same result

Try out some Boolean Function
Minimization
(a) x  x  y
(b) x x  y 
(c) x  y  z  x  y  z  x  y
(d) x  y  x  z  y  z
(e) x  y x  z y z 

 The complement of a Boolean function is obtained by
interchanging:
 Operators OR and AND
 Complementing each literal
 This is based on De Morgan’s theorems, whose
general form is:
A1+A2+A3+...+An = A1A2 A3...An
A1A2 A3 ...An = A1+A2+A3+...+An
Complement of a Boolean Function

Complementing a Boolean
Function (Example)
F1 =xyz+xyz
T
o obtain F1, we first interchange the OR and the AND
operators giving
x+y+z x+y+z
Now we complement each literal giving
F1 =x+y+z x+y+z
Ref Page. 73 Chapter 06: Boolean Algebra and Logic Circuits Slide 28/86

Minterms
: n variables forming an AND term, with
each variable being primed or unprimed,
provide 2n possible combinations called
minterms or standard products
: n variables forming an OR term, with
each variable being primed or unprimed,
provide 2n possible combinations called
maxterms or standard sums
Maxterms
Canonical Forms of Boolean Functions

Minterms and Maxterms for three Variables
Variables Minterms Maxterms
x y z Term Designation Term Designation
0 0 0 x  y  z m0 x  y  z M0
0 0 1
x  y  z m1 x  y  z M1
0 1 0
x  y  z m2 x  y  z M2
0 1 1 x  y  z m3 x  y  z M3
1 0 0 x  y  z m4 x  y  z M4
1 0 1 x  y  z m5 x  y  z M5
1 1 0 x  y  z m6
x  y  z M6
1 1 1 x  y  z m7
x  y  z M7
Note that each minterm is the complement of its corresponding maxterm and vice-versa

A sum-of-products (SOP) expression is a product term
(minterm) or several product terms (minterms) logically
added (ORed) together. Examples are:
x
x+yz
xy+xy
x+ y
xy+z
xy+xyz
Sum-of-Products (SOP) Expression

1. Construct a truth table for the given Boolean function
2. Form a minterm for each combination of the
variables, which produces a 1 in the function
3. The desired expression is the sum (OR) of all the
minterms obtained in Step 2
Steps to Express a Boolean Function
in its Sum-of-Products Form

Expressing a Function in its
Sum-of-Products Form (Example)
The following 3 combinations of the variables produce a 1 in case of F1 :
001, 100, and 111
x y z F1
0 0 0 0
0 0 1 1
0 1 0 0
0 1 1 0
1 0 0 1
1 0 1 0
1 1 0 0
1 1 1 1

Sum-of-Products Form (Example)
 Their corresponding minterms are:
x y z, x y z, and x y  z
 Taking the OR of these minterms, we get
F1 =xy z+x y z+x y z=m1+m4 m7
F1 xy z=1,4,7

Product-of Sums (POS) Expression
A product-of-sums (POS) expression is a sum term
(maxterm) or several sum terms (maxterms) logically
multiplied (ANDed) together. Examples are:
x
x+y
x+yz
x+yx+yx+y
x + yx+ y+z
x+yx+y

1. Construct a truth table for the given Boolean function
2. Form a maxterm for each combination of the variables,
which produces a 0 in the function
3. The desired expression is the product (AND) of all the
maxterms obtained in Step 2
Steps to Express a Boolean Function
in its Product-of-Sums Form

Product-of-Sums Form
 The following 5 combinations of variables produce a 0 in case of F1 :
000, 010, 011, 101, and 110
x y z F1
0 0 0 0
0 0 1 1
0 1 0 0
0 1 1 0
1 0 0 1
1 0 1 0
1 1 0 0
1 1 1 1

Product-of-Sums Form
 Their corresponding maxterms are:
x+y+ z, x+y+ z, x+y+ z,
x+y+ zand x+y+ z
 Taking the AND of these maxterms, we get:
F1 =x+y+zx+y+zx+y+zx+y+z
x+y+z=M0M2M3M5M6
F1 x,y,z= Π
0,2,3,5,6

= Σ
To convert from one canonical form to another,
interchange the symbol and list those numbers missing
from the original form.
Example:
Fx,y,z= Π
0,2,4,5= Σ
1,3,6,7
Fx,y,z 1,4,7= Σ
0,2,3,5,6
Conversion Between Canonical Forms
(Sum-of-Products and Product-of-Sums)

Logic Gates

 Logic gates are electronic circuits that operate on one
or more input signals to produce standard output
signal
 Are the building blocks of all the circuits in a computer
 Some of the most basic and useful logic gates are
AND, OR, NOT, NAND and NOR gates
Logic Gates

realization of logical multiplication (AND)
 Physical
operation
 Generates an output signal of 1 only if all input
signals are also 1
AND Gate

Inputs Output
A B C = A  B
0 0 0
0 1 0
1 0 0
1 1 1
A
B
C = A  B
AND Gate (Block Diagram Symbol
and Truth Table)

 Physical realization of logical addition (OR) operation
 Generates an output signal of 1 if at least one of the
input signals is also 1
OR Gate

C = A + B
A
B
Inputs Output
A B C = A + B
0 0 0
0 1 1
1 0 1
1 1 1
OR Gate (Block Diagram Symbol
and Truth Table)

 Physical realization of complementation operation
 Generates an output signal, which is the reverse of
the input signal
NOT Gate

Input Output
A A
0 1
1 0
A A
NOT Gate (Block Diagram Symbol
and Truth Table)

 Complemented AND gate
 Generates an output signal of:
 1 if any one of the inputs is a 0
 0 when all the inputs are 1
NAND Gate

Inputs Output
A B C =A+B
0 0 1
0 1 1
1 0 1
1 1 0
A
B C=AB=AB=A+B
NAND Gate (Block Diagram Symbol
and Truth Table)

 Complemented OR gate
 Generates an output signal of:
 1 only when all inputs are 0
 0 if any one of inputs is a 1
NOR Gate

Inputs Output
A B C =A  B
0 0 1
0 1 0
1 0 0
1 1 0
A
B C=AB=AB=A  B
NOR Gate (Block Diagram Symbol
and Truth Table)

Logic Cicruits

 When logic gates are interconnected to form a gating /
logic network, it is known as a combinational logic circuit
 The Boolean algebra expression for a given logic circuit
can be derived by systematically progressing from input
to output on the gates
 The three logic gates (AND, OR, and NOT) are logically
complete because any Boolean expression can be
realized as a logic circuit using only these three gates
Logic Circuits

Finding Boolean Expression
of a Logic Circuit (Example 1)
B
C
A
A
NOT
OR
B + C
D=AB + C
AND

Finding Boolean Expression
of a Logic Circuit (Example 2)
A
B
NOT
OR
C=A+BAB
A B
AND
A  B
AB
AND

Constructing a Logic Circuit from a Boolean
Expression (Example 1)
OR
AB
AND
A B + C
A
B
C
Boolean Expression = A B + C

AND
A B
A
B
Boolean Expression = AB+CD+EF
C D
AND
C
D
E F
AND
E
F
AB+CD+EF
AND
A B
NOT
EF
NOT
Constructing a Logic Circuit from a Boolean
Expression (Example 2)

 NAND gate is an universal gate, it is alone
sufficient to implement any Boolean
expression
 To understand this, consider:
 Basic logic gates (AND, OR, and NOT) are
logically complete
 Sufficient to show that AND, OR, and NOT
gates can be implemented with NAND
gates
Universal NAND Gate

(a) NOT gate implementation.
A
A  A = A + A = A
(b) AND gate implementation.
A
B
A  B  A B
A  B
Implementation of NOT, AND and OR
Gates by NAND Gates

A B  A +B  A  B
A
B
A  A = A
BB=B
(c) OR gate implementation.
Implementation of NOT, AND and OR
Gates by NAND Gates

Step 2: Draw a second logic diagram with the equivalent NAND
logic substituted for each AND, OR, and NOT gate
Step 3: Remove all pairs of cascaded inverters from the
diagram as double inversion does not perform any
logical function. Also remove inverters connected to
single external inputs and complement the
corresponding input variable
Step 1: From the given algebraic expression, draw the logic
diagram with AND, OR, and NOT gates. Assume that
both the normal (A) and complement (A) inputs are
available
Method of Implementing a Boolean
Expression with Only NAND Gates

Implementing a Boolean Expression with
Only NAND Gates (Example)
Boolean Expression =
(a) Step 1: AND/OR implementation
B
D
A
C
AB
A
B
A+BD
BD
CA+BD
A  B+CA+BD
A  B+CA+BD

AND
OR
OR
5
3
4
AND
B
D
2
AND
A
C
1
A
B
AB
AB + CA+BD
A+BD
CA+BD
BD
(b) Step 2: Substituting equivalent NAND functions

A
B
B
D
(c) Step 3: NAND implementation.
AB+CA+BD
A
C
1
2
3
4
5

 NOR gate is an universal gate, it is alone sufficient to
implement any Boolean expression
 To understand this, consider:
 Basic logic gates (AND, OR, and NOT) are logically
complete
 Sufficient to show that AND, OR, and NOT gates can
be implemented with NOR gates
Universal NOR Gate

(a) NOT gate implementation.
A
A  A = A  A = A
(b) OR gate implementation.
A
B
A  B  A  B
A  B
Implementation of NOT, OR and AND
Gates by NOR Gates

A
B
A  A = A
A +B  A B  A B
B  B = B
(c) AND gate implementation.
Implementation of NOT, OR and AND
Gates by NOR Gates

diagram with AND, OR, and NOT gates. Assume that
inputs are
available
Step 2: Draw a second logic diagram with equivalent NOR logic
substituted for each AND, OR, and NOT gate
Step 3: Remove all parts of cascaded inverters from the
diagram as double inversion does not perform any
logical function. Also remove inverters connected to
single external inputs and complement the
corresponding input variable
A
both the normal A and complement
Method of Implementing a Boolean
Expression with Only NOR Gates
Step 1: For the given algebraic expression, draw the logic

Only NOR Gates (Examples)
A
B
B
D
A
C
(a) Step 1: AND/OR implementation.
A+BD
BD
CA+BD
=
AB
Boolean Expression AB+CA+BD

2
1
AN
D
A
B
D
B
AN
D
OR
5 6
4
AN
D
OR
3
A
C
A B
BD
CA+BD
A B + CA+BD
A+BD
(b) Step 2: Substituting equivalent NOR functions.

(c) Step 3: NOR implementation.
A
B
3
4
5
1
2
6
B
D
A
C

A B =A  B + A  B
C =AB =AB+AB
C =AB =AB+AB

A
B
A
B
Also, ABC = ABC= AB C
Exclusive-OR Function

Inputs Output
A B C =A B
0 0 0
0 1 1
1 0 1
1 1 0
Exclusive-OR Function (Truth Table)

Equivalence Function with Block Diagram
Symbol
A
B
C = A ☉ B = AB+AB
Also, (A ☉ B) ☉ = A ☉ (B ☉ C) = A ☉ B ☉ C
A☉ B = A  B+ A  B

Inputs Output
A B C = A ☉ B
0 0 1
0 1 0
1 0 0
1 1 1
Equivalence Function (Truth Table)

Design of
Combinational Circuits

1. State the given problem completely and exactly
2. Interpret the problem and determine the available input
variables and required output variables
3. Assign a letter symbol to each input and output variables
4. Design the truth table that defines the required relations
between inputs and outputs
5. Obtain the simplified Boolean function for each output
6. Draw the logic circuit diagram to implement the Boolean
function
Steps in Designing Combinational Circuits

S = AB+AB
C = AB
Boolean functions for the two outputs.
Inputs Outputs
A B C S
0 0 0 0
0 1 0 1
1 0 0 1
1 1 1 0
Designing a Combinational Circuit
Example 1 – Half-Adder Design

Logic circuit diagram to implement the Boolean functions
A
B
A
B
S = AB+AB
C = AB
A
B
AB
AB
Example 1 – Half-Adder Design

Truth table for a full adder
Example 2 – Full-Adder Design
Inputs Outputs
A B D C S
0 0 0 0 0
0 0 1 0 1
0 1 0 0 1
0 1 1 1 0
1 0 0 0 1
1 0 1 1 0
1 1 0 1 0
1 1 1 1 1

Boolean functions for the two outputs:
S = ABD+ABD+ABD+ABD
C = ABD+ABD+ABD+ABD
= AB+AD+BD (when simplified)

A
B
D
A
A
B
A
B
D
(a) Logic circuit diagram for sums
B
D
D
S
A B D
A B D
A B D
A B D

C
A B
A D
B D
A
B
A
D
B
D
(b) Logic circuit diagram for carry

Designing a Combinational Circuit:
Full-Adder Design using Half-Adders
HA
HA
A
B
D
C
S
AB
AB AB  A B
A  B D
ABD

Parallel Binary Adder
FA FA FA HA
A4
B4
S5 S4
A3
B3
A2
B2
A1
B1
S3
S2 S1
Carry Carry Carry

Slide 86/86
Chapter 06: Boolean Algebra and Logic Circuits
Key Words/Phrases
 Absorption law
 AND gate
 Associative law
 Boolean algebra
 Boolean expression
 Boolean functions
 Boolean identities
 Canonical forms for
Boolean functions
 Combinational logic
circuits
 Cumulative law
 Complement of a
function
 Complementation
 De Morgan’s law
 Distributive law
 Dual identities
 Equivalence function
 Exclusive-OR function
 Exhaustive enumeration
method
 Half-adder
 Idempotent law
 Involution law
 Literal
 Logic circuits
 Logic gates
 Logical addition
 Logical multiplication
 Maxterms
 Minimization of Boolean
functions
 Minterms
 NAND gate
 NOT gate
 Operator precedence
 OR gate
 Parallel Binary Adder
 Perfect induction
method
 Postulates of Boolean
algebra
 Principle of duality
 Product-of-Sums
expression
 Standard forms
 Sum-of Products
expression
 Truth table
 Universal NAND gate
 Universal NOR gate

Chapter 07: Processor and Memory Slide 1/32
Pradeep K. Sinha
Priti Sinha
Chapter 7
Processor and
Memory

Slide 2/32
Chapter 07: Processor and Memory
 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
Learning Objectives

Slide 3/32
Basic Processor & Memory Architecture
of a Computer System
Cache memory
Decoder
Program control
register
Control Unit Arithmetic Logic Unit
Central Processing Unit
ROM PROM EPROM
Main memory (RAM)
Instruction
register
Memory buffer
register
I/O
register
General-purpose
register
Memory address
register
Accumulator
register
General-purpose
register
General-purpose
register
General-purpose
register
S
E
C
O
N
D
A
R
Y
S
T
O
R
A
G
E
D
E
V
I
C
E
S
I/O
interfaces
Storage
interfaces
I/O
D
E
V
I
C
E
S
Ref. Page 105

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
 No other single component of a computer determines
its overall performance as much as the CPU

 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
Control Unit (CU)

 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
Arithmetic Logic Unit (ALU)

 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
Instruction Set

 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
Registers

Functions of Commonly Used Registers
Sr. No. Name of register Function
1 Memory Address (MAR)
Holds address of the active memory
location
2 Memory Buffer (MBR)
Holds information on its way to and from
memory
3 Program Control (PC)
Holds address of the next instruction to be
executed
4 Accumulator (A)
Accumulates results and data to be
operated upon
5 Instruction (I)
Holds an instruction while it is being
executed
6 Input/Output (I/O) Communicates with I/O devices

 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
Execution of Instructions

 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)
 We measure processing speed of PCs in MHz or GHz, of
workstations and servers in MIPS or BIPS, and of supercomputers
in GFLOPS (gigaflops, which refers to a billion FLOPS) or TFLOPS
(teraflops, which refers to 1012 FLOPS), or PFLOPS (petaflops,
which refers to 1015 FLOPS)
Processor Speed

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

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

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

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
Main Memory

Property Desirable
Primary
storage
Secondary
storage
Storage
capacity
Large storage capacity Small Large
Access Time Fast access time Fast Slow
Cost per bit of
storage
Lower cost per bit High Low
Volatility Non-volatile Volatile Non-volatile
Access Random access
Random
access
Pseudo-
random
access or
sequential
access
Storage Evaluation Criteria

Main Memory Organization
Addresses of
a memory
Words of a
memory
0
1
2
3
4
5
N-2
N-1
Each word
contains the
same number of
bits = word
length
Bit 1 Bit 2

 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
Main Memory Organization

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

B
O
M
B
A
Y
0025
0026
0027
0028
0029
0030
0031
4096
D
E
L
H
I
0051
0052
0053
0054
0055
0056
4096
 Each memory location
can store only a single
character
 Slower in speed of
calculation than fixed
world-length memory
 Used in small business
computers for
optimizing the use of
storage space
Note: With memory becoming cheaper and larger day-by-day, most
modern computers employ fixed-word-length memory organization
Variable Word-length Memory
Address
Numbers
Address
Numbers

 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
Memory Capacity

Types of Memory Chips
Memory chips
Volatile and writable Non-volatile and read-only
Static
(SRAM)
Dynamic
(DRAM)
Manufacturer-
programmed
(ROM)
User-programmed
PROM EPROM
EEPROM
UVEPROM

 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)
Random Access Memory (RAM)

 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
Read Only Memory (ROM)

Type Usage
Manufacturer-
programmed ROM
Data is burnt by the
manufacturer of the electronic
equipment in which it is used.
User-programmed ROM
or
Programmable ROM
(PROM)
The user can load and store
“read-only” programs and data
in it
Erasable PROM (EPROM)
The user can erase information
stored in it and the chip can be
reprogrammed to store new
information
Types of ROMs

Type Usage
Ultra Violet EPROM
(UVEPROM)
A type of EPROM chip in which the
stored information is erased by
exposing the chip for some time
to ultra-violet light
Electrically EPROM
(EEPROM)
or
Flash memory
A type of EPROM chip in which the
stored information is erased by
using high voltage electric pulses
Types of ROMs

 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”
Cache Memory

 Accumulator Register (AR)
 Address
 Branch Instruction
 Cache Memory
 CISC (Complex Instruction Set
Computer) architecture
 Clock cycles
 Clock speed
 Control Unit
 Electrically EPROM (EEPROM)
 Erasable Programmable Read-
Only Memory (EPROM)
 Explicitly Parallel Instruction
Computing (EPIC)
 Fixed-word-length memory
 Flash Memory
 Input/Output Register (I/O)
 Instruction Register (I)
 Instruction set
 Kilobytes (KB)
 Main Memory
 Manufacturer-Programmed ROM
 Megabytes (MB)
 Memory
 Memory Address Register (MAR)
 Memory Buffer Register (MBR)
 Microprogram
 Multi-core processor
 Non-Volatile storage Processor
 Program Control Register (PC)
 Programmable Read-Only Memory
(PROM)
 Random Access Memory (RAM)
Key Words/Phrases

 Read-Only Memory (ROM)
 Register
 RISC (Reduced Instruction Set Computer)
architecture
 Single In-line Memory Module (SIMM)
 Ultra Violet EPROM (UVEPROM)
 Upward compatible
 User-Programmed ROM
 Variable-word-length memory
 Volatile Storage
 Word length
 Word size
Key Words/Phrases

Chapter 08: Secondary Storage Devices Slide 1/117
Pradeep K. Sinha
Priti Sinha
Chapter 8
Secondary Storage
Devices

 Secondary storage devices and their need
 Classification of commonly used secondary storage
devices
 Difference between sequential and direct access
storage devices
 Basic principles of operation, types, and uses of
popular secondary storage devices such as magnetic
tape, magnetic disk, and optical disk
Learning Objectives
Slide 2/117
Chapter 08: Secondary Storage Devices

 Commonly used mass storage devices
 Introduction to other related concepts such as RAID,
Jukebox, storage hierarchy, etc.
Learning Objectives
Slide 3/117

 Limited capacity because the cost per bit of storage
is high
 Volatile - data stored in it is lost when the electric
power is turned off or interrupted
Limitations of Primary Storage
Slide 4/117
Ref. Page 122

 Used in a computer system to overcome the limitations
of primary storage
 Has virtually unlimited capacity because the cost per bit
of storage is very low
 Has an operating speed far slower than that of the
primary storage
 Used to store large volumes of data on a permanent
basis
 Also known as auxiliary memory
Secondary Storage
Slide 5/117
Ref. Page 122

Classification of Commonly Used Secondary
Storage Devices
Slide 6/117
Ref. Page 122

Sequential and Direct-
Access Storage Devices

 Arrival at the desired storage location may be preceded
by sequencing through other locations
 Data can only be retrieved in the same sequence in
which it is stored
 Access time varies according to the storage location of
the information being accessed
 Suitable for sequential processing applications
most, if not all, of the data records need
processed one after another
where
to be
 Magnetic tape is a typical example of such a storage
device
Sequential-access Storage Devices
Slide 8/117
Ref. Page 123

 Devices where any storage location may be selected
and accessed at random
 Permits access to individual information in a more
direct or immediate manner
 Approximately equal access time is required for
accessing information from any storage location
 Suitable for direct processing applications such as on-
line ticket booking systems, on-line banking systems
 Magnetic, optical, and magneto-optical disks are typical
examples of such a storage device
Direct-access Storage Devices
Slide 9/117
Ref. Page 123

Magnetic Tapes

 Commonly used sequential-access secondary storage
device
 Physically, the tape medium is a plastic ribbon, which is
usually ½ inch or ¼ inch wide and 50 to 2400 feet long
 Plastic ribbon is coated with a magnetizable recording
material such as iron-oxide or chromium dioxide
 Data are recorded on the tape in the form of tiny
invisible magnetized and non-magnetized spots
(representing 1s and 0s) on its coated surface
 Tape ribbon is stored in reels or a small cartridge or
cassette
Magnetic Tape Basics
Slide 11/117
Ref. Page 124

Illustrates the concepts of frames, tracks, parity bit, and character-by-character data
storage
Magnetic Tape - Storage Organization
(Example 1)
7
6
5
4
3
2
1
A frame
Characters for
corresponding codes
Each vertical
line represents
a binary 1 bit
Track/channel
numbers
0 1 2 3 4 5 6 7 8 9
Zone
Numeric
A B C D E F G H I
Parity bit
Slide 12/117
Ref. Page 125

Magnetic Tape - Storage Organization
(Example 2)
Illustrates the concepts of frames, tracks, parity bit, and character-by-character data storage
0 1 2 3 4 5 6 7 8 9 A B C
3
4
5
6
7
A frame for
each character
Track/channel
numbers
Characters for
corresponding codes
Each vertical
line represents
a binary 1 bit
8
9
8’s digit
2’s digit
Added zone
Added zone
Zone
Parity bit
Zone
Unit’s digit 2
4’s digit 1
Track
representation
Slide 13/117
Ref. Page 125

 Storage capacity of a tape =
Data recording density x Length
 Data recording density is the amount of data that can be
stored on a given length of tape. It is measured in bytes
per inch (bpi)
 Tape density varies from 800 bpi in older systems to
77,000 bpi in some of the modern systems
 Actual storage capacity of a tape may be anywhere from
35% to 70% of its total storage capacity, depending on
the storage organization used
Magnetic Tape Storage Capacity
Slide 14/117
Ref. Page 126

 Refers to characters/second that can be transmitted to
the memory from the tape
 Transfer rate measurement unit is bytes/second (bps)
 Value depends on the data recording density and the
speed with which the tape travels under the read/write
head
 A typical value of data transfer rate is 7.7 MB/second
Slide 15/117
Ref. Page 126
Magnetic Tape – Data Transfer Rate

 Used for writing/reading of data to/from a magnetic
tape ribbon
 Different for tape reels, cartridges, and cassettes
 Has read/write heads for reading/writing of data on
tape
 A magnetic tape reel/cartridge/cassette has to be first
loaded on a tape drive for reading/writing of data on it
 When processing is complete, the tape is removed
from the tape drive for off-line storage
Magnetic Tape – Tape Drive
Slide 16/117
Ref. Page 126

 Tape drive is connected to and controlled by a tape
controller that interprets the commands for operating the
tape drive
 A typical set of commands supported by a tape controller
are:
Read reads one block of data
Write writes one block of data
Write tape header label used to update the contents of tape header label
Erase tape erases the data recorded on a tape
Back space one block rewinds the tape to the beginning of previous block
Magnetic Tape – Tape Controller
Slide 17/117
Ref. Page 126

Forward space one block
Forward space one file
Rewind
Unload
forwards the tape to the beginning
of next block
forwards the tape to the beginning
of next file
fully rewinds the tape
releases the tape drive’s grip so
that the tape spool can be
unmounted from the tape drive
Magnetic Tape – Tape Controller
Slide 18/117
Ref. Page 126

 ½-inch tape reel
 ½-inch tape cartridge
 ¼-inch streamer tape
 4-mm digital audio tape (DAT)
Types of Magnetic Tape
Slide 19/117
Ref. Page 126

 Uses ½ inch wide tape ribbon stored on a tape reel
 Uses parallel representation method of storing data, in
which data are read/written a byte at a time
 Uses a read/write head assembly that has one
read/write head for each track
 Commonly used as archival storage for off-line storage
of data and for exchange of data and programs
between organizations
 Fast getting replaced by tape cartridge, streamer tape,
and digital audio tape they are more compact, cheaper
and easier to handle
Half-inch Tape Reel
Slide 20/117
Ref. Page 126

Half-inch Tape Reel
Slide 21/117
Ref. Page 126

Tape Drive of Half-inch Tape Reel
Supply reel Take-up reel
Magnetic tape
Read/write
head assembly
Vacuum
columns
Tape loops
varying in length
Slide 22/117
Ref. Page 126

 Uses ½ inch wide tape ribbon sealed in a cartridge
 Has 36 tracks, as opposed to 9 tracks for most half-inch
tape reels
 Stores data using parallel representation. Hence, 4 bytes
of data are stored across the width of the tape. This
enables more bytes of data to be stored on the same
length of tape
 Tape drive reads/writes on the top half of the tape in one
direction and on the bottom half in the other direction
Half-inch Tape Cartridge
Slide 23/117
Ref. Page 126

Half-inch Tape Cartridge
Slide 24/117
Ref. Page 126

 Uses ¼ inch wide tape ribbon sealed in a cartridge
 Uses serial representation of data recording (data bits
are aligned in a row one after another in tracks)
 Can have from 4 to 30 tracks, depending on the tape
drive
 Depending on the tape drive, the read/write head
reads/writes data on one/two/four tracks at a time
 Eliminates the need for the start/stop operation of
traditional tape drives
Quarter-inch Streamer Tape
Slide 25/117
Ref. Page 126

 Can read/write data more efficiently than the
traditional tape drives because there is no start/stop
mechanism
 Make more efficient utilization of tape storage area
than traditional tape drives because IBGs are not
needed
 The standard data formats used in these tapes is
known as the QIC standard
Quarter-inch Streamer Tape
Slide 26/117
Ref. Page 126

1 0 1 1 0 0 1 1 1 0 1 0 .
. .
Unused
portion
of the
tape
0 0 1 0 1 0 0 1 1 1 0 1 .
Unused
portion
of the
tape
Recording area
begins here
Recording area
ends here
Tracks
1
2
3
4
5
6
7
8
Quarter-inch Streamer Tape (Example)
Slide 27/117
Ref. Page 126

 Uses 4mm wide tape ribbon sealed in a cartridge
 Has very high data recording density
 Uses a tape drive that uses helical scan technique for
data recording, in which two read heads and two write
heads are built into a small wheel
 DAT drives use a data recording format called Digital
Data Storage (DDS), which provides three levels of
error-correcting code
 Typical capacity of DAT cartridges varies from
4 GB to 14 GB
4mm Digital Audio Tape (DAT)
Slide 28/117
Ref. Page 126

Moving tape
Read head B
Write head B
Read head A
scan
Write head A
Spinning
helical
Shaft
The Helical Scan Techniques
Used in DAT Drives
Slide 29/117
Ref. Page 126

 Storage capacity is virtually unlimited because as many
tapes as required can be used for storing very large
data sets
 Cost per bit of storage is very low for magnetic tapes.
 Tapes can be erased and reused many times
 Tape reels and cartridges are compact and light in
weight
 Easy to handle and store.
 Very large amount of data can be stored in a small
storage space
Advantages of Magnetic Tapes
Slide 30/117
Ref. Page 126

 Compact size and light weight
 Magnetic tape reels and cartridges are also easily
portable from one place to another
 Often used for transferring data and programs from
one computer to another that are not linked together
Advantages of Magnetic Tapes
Slide 31/117
Ref. Page 126

 Due to their sequential access nature, they are not
suitable for storage of those data that frequently
require to be accessed randomly
 Must be stored in a dust-free environment because
specks of dust can cause tape-reading errors
 Must be stored in an environment with properly
controlled temperature and humidity levels
 Tape ribbon may get twisted due to warping, resulting
in loss of stored data
 Should be properly labeled so that some useful data
stored on a particular tape is not erased by mistake
Limitations of Magnetic Tapes
Slide 32/117
Ref. Page 126

 For applications that are based on sequential data
processing
 Backing up of data for off-line storage
 Archiving of infrequently used data
 Transferring of data from one computer to another that
are not linked together
 As a distribution media for software by vendors
Uses of Magnetic Tapes
Slide 33/117
Ref. Page 126

Illustrating the use of tapes in a sequential application.
Processing
Inventory
master file
Transaction file
New inventory
master file
New transaction file
New inventory
master file
Next
processing
Uses of Magnetic Tapes
Slide 34/117
Ref. Page 126

Magnetic Disks

 Commonly used direct-access secondary storage device.
 Physically, a magnetic disk is a thin, circular
plate/platter made of metal or plastic that is usually
coated on both sides with a magnetizable recording
material such as iron-oxide
 Data are recorded on the disk in the form of tiny
invisible magnetized and non-magnetized spots
(representing 1s and 0s) on the coated surfaces of the
disk
 The disk is stored in a specially designed protective
envelope or cartridge, or several of them are stacked
together in a sealed, contamination-free container
Magnetic Disk - Basics
Slide 36/117
Ref. Page 129

 A disk’s surface is divided into
a number of invisible
concentric circles called tracks
 The tracks are numbered
consecutively from outermost
to innermost starting from
zero
 The number of tracks on a
disk may be as few as 40 on
small, low-capacity disks, to
several thousand on large,
high-capacity disks
Magnetic Disk – Storage Organization
Illustrates the Concept of Tracks
… …
Track
199
200
Tracks
Track 000
Slide 37/117
Ref. Page 130

Illustrates the Concept of Sectors
A sector
 Each track of a disk is
subdivided into sectors
 There are 8 or more
sectors per track
 A sector typically contains
512 bytes
 Disk drives are designed to
read/write only whole
sectors at a time
Slide 38/117
Ref. Page 130

Disk Pack
Slide 39/117
Ref. Page 130
 Data is accessed from a disk by specifying its disk address
 It is comprised of sector number
, track number
, and surface
number
 Operating systems combine two or more sectors to form a cluster
 In this case, the smallest unit of data access from a disk is a
cluster, instead of a sector
 Read/write operations read/write a whole cluster at a time
 Multiple disks are stacked together as a disk pack
 Disk pack is sealed and mounted on a disk drive consisting of a
motor to rotate the disk pack about its axis
 Disk drive has an access arms assembly having separate
read/write heads for each surface of the disk pack

Cylinder-Head-Sector (CHS)
Slide 40/117
Ref. Page 130
 Corresponding tracks on all recording surfaces of a disk
pack together form a cylinder
 Addressing scheme is called CHS (Cylinder-Head-Sector)
addressing
 It is also known as disk geometry

(Illustrates the Concept of Cylinder)
No. of disk platters = 4, No. of usable surfaces = 6. A set of corresponding
tracks on all the 6 surfaces is called a cylinder.
Central shaft
Upper surface
not used
Surface - 0
Surface - 1
Surface - 2
Surface - 3
Lower surface
not used
Surface - 4
Surface - 5
Slide 41/117
Ref. Page 130
Cylinder
Access arms assembly
Direction of movement of
access arms assembly
Read/Write head

Storage capacity of a disk system = Number of recording surfaces
 Number of tracks per surface
 Number of sectors per track
 Number of bytes per sector
Slide 42/117
Ref. Page 130
Magnetic Disk – Storage Capacity

 Data is recorded on the tracks of a spinning disk surface and read
from the surface by one or more read/write heads
 Read/write heads are mounted on an access arms assembly
 Access arms assembly moves in and out
 Read/write heads move horizontally across the surfaces of the
disks
 In case of a disk pack all heads move together
 Read/write heads are of flying type
 They do not have direct contact with disk surfaces
Access Mechanism
Slide 43/117
Ref. Page 130

Magnetic Disk Pack – Access Mechanism
Central shaft
One read/write
head per surface
Access arms
assembly
Vertical cross section of a disk system. There is one read/write head per
recording surface
Direction of movement of
access arms assembly
Disk platters
.
.
.
Slide 44/117
Ref. Page 130

 Disk access time is the interval between the instant a
computer makes a request for transfer of data from a
disk system to the primary storage and the instant this
operation is completed
 Disk access time depends on the following three
parameters:
– Seek Time: It is the time required to position the
read/write head over the desired track, as soon as
a read/write command is received by the disk unit
– Latency: It is the time required to spin the desired
sector under the read/write head, once the
read/write head is positioned on the desired track
Magnetic Disk – Access Time
Slide 45/117
Ref. Page 130

– Transfer Rate: It is the rate at which data are
read/written to the disk, once the read/write head
is positioned over the desired sector
 As the transfer rate is negligible as compared to seek
time and latency,
Average access time
= Average seek time + Average latency
Magnetic Disk – Access Time
Slide 46/117
Ref. Page 130

 Process of preparing a new disk by the computer
system in which the disk is to be used.
 For this, a new (unformatted) disk is inserted in the disk
drive of the computer system and the disk formatting
command is initiated
 Low-level disk formatting
 Disk drive’s read/write head lays down a magnetic
pattern on the disk’s surface
 Enables the disk drive to organize and store the
data in the data organization defined for the disk
drive of the computer
Disk Formatting
Slide 47/117
Ref. Page 130

 OS-level disk formatting
 Creates the File Allocation T
able (FAT) that is a
table with the sector and track locations of data
 Leaves sufficient space for FAT to grow
 Scans and marks bad sectors
 One of the basic tasks handled by the computer’s
operating system
 Enables the use of disks manufactured by third party
vendors into one’s own computer system
Disk Formatting
Slide 48/117
Ref. Page 130

 Unit used for reading/writing of data on/from a
magnetic disk
 Contains all the mechanical, electrical and electronic
components for holding one or more disks and for
reading or writing of information on to it
Magnetic Disk – Disk Drive
Slide 49/117
Ref. Page 130

 Although disk drives vary greatly in their shape, size
and disk formatting pattern, they can be broadly
classified into two types:
– Those with interchangeable magnetic disks,
which allow the loading and unloading of
magnetic disks as and when they are needed for
reading/writing of data on to them
– Those with fixed magnetic disks, which come
along with a set of permanently fixed disks. The
disks are not removable from their disk drives
Magnetic Disk – Disk Drive
Slide 50/117
Ref. Page 130

 Disk drive is connected to and controlled by a disk
controller, which interprets the commands for
operating the disk drive
 Typically supports only read and write commands,
which need disk address (surface number
,
and sector number) as
cylinder/track number
,
parameters
 Connected to and controls more than one disk drive, in
which case the disk drive number is also needed as a
parameters of read and write commands
Magnetic Disk – Disk Controller
Slide 51/117
Ref. Page 130

Magnetic Disks
Zip/Bernoulli Disks Disk Packs Winchester Disks
Types of Magnetic Disks
Slide 52/117
Ref. Page 130

 Round, flat piece of rigid metal (frequently aluminium)
disks coated with magnetic oxide
 Come in many sizes, ranging from 1 to 14-inch diameter.
 Depending on how they are packaged, hard disks are of
three types:
 Zip/Bernoulli disks
 Disk packs
 Winchester disks
 Primary on-line secondary storage device for most
computer systems today
Hard Disks
Slide 53/117
Ref. Page 130

 Uses a single hard disk platter encased in a plastic
cartridge
 Disk drives may be portable or fixed type
 Fixed type is part of the computer system, permanently
connected to it
 Portable type can be carried to a computer system,
connected to it for the duration of use, and then can be
disconnected and taken away when the work is done
 Zip disks can be easily inserted/removed from a zip drive
just as we insert/remove floppy disks in a floppy disk
drive
Zip/Bernoulli Disks
Slide 54/117
Ref. Page 130

 Uses multiple (two or more) hard disk platters
mounted on a single central shaft
 Disk drives have a separate read/write head for each
usable disk surface (the upper surface of the top-most
disk and the lower surface of the bottom most disk is
not used)
 Disks are of removable/interchangeable type in the
sense that they have to be mounted on the disk drive
before they can be used, and can be removed and
kept off-line when not in use
Disk Packs
Slide 55/117
Ref. Page 130

 Uses multiple (two or more) hard disk platters
mounted on a single central shaft
 Hard disk platters and the disk drive are sealed
together in a contamination-free container and cannot
be separated from each other
Winchester Disks
Slide 56/117
Ref. Page 130

 For the same number of disks, Winchester disks have
larger storage capacity than disk packs because:
– All the surfaces of all disks are used for data
recording
They employ much greater precision of data recording,
resulting in greater data recording density
 Named after the 30-30 Winchester rifle because the early
Winchester disk systems had two 30-MB disks sealed
together with the disk drive
Winchester Disks
Slide 57/117
Ref. Page 130

 More suitable than magnetic tapes for a wider range of
applications because they support direct access of data
 Random access property enables them to be used
simultaneously by multiple users as a shared device. A
tape is not suitable for such type of usage due to its
sequential-access property
 Suitable for both on-line and off-line storage of data
Advantages of Magnetic Disks
Slide 58/117
Ref. Page 130

 Except for the fixed type Winchester disks, the storage
capacity of other magnetic disks is virtually unlimited
as many disks can be used for storing very large data
sets
 Due to their low cost and high data recording densities,
the cost per bit of storage is low for magnetic disks.
 An additional cost benefit is that magnetic disks can be
erased and reused many times
 Floppy disks and zip disks are compact and light in
weight. Hence they are easy to handle and store.
 Very large amount of data can be stored in a small
storage space
Slide 59/117
Ref. Page 130

 Due to their compact size and light weight, floppy disks
and zip disks are also easily portable from one place to
another
 They are often used for transferring data and programs
from one computer to another, which are not linked
together
 Any information desired from a disk storage can be
accessed in a few milliseconds because it is a direct
access storage device
Slide 60/117
Ref. Page 130

 Data transfer rate for a magnetic disk system is
normally higher than a tape system
 Magnetic disks are less vulnerable to data corruption
due to careless handling or unfavorable temperature
and humidity conditions than magnetic tapes
Slide 61/117
Ref. Page 130

 Although used for both random processing and
sequential processing of data, for applications of the
latter type, it may be less efficient than magnetic
tapes
 More difficult to maintain the security of information
stored on shared, on-line secondary storage devices,
as compared to magnetic tapes or other types of
magnetic disks
Limitations of Magnetic Disks
Slide 62/117
Ref. Page 130

 For Winchester disks, a disk crash or drive failure often
results in loss of entire stored data. It is not easy to
recover the lost data. Suitable backup procedures are
suggested for data stored on Winchester disks
 Some types of magnetic disks, such as disk packs and
Winchester disks, are not so easily portable like
magnetic tapes
 On a cost-per-bit basis, the cost of magnetic disks is
low, but the cost of magnetic tapes is even lower
Slide 63/117
Ref. Page 130

 Must be stored in a dust-free environment
 Floppy disks, zip disks and disk packs should be
labeled properly to prevent erasure of useful data by
mistake
Slide 64/117
Ref. Page 130

 For applications that are based on random data
processing
 As a shared on-line secondary storage device.
Winchester disks and disk packs are often used for
this purpose
 As a backup device for off-line storage of data. Floppy
disks, zip disks, and disk packs are often used for this
purpose
Uses of Magnetic Disks
Slide 65/117
Ref. Page 130

 Archiving of data not used frequently, but may be
used once in a while. Floppy disks, zip disks, and
disk packs are often used for this purpose
 Transferring of data and programs from one
computer to another that are not linked together. Zip
disks are often used for this purpose
Uses of Magnetic Disks
Slide 66/117
Ref. Page 130

Optical Disks

 Consists of a circular disk, which is coated with a thin
metal or some other material that is highly reflective
 Laser beam technology is used for recording/reading
of data on the disk
 Also known as laser disk / optical laser disk, due to
the use of laser beam technology
 Proved to be a promising random access medium for
high capacity secondary storage because it can store
extremely large amounts of data in a limited space
Optical Disk – Basics
Slide 68/117
Ref. Page 137

 Has one long spiral track, which starts at the outer edge
and spirals inward to the center
 Track is divided into equal size sectors
Difference in track patterns on optical and magnetic disks.
(a) Track pattern on an optical disk (b) Track pattern on a magnetic disk
Optical Disk – Storage Organization
Slide 69/117
Ref. Page 138

Storage capacity of an optical disk
= Number of sectors
 Number of bytes per sector
The most popular optical disk uses a disk of 5.25 inch
diameter with formatted storage capacity of around 650
Megabytes
Optical Disk – Storage Capacity
Slide 70/117
Ref. Page 139

Optical Disk – Access Mechanism
Land
Laser
beam
source
Laser beam is
scattered by a pit
Pit
Land
Pit Pit
Prism Sensor Prism Sensor
Laser beam is
reflected by a land
Slide 71/117
Ref. Page 139
Land
Laser
beam
source

 With optical disks, each sector has the same length
regardless of whether it is located near or away from
the disk’s center
 Rotation speed of the disk must vary inversely with
the radius. Hence, optical disk drives use a constant
linear velocity (CLV) encoding scheme
 Leads to slower data access time (larger access time)
for optical disks than magnetic disks
 Access times for optical disks are typically in the
range of 100 to 300 milliseconds and that of hard
disks are in the range of 10 to 30 milliseconds
Optical Disk – Access Time
Slide 72/117
Ref. Page 140

 Uses laser beam technology for reading/writing of data
 Has no mechanical read/write access arm
 Uses a constant linear velocity (CLV) encoding scheme,
in which the rotational speed of the disk varies inversely
with the radius
Optical Disk Drive
Slide 73/117
Ref. Page 140

Optical Disk Drive
Tray
eject
button
Light indicator
Volume control button used
when the drive is used to play
an audio CD
Optical disk tray
Is placed on top
of this groove
Optical disk
Direction
of movement
of the tray
Headphone socket
enables a user to
plug-in headphones
to recorded sound
when the drive is
used to play audio
CDs.
Slide 74/117
Ref. Page 140

The types of optical disks in use today are:
CD-ROM
 Stands for Compact Disk-Read Only Memory
 Packaged as shiny, silver color metal disk of 5¼
inch (12cm) diameter, having a storage capacity of
about 650 Megabytes
 Disks come pre-recorded and the information
stored on them cannot be altered
 Pre-stamped (pre-recorded) by their suppliers, by a
process called mastering
Types of Optical Disks
Slide 75/117
Ref. Page 140

 Provide an excellent medium to distribute large
amounts of data in electronic dorm at low cost.
 A single CD-ROM disk can hold a complete
encyclopedia, or a dictionary, or a world atlas, or
biographies of great people, etc
 Used for distribution of electronic version of
conference proceedings, journals, magazines,
books, and multimedia applications such as video
games
 Used by software vendors for distribution of
software to their customers
Slide 76/117
Ref. Page 140

WORM Disk / CD-Recordable (CD-R)
 Stands for Write Once Read Many. Data can be written
only once on them, but can be read many times
 Same as CD-ROM and has same storage capacity
 Allow users to create their own CD-ROM disks by using
a CD-recordable (CD-R) drive that can be attached to
a computer as a regular peripheral device
 Data to be recorded can be written on its surface in
multiple recording sessions
Slide 77/117
Ref. Page 140

 Sessions after the first one are always additive
and cannot alter the etched/burned information of
earlier sessions
 Information recorded on them can be read by any
ordinary CD-ROM drive
 They are used for data archiving and for making a
permanent record of data. For example, many
banks use them for storing their daily transactions
Slide 78/117
Ref. Page 140

CD-Read/Write (CD-RW)
 Same as CD-R and has same storage capacity
 Allow users to create their own CD-ROM disks by
using a CD-recordable (CD-R) drive that can be
attached to a computer as a regular peripheral
device
 Data to be recorded can be written on its surface in
multiple recording sessions
 Made of metallic alloy layer whose chemical
properties are changed during burn and erase
 Can be erased and written afresh
Slide 79/117
Ref. Page 140

Slide 80/117
Ref. Page 140
 Digital Video (or Versatile) Disk (DVD)
 DVD is a standard format for distribution and interchange of
digital content
 Pits are about 4½ times as dense on a DVD as on a CD
 Stores about seven times more data per side
 Greater density is due to a more efficient data modulation
scheme and error correction method
 DVD follows Eight-to-Fourteen Modulation Plus (EFMPlus)
encoding
 Two variants of DVD – single-layer disk and double-layer
disk
 Single-layer disk has storage capacity of 4.7 GB
 Double-layer disk has storage capacity of 8.5 GB(Continued on next slide)

 Physical layer specification defines following types of physical
media:
 DVD-ROM: Used for mass distribution of pre-recorded
software programs and multimedia
 DVD-RAM: Used for general read-and-write applications
 DVD-R: Used for low-cost, write-once recordable media
 DVD-RW: Rewritable version of DVD-R
Slide 81/117
Ref. Page 140

 Logical layer specification defines recording formats for video
and audio data
 DVD-video
 Now the most dominant movie storage format
 Allows storage of video in 4:3 or 16:9 aspect ratio in
MPEG-2 video format
 Audio is usually Dolby Digital (AC-3) or Digital Theater
System (DTS)
 Can be either monaural or 5.1 surround sound
 It has multiple selectable language soundtracks and
subtitles
Slide 82/117
Ref. Page 140

 DVD-audio
 Offers multiple choices of sampling rate and number of bits
per sample
 Specification also supports up to six channels of
multichannel
 Surround sound with 24-bit sampling at a 48 KHz rate
 Provision for visual menus, still images, and video to
accompany the audio program
Slide 83/117
Ref. Page 140

Advantages of Optical Disks
Slide 84/117
Ref. Page 140
 Cost-per-bit of storage for optical disks is very low
 Use of a single spiral track makes optical disks an ideal
storage medium for reading large blocks of sequential data
 Optical disk drives do not have any mechanical read/write
heads
 Optical disks have data storage life in excess of 30 years
 Data once stored on CD-ROM/WROM disks becomes
permanent, there is no danger of losing stored data
 Due to their compact size and lightweight, optical disks are
easy to handle
 Can use a computer having a CD-ROM drive, a sound card,
and speakers as a music system
 Can use a computer having a DVD drive to play DVDs

Limitations of Optical Disks
Slide 85/117
Ref. Page 140
 Data access speed of optical disks is slower than that of
magnetic disks
 Optical disks require more complicated drive mechanism
 Optical disk is prone to scratches, dust, sticky prints etc.
while handling
 Optical disks must be labeled properly

Uses of Optical Disks
Slide 86/117
Ref. Page 140
 For distributing large amounts of data at low cost
 For distribution of electronic version of conference
proceedings, journals, magazines, books, product catalogs,
etc.
 For distribution of audio such as songs
 For distribution of new or upgraded versions of software
products
 For storage and distribution of wide variety of multimedia
applications
 For archiving of data not used frequently
 To make permanent storage of proprietary information
 DVDs have become a popular medium for distribution of
movies

Memory Storage Devices

 A new breed of electronic secondary storage devices
 They are faster and more reliable than
secondary storage devices because they do
mechanical component
conventional
not use any
 Some popular ones are:
 Solid State Drive (SSD)
 Flash Drive (Pen Drive)
 Memory Card (SD/MMC)
Slide 88/117
Ref. Page 144

 Is a new alternative to Hard Disk Drive (HDD) based
secondary storage in computer systems
 It consists of interconnected flash memory chips
 It is built entirely out of semiconductors (hence the name
solid state) and does not have any moving parts
 It is more expensive than HDD of same capacity, but is more
reliable, rugged, compact and faster in data access speed
Solid State Drive (SSD)
Slide 89/117
Ref. Page 144

(a) Hard Disk Drive (HDD) (b) Solid State Drive (SSD)
Figure 8.16. Inside view of HDD and SSD. When packaged in an enclosure, both may
look similar from outside, but internally their design is very different.
Inside View of HDD and SSD
Slide 90/117
Ref. Page 144

Flash Drive (Pen Drive)
 Flash drive is a compact device of the size of a pen
 Comes in various shapes and stylish designs
 May have different added features
 It is a plug-and-play device
 Plugs into a USB (Universal Serial Bus) port
 Computer detects it automatically as a removable drive
 Once done, it can be simply plugged out of the USB port
 Flash drive does not require any battery, cable, or software
 It is the most preferred external data storage
Slide 91/117
Ref. Page 144

Slide 92/117
Ref. Page 144
 It is based on flash memory storage technology
 Flash memory is non-volatile, Electrically Erasable
Programmable Read Only Memory (EEPROM) chip
 It is a highly durable solid-state storage having data
retention capability of more than 10 years

A Flash Drive (Pen Drive)
Write protect tab
Cover
Main body
Read/write
light indicator
Part that plugs into a
computer’s USB port
Strap hole (can be used
to hang it With a string
Slide 93/117
Ref. Page 144

cards are available as removable
storage device in different types of electronic equipment
 The most popular ones are Secure Digital (SD) and
Multimedia Card (MMC)
 These cards are used in various types of digital devices
 Each of these cards has its own interface and specific design
features
Memory Card (SD/MMC)
 Flash memory based
Slide 94/117
Ref. Page 144

Flash Memory Based Card
Write-protect lock
(slides down/up to lock/
unlock write operation)
Direction notch
(guides which side of the
card should be inserted first
in the electronic equipment)
Slide 95/117
Ref. Page 144
Vendor name
Storage
capacity

 Both SSD and HDD coexist in such systems
 The two commonly used configurations are:
 Dual-drive system
 SSD as cache and HDD as normal secondary storage
Hybrid Secondary Storage Drives
Slide 96/117
Ref. Page 144

Mass Storage Devices

 As the name implies, these are storage systems
having several trillions of bytes of data storage
capacity
 They use multiple units of a storage media as a single
secondary storage device
 The three commonly used types are:
1. Disk array, which uses a set of magnetic disks
2. Automated tape library, which uses a set of
magnetic tapes
3. CD-ROM Jukebox, which uses a set of CD-ROMs
 They are relatively slow having average access times
in seconds
Mass Storage Devices
Slide 98/117
Ref. Page 148

 Set of hard disks and hard disk drives with a
controller mounted in a single box, forming a single
large storage unit
 It is commonly known as a RAID (Redundant Array
of Inexpensive Disks)
 As a secondary storage device, provides enhanced
storage capacity, enhanced performance, and
enhanced reliability
Disk Array
Slide 99/117
Ref. Page 148

 Enhanced storage capacity is achieved by using
multiple disks
 Enhanced performance is achieved by using parallel
data transfer technique from multiple disks
 Enhanced reliability is achieved by using techniques
such as mirroring or striping
 In mirroring, the system makes exact copies of files
on two hard disks
 In striping, a file is partitioned into smaller parts and
different parts of the file are stored on different disks
Disk Array
Slide 100/117
Ref. Page 148

RAID Controller
Computer
Multiple
disks
A RAID Unit
Slide 101/117
Ref. Page 148

 Set of magnetic tapes and magnetic tape drives with
a controller mounted in a single box, forming a
single large storage unit
 Large tape library can accommodate up to several
hundred high capacity magnetic tapes bringing the
storage capacity of the storage unit to several
terabytes
 Typically used for data archiving and as on-line data
backup devices for automated backup in large
computer centers
Automated Tape Library
Slide 102/117
Ref. Page 148

 Set of CD-ROMs and CD-ROM drives with a controller
mounted in a single box, forming a single large
storage unit
 Large CD-ROM jukebox can accommodate up to
several hundred CD-ROM disks bringing the storage
capacity of the storage unit to several terabytes
 Used for archiving read-only data in such
applications as on-line museums, on-line digital
libraries, on-line encyclopedia, etc
CD-ROM Jukebox
Slide 103/117
Ref. Page 148

Data Backup

What is Data Backup?
Slide 105/117
Ref. Page 150
 Data backup is the process of creating a copy of some
data from an on-line storage device to a secondary
storage backup device
 Copy is used for off-line storage
 It can be retrieved from the backup device and stored
back on the on-line storage device

Why Backup Data?
Slide 106/117
Ref. Page 150
 On-line storage device can be damaged or lost in any of
the following ways
 A disk crash
 A virus attack
 A hardware malfunction
 An unintended accidental deletion of useful files
 A natural disaster like fire or earthquake damaging the
computer system
 Amount of time it would take us to re-create all files is far
greater than the few minutes it takes to back them up

Types of Backup
Slide 107/117
Ref. Page 150
 Full backup
 All data on an on-line secondary storage device is copied
on a backup device at the time of backup
 Full backup is simpler and a little safer
 T
o restore a particular file we need to search for it at
only one place
 Incremental backup
 Only newly created files or files that have been changed
since the last backup are copied on backup device from
on-line secondary storage device at the time of backup
 Incremental backup is faster than full backup
 To restore a particular file we need to search for it on
several backups

Backup Policy
Slide 108/117
Ref. Page 150
 What is the periodicity of backup?
 Normally, periodicity depends on the nature of usage
and criticality of stored data
 Whether to take full or incremental backup?
 If a user creates only a few files, daily/weekly
incremental backup is sufficient
 If a user frequently creates many files, weekly full
backups are safer
 What storage media to use for backup?
 Small backups are taken normally on CD/pen drives
 Whereas larger backups are taken on magnetic tapes
(Continued on next slide…)

 Who takes backup?
 In case of PCs, it is the PC user
 In case of large computer centers, normally the
administrators of the system
 Where to store the backup media with the backed up data?
 It is suggested to store the backup media in a building
that is away from the building where backup was taken
to protect the data against natural calamities
Backup Policy
Slide 109/117
Ref. Page 150

On-line, Near-line, and
Off-line Storage

Slide 111/117
On-line, Near-line, and Off-line Storage
 On-line storage
 On-line storage device is under direct control of the
processing unit of the computer
 Near-line storage
 Near-line storage device is an intermediate storage
between on-line storage and off-line storage
 Off-line storage
 Off-line storage is not under direct control of any
computer
Ref. Page 151

Hierarchical Storage
System (HSS)

Hierarchical Storage System (HSS)
Slide 113/117
Ref. Page 153

Hierarchical Storage Management (HSM)
Slide 114/117
Ref. Page 153
 HSM software is an integral part of an HSS
 It automatically moves the more frequently used data (files)
to higher layers of the HSS (having faster access time) from
its lower layers (having slower access time)
 For this, it continuously monitors the data access pattern by
the users of HSS

Hierarchical Storage Management (HSM)
Slide 115/117
Ref. Page 153
 Important issue in HSS is how to decide which data should
reside on which storage tier
 This is handled automatically by a software called Hierarchical
Storage Management (HSM)
 All HSSs have HSM software, which monitors the way data is
used, and makes decisions as to which data can be moved
safely to slower devices
 Frequently used data are stored on on-line storage
 Moved eventually by HSM to near-line storage if they are not
accessed for a certain period
 Users do not need to know or keep track of where the
accessed data is stored and how to get it back
 Computer retrieves the data automatically

 Automated tape library
 Auxiliary memory
 Block
 Blocking
 Blocking factory
 CD-ROM
 CD-ROM jukebox
 Check bit
 Cylinder
 Data transfer rate
 Direct access device
 Disk array
 Disk controller
 Disk drive
 Disk formatting
 Disk pack
 DVD
 Even parity
 File Allocation Tube (FAT)
 Floppy disk
 Hard disk
 Hard Disk Drive (HDD)
 Hierarchical Storage System (HSS)
 Inter-block gap (IBG)
 Inter-record gap (IRG)
 Land
 Latency
 Magnetic disk
 Magnetic tape
 Magnetic tape drive
 Mass storage devices
 Master file
 Odd parity
 Off-line storage
 On-line storage
 Optical disk
 Parallel representation
 Parity bit
 Pit
Key Words/Phrases
Slide 116/117

 QIC Standard
 Record
 Redundant Array of Inexpensive Disks (RAID)
 Secondary storage
 Sector
 Seek time
 Sequential access device
 Solid State Drive (SSD)
 Storage hierarchy
 Tape controller
 Track
 Transaction file
 Winchester disk
 WORM disk
 Zip disk
Key Words/Phrases
Slide 117/117

Chapter 09: Input-Output Devices Slide 1/73
Pradeep K. Sinha
Priti Sinha
Chapter 9
Input-Output
Devices

Slide 2/73
Chapter 09: Input-Output Devices
 Input/Output (I/O) devices
 Commonly used input devices
 Commonly used output devices
 Other concepts related to I/O devices
Learning Objectives

I/O Devices
Ref. Page 158 Chapter 09: Input-Output Devices Slide 3/73
 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 results of processing from
primary storage to users

Role of I/O Devices
Input
data
from
external
world
Results of
processing
in human
acceptable
form
Input data coded
in internal form
Processed data
in internal form
CPU
and
Memory
Input
Devices
Output
Devices

Chapter 10: Computer Software Slide 5/36
Input Devices

Commonly Used Input Devices
 Keyboard devices
 Point-and-draw devices
 Data scanning devices
 Digitizer
 Electronic cards based devices
 Speech recognition devices
 Vision based devices

Keyboard Devices
 Allow data entry into a computer system by pressing a
set of keys (labeled buttons) neatly mounted on a
keyboard connected to a computer system
 101-keys QWERTY keyboard is most popular

The Layout of Keys on a
QWERTY Keyboard

Point-and-Draw Devices
 Used to rapidly point to and select a graphic icon or
menu item from multiple options 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

Mouse
 Mouse is the most popular point-and-draw device
 Mouse is a small hand-held device that fits comfortably in a
user’s palm
 It rolls on a small bearing and has one or more buttons 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 called hot
spot

Click Button
Mouse

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 wheels that spin to
match the speed of the ball. Each wheel of the mouse is
connected to a sensor
 As the mouse ball rolls when a user moves the mouse, the
sensors detect how much each wheel spins and send this
information to the computer in the form of changes to the
current position

Types of Mouse
 Optical mouse
 An optical mouse has no mechanical parts like the ball and
wheels
 It has a built-in photo-detector
 When a user moves the mouse on a special pad with gridlines,
the photo-detector senses 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 buttons mouse
 Mouse can have one, two, or three buttons
 With a mouse having multiple buttons, the leftmost button is
the main button that allows for most mouse operations
 A user can configure another button as main button

 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 a computer
 Wired and cordless mouse
 Wired mouse is connected to a computer with a small cord
 A cordless mouse operates by transmitting a low-intensity
radio or infrared signal
Types of Mouse

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

Click button
Ball is rolled
with fingers
Trackball

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 holds the stick in his/her 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 graphics cursor at a desired
position
 Joysticks 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

Click button
Socket
Light
indicator
Stick
Joystick

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 transmits 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
 User writes on the pad with the electronic pen whatever data he/she
wants to input to the computer
 This input device with handwriting recognition software is used often as
an easy way to input text and freehand drawings into computer

Touch Screen
 Most simple, intuitive, and easiest to learn of all input
devices
 Enables users 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 automatic teller machine or ATM)

Data Scanning Devices
 Input devices that enable direct data entry into a
computer system 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 timeliness
of the information processed
 Demand high quality of input documents
 Some data scanning devices are also capable of
recognizing marks or characters
 Form design and ink specification usually becomes more
critical for accuracy

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

A flat-bed scanner A hand-held scanner
Two Common Types of Image Scanners

Optical Character Recognition (OCR)
Device
 Scanner equipped with a character recognition software
(called OCR software) that converts the bit map images
of characters to equivalent ASCII codes
 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)

Optical Mark Reader (OMR)
 Scanner capable of recognizing 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 focusing
a light on the page being scanned and detecting the
reflected light pattern from the marks

(a) Question sheet
A sample use of OMR for grading tests with objective type questions
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
2. The full form of CPU is:
a) Cursor Positioning Unit
b) Central Power Unit
c) Central Processing Unit
d) None of the above
3. Which is the largest unit of storage among the following:
a) Terabyte
b) Kilobyte
c) Megabyte
d) Gigabyte
(b) Pre-printed answer sheet
1.
a b c d
2.
a b c d
3.
a b c d
Indicates direction in which the
sheet should be fed to the OMR
Sample Use of OMR

Bar-code Reader
 Scanner used for reading (decoding) bar-coded data
 Bar codes represent 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

21000 67520
Product category character
0 – grocery products
3 – drugs and health related
products, etc.
Manufacturer/supplier
identification number Specific product code
number
0
An Example of UPC Bar Code

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

 It consists of numerals 0 to 9 and four special characters
 MICR is not adopted by other industries because it supports only
14 symbols
MICR Character Set (E13B Font)

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

Stylus
Digitizing tablet
Table top
Cursor
Digitizer

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

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

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

 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
Uses of Speech Recognition Systems

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

Output Devices

Commonly Used Output Devices
 Monitors
 Printers
 Plotters
 Screen image projector
 Voice response systems

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
 Temporary in nature and vanish after use
 Examples are output displayed on a terminal screen or spoken out
by a voice response system
 Hard-copy output
 Produced on a paper or some material that can be touched and
carried for being shown to others
 Permanent in nature and can be kept in paper files or can be
looked at a later time when the person is not using the computer
 Examples are output produced by printers or plotters on paper

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

Monitor
Keyboard
A video display terminal consists of a monitor and a keyboard
Monitors

 Cathode-ray-tube (CRT) 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 systems like notebook computers. Now they
are also used with non-portable desktop computer
systems because they occupy less table space.
Types of Monitors

CRT Monitor LCD Monitor
CRT and LCD Monitors

Printers
Most common output devices for producing hard-copy
output

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

ABCDEFGHIJKLM
NOPQRSTUVWXYZ
0123456789- . ,
&/$*#%@=(+)
Formation of Characters as a pattern of dots

Dot Matrix Printer Printing Mechanism
Paper below
the ribbon
Direction of movement
of print head pins
Print head
pins
Inked
ribbon
Print head
Direction of movement
of print head
Printed characters
formed of dots in a 5
x 7 matrix

Dot Matrix Printer

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

 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
Inkjet Printers

An Inkjet Printer

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

Printing Mechanism of a Drum Printer
Paper
Ribbon
W W W W W W W W W W W W W W
V V V V V V V V V V V V V V
U U U U U U U U U U U U U U
T T T T T T T T T T T T T T
S S S S S S S S S S S S S S
R R R R R R R R R R R R R R
Q Q Q Q Q Q Q Q Q Q Q Q Q Q
P P P P P P P P P P P P P P
O O O O O O O O O O O O O O
N N N N N N N N N N N N N N
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.
Solid cylindrical
drum with
embossed
characters
Hammers (one for
each band)

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

 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
 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
Chain/Band Printers

Printing Mechanism of a Chain/Band Printer
One section of 48
characters
Ribbon
Paper
Direction of
movement
of the chain
Hammers
132 print positions
Complete chain is
composed of five
sections of 48
characters each

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

 Can print many special characters, different sizes of
 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
Laser Printers

A Laser Printer

Plotters
 Plotters 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 made is placed over a drum that
can rotate in both clockwise and anti-clockwise
directions
 Flatbed plotter, in which the paper on which the
design has to be made is spread and fixed over a
rectangular flatbed table

Plotters
A flatbed plotter
Design drawn
on the paper
Paper
A drum plotter
Paper
Design drawn
on the paper

3D Printers
 They print (create) 3D objects
 They use Additive Manufacturing technique
 They follow a 3-step process:
1. First create a 3D digital file (3D model) of the object
2. Then slice the 3D model into horizontal layers
3. Then upload the sliced file and print

Types of 3D Printers
 3D printers mainly differ in the way they build an object layer-
by-layer and the material they use for manufacturing objects
 Some commonly used 3D printing technologies are:
 Fused Deposition Modeling (FDM)
 STereoLithography (STL)
 Digital Light Processing (DLP)
 Selective Layer Sintering (SLS)

Applications of 3D Printers
 Rapid prototyping
 Rapid manufacturing of customized designs
 Manufacturing body/engine parts
 Manufacturing implants and prosthetics
 Manufacturing hearing aid and dental appliances
 Manufacturing museum souvenirs

Fused Deposition Modeling (FDM)

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

Operations buttons
On/Off light indicator
Projection lens
Screen Image Projector

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

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.

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

 3D Printer
 Bard code reader
 Cathode Ray Tube (CRT)
 Chain/Band printer
 Data scanning device
 Digital Light Processing (DLP)
 Digitizer
 Digitizing tablet
 Dot-Matrix printer
 Drum plotter
 Drum printer
 Electronic card reader
 Electronic Pen
 Flatbed plotter
 Flatbed Scanner
 Fused Deposition Modeling (FDM)
 Graphical User Interface
 Hand-held scanner
 Hard-copy output
 Image Scanner
 Information Kiosk
 Inkjet printer
 Input/Output device
 Joystick
 Keyboard device
 Laser printer
 Magnetic-Ink Character Recognition
(MICR)
 Monitor
 Mouse
 Optical Character Recognition (OCR)
 Optical Mark Reader (OMR)
 Peripheral device
 Phonemes
 Plotter
 Point-and-draw device
 Printer
 QWERTY keyboard
 Screen Image Projector
Key Words/Phrases

 Selective Layer Sintering (SLS)
 Soft-copy output
 Speech synthesizer
 STereoLithography (STL)
 Stylus
 Touch Screen
 Trackball
 Universal Product Code (UPC)
 Video Display Terminal (VDT)
 Vision-input system
 Voice recognition device
 Voice reproduction system
 Voice response system
Key Words/Phrases

Chapter 10
Computer Software
Pradeep K. Sinha
Priti Sinha

Slide 2/37
Chapter 10: Computer Software
 Term “Software” and its relationship with “Hardware”
 Various types of software and their examples
 Relationship among hardware, system software,
application software, and users of a computer system
 Different ways of acquiring software
 Various steps involved in software development
 Software Engineering and CASE tools
 Firmware and Middleware
Learning Objectives

Software, Firmware
and Middleware

 Hardware refers to the physical devices of a
computer system.
 Software refers to a collection of programs,
procedures, and associated documents describing the
programs, and how they are to be used.
 Program is a sequence of instructions written in a
language that can be understood by a computer
 Software package is a group of programs that solve
a specific problem or perform a specific type of job
(for example, word-processing package)
Software

Relationship Between Hardware and
Software
 Both hardware and software are necessary for a
computer to do useful job. They are complementary
to each other
 Same hardware can be loaded with different software
to make a computer system perform different types
of jobs
 Except for upgrades, hardware is normally a one-
time expense, whereas software is a continuing
expense
 Upgrades refer to renewing or changing components
like increasing the main memory, or hard disk
capacities, or adding speakers, modems, etc.

Types of Software
Most software can be divided into two major categories:
 System software are designed to control the
operation and extend the processing capability of a
computer system
 Application software are designed to solve a
specific problem or to do a specific task

 Make the operation of a computer system more effective
and efficient
 Help hardware components work together and provide
support for the development and execution of application
software
 Programs included in a system software package are
called system programs and programmers who
prepare them are called system programmers
 Examples of system software are operating systems,
programming language translators, utility programs, and
communications software
System Software

 Solve a specific problem or do a specific task
 Programs included in an application software
package are called application programs and the
programmers who prepare them are called
application programmers
 Examples of application software are word
processing, inventory management, preparation of
tax returns, banking, etc.
Application Software

Logical System Architecture
USERS
APPLICATION SOFTWARE
SYSTEM SOFTWARE
HARDWARE
Physical devices/components of
the computer system
Software that constitute the operating and programming
environment of the computer system
Software that do a specific task or solve a specific problem
Users normally interact with the system via the user
interfaces provided by the application software

Firmware
 Firmware refers to a sequence of instructions (software)
substituted for hardware
 This software is stored in a read-only memory (ROM) chip of
the computer
 Initially, vendors supplied only system software in the form of
firmware
 Many vendors now supply even application programs as
firmware
 Firmware is frequently a cost-effective alternative to wired
electronic circuits
 Firmware has today made it possible to produce smart
machines of all types

Middleware
 Basic idea here is to have a separate software layer that acts
as “glue” between the client and server parts of an application
 Provides a programming abstraction as well as masks the
heterogeneity of underlying networks, hardware, and
operating systems
 This software layer is known as middleware because it sits in
the middle, between the operating system and applications
 Middleware is defined as a set of tools and data that helps
applications use networked resources and services

Two-tier, Client-server Architecture
Client part of
application software –
Includes user
interface, application
logic, messaging
services, and
management and
support services
Operating system and
network interfaces
Client computer
Server part of
Includes application-
specific services,
application logic,
messaging services,
and management and
support services
network interfaces
Server computer
Network connection

Three-tier, Client-server Architecture
Network connection
Client part of
Includes user interface
and business and
application logic
network interfaces
Client computer
Middleware services –
Includes APIs and
client part of
messaging,
management, and
support services
Server part of
Includes application -
specific services
network interfaces
Server computer
Middleware services –
Includes APIs and
server part of
messaging,
management, and
support services

Acquiring Software

Ways of Acquiring Software
 Buying pre-written software
 Ordering customized software
 Developing customized software
 Downloading public-domain software
Each of these ways of acquiring software has its own
advantages and limitations

Buying Pre-written Software
 Prepare a list of all available software packages that can
perform the desired task
 Select those software packages only that meet the system
specifications
 Choose the best one
 Find out the source from where you can purchase the finally
selected software at the cheapest price

Advantages and Limitations of
Buying Pre-written Software
 Usually costs less
 Planned activity can be stared almost immediately
 Often, operating efficiency and the capability to meet
specific needs of user more effectively in not as good
for pre-written software packages as for in-house
developed software packages

Ordering Customized Software
 If none of the available pre-written software packages meet
the specific requirements of a user it becomes necessary for
the user to create a customized software package
 If a team does not exist in-house, the user must get it
created by another organization by placing an order for it
 Following steps are followed for this:
 User prepares a list of all user requirements carefully
 User then floats a tender for inviting quotations for creation of
the requisite software
 After receiving the quotations, the user selects a few of them
for further interaction based on the cost quoted by them, their
reputation in the market, their submitted proposal, etc.
 User then personally interacts with the representative(s) of
each of the selected vendors

Ordering Customized Software
 User makes a final choice of the vendor to offer the contract for
creation of the requisite software
 Selected vendor then creates the software package and delivers
it to the user
 Vendor need not develop everything from scratch
 User may choose to place the order for both hardware and
software to a single vendor
 Vendor develops the software on the chosen hardware, and
delivers the software along with the hardware to the user
 This is referred to as an end-to-end solution or a turnkey solution

Advantages & Limitations of Ordering
Customized Software
 User need not maintain its own software development team,
which is an expensive affair
 User needs to always depend on the vendor for carrying out
the changes and the vendor may separately charge for
every request for change

Developing Customized Software
 If no pre-written software package meets the specific
requirements, and if the organization has in-house software
development team, it may choose to develop a customized
software package in-house
 Following steps are followed for in-house development of a
software package:
 Organization first constitutes a project team to develop the
software
 Team studies the requirements and plans functional modules
 It then analyzes which of the functional modules need to be
developed, and which of the functional modules’ requirements
are met with existing pre-written software
 Team next plans their programs and does coding, testing,
debugging, and documentation

Developing Customized Software
 Team then tests all the modules in an integrated manner
 Team then deploys the software for use by users
 Users then use the software and the project team members
responsible for maintenance activities maintain it

 Easier to carry out changes in the software, if it is
developed in-house
 Developing software in-house means a major
commitment of time, money, and resources
 In-house software development team needs to be
maintained and managed
Advantages & Limitations of Developing
Customized Software

Downloading Public-domain
Software
 Public-domain software is software available free or for a
nominal charge from the bulletin boards or user-group
libraries on the Internet
 Public-domain software is also referred to as shareware/
freeware
 They are also known as community-supported software as
mostly the authors do not support the product directly and
users of the software support and help each other
 Open Source Software (OSS): Usually, OSS allows a user to
download, view, modify, and distribute modified source code
to others

 Available for free or as shareware, and are usually accompanied
with source code
 Usually community-supported as author does not support users
directly
 Can be downloaded and used immediately
 They may not be properly tested before release
 Open Source Software (OSS) are becoming popular due to:
 Allows any user to download, view, modify, and redistribute
 User can fix bugs or change software to suit needs
 Copyright is protected for both original and subsequent
authors
 Not all open source software are free and vise-verse
Advantage & Limitations of Downloading
Public-domain Software

Software Development
Life Cycle (SDLC)

Software Development Life Cycle
(SDLC)
Requirement
specification
System analysis
and design
Implementation
Testing and
debugging
Deployment
Maintenance
Ref. Page 195

 Requirement specification
 Team defines all possible requirements of the software in this
phase
 System analysis and design
 Team studies the requirements specified in the first phase with
respect to available hardware and software technologies and
prepares a system design document
 Implementation
 This phase is also known as construction or code generation
because in this phase, the team constructs the various
software components specified in system design document
Ref. Page 195
Software Development Life Cycle (SDLC)

 Testing and debugging
 Team integrates the independently developed and tested
modules into a complete system
 Team then tests the integrated system to check if all modules
coordinate properly with each other
 Deployment
 Team deploys the software at user(s) site on (or along with)
associated hardware for use by intended user
 Maintenance
 Team fixes problems in the system in this phase
Ref. Page 195
Software Development Life Cycle (SDLC)

Software Engineering

What is Software Engineering?
Ref. Page 197
 Software is a set of computer programs, procedures, and
associated documents
 Engineering is systematic application of scientific knowledge
in creation and building of cost-effective solutions
 Software engineering is systematic application of principles
of computer science and mathematics in creation and
building of cost-effective software solutions

Need for Software Engineering
Ref. Page 197
 With software products growing in scale and complexity,
number of software developers involved in a software
development project has been increasing proportionately
 Managing the development of large software products and
maintaining them is a difficult task
 Progressively larger software products in sensitive
applications are being used
 Required correctness and reliability of software products is
increasing
 Quality and productivity demands for software products led
to the introduction of systematic practices (later on known as
software engineering practices)

Goals of Software Engineering
Ref. Page 197
 Correctness should be of very high degree
 Correctness refers to the degree to which a software product
performs its intended functions properly, consistently, and
predictably
 Usability should be of very high degree
 Usability refers to the ease with which a software product and
its associated documentation are usable
 Should be cost-effective
 Cost-effectiveness means that the total development and
operational costs of a software product should be as low as
possible

Principles of Software Engineering
Ref. Page 197
 Precise requirements definition
 Designer of a software product must define its requirements
precisely
 Modular structure
 Designer of a software product must structure it in a modular
fashion
 Modular design helps in distribution of development task of
different modules to different programmers
 Abstraction
 Software product should use abstraction and information hiding
 Object-oriented programming takes care of this aspect of
software engineering
 Abstraction helps in easy reusability of existing modules

Ref. Page 197
 Uniformity
 Software product should maintain uniformity in design, coding,
documentation, etc. Uniformity ensures consistency
 CASE (Computer Aided Software Engineering) tools
provide a wide range of features for creation of better and
more reliable software products
 Design specification tools
 Allow programmers to design visually screens, menus, database
tables, reports, dialog boxes, and other key components of a program
 Code generation tools
 Generate source code (programs) from the design specification of a
software product

Ref. Page 197
 Testing and debugging tools
 Help programmers in testing and debugging of their programs
 Source-code analysis tools
 Help in optimizing a program by pointing out unreachable lines of
code and functions that the program never uses (calls)
 Documentation tools
 Assist in automatic generation of technical documents for a software
product

 Application programmers
 Application programs
 Application software
 CASE tools
 Computer program
 Customized software
 Database
 Education software
 End-to-end solution
 Entertainment software
 Firmware
 Graphics software
 Hardware
 Middleware
 Open Source Software
 Personal assistance software
 Pre-written software
 Public-domain software
 Shareware
 Software
 Software Development
Life Cycle (SDLC)
 Software Engineering
 Software package
 Spreadsheet
 System programmers
 System programs
 System software
 Turnkey solution
 User-supported
software
 Utilities
 Waterfall model
 Word-processing
Key Words/Phrases

Chapter 11: Planning the Computer Program Slide 1/50
Chapter 11
Planning the
Computer Program
Pradeep K. Sinha
Priti Sinha

Slide 2/50
Chapter 11: Planning the Computer Program
 Programs must be planned before they are written
 Planning the logic of a computer program
 Commonly used tools for program planning
 Algorithm
 Flowchart
 Pseudocode
Learning Objectives

Purpose of Program
Planning and Algorithm

Purpose of Program Planning
Ref. Page 202
 To write a correct program, a programmer must write
each and every instruction in the correct sequence
 Logic (instruction sequence) of a program can be very
complex
 Hence, programs must be planned before they are
written to ensure program instructions are:
 Appropriate for the problem
 In the correct sequence

What is an Algorithm?
Ref. Page 203
 Algorithm refers to the logic of a program
 It is a step-by-step description of how to arrive at a solution
to a given problem
 Is defined as a sequence of instructions that when executed
in the specified sequence, the desired results are obtained
 Instructions must possess following characteristics:
 Each instruction should be precise and unambiguous
 Each instruction should be executed in a finite time
 No instruction should be repeated infinitely. This ensures that
the algorithm terminates ultimately
 After executing the instructions (when the algorithm
terminates), the desired results are obtained

Sample Algorithm (Example 1)
Ref. Page 204
There are 50 students in a class who appeared in their
final examination. Their mark sheets have been given to
you.
The division column of the mark sheet contains the
division (FIRST, SECOND, THIRD or FAIL) obtained by the
student.
Write an algorithm to calculate and print the total number
of students who passed in FIRST division.

Ref. Page 204
Step 1: Initialize Total_First_Division and
Total_Marksheets_Checked to zero.
Step 2: Take the mark sheet of the next student.
Step 3: Check the division column of the mark sheet to see if it is
FIRST, if no, go to Step 5.
Step 4: Add 1 to Total_First_Division.
Step 5: Add 1 to Total_Marksheets_Checked.
Step 6: Is Total_Marksheets_Checked = 50, if no, go to Step 2.
Step 7: Print Total_First_Division.
Step 8: Stop.

There are 100 employees in an organization. The organization
wants to distribute annual bonus to the employees based on their
performance. The performance of the employees is recorded in
their annual appraisal forms.
Every employee’s appraisal form contains his/her basic salary and
the grade for his/her performance during the year. The grade is of
three categories – ‘A’ for outstanding performance, ‘B’ for good
performance, and ‘C’ for average performance.
It has been decided that the bonus of an employee will be 100% of
the basic salary for outstanding performance, 70% of the basic
salary for good performance, 40% of the basic salary for average
performance, and zero for all other cases.
Write an algorithm to calculate and print the total bonus amount to
be distributed by the organization.
Ref. Page 204

Ref. Page 204
Step 1: Initialize Total_Bonus and Total_Employees_Checked to zero.
Step 2: Initialize Bonus and Basic_Salary to zero.
Step 3: Take the appraisal form of the next employee.
Step 4: Read the employee’s Basic_Salary and Grade.
Step 5: If Grade = A, then Bonus = Basic_Salary. Go to Step 8.
Step 6: If Grade = B, then Bonus = Basic_Salary x 0.7. Go to Step 8.
Step 7: If Grade = C, then Bonus = Basic_Salary x 0.4.
Step 8: Add Bonus to Total_Bonus.
Step 9: Add 1 to Total_Employees_Checked.
Step 10: If Total_Employees_Checked < 100, then go to Step 2.
Step 11: Print Total_Bonus.
Step 12: Stop.

Representation of Algorithms
Ref. Page 204
 As programs
 As flowcharts
 As pseudocodes
When an algorithm is represented in the form of a
programming language, it becomes a program
Thus, any program is an algorithm, although the
reverse is not true

Flowcharts

What is a Flowchart?
Ref. Page 205
 Flowchart is a pictorial representation of an algorithm
 Programmers often use it as a program-planning tool
 It uses boxes of different shapes to denote different types
of instructions
 Process of drawing a flowchart for an algorithm is known as
flowcharting

Why Use Flowcharts?
Ref. Page 205
 Algorithm is first represented as a flowchart
 Flowchart is then expressed in a programming language
 Main advantages of this two-step approach in program
writing are:
 While drawing a flowchart, a programmer can concentrate fully
on the logic of the solution
 Since a flowchart shows the flow of operations in pictorial form,
a programmer can detect any error in the logic
 Once the flowchart is ready, the programmer can concentrate
on coding the operations in each box of the flowchart as
statements of the programming language

Why Use Flowcharts?
Ref. Page 205
 This two-step approach ensures an error-free
program
 It is a good practice to have a flowchart along with a
computer program because the flowchart often
serves as a document for the computer program

Basic Flowchart Symbols
Terminal Processing
Decision
Input/Output
Flow lines Connectors
Ref. Page 205

Examples of Decision Symbol
Is I = 10?
No
Yes
(a) A two-way branch decision. (b) A three-way branch decision.
A > B
A = B
A < B
Ref. Page 205
Compare
A & B

I = ?
(c) A multiple-way branch decision.
= 0 = 1 = 2 = 3 = 4 = 5 = Other
Examples of Decision Symbol
Ref. Page 205

Sample Flowchart (Example 3)
Ref. Page 205
A student appears in an examination, which consists of
total 10 subjects, each subject having maximum marks
of 100.
The roll number of the student, his/her name, and the
marks obtained by him/her in various subjects are
supplied as input data.
Such a collection of related data items, which is treated
as a unit is known as a record.
Draw a flowchart for the algorithm to calculate the
percentage marks obtained by the student in this
examination and then to print it along with his/her roll
number and name.

Start
Read input data
Add marks of all
subjects giving Total
Percentage = Total / 10
Write output data
Stop
Ref. Page 205

50 students of a class appear in the examination of
Example 3.
Draw a flowchart for the algorithm to calculate and print
the percentage marks obtained by each student along
with his/her roll number and name.
Ref. Page 205

Flowchart for the solution
of Example 4 with an
infinite (endless) process
loop.
Add marks of all
Write output data
Start
Read input data
Ref. Page 205

Flowchart for the solution
of Example 4.
Start
Read input data
Count = 0
Add marks of all subjects giving Total
Percentage = Total/10
Write output data
Add 1 to Count
No
Is Count = 50?
Yes
Stop
Ref. Page 205

Generalized flowchart
for the solution of
Example 4 using the
concept of trailer
record. Here the
process loop is
terminated by detecting
a special non-data
record.
Stop
Yes
Add marks of all subjects
giving Total
No
Is Rollno = 0000000?
Start
Read input data
Write output data
Ref. Page 205

For the examination of Example 3, we want to make a
list of only those students who have passed (obtained
30% or more marks) in the examination.
In the end, we also want to print out the total number of
students who have passed.
Assuming that the input data of all the students is
terminated by a trailer record, which has sentinel value
of 9999999 for Rollno, draw a flowchart for the
algorithm to do this.
Ref. Page 205

Percentage = Total/10
Start
Count = 0
Is Rollno = 9999999?
No
Add 1 to Count
Read input data
Is Percentage = > 30?
Yes
Write output data
No
Write Count
Stop
Yes
Ref. Page 205

Suppose the input data of each student for the examination of
Example 3 also contains information regarding the sex of the
candidate in the field named Sexcode having values M (for
male) or F (for female).
We want to make a list of only those female students who have
passed in second division (obtained 45% or more but less than
60% marks).
In the end, we also want to print out the total number of such
students.
Assuming that the input data of all the students is terminated
by a trailer record, which has a sentinel value of Z for Sexcode,
draw a flowchart for the algorithm to do this.
Ref. Page 205

Yes
Yes
No
Start
Count = 0
No
1
Read input data
Is Sexcode = Z?
Is Sexcode = F?
1
2
3
Ref. Page 205

No
No
Yes
Add 1 to Count
Yes
Write output data
Is Percentage < 60?
Is Percentage = > 45?
Stop
Write Count
2
1
1
1
3
Ref. Page 205

Levels of Flowchart
Ref. Page 205
 Flowchart that outlines the main segments of a program
or that shows less details is a macro flowchart
 Flowchart with more details is a micro flowchart, or
detailed flowchart
 There are no set standards on the amount of details that
should be provided in a flowchart

Example of Micro Flowchart
Part of a macro
flowchart
Add marks of all
1
I = 1
Total = 0
Total = Total + Marks (I)
I = I + 1
Is I > 10?
Yes
1
No
A micro
Flowchart
Ref. Page 205

 First chart the main line of logic, then incorporate detail
 Maintain a consistent level of detail for a given flowchart
 Do not chart every detail of the program. A reader who is
interested in greater details can refer to the program itself
 Words in the flowchart symbols should be common
statements and easy to understand
Flowcharting Rules
Ref. Page 205

 Be consistent in using names and variables in the
flowchart
 Go from left to right and top to bottom in
constructing flowcharts
 Keep the flowchart as simple as possible. Crossing of
flow lines should be avoided as far as practicable
 If a new flowcharting page is needed, it is
recommended that the flowchart be broken at an
input or output point.
 Properly labeled connectors should be used to link
the portions of the flowchart on different pages
Flowcharting Rules
Ref. Page 205

Advantages of Flowcharts
Ref. Page 205
 Better communication
 Flowchart is a pictorial representation of a program
 Effective analysis
 Macro flowchart, which charts the main line of logic of a
software system, becomes the system’s model
 Effective synthesis
 Group of programmers are associated with the design of a big
software system
 Each programmer is responsible for designing only a part of
the entire system
 Flowcharts of all programmers put together can help visualize
the overall system design

Advantages of Flowcharts
Ref. Page 205
 Proper program documentation
 Documentation involves collecting, organizing, storing, and
maintaining a complete historical record of programs, and other
documents associated with a system
 Flowcharts often provide valuable documentation support
 Efficient coding
 Once a flowchart is ready, programmers find it very easy to write
the corresponding program because the flowchart acts as a road
map
 Systematic debugging
 Flowchart is very helpful in detecting, locating, and removing
mistakes (bugs) in a program in a systematic manner
 Systematic testing
 Flowchart is very helpful in designing test data for systematic
testing of programs

Limitations of Flowchart
Ref. Page 205
 Flowcharts are very time consuming and laborious to
draw (especially for large complex programs)
 Redrawing a flowchart for incorporating changes/
modifications is a tedious task
 There are no standards determining the amount of detail
that should be included in a flowchart

Pseudocode

What is Pseudocode?
Ref. Page 217
 Pseudocode is another program-planning tool used for
planning program logic
 “Pseudo” means imitation or false and “Code” refers to the
instructions written in a programming language
 Pseudocode is an imitation of actual computer instructions
 Pseudo-instructions are phrases written in a natural language
 Pseudocode uses a structure that resembles computer
instructions
 A programmer can concentrate solely on developing the logic
of a program without worrying about the syntax
 He/she can convert the pseudocode easily into a suitable
programming language

Basic Logic (Control) Structures
Ref. Page 218
Any program logic can be expressed by using only
following three simple logic structures:
1. Sequence logic,
2. Selection logic, and
3. Iteration (or looping) logic
Programs structured by using only these three logic
structures are called structured programs, and the
technique of writing such programs is known as
structured programming

It is used for performing instructions one after another
in sequence.
Sequence Logic
Process 1
(b) Pseudocode
Process 2
Process 1
Process 2
(a) Flowchart
Ref. Page 218

Selection Logic
Ref. Page 219
• Also known as decision logic, it is used for making
decisions
• Three popularly used selection logic structures are
1. IF…THEN…ELSE
2. IF…THEN
3. CASE

Selection Logic (IF…THEN…ELSE Structure)
THEN
ELSE
Process 1
Process 2
IF Condition
ENDIF
(b) Pseudocode
THEN
Process 1
ELSE
Process 2
Yes No
Ref. Page 219
(a) Flowchart
IF (condition)

(b) Pseudocode
THEN
ENDIF
IF Condition
Process 1
THEN
Process 1
Yes No
(a) Flowchart
IF (condition)
Selection Logic (IF…THEN Structure)
Ref. Page 219

Selection Logic (CASE Structure)
(b) Pseudocode
CASE Type
Case Type 1:
Case Type 2:
Process 1
Process 2
ENDCASE
Case Type n: Process n
Type 1
Type n
Process 2
Process 1
Process n
Yes
Yes
Yes
No
Type 2
No
No
(a) Flowchart
Ref. Page 219

Iteration (or Looping) Logic
Ref. Page 219
 Used to produce loops in program logic when one or
more instructions may be executed several times
depending on some conditions
 Two popularly used iteration logic structures are
1. DO…WHILE
2. REPEAT…UNTIL

(DO…WHILE Structure)
(b) Pseudocode
DO WHILE Condition
Process 1
Process n
ENDDO
Process 1
False
(a) Flowchart
Process n
T
rue
Ref. Page 219
Condition?
Block

(REPEAT…UNTIL Structure)
REPEAT
Process 1
Process n
UNTIL Condition
(b) Pseudocode
Process 1
Process n
False
Condition?
True
(a) Flowchart
Ref. Page 219

Sample Pseudocode (for Example 6)
Set Count to zero
Read first student record
DO WHILE Sexcode is not equal to Z
IF Sexcode = F THEN
Calculate Percentage
IF Percentage = > 45 THEN
IF Percentage < 60 THEN
Write output data
Add 1 to Count
ENDIF
ENDIF
ENDIF
Read next student record
ENDDO
Write Count
Stop
Ref. Page 219

Advantages of Pseudocode
Ref. Page 219
 Converting a pseudocode to a programming language
is much more easier than converting a flowchart to a
programming language
 As compared to a flowchart, it is easier to modify the
pseudocode of a program logic when program
modifications are necessary
 Writing of pseudocode involves much less time and
effort than drawing an equivalent flowchart as it has
only a few rules to follow

Limitations of Pseudocode
Ref. Page 219
 In case of pseudocode, a graphic representation of
program logic is not available
 There are no standard rules to follow in using
pseudocode
 Different programmers use their own style of writing
pseudocode and hence communication problem
occurs due to lack of standardization
 For a beginner, it is more difficult to follow the logic
of or write pseudocode, as compared to flowcharting

Key Words/Phrases
 Algorithm
 Basic logic structures
 Control structures
 Flowchart
 Iteration logic
 Looping logic
 Micro flowchart
 Macro flowchart
 Pseudocode
 Program Design Language (PDL)
 Sequence logic
 Selection logic
 Sentinel value
 Structured programming
 Trailer record

Chapter 12: Computer Languages Slide 1/65
Chapter 12
Computer
Languages
Pradeep K. Sinha
Priti Sinha

Slide 2/65
Chapter 12: Computer Languages
 Computer languages or programming languages
 Three broad categories of programming languages –
machine, assembly, and high-level languages
 Commonly used programming language tools such as
assembler, compiler, linker, and interpreter
 Concepts of object-oriented programming languages
 Some popular programming languages such as
FORTRAN, COBOL, BASIC, Pascal, C, C++, C#, Java,
Python, LISP and SNOBOL
 Related concepts such as Subprogram, Characteristics of
a good programming language, and factors to consider
while selecting a language for coding an application
Learning Objectives

Analogy with
Natural Languages

Analogy with Natural Languages
 Language is a means of communication
 Programmer uses a computer language to instruct a computer
what he/she wants it to do
 Set of words allowed in a language is called its vocabulary
 Each word in the vocabulary has a definite unambiguous
meaning
 Most computer languages use a very limited vocabulary
 Words and symbols of a computer language must be used as
per the set rules, known as syntax rules

Broad Classification of Computer Languages
 Machine language
 Assembly language
 High-level language

Machine Language

Machine Language
 Machine language programs are written normally as strings
of binary 1s and 0s
 Circuitry of a computer is wired in a manner that it
recognizes the machine language instructions and converts
them into electrical signals needed to execute them
 A machine language instruction normally has a two-part
format: operation code tells the computer what function to
perform, and operand tells where to find or store the data
OPCODE
(operation code)
OPERAND
(address/location)
Instruction format

Machine Language
 Every computer has a set of operation codes called its
instruction set
 Typical operations included in the instruction set are:
 Arithmetic operations
 Logical operations
 Branch operations
 Data movement operations between memory locations and
registers
 Data movement operations from/to input/output devices

A Sample Machine Language Program
001000000000001100111001 10001471
001100000000010000100001 14002041
011000000000011100101110 30003456
101000111111011100101110 50773456
000000000000000000000000 00000000
In Binary In Decimal
(Difficult to read and understand) (Easier to read and understand)

Advantages & Limitations of
Machine Language
Advantage
 Can be executed very fast
Limitations
 Machine dependent
 Difficult to program
 Error prone
 Difficult to modify

Assembly Language

Assembly Language
 Assembly language programming helped in overcoming
limitations of machine language programming
 By using alphanumeric mnemonic codes instead of numeric
codes for instructions in instruction set
 Allowing use of alphanumeric names instead of numeric
addresses
 Providing additional instructions, called pseudo-instructions
 A language that allows use of letters and symbols instead of
numbers for representing instructions and storage locations is
called assembly language or symbolic language
 A program written in an assembly language is called assembly
language program or symbolic program

Sample Assembly Language Program
START PROGRAM AT 0000
START DATA AT 1000
SET ASIDE AN ADDRESS FOR FRST
SET ASIDE AN ADDRESS FOR SCND
SET ASIDE AN ADDRESS FOR ANSR
CLA FRST
ADD SCND
STA ANSR
HLT

Assembler
 We must convert an assembly language program into its
equivalent machine language program before executing it
 Translator program called assembler does this translation
 Assembler is system software supplied by computer
manufacturers
Assembly language
program
(Source program)
One-to-one correspondence
(Object program)
Machine language
program
Input Output
Assembler

Advantages of Assembly Language
Over Machine Language
 Easier to understand and use
 Easier to locate and correct errors
 Easier to modify
 No worry about addresses
 Easily relocatable
 Efficiency of machine language

Limitations of Assembly Language
 Machine dependent
 Knowledge of hardware required
 Machine level coding

 Mainly used today to fine-tune important parts of
programs written in a high-level language to improve
the program’s execution efficiency
Typical Uses of Assembly Language

Assembly Languages with
Macro Instructions
 Any assembly language instruction that gets translated
into several machine language instructions is called a
macro instruction
 Several assembly languages support such macro
instructions to speed up the coding process
 Assemblers of such assembly languages are designed to
produce multiple machine language instructions for each
macro instruction of the assembly language

High-level Language

High-Level Languages
 Machine independent
 Do not require programmers to know anything about the
internal structure of computer on which high-level
language programs will be executed
 Deal with high-level coding, enabling the programmers
to write instructions using English words and familiar
mathematical symbols and expressions

 Translator program (software) that translates a high-
level language program into its equivalent machine
language program
 Compiles a set of machine language instructions for
every program instruction in a high-level language
Compiler

(Source program)
High-level language
program
One-to-many correspondence
(Object program)
Machine language
program
Input Output
Compiler
Compiler

Separate Compiler for Each High-level
Language Supported
Machine code for P1
Machine code for P2
Compiler for
language L1
Compiler for
language L2
Program P1 in high-
level language L1
Program P2 in high-
level language L2
A computer supporting languages L1 and L2

Compiler for
language L1
on computer A
Program P1 in high-
level language L1
Machine code for
P1 that will run
on computer A
Executed on
computer A
Same results obtained
Compiler for
language L1
on computer B
Machine code for
P1 that will run
on computer B
Executed on
computer B
A High-level Language is Machine
Independent

Syntax Errors
In addition to doing translation job, compilers also
automatically detect and indicate syntax errors
Syntax errors are typically of following types:
 Illegal characters
 Illegal combination of characters
 Improper sequencing of instructions in a program
 Use of undefined variable names
Note : A compiler cannot detect logic errors in a program

START
Edit
source program
Syntax
errors
detected?
Yes
Compile
source program
Source program
Generate list of coded
error messages
Generate
object program
Object program
STOP
No
The Process of Removing Syntax Errors
From A Source Program

 For a large software, storing all the lines of program
code in a single source file will be:
– Difficult to work with
– Difficult to deploy multiple programmers to
concurrently work towards its development
– Any change in the source program would require the
entire source program to be recompiled
 Hence, a modular approach is generally adapted to
develop large software where the software consists of
multiple source program files
 No need to write programs for some modules as it might
be available in library offering the same functionality
Linker

Linker
 Each source program file can be independently
modified and compiled to create a corresponding
object program file
 Linker program (software) is used to properly
combine all the object program files (modules)
 Creates the final executable program (load module)

Linker
Prog-1.src Prog-2.src Prog-n.src
Prog-1.obj Prog-2.obj Prog-n.obj
Prog-i.lib
Executable
program file
Compilation
process
Linking
process
Source programs
Object programs
Library modules
Load module

 Interpreter is a high-level language translator
 Takes one statement of a high-level language
program, translates it into machine language
instructions
 Immediately executes the resulting machine language
instructions
 Compiler simply translates the entire source program
into an object program and is not involved in its
execution
Interpreter

Interpreter
Result of
program
execution
Input Output
Interpreter (translates and executes
statement-by-statement)
High-level
language
program
(Source program)

Interpreter
 As compared to compilers, interpreters are easier to write
 The main advantage of interpreters over compilers is that an
interpreter flags a syntax error in a program statement to a
programmer as soon as it interprets the program statement
 Main disadvantage of interpreters over compilers is that they
are slower than compilers
 To combine the advantages of both interpreters and
compilers, computer system provides both a compiler and an
interpreter for a high-level language
 Assemblers, compilers, and interpreters are also referred to
as language processors

Intermediate Language Compiler &
Interpreter
 New type of compiler and interpreter combines the
speed, ease, and control of both compiler and
interpreter
 Compiler first compiles the source program to an
intermediate object program
 Intermediate object program is not a machine
language code but written in an intermediate
language that is virtually machine independent
 Interpreter takes intermediate object program,
converts it into machine language program and
executes it

Benefits of Intermediate Language
Compiler & Interpreter
 Intermediate object program is in compiled form and thus is
not original source code, so safer and easier to share
 Intermediate object program is based on a standard
Intermediate Definition Language (IDL)
 Interpreter can be written for any computer architecture and
operating system providing virtual machine environment to the
executing program
 Newer Interpreter compiles intermediate program, in memory,
into final host machine language program and executes it
 This technique is called Just-In-Time (JIT) Compilation

Advantages of High-Level Languages
 Machine independent
 Easier to learn and use
 Fewer errors during program development
 Lower program preparation cost
 Better documentation
 Easier to maintain

Limitations of High-Level Languages
 Lower execution efficiency
 Less flexibility to control the computer’s CPU, memory
and registers

Object-Oriented
Languages

What is Object-Oriented Programming
(OOP)?
 Essence of OOP is to solve a problem by:
 Identifying the real-world objects of the problem and the
processing required of those objects
 Then creating simulations of those objects, their processes,
and the required communications between the objects
 OOP makes programming simpler, easier, and faster
 OOP philosophy is now used in almost all popular

Fundamental Concepts of OOP
 Object
 An object is the primitive element of a program written in an
OOP language
 Each object consists of a set of procedures and some data
 Method
 A method of an object defines the set of operations that the
object will execute when it receives a message
 Methods are like function definitions
 Entire collection of methods of an object is called the message
protocol, or message interface
 Message
 Mechanism to support communication between objects is
through messages

Fundamental Concepts of OOP
 Class
 A class is a description of one or more similar objects
 A class can have multiple instances
 Each instance of a class is known as an object of the class
 Class variables are variables stored in the class whose values
are shared by all instances
 Instance variables are variables for which local storage is
available in the instances (objects)
 Inheritance
 Inheritance is a mechanism to share code and behavior
 A child class inherits all of the instance variables, instance
methods, and class methods of its parent class
 A child class can inherit from multiple parent classes. This is
called multiple inheritance

Person
Male Female
Boy Man
Ram Shyam Mohan Seeta Geeta
Instances
Classes
Example of Class, Instance, and
Inheritance

Example of Objects, Class, and
Inheritance
Instance variables of ‘B’
Variables of ‘A’
Methods of ‘A’
Class ‘A’
Class ‘A’
Instance variables of ‘A’
Object ‘a’
(Instance of ‘A’)
Inherits from ‘A’
Variables of ‘B’
Class ‘B’
(Sub-class of
Class ‘A’)
Class ‘B’
Inherited instance variables of ‘A’
Object ‘b’
(Instance of ‘B’)
Methods of ‘B’

Key Elements of Object-Oriented Paradigm
Sr.
No.
Element Meaning
1 Abstraction Abstraction means that an object’s characteristics are broken
into manageable chunks as defined and documented in its
class description.
2 Encapsulation Encapsulation stipulates that code and data are stored as one
unit. Encapsulation also enables selective or total information
hiding, since it can make portions of the code and data
inaccessible from outside the unit.
3 Modularity Modularity defines the unit reuse. These units group
abstractions together.
4 Hierarchy Hierarchy allows an object’s behaviors to be refined
(subclasses) without recoding of the parent object (the
superclass). Some OO languages allow an object to have
more than one superclass, a feature that is known as multiple
inheritance. Inheritance hierarchies enable ranking/ordering
of abstractions.
5 Messages Messages, similar in use to function calls, are requests to
perform an operation on an instantiated object.

Some High-level
Languages

 Stands for FORmula TRANslation
 Originally developed by John Backus and his team at
IBM followed by several revisions
 Standardized by ANSI as FORTRAN 77 and FORTRAN 90
 FORTRAN 2018 is the latest released version till date
 Designed for solving scientific & engineering problems
 Oriented towards solving problems of a mathematical
nature
 Popular language amongst scientists and engineers
FORTRAN

 Stands for COmmon Business Oriented Language
 Originally developed started under Grace Hopper
followed by COnference on DAta SYstems Languages
(CODASYL)
 Standardized by ANSI as COBOL 74, COBOL 85, and
COBOL 2002
 COBOL 2014 is the latest COBOL standard as on date
 Designed for programming business data processing
applications
 Designed to have the appearance and structure of a
business report written in English, hence often referred
to as a self-documenting language
COBOL

 Stands for Beginners All-purpose Symbolic Instruction
Code
 Developed by Professor John Kemeny and Thomas Kurtz
at Darmouth College in the United States
 Standardized by ANSI as BASIC 78
 Designed to be an interactive language and to use an
interpreter instead of a compiler
 Simple to implement, learn and use language. Hence, it
was a widely used language on personal computers
 Flexible and reasonably powerful language and can be
used for both business and scientific applications
BASIC

 Named after the famous seventeenth-century French
mathematician Blaise Pascal
 Developed by Professor Nicklaus Wirth of Federal
Institute of Technology in Zurich
 Encourages programmers to write well-structured,
modular programs, instills good programming practices
 Recognized as an educational language and is used to
teach programming to beginners
 Suitable for both scientific & business applications
 Has features to manipulate numbers, vectors, matrices,
strings, sets, records, files, and lists
Pascal

C
 Developed in 1972 at AT&T’s Bell laboratories, USA
by Dennis Ritchie and Brian Kernighan
 Standardized by ANSI and ISO as C89, C90, C99
 High-level programming languages (mainly machine
independence) with the efficiency of an assembly
language
 Language of choice of programmers for portable
systems software and commercial software packages
like OS, compiler, spreadsheet, word processor, and
database management systems

C++ (C plus plus)
 Named C++ as ++ is increment operator and C
language is incremented to its next level with C++
 Developed by Bjarne Stroustrup at Bell Labs in the
early 1980s
 Contains all elements of the basic C language
 Expanded to include numerous object-oriented
programming features
 Provides a collection of predefined classes, along with
the capability of user-defined classes
 Being a superset of C, it is an extremely powerful and
efficient language. However, it is more difficult to learn
than C

Java
 Development started at Sun Microsystems in 1991 by a
team led by James Gosling
 Developed to be similar to C++ with fewer features to
keep it simple and easy to use
 Compiled code is machine-independent and developed
programs are simple to implement and use
 Uses just-in-time compilation
 Used in embedded systems such as hand-held devices,
telephones and VCRs
 Comes in two variants – Java Runtime Engine (JRE) and
Java Software Development Kit (SDK)

C# (C Sharp)
 Object-oriented programming language developed by
Anders Hejlsberg and released by Microsoft as part of
Microsoft’s .NET technology initiative
 Standardized by ECMA and ISO
 Syntactically and semantically very close to C++ and
adopts various object-oriented features from both C++
and Java
 Compilers target the Common Language Infrastructure
(CLI) implemented by Common Language Runtime (CLR)
of .NET Framework
 CLR provides important services such as, memory
management, exception handling, and security

Python
 A high level programming language, first released in 1991
by Guido van Rossum of Netherlands
 Being a Free and Open Source Software (FOSS), it has a
large, world-wide development community
 It is now managed by Python Software Foundation, a non-
profit community
 It now ranks among top ten popular programming
languages

Key Features of Python Include
 Simple to learn and easy to read and understand
 Both procedure-oriented and object-oriented programming is
possible
 Highly portable
 Interpreted language
 Extensible and embeddable language
 Rich library support

LISP
 Stands for LISt Processing
 Developed in 1959 by John McCarthy of MIT
 Designed to have features for manipulating non-
numeric data, such as symbols and strings of text
 Due to its powerful list processing capability, it is
extensively used in the areas of pattern recognition,
artificial intelligence, and for simulation of games
 Functional programming language in which all
computation is accomplished by applying functions to
arguments

SNOBOL
 Stands for StriNg Oriented symBOlic Language
 Used for non-numeric applications
 Powerful string manipulation features
 Widely used for applications in the area of text
processing

Selecting a Language for
Coding an Application

Characteristics of a Good
Programming Language
 Simplicity
 Naturalness
 Abstraction
 Efficiency
 Structured Programming Support
 Compactness
 Locality
 Extensibility
 Suitability to its environment

Factors for Selecting a Language for
Coding an Application
 Nature of the application
 Familiarity with the language
 Ease of learning the language
 Availability of program development tools
 Execution efficiency
 Features of a good programming language

Subprogram

Subprogram
 Program written in a manner that it can be brought into
use in other programs and used whenever needed
without rewriting
 Also referred to as subroutine, sub-procedure, or function
 Subprogram call statement contains the name of the
subprogram followed by a list of parameters enclosed
within a pair of parentheses
 Intrinsic subprograms (also called built-in-functions) are
those provided with the programming language
 Programmer-written subprograms are written and used
as and when they are needed

sqrt (x)
Set of instructions that
perform the intended task
Subprogram name Parameter
Subprogram header
Subprogram body
Structure of a Subprogram

Flow of Control in Case of Subprogram Calls
A subprogram
Flow of control
A program that calls
the subprogramtwice
subprogram header
subprogrambody
subprogram call statement
next statement
subprogram call statement
next statement
9
5
8
4
6
7
3
1 2

Key Words/Phrases
Slide 64/65
 Assembler
 Assembly language
 BASIC
 Built-in function
 C
 C++
 C#
 COBOL
 Coding
 Compiler
 Computer language
 FORTRAN
 Function
 High-level language
 HotJava Interpreter
 Intrinsic subprogram
 Intermediate compiler and
Interpreter
 Java
 Just-in-time compilation
 Language processor
 Linker
 LISP
 Load module
 Logic error
 Low-level language
 Machine language
 Macro instructions
 Object program
 Object-oriented programming
 Opcode
 Operand
 Pascal
 Programmer
 Programming
 Programming language
 Pseudo instruction
 Python
 Self-documenting language

Key Words/Phrases
Slide 65/65
 SNOBOL
 Source program
 Sub-procedure
 Subprogram
 Subroutine
 Symbolic language
 Syntax error
 Syntax rules
 Programmer-written subprograms

Chapter 13: System Implementation and Operation Slide 1/35
Dr. Pradeep K. Sinha & Priti Sinha
Chapter 00
Title
Pradeep K. Sinha
Priti Sinha
Chapter 13
System
Implementation
and Operation

Slide 2/35
Chapter 13: System Implementation and Operation
 Main activities of implementation and operation
phase of software
 Software testing and debugging
 Software documentation
 Software deployment and changeover processes
 System evaluation and
 Software maintenance
Learning Objectives

Program Errors,
Testing and Debugging

Testing and Debugging
Ref. Page 263 Chapter 13: System Implementation and Operation Slide 4/35
 Program errors are known as bugs
 Process of detecting and correcting these errors is called
debugging
 Testing is the process of making sure that the program
performs the intended task
 Debugging is the process of locating and eliminating
program errors

Types of Program Errors
 Syntax errors
 Occurs when the rules or syntax of the programming
language are not followed
 For example, incorrect punctuation, incorrect word
sequence, undefined terms, and misuse of terms
 Syntax errors are detected by a language processor
 Logic errors
 Occurs due to errors in planning a program’s logic
 Such errors cause the program to produce incorrect
output.
 These errors cannot be detected by a language
processor

Testing of a Program
 Testing procedure involves running program to
process input test data, and comparing obtained
results with correct results
 Test data must test each logical function of the
program, and should include all types of possible
valid and invalid data

Debugging a Program for Syntax Errors
 Relatively easier to detect and correct syntax errors
than logic errors in a program
 Language processors are designed to automatically
detect syntax errors
 Single syntax error often causes multiple error
messages to be generated by the language processor
 Removal of the syntax error will result in the removal
of all associated error messages

Debugging a Program for Logic Errors
 Logic errors are more difficult to detect than syntax
errors as computer does not produce any error
message for such errors
 One or more of following methods are commonly used
for locating logic errors:
 Doing hand simulation of the program code
 Putting print statements in the program code
 Using a debugger (a software tool that assists a
programmer in following the program’s execution
step-by-step)
 Using memory dump (printout of the contents of
main memory and registers)

Unit and Integrated Testing
 In unit testing, each module of software is tested
independently for its functionality by the programmer
who developed the module.
 In integrated testing, the team integrates the
independently developed and tested modules into a
compete system, and tests the integrated system to
check if all modules coordinate properly.

Alpha and Beta Testing
 Software internally released for testing is known as
alpha version and the test conducted on it is called
alpha testing
 Software released for additional testing to a selected
set of external users is beta version and test
conducted on it called is beta testing

Difference Between Testing and Debugging
Sr. No. Testing Debugging
1  Testing is the process of
validating the correctness of
a program
 Its objective is to
demonstrate that the
program meets its design
specifications
 Debugging is the process of
eliminating errors in a program
 Its objective is to detect the cause of
error and remove known errors in the
program
2  Testing is complete when all
desired verifications against
specifications are completed
 Debugging is complete when all known
errors in the program are fixed
 Note that debugging process ends only
temporarily because it restarts
whenever a new error is detected in
the program

Sr. No. Testing Debugging
3  Testing is a definable process
which can and should be
planned and scheduled
properly
 Debugging being a reactive process cannot
be planned ahead of time
 It is carried out whenever errors are
detected in a program
4  Testing can begin in the early
stages of software
development.
 Although the test runs of a
program are carried out only
after the program is coded,
but the decision of what to
test, how to test, and with
what kind of data to test, can
and should be done before
the coding is started
 Debugging can begin only after the program
is ready
 The approach used for debugging largely
depends on the personal choice of the
programmer and the type of error in the
program
Difference Between Testing and Debugging

Software Documentation

What is Documentation?
 It is the process of collecting, organizing, storing, and
maintaining a complete historical record of programs and
other documents used or prepared during the different
phases of the life cycle of software
 It is an on-going process that starts as early as in the study
phase of the software and continues until its
implementation and operation phase
 Maintenance team has to carry out documentation from
time-to-time, whenever it modifies the software

Need for Documentation
 Solves the problem of indispensability of an individual for an
organization
 Makes software easier to modify and maintain in future
 Helps in restarting a software project postponed earlier due
to some reason

Forms of Documentation
 Requirement specification document
 Before developing some software, the development team
must analyze its requirements and document them
 Requirement specification document is an outcome of this
exercise
 Specifies the objectives of developing the software and its
usefulness to various categories of users
 Specifies the functionalities, capabilities, performance, inputs,
and outputs requirements of the software
 Specifies what all the software will do when developed
 Design document
 Defines overall architecture of the software
 Specifies various hardware and software components of the
software and interfaces between the components

 Includes a hierarchy of software components, rules for
component selection, and interfaces between the components
 Comments
 From maintenance point of view, comments are necessary
 All high-level languages provide the facility to write comments
in the source code of a program
 Use of this facility by programmers for proper documentation
of their programs is highly recommended
 Comments should be used intelligently to improve the quality
and understandability
 Comments should not be redundant, incorrect, incomplete, or
written in a manner that is difficult to understand

 System manual
 Standard system manuals contain the following information:
 Specific module names along with their description and
purpose
 Detailed system flow charts and program flow charts for each
module
 Description of the program listings and the control procedures
 Source listing of all the programs with full details of all
modifications
 Specifications of all input and output media
 Specimen of all types of input and output
 File layout
 Structure and description of all test data, test results, storage
dumps, trace program printouts, etc. (Continued on next slide…)

 User manual
 User manual describes how to use the software
 User manual must contain following information:
 Installation and operational details of software
 Loading and unloading procedures
 Starting, running, and terminating procedures
 Description and example of any control statements used
 All console commands with errors and console messages, their
meaning, reply, and/or operation action
 List of error conditions with explanation for their re-entry into the
system
 List of programs, which users must execute before and after
execution of each program
 Special checks (if any) and security measures, etc.

 Commonly used ways to describe each feature of
software in a user manual are:
 Commands/Functions list
 It lists the commands or functions of the software alphabetically
or grouped logically
 Tutorial
 It contains tutorials for various functionalities or tasks of software
 Online help
 It contains online information, which users can use whenever
needed while using the software without the need to refer to any
other document

 Marketing document: It consists of the following:
 Usefulness of the software product
 Its salient features
 Its comparison with other competing products
 Its system requirements (hardware, operating system, etc.)

Documentation Standard
It deals with:
 How to do documentation?
 How to choose meaningful program variable names?
 How to design the GUI?
 How and up to what detail to include comments?
 What diagrams, charts, reports, outputs, etc. are
necessary for completing documentation?

Software Deployment

Changeover to the New System
 When a software is ready for use, it is deployed at site for use
by the intended users
 At this stage, a changeover from the old system of operation
to the new system takes place
 Three normally followed methods to carry out the changeover
process are:
 Immediate changeover
 Parallel run
 Phased conversion

Old system New system
Cut-off date
Old system in
operation
New system in
operation
Time
(a) Immediate changeover

Old system
New system
Time
(b) Parallel run
Overlapping period of
complete operation of
both the old and the new
systems
Old system
in operation
New
system in
operation

Old system
completely
operational
Old system
New system
Old and new systems
in operation in parts
Time
(c) Phased conversion
New system
completely
operational

System Evaluation

Slide 29/35
Chapter 13: System Implementation and Operation
System Evaluation
 Process of evaluating a system (after it is put in
operation) to verify whether or not it is meeting its
objectives
 Points normally considered for evaluating a system are:
 Performance evaluation
 Cost analysis
 Time analysis
 User satisfaction
 Ease of modification
 Failure rate
Ref. Page 273

Software Maintenance

Definition
 Process of modifying software system or component after
deployment to correct faults, add functionality, improve
performance or other attributes, or adapt to a change in
environment

Need for Software Maintenance
 Any software needs modification from time-to-time due to
one or more of the following reasons:
 Changes in business conditions or operations of the
organization
 Changes in organizational policies or enforcement of new laws
 Changes in user needs
 Changes in technology

Importance of Software Maintenance
 Maintenance is an important phase in SDLC
 On an average, maintenance cost of software systems is two
to four times the development cost

Controlling Modifications
 Frequent change is disrupting and disturbing
 Some control over changes is required for which a change
control board is constituted
 Change control board evaluates all requests for change and
approves major changes
 It need not approve normal maintenance operations
 Major changes are those that alter the system significantly
 Whenever a programmer modifies a program, the concerned
members must also modify the associated documents

 Alpha testing
 Beta testing
 Bugs
 Changeover operations
 Comments
 Debugger
 Debugging
 Documentation
 Immediate changeover
 Integrated testing
 Logic errors
 Memory dump
 Parallel run
 Phased conversion
 Software maintenance
 Syntax errors
Key Words/Phrases
 System evaluation
 System manual
 Testing
 Unit testing
 User manual

Chapter 14: Operating Systems Slide 1/81
Chapter 14
Operating Systems
Pradeep K. Sinha
Priti Sinha

Slide 2/81
Chapter 14: Operating Systems
Learning Objectives
 Definition and need for operating system
 Main functions of an operating system
 Commonly used mechanisms for:
 Process management
 Memory management
 File management
 Device management
 Security
 Command interpretation
 Some commonly used OS capability enhancement software
 Some popular operating systems

Definition, Need and
Functions of an OS

 Integrated set of programs that controls the resources
(the CPU, memory, I/O devices, etc.) of a computer
system
 Provides its users with an interface or virtual machine
that is more convenient to use than the bare machine
 Two primary objectives of an OS are:
 Making a computer system convenient to use
 Managing the resources of a computer system
Definition and Need for OS
Ref. Page 277

Operating system layer hides details of hardware from
programmers and other users and provides them with a
convenient interface for using the system
Logical Architecture of a Computer System
Users
Other system
software and application programs
Operating system
Computer hardware
Ref. Page 278

 File management
 Device management
 Security
Main Functions of an OS
Ref. Page 278

 Throughput: Amount of work that the system is able to
do per unit time
 Turnaround time: Interval from the time of submission
of a job to the system for processing to the time of
completion of the job
 Response time: Interval from the time of submission of a
job to the system for processing to the time the first
response for the job is produced by the system
Parameters for Measuring System
Performance
Ref. Page 279

Process Management

 A process (also called job) is a program in execution
 Process management module of an operating system
manages the processes submitted to a system in a
manner to minimize idle time of processors (CPUs, I/O
processors, etc.) of the system
Process Management
Ref. Page 280

 Manual loading mechanism: Jobs were manually
loaded one after another in a computer by the
computer operator
 Batch processing mechanism: Batch of jobs was
submitted together to the computer and job-to-job
transition was done automatically by the operating
system
 Job Control Language (JCL): Control statements
were used to identify a new job in a batch of jobs and
to determine its resource requirements
Process Management Mechanisms in
Early Systems
Ref. Page 280

Use of Job Control Statements in Batch
Processing (An Example)
$END
Data for program
$COBOL
$JOB, ONGC05839,
USER=SINHA
Ref. Page 280
$RUN
$LOAD
COBOL program

Uniprogramming
Main memory
OS area
Execution
in
progress
CPU
User program
area
User job
Ref. Page 280
Operating system

 A job does not need CPU for entire duration of its processing
 Depending on CPU utilization during the course of processing,
jobs are of two types
 CPU-bound jobs, which mostly perform computations
with little I/O operations
 I/O-bound jobs, which mostly perform I/O operations
with little computation
 In a uniprogramming system, CPU is idle whenever the
currently executing job performs I/O operations
Uniprogramming
Ref. Page 280

Multiprogramming
Ref. Page 280
 Multiprogramming is interleaved execution of two or more
different and independent programs by a computer
 Multiprogramming enables two or more user programs to
reside simultaneously in main memory and carries out their
interleaved execution
 With multiple user programs residing simultaneously in main
memory, whenever a user program that was executing goes
to perform I/O operations, the operating system allocates CPU
to another user program in main memory
 In multiprogramming, several user programs share CPU time
to keep it busy
 Note that multiprogramming does not mean execution of
instructions from several programs simultaneously

Secondary disk
storage
Main memory
Writing output
data
CPU
Operating system
Job A
Job B
Job C
(Waiting for CPU)
Execution
in
progress
A typical scenario of jobs in a multiprogramming system
Multiprogramming
Ref. Page 280

Job processing
completed
Ready Running
Blocked
New job
Job is allocated the
CPU for execution
I/O
completed
Job must wait for I/O
completion
Three different states of jobs in main memory in a multiprogramming system
Multiprogramming
Ref. Page 280

 Large memory
 Memory protection
 Job status preservation
 Proper job mix (CPU and I/O bound jobs)
 CPU scheduling
Ref. Page 280
Requirements of Multiprogramming Systems

PCB is used to preserve the job status of each loaded
process in a multiprogramming system
Process Control Block (PCB)
process identifier
process state
program counter
values of various CPU
registers
accounting and
scheduling information
I/O status information
Ref. Page 280

Multitasking
Ref. Page 280
 Multitasking is single-user variation of multiprogramming
concept
 Both refer to the same concept of a system’s capability to
work concurrently on more than one task
 Some authors prefer to use the term multiprogramming for
multi-user systems and multitasking for single-user systems
 Multitasking eases user operation and saves lots of time when
a user has to switch between two or more applications while
performing a job
 Multiprogramming is interleaved execution of multiple jobs in
a multi-user system, while multitasking is interleaved
execution of multiple jobs in a single-user system

Multithreading
Ref. Page 280
 Threads are a popular way to improve application
performance
 In traditional operating systems, the basic unit of CPU
utilization is a process
 Each process has its own program counter
, its own register
states, its own stack, and its own address space
 In operating systems with threads facility, the basic unit of
CPU utilization is a thread
 A process consists of an address space and one or more
threads of control

 Each thread of a process has its own program counter, its
own register states, and its own stack
 All the threads of a process share the same address space
 All threads of a process also share the same set of operating
system resources
 Threads are often referred to as lightweight processes and
traditional processes are referred to as heavyweight
processes
Multithreading
Ref. Page 280

(a) (b)
(a) Single-threaded and (b) multithreaded processes. A single-
threaded process corresponds to a process of a traditional
operating system. [Reproduced with permission, from the
book titled Distributed Operating Systems: Concepts and
Design by Pradeep K. Sinha. © 1997 IEEE, USA].
Address space
Threa
d
Address space
Thread Thread Thread
Multithreading System
Ref. Page 280

Motivations for Using Threads
Ref. Page 280
 Overhead involved in creating a new process is considerably
greater than that for creating a new thread within a process
 New thread uses the address space of its process
 Overhead involved in CPU switching among peer threads is
very small as compared to CPU switching among processes
 Resources are shared more efficiently among multiple threads
of a process than among multiple processes
 Users find the threads model more intuitive for application
programming

 System with two or more CPUs having ability to execute
multiple processes concurrently
 Multiple CPUs are used to process either instructions from
different and independent programs or different
instructions from the same program simultaneously
 Types of multiprocessing:
 Tightly-coupled: Single system-wide primary memory
shared by all processors
 Loosely-coupled: Each processor has its own local
memory
Multiprocessing
Ref. Page 280

I/O Units
I/O
Processors
CPU
Main
memory
CPU, Memory, and I/O Processors of a
Computer System
Ref. Page 280

Multiprocessing System
CPU-1 Main memory CPU-2
I/O processors I/O processors
I/O units I/O units
Ref. Page 280

Difference between Multiprogramming and
Multiprocessing
Ref. Page 280
 Multiprocessing is simultaneous execution of two or more
processes by a computer system having more than one CPU
 Multiprogramming is interleaved execution of two or more
processes by a single-CPU system
 Multiprogramming involves execution of a portion of one
program, then a portion of another, etc., in brief consecutive
periods
 Multiprocessing involves simultaneous execution of several
program segments of the same or different programs

 Simultaneous interactive use of a computer system by
many users in such a way that each one feels that
he/she is the sole user of the system
 Many user terminals are connected to the same
computer simultaneously
 Uses multiprogramming with a special CPU scheduling
algorithm
 Short period during which a user process gets to use
CPU is known as time slice, time slot, or quantum
 CPU is taken away from a running process when the
allotted time slice expires
Time-sharing
Ref. Page 280

Process State Diagram for a Time-Sharing
System
Ready Running
Blocked
New job
Job is allocated to
CPU for execution
Job processing
completed
I/O
completed
Job must wait for
I/O completion
Allotted time slice is over
Process state diagram for a time-sharing system
Ref. Page 280

 Time-sharing systems require following additional hardware
and software
 Number of user terminals
 Large memory to support multiprogramming
 Memory protection mechanism to prevent a job’s instructions and
data from other jobs
 Job status preservation mechanism to preserve a job’s status
information when the operating system takes away CPU from it,
and restores this information back
 Special CPU scheduling algorithm that allocates CPU for a short
period one-by-one to each user process
 Interrupt mechanism to send an interrupt signal to CPU after
every time slice
Ref. Page 280
Requirements of Time-sharing Systems

 Reduces CPU idle time
 Provides advantages of quick response time
 Offers good computing facility to small users
Advantages of Time-sharing Systems
Ref. Page 280

Memory Management

 Memory is important resource of a computer system
that must be properly managed for the overall system
performance
 Memory management module:
 Keeps track of parts of memory in use and parts not in use
 Allocates memory to processes as needed and deallocates
when no longer needed
Memory Management
Ref. Page 290

 Used in systems that process one job only at a time, and
all system resources are available exclusively for the job
until it completes
 Simple and easy to implement
 Does not lead to proper utilization of the main memory as
unoccupied memory space by the currently active user
process remains unused
 Used only on very small or dedicated computer systems
Uniprogramming Memory Model
Ref. Page 290

Operating system area Operating system
User process
Unused
User area
Uniprogramming Memory Model
Ref. Page 290

 In a multiprogramming system, multiple user processes
can reside simultaneously in main memory
 Two memory management schemes used to facilitate this
are:
 Multiprogramming with fixed number of memory partitions:
User area of the memory is divided into a number of fixed-
sized partitions
 Multiprogramming with variable number of memory
partitions: Number, size and location of the partitions vary
dynamically as processes come and go
Multiprogramming Memory Models
Ref. Page 290

Multiprogramming with Fixed Number of
Memory Partition
Operating system
Partition 1
Partition 2
Partition 3
Partition n
Operating system area
User area divided into n
equal-sized partitions
Ref. Page 290

Operating
system
Free
Operating
system
Free
P1
Operating
system
P1
P2
Free
User
area
P1
comes
P2
comes
P3
comes
(a) (b) (c)
Operating
system
P1
P2
P3
Free
(d)
The number, size, and location of the partitions vary dynamically as
processes come and go. (contd…)
Multiprogramming with Fixed Number of
Memory Partition
Time (a), (b), …, (h)
Ref. Page 290

P2
terminates
Operating
system
Free 3
P4
Free 2
P3
Free 1
Operating
system
P1
P2
Free 2
P3
Free 1
(e) (f) (g) (h)
The number, size, and location of the partitions vary dynamically as processes come and go.
P4
Comes which
cannot fit in
Free 1 so is
allocated
space from
Free 2
Operating
system
P1
P4
Free 2
P3
Free 1
P1
terminates
Operating
system
P5
Free 3
P4
Free 2
P3
Free 1
comes
Ref. Page 290
which can
fit in
Free 3
P5
Multiprogramming with Variable Number of
Memory Partitions

Virtual Memory
Ref. Page 290
 Conventional memory management schemes suffer from two
main limitations
 Operating system cannot load a process until sufficient free
memory for loading the entire process becomes available
 Operating system cannot load a process if main memory size is
less than the total memory required
 Virtual memory is a memory management scheme that
overcomes these limitations by allowing execution of a
process without the need to load the process in main memory
completely

How is Virtual Memory Realized?
Ref. Page 290
 On-line secondary storage
 On-line secondary storage device having much larger capacity
than main memory
 Swapping
 Swapping is the process of transferring a block of data from on-
line secondary storage to main memory or vice-versa
 Demand paging
 Instead of loading an entire process before its execution can
start, the operating system uses a swapping algorithm
 When operating system needs to swap to continue a process’s
execution, it invokes a page-replacement algorithm to create one
for the accessed page
 Page replacement deals with selecting a page that is residing in
memory but is not in use currently (Continued on next slide…)

 Virtual memory is often described as a hierarchy of two
storage systems – one is a low-cost, large-capacity, low-
speed system (on-line disk storage), and the other is a high-
cost, small-capacity, high-speed system (main memory)
Ref. Page 290
How is Virtual Memory Realized?

 Provides a large virtual memory to programmers on a
system having smaller physical memory
 Enables execution of a process on a system whose main
memory size is less than the total memory required by the
process
 Enables a process’s execution to be started even when
sufficient free memory for loading the entire process is not
available
 Makes programming easier as programmers no longer
need to worry about the memory size limitations
 Often leads to less I/O activity resulting in better
throughput, turnaround time, and response time
Advantages of Virtual Memory
Ref. Page 290

 Difficult to implement because it requires algorithms to
support demand paging
 If used carelessly, it may substantially decrease
performance due to high page fault rate
Disadvantages of Virtual Memory
Ref. Page 290

File Management

 A file is a collection of related information
 Every file has a name, its data and attributes
 File’s name uniquely identifies it in the system and is used
by its users to access it
 File’s data is its contents
 File’s attributes contain information such as date & time of
its creation, date & time of last access, date & time of last
update, its current size, its protection features, etc.
 File management module of an operating system takes
care of file-related activities such as structuring,
accessing, naming, sharing, and protection of files
File Management
Ref. Page 294

File Access Methods
Ref. Page 294
 Sequential access files
 Operating systems use sequential access files for storage of files
on sequential access storage media
 A process can read the bytes or records in the file in the order in
which they are stored
 Random access files
 Operating systems use random access files for storage of files on
random access storage media
 Applications can access the contents of a random access file
randomly, irrespective of the order in which the bytes or records
are stored

File Operations (Examples)
Ref. Page 294
File operation Usage
Create Is used to create a new file.
Delete Is used to delete an existing file that is no longer needed.
Open Is used to open an existing file when a user wants to start using it.
Close Is used to close a file when the user has finished using it.
Read Is used to read data stored in a file.
Write Is used to write new data in a file.
Seek Is used with random access files to first position read/write pointer
to a specific place in file so that data can be read from, or written to,
that position.
Get attributes Is used to access the attributes of a file.
Set attributes Is used to change user-settable attributes (such as, protection
mode) of a file.
Rename Is used to change name of an existing file.
Copy Is used to create a copy of a file, or to copy a file to an I/O device,
such as a printer.

File naming deals with the rules for naming files in an
operating system. This may include such rules as:
 Maximum number of characters that a file name may
have
 Special characters allowed in a file name
 Distinction between upper case and lower case letters
 Multi-part file names allow file extensions to be part of a
file name. File extensions indicate something about the
file and its content
 Used by applications to check for the intended type of
file before operating on it
File Naming
Ref. Page 294

File Extensions (Example)
Ref. Page 294
File
extension
Its meaning
.bas Basic source program file
.c C source program file
.ftn Fortran source program file
.pas Pascal source program file
.obj Object file (compiler output, not yet linked)
.bin Executable binary program file
.lib Library of .obj files used by the linker
.dat Data file
.hlp Text file for HELP command
.man Online manual page file

File Extensions (Example)
Ref. Page 294
File
extension
Its meaning
.txt General text file
.bak Backup file
.doc Microsoft word document file
.wav Microsoft windows sound file
.wk4 Lotus 1-2-3 spreadsheet file
.xls Microsoft Excel spreadsheet file
.jpg JPEG graphics file
.gif GIF graphics file

Device Management

Controlling I/O Devices
Ref. Page 297
 Computer uses device controllers to connect I/O devices to it
 Each device controller is in charge of and controls a set of
devices of a specific type
 Device controller maintains some local buffer storage and is
responsible for moving data between an I/O device that it
controls and its local buffer storage
 Device controller also has a few registers that it uses for
communicating with CPU
 These registers are part of the regular memory address space
 This scheme is called memory-mapped I/O

 Two methods to transfer data from the controller’s local buffer
to the appropriate memory area of the computer are:
 Non-DMA transfer
 As soon as transfer of data from input device to the controller’s
local buffer is complete, the controller sends an interrupt signal to
CPU
 CPU then stops what it is doing currently, and transfers control of
execution to the starting address of the service routine, which
handles the interrupt
 Interrupt service routine transfers the data from local buffer of
the device controller to main memory
Ref. Page 297

 DMA transfer
 When the operating system prepares for data transfer
operation, it writes the relevant commands and their associated
parameters into the controller’s registers
 After the controller has read the data from the device into its
buffer, it copies the data one byte or word at a time from its
buffer into main memory at the specified memory address
 It does not involve the CPU
 Device controller sends an interrupt to CPU only after it
completes copying the entire data
Ref. Page 297

 Operating systems provide simple and easy user interface to
all I/O devices
 They achieve this by organizing the software for using I/O
devices as a series of layers
 Lower layers hide the internal details
 Upper layers present a nice, clean, uniform interface to the
users
Simple and Easy User Interface to
I/O Devices
Ref. Page 297

Layers of I/O System
User-level software
Device-independent
software
Device drivers
Interrupt handlers
I/O devices hardware
I/O software
layers
I/O hardware
Supports standard I/O system calls as library
procedures.
Ref. Page 297
Performs I/O functions that are common to all
devices and maps symbolic device names to the
proper device driver.
Converts I/O requests into suitable commands
for the appropriate device controller and writes
the relevant commands and their associated
parameters into the controller’s registers.
Causes interrupt to wakeup the device driver
after it completes data transfer.
Performs actual data I/O.

Security

 Deals with protecting the various resources and information
of a computer system against destruction and unauthorized
access
 External security: Deals with securing computer against
external factors such as fires, floods, earthquakes, stolen
disks/tapes, etc. by maintaining adequate backup, using
security guards, allowing access to sensitive information to
only trusted employees/users, etc.
 Internal security: Deals with user authentication, access
control, and cryptography mechanisms
Security
Ref. Page 298

 User authentication: Deals with the problem of
verifying the identity of a user (person or program)
before permitting access to the requested resource
 Access Control: Once authenticated, access control
mechanisms prohibit a user/process from accessing those
resources/information that he/she/it is not authorized to
access
 Cryptography: Means of encrypting private information
so that unauthorized access cannot use information
Security
Ref. Page 298

Command Interpretation

 Provides a set of commands using which the user can give
instructions to the computer for getting some job done by
it
 Commands supported by the command interpretation
module are known as system calls
Ref. Page 299

Two types of user interfaces supported by various operating
systems are:
 Command-line interface: User gives instructions to
the computer by typing the commands
 Graphical User Interface (GUI): User gives
commands to the system by selecting icon or menu
item displayed on the screen with the use of a point-
and-draw device
Ref. Page 299

OS Capability
Enhancement Software

Slide 65/81
Chapter 14: Operating Systems
 Perform several tasks of routine nature, frequently
needed by users but are not provided as part of the OS
 They are primarily grouped into three categories:
 Translating programs: Translate a source program
into an object program
 Library programs: Consist of frequently used
functions and operations
 Utility programs: Assist users with system
maintenance tasks such as disk formatting, data
compression, data backups, antivirus utilities
OS Capability Enhancement Software
Ref. Page 300

Some Popular
Operating Systems

 Developed in the early 1970s at Bell Laboratories by Ken
Thompson and Dennis Ritchie
 Written in C high-level language, hence, highly portable
 Multi-user, time-sharing OS
 Used on a wide variety of computers ranging from
notebook computers to super computers
 Especially prevalent on RISC workstations such as those
from Sun Microsystems, Hewlett-Packard, IBM, and
Silicon Graphics
 Structured in three layers – kernel, shell, and utilities
UNIX OS
Ref. Page 302

 Stands for Microsoft Disk Operating System.
 Single-user OS for IBM and IBM-compatible
computers (PC)
personal
 Structured in three layers – BIOS (Basic Input Output
System), kernel, and shell
 Very popular in the 1980s. Not in much use now after
development of Microsoft Windows OS in 1990s
MS-DOS
Ref. Page 302

 Developed by Microsoft to overcome limitations of MS-
DOS operating system
 Single-user, multitasking OS
 Native interface is a GUI
 Designed to be not just an OS but also a complete
operating environment
 OS of choice for most PCs after 1990
Microsoft Windows
Ref. Page 302

 Supports multiprogramming and is designed to take
systems having
advantage of multiprocessing on
multiple processors
 Native interface is a GUI
 Built-in networking and communications features
 Provides strict system security
 Rich set of tools for software development
 Can run Microsoft Windows applications and many UNIX
applications directly
Microsoft Windows Server
Ref. Page 302
(Earlier Known as Windows NT)
 Multi-user, time-sharing OS developed by Microsoft
 Designed to have UNIX-like features so that it can be
used for powerful workstations, network, and database
servers

 Open-source OS enhanced and backed by thousands of
programmers world-wide
 Multi-tasking, multiprocessing OS, originally designed to
be used in PCs
 Name “Linux” is derived from its inventor Linus Torvalds
 Several Linux distributions available (Red Hat, SuSE).
Difference in distribution is mostly set of tools, number
and quality of applications, documentation, support, and
service
Linux
Ref. Page 302

 Designed in mid 1980s by Apple Incorporation
 Main objective was ‘ease of use’
 First OS to introduce the idea of GUI (Graphical
User Interface), which was later adopted by
almost all Operating Systems
Mac OS
Ref. Page 302

 Intuitive user interface
 Interoperable with iOS and WatchOS
 Supported with a large set of built-in applications
 iCloud facility
 Privacy and security features help users work in a
trusted environment
 Flexibility to work with Windows OS
 Use by differently abled users
Key Features of Mac OS Include
Ref. Page 302

 Designed in 2007 by Apple Incorporation for its
mobile devices such as iPad, iPhone and iPod.
 Provides a protective shell for each application
(app) to prevent other apps from tampering them
 Two apps can communicate directly, if approved
iOS
Ref. Page 302

 Highly intuitive user interface
 Facility to write, mark and draw
 Facility to ask for information or instruct using voice
interface
 Interoperable with Mac OS and WatchOS
 Supported with a large set of applications and games
 iCloud facility
 Multitasking facility
 Camera, music and maps
 Privacy and security features help users work in a trusted
environment
Key Features of iOS Include
Ref. Page 302

 Designed in 2015 by Apple Incorporation for its smart wrist
watch (Apple Watch)
 It is based on iOS and has many similarities with iOS in
terms of features
WatchOS
Ref. Page 302

 Health Kit
 Music
 Contact list, calendar, with notifications for important dates,
appointment, etc., calculator and many other useful
applications
 Ability to share data with other Apple devices
Key Features of WatchOS Include
Ref. Page 302

 An open source OS for mobile devices from Google
 Google developed it from Open Handset Alliance (OHA), a
business alliance of companies to develop open standard for
mobile devices
 It is Linux based, as it uses Linux kernel at its core for basic
system functionalities
 It has millions of applications, making it the most versatile
software environment for mobile devices
Android OS
Ref. Page 302

 Lets users choose their hardware device
 Portable across current and future hardware platforms
 Its architecture is flexible because it is component based
 It supports all Google services (Gmail, Google search, etc.)
 It supports 2D and 3D graphics, video streaming, and
multilingual interface
 It supports multiple keyboards and makes them easy to
install
 It supports multi-layer security
Key Features Android OS Include
Ref. Page 302

 Access control
 Android OS
 Batch processing
 Command-line interface (CLI)
 CPU-bound jobs
 Cryptography
 Demand paging
 Device manageemnt
 External security
 File
 File attributes
 File extensions
 File management
 Graphical User Interface (GUI)
 I/O-bound jobs
 iOS
 Internal security
 Job
 Job control language (JCL)
 Library programs
 Lightweight processes
 Linux
 Loosely coupled system
 Mac OS
 Memory partition
 Microsoft Windows
 Microsoft Windows NT
 MS-DOS
 Multiprocessing
 Multiprogramming
 Multiprogramming with fixed tasks (MFT)
 Multiprogramming with variable tasks (MVT)
 Multitasking
 Multithreading
 Operating system
 Process
 Process Control Block (PCB)
 Random access files
 Response time
Keywords/Phrases

 Security
 Sequential access files
 Swapping
 Throughput
 Tightly coupled system
 Time-sharing
 Time slice
 Time slot
 Translating programs
 Turnaround time
 Uniprogramming system
 Unix
 User authentication
 Utility programs
 Virtual machine
 Virtual memory
 WatchOS
Keywords/Phrases

Chapter 15: Application Software Packages Slide 1/26
Pradeep K. Sinha
Priti Sinha
Chapter 15
Application
Software Packages

Slide 2/26
Chapter 15: Application Software Packages
In this chapter you will learn about :
 Word-processing package
 Spreadsheet package
 Graphics package
 Personal assistance package
Learning Objectives

Word-Processing Package

 Word-processing describes use of hardware and software
to create, edit, view, format, store, retrieve, and print
documents (written material such as letters, reports,
books, etc.)
 Word-processing package enables us to do all these on
a computer system

 Entering text
 Editing text
 Formatting page style
 Formatting text
 Entering mathematical
symbols
 Displaying documents
 Saving, retrieving and
deleting documents
 Printing documents
 Importing text, graphics and
images
 Searching and replacing text
string
 Checking spelling
 Checking grammar and style
Commonly Supported Features in a

 Style sheet: Pre-stored page format that can be used
while creating a new document or can be applied to an
existing document
 Font: Complete set of characters with the same style
and size. A word-processing package comes with several
standard fonts
 Points: A point is 1/72 of an inch, and the size refers to
the distance from the top of the tallest character to the
bottom of the character that extends the lowest. Font
size is measured in points
Word-Processing (Few Terminologies)

 Three commonly used font styles are italic, bold and
underline.
 Justification: Alignment of text on the left or the right
margin, or on both margins. Four types of justification
are:
 Left-justification
 Right-justification
 Center-justification
 Full-justification
Word-Processing (Few Terminologies)

This sentence is written in Times New Roman font.
This sentence is written in Helvetica font.
This sentence is written in Palatino font.
This sentence is written in Courier New font.
This sentence is written in Antique Olive font.
Different Font Types (Examples)

This sentence is written in 10 point Times New Roman font.
This sentence is written in 36 point Times
New Roman font.
Different Font Sizes (Examples)

Different Font Styles (Examples)
This sentence is written in italic style.
This sentence is written in bold style.
This sentence is written in underline style.
You can even make individual words italic, bold,
or underline.

The term hardware refers to the physical devices of a
computer system. Thus, the input, storage, processing,
control, and output devices are hardware.
(a) Left Justified text
(b) Right Justified text
(c) Centered text
Different Justification Styles (Examples)

Mathematical Symbols (Examples)






 
 
 u 
S   u 1 u 2 
t R t   u
(u)
(2 )

 a,b,c   a,b   a,b r  a,c  s

Spreadsheet Package

 Spreadsheet package is a numeric data analysis tool
that allows us to create a computerized ledger
 Useful for any numerical analysis problem whose data
can be organized as rows and columns
Spreadsheet Package

 Maintaining and analyzing inventory, payroll, and other
accounting records by accountants
 Preparing budgets and bid comparisons by business analysts
 Recording grades of students and carrying out various types
of analysis of the grades by educators
 Analyzing experimental results by scientists and researchers
 Tracking stocks and keeping records of investor accounts by
stockbrokers
 Creating and tracking personal budgets, loan payments, etc.
by individuals
Few Uses of Spreadsheet Package

 Support for a large number of cells
 Support for addressing a range of cells by the addresses of
the endpoint cells
 Support for different types of cell data (such as label,
numeric value, formula, and date & time)
 Support for use of relative and absolute cell addresses in
formula
 Support for a wide range of commands
 Support for displaying numeric data in the form of graphs
and charts
Common Features of Spreadsheet
Package

A B C D E F
1 FINAL EXAM MARKS SHEET(CLASS-X: 2020)
2
3 NAME PHYS CHEM MATHS TOTAL PERCENT
4
5 P. Davis 92 95 88 275 91.66
6 A. Raje 86 82 94 262 87.33
7 D. Rana 75 83 85 243 81.00
8 M. Ray 77 75 72 224 74.66
9 J. Smith 94 92 96 282 94.00
10
11
Column
letters
Row numbers
A label running across
multiple columns
A label
Cell F4
Cell C11
Numeric
Value in a
Cell
Alphabetic Value
in a Cell
Result of the function
@SUM(B9..D9)
Result of the
formula
+ E9/3
Sample Spreadsheet

Examples of a Line Graph, a Bar Chart
and a Pie Chart
(a) A line graph (b) A bar chart
10%
40%
35%
15%
(c) A pie chart

Graphics Package

Graphics package enables us to use a computer system
for creating, editing, viewing, storing, retrieving and
printing designs, drawings, pictures, graphs and anything
else that can be drawn in the traditional manner
Graphics Package

 Drawing designs
 Painting drawings and pictures
 Presenting graphs and charts
 Dragging-and-dropping graphic objects
 Importing graphic objects
 Capturing screen snapshots
Common Features of Graphics Package

 Computer-aided-design (CAD): Integration of
computers and graphics design packages for the purpose
of automating the design and drafting process
 Vector graphics: Graphic object composed of patterns of
lines, points, circles, arcs and other geometric shapes
that can be easily represented by few geometric
parameters
 Raster graphics: Graphic object composed of patterns of
dots called pixels
Computer Graphics (Few Terminologies)

Personal Assistance
Package

Personal-assistance package allows individuals to:
 Use personal computers for storing and retrieving their
personal information
 Planning and managing their schedules, contacts,
finances and inventory of important items
Personal-assistance Package

 Calendar
 To-do list
 Address book
 Investments book
 Inventory book
Common Features of Personal
Assistance Package

Slide 26/26
 Bit-mapped image
 Bold
 Cell
 Center justification
 Clip-art library
 Computer Aided Design (CAD)
 Font
 Full justification
 Graphics package
 Italic
 Justification
 Landscape mode
 Left justification
 Personal assistance package
 Portrait mode
 Raster graphics
 Right justification
 Spreadsheet package
 Style sheet
 Underline
 Vector graphics
 What You See Is What you Get
(WYSIWYG)
 Word-processing
 Word-processing package
Key Words/Phrases

Chapter 16: Business Data Processing Slide 1/52
Pradeep K. Sinha
Priti Sinha
Chapter 16
Business Data
Processing

Slide 2/52
Chapter 16: Business Data Processing
 Difference between data and information
 Data storage hierarchy commonly used to facilitate data
processing
 Standard methods of organizing data
 File Management System (FMS)
 Database Management System (DBMS)
 Basic concepts and main components of FMS and DBMS
Learning Objectives

Basic Concepts

 Data is a collection of facts – unorganized but able to
be organized into useful information
 Information is data arranged in an order and form that
is useful to the people who receive it
 Data processing is a series of actions or operations
that converts data into useful information
 A data processing system includes resources such as
people, procedures, and devices used to process input
data for producing desirable output
Data Processing
Ref. Page 330

Data Storage Hierarchy
Multiple related characters are combined to form a field.
Character
Field
Record
File
Database
Level 0 Bit
Level 1
Level 2
Level 3
Level 4
Level 5
A single binary digit (0 or 1).
Multiple related bits are combined to form a character (byte).
Multiple related fields are combined to form a record.
Multiple related records are combined to form a file.
Multiple related files are integrated to form a
database.
Ref. Page 331

Employee Code First Name
0001 Pradeep
Last Name Hours worked Hourly rate Tax rate
Sinha 45 12.00 0.08
Fields
Employe
000
e Code
2
First Name Last Name Hours worked Hourly rate Tax rate
Ravi Patel 42 10.00 0.07
Employe
000
e Cod
3
Name Last Name Hours worked Hourly rate Tax rate
e First
Pratap Singh 43 15.00 0.10
Emplo
00
yee Cod
04
Last Name Hours worked Hourly rate Tax rate
e First Name
Kumar Rana 40 14.00 0.09
A
record
A field having
4 characters
Records
of a file
Relationship Among
Character, Field, Record, and File
Ref. Page 332

Standard Methods of
Organizing Data

File-oriented Approach
Ref. Page 333
 Application’s data is organized into one or more files and the
application program(s) processes the data stored in these
files to generate desired output
 It is customary to use a master file of permanent data, and
transaction files containing data of temporary nature

Limitations of File-oriented Approach
Ref. Page 333
 Limited query flexibility
 When the key field is not relevant to desired information, it
needs to search entire file
 Data redundancy
 Repetition of same data items in more than one file is
known as data redundancy
 It leads to increase in cost of data entry and data storage
 Data integrity problem
 Data integrity refers to consistency of data in all files
 Any change in a data item must be carried out in every file
containing that field

Limitations of File-oriented Approach
Ref. Page 333
 Lack of program/data independence
 An application program usually contains data format
statements, which define the format of each data field precisely
as the application needs it for processing
 Data dependence occurs when data is dependent on application
 Limited data security flexibility
 Offers file-level data security feature
 It can enforce data access restrictions on an entire file only, not
on a record or a field of data item

Database-oriented Approach
Ref. Page 333
 This approach integrates together data from multiple related
files in the form of a database having following properties:
 Provides greater query flexibility
 Reduces data redundancy
 Solves data integrity (inconsistency) problem
 Makes data independent of application programs
 Includes data security features at database level, record level,
and even at field level

File Management System

What is File Management System?
Ref. Page 334
 File-oriented approach of organizing data provides a set
of programs to facilitate users to organize, create, delete,
update, and manipulate their files
 All these programs together form a File Management
System (FMS)

A file management system supports following file types:
 Transaction file: Stores input data until it can be
processed
 Master file: Contains all current data relevant to an
application
 Output file: Stores output produced by one program
that is used as input to another program
 Report file: Holds a copy of a report generated by an
application
 Backup file: Copy of a file, created as a safety
precaution against loss of data
File Types
Ref. Page 334

File Organization
Ref. Page 334
 Deals with physical organization of records of a file for
depends on
convenience of their storage and retrieval
 Selection of a particular file organization
application type
every
 File organization requires use of some key field in
record in a file
 Key field value must be unique for each record of the file

Sequential Files
Ref. Page 334
 A sequential file stores its records one after another in
ascending/descending order of their key field values
 A computer processes a sequential file in the order in which
the file stores its records
 Sequential file organization is the most efficient and
economical file organization for applications in which we have
to update a large number of file records at regularly
scheduled intervals
 Activity ratio is ratio of total number of records in transaction
file and total number of records in master file

Sequential Files
Ref. Page 334
 Advantages
 Simple to understand and use
 Easy to organize and maintain
 Need relatively inexpensive I/O media and devices
 Efficient and economical to use for applications in which activity
ratio is high
 Disadvantages
 Inefficient and uneconomical to use for applications in which
activity ratio is low
 Limited to batch-processing environment because of the need to
accumulate transactions in batches
 Precludes possibility of up-to-the-minute data because of the need
to accumulate transactions in batches
 Requires extra overhead of sorting the files before using them for
processing
 Leads to data redundancy problem

Direct Files
Ref. Page 334
 Direct/random file organization is suitable for applications that
directly locate any record by its key field value, without having to
search through a sequence of other records
 A direct file stores each record at a location to which the address-
generating function maps the record’s key field value
 This mechanism is known as hashing and the address-generating
function is called hashing algorithm
 Hashing algorithm sometimes maps the key values of two or more
records to same storage address. This problem is known as collision
 To search a record, given its key value, the computer applies the
hashing algorithm on the given key to generate its corresponding
address
 If required, an application can process the records of a direct file
sequentially in ascending/descending sequence of key field value

Direct Files
Ref. Page 334
 Advantages
 Can quickly locate and retrieve any record directly
 Does not require sorting of transactions
 Does not require accumulation of transactions in batches
 Can support interactive online applications
 Application can process direct file records sequentially
 Disadvantages
 Require relatively expensive hardware and software resources
 Due to address generation overhead involved, they are less
efficient and economical than sequential files for high activity ratio
applications
 Often require special security and access synchronization
mechanisms

Indexed Sequential Files
Ref. Page 334
 In indexed sequential file organization, there are two files for
every data file – data file and index file
 Data file can store the records in random sequence
 Index file stores the index keys in sorted sequence on index
key value
 This technique of file management is known as Indexed
Sequential Access Method (ISAM) and files of this type are
called ISAM files

Indexed Sequential File: Example
Employee
code (key)
Address location
0001 1003
0002 1001
0003 1004
0004 1002
Address
location
Employee record
1001 0002 R. S. Patel …
1002 0004 R. K. Rana …
1003 0001 K. P. Sinha …
1004 0003 N. P. Singh …
Index file Data file
Ref. Page 334

Indexed Sequential Files
Ref. Page 334
 Advantages
 Applications in which activity ratio is high, can use index sequential
files quite efficiently for sequential processing
 Applications in which activity ratio is low, can also use index
sequential files quite efficiently for direct access processing
 Disadvantages
 Require relatively expensive hardware and software resources
 Require more storage space than other types of files
 Are unsuitable for online applications requiring direct access to
records

File Utilities
Ref. Page 334
 Are routines, which perform generic operations on data files
 Sorting utility
 Arranges records of a file in some defined sequence
 Keys determine the sorting sequence of the file’s records
 Enables users to specify their sequencing requirements for a
file by means of input parameters
 Reads un-sequenced records of an input file, and by means of
various copying techniques, ultimately produces an output file
containing records of the input file in desired sequence
 Searching utility
 Finds a particular record in a file
 Matches the specified key values with their values in each
record to search the desired record
 Efficiency of a search algorithm depends on file organization

File Utilities
Ref. Page 334
 Searching a record
requires much less
sequential file
from a direct or index sequential file
time than searching a record from a
 Merging utility
 Combines records of two or more ordered (sorted) files into a
single ordered file
 Requires records of each of the input files to be sorted in the
same order, although their record layout need not be identical
 Places records from each of the input files in their correct
relative order, producing an output file having all records in the
same order as input files
 Copying utility
 Produces a copy of a file either from one unit of a storage
device to another similar unit or from one storage medium to
another (Continued on next slide…)

File Utilities
Ref. Page 334
 Users often use file copying utility to take back-up copies of
files
 Copying utilities are also known as peripheral interchange
programs (PIP) since users often use them to copy a file from
one peripheral device to another
 Printing utility
 Printing utility prints a file on a printer to produce hard copy of
its contents
 Provides the facility to print file contents in different formats
 Provides some selection and editing facilities to enable printing
of parts of files
 Provides special formats for printing files that contain program
instructions rather than data

File Utilities
Ref. Page 334
 Maintenance utility
 Copies data from one or more files to a new file selectively, or
updates a file’s contents selectively

Sorting on One Key and Two Keys: Examples
Ref. Page 334
Employee
code
Department
code
Other fields
(Name,
Address,
Qualification,
Basic salary,
etc.)
101 2 ---
123 3 ---
124 1 ---
176 2 ---
178 1 ---
202 3 ---
213 1 ---
Employee
code
Department
code
Other fields
(Name, Address,
Qualification, Basic
salary, etc.)
124 1 ---
178 1 ---
213 1 ---
101 2 ---
176 2 ---
123 3 ---
202 3 ---
Sorting on one key in ascending
employee-code sequence
Sorting on two keys in ascending employee-code (secondary
key) within ascending department-code (primary key)

Merging Utility: Example
Employee
code
Other
fields
125 …
127 …
137 …
146 …
159 …
Employee
code
Other
fields
112 …
119 …
125 …
127 …
129 …
137
139 …
146 …
150 …
152 …
159 …
Employee
code
Other
fields
112 …
119 …
129 …
139
150 …
152 …
Input file Output file Input file
File A
File B
File C
Merging of files A and B to produce file C
Ref. Page 334

Database Management
System

 In database-oriented approach of organizing data, a
set of programs is provided to facilitate users in
organizing, creating, deleting, updating, and
manipulating data in a database
 All these programs together form a Database
Management System (DBMS)
Database Management System

 Database model defines the manner in which the
various files of a database are linked together.
 Four commonly used database models are:
 Hierarchical
 Network
 Relational
 Object-oriented
Database Models

Hierarchical Databases
 Hierarchical database links its data elements as an inverted
tree structure
 Below the single-root data element are subordinate elements,
each of which, in turn, has its own subordinate elements, and
so on
 Tree can grow to multiple levels
 There may be many children elements under each parent
element, but there can be only one parent element for any
child element
 Main limitation of hierarchical database is that it does not
support flexible data access
 Applications can access its data elements only by following
paths formed by branches of the tree structure

Hierarchical Database: Example
Organization
Personnel
department
Finance
department
Technical
department
Managers Support
staff
Managers Engineers Technicians
Support
staff
Managers Support
staff
A parent element
A child element

Network Databases
 Network database is an extension of hierarchical database
 Organizes its data elements in such a manner that they
have parent-child relationship among them
 Designer must determine all types of relationships among
data elements while designing the database
 A child data element can have more than one parent
element or no parent element at all
 Parent and child elements can have many-to-many
relationships

Network Database: Example
College
English Hindi Mathematics
Computer
Science
Seeta Geeta Ram Mohan Sohan Raju
A child element can have more than one parent element
This child element has no parent element
Courses
Students

Relational Databases
 Relational database organizes its data elements as multiple
tables with rows and columns
 Each table column represents a data field, and each row
represents a data record (also known as a tuple)
 Relational database model provides greater flexibility of data
organization and future enhancements in database as
compared to hierarchical and network database models
 Applications can organize their data elements in a relational
database in a manner that is identical to real-life relationships
between data elements

Relational Databases
 For adding new data to an existing relational database, there
is no need to redesign the database afresh
 Users can also reorganize data elements, when necessary, to
create new tables by selecting certain rows or specific
columns from other tables, or by joining columns and rows
from two separate tables

Membership
No.
Member’s
name
Member’s Address
83569 K. N. Raina C-15, Sarita Vihar, Pune-7
62853 D. P. Singh A-22, Anand Park, Pune-5
12859 R. Pandey D-18, Vrindavan, Pune-7
32228 R. S. Gupta A-12, Nandanvan, Pune-2
23466 S. K. Ray B-05, Royal Villa, Pune-3
11348 P. K. Sen B-16, Anand Park, Pune-5
16185 T. N. Murli A-11, Vrindavan, Pune-7
(a) Members data table.
Borrower
(Membership No.)
Book No.
(ISBN)
Due Date
(DD-MM-YYYY)
12859 27-21675-2 10-12-2020
11348 89303-530-0 08-11-2020
32228 13-201702-5 10-11-2020
16185 22-68111-7 05-12-2020
12859 71606-214-0 06-11-2020
62853 13-48049-8 15-11-2020
11348 18-23614-1 12-11-2020
Relational Database: Example
(b) Borrowed books data table
Book No. (ISBN) Book Title Author
13-201702-5 Concepts of Physics H. C. Verma
13-48049-8 Concepts of Chemistry S. S. Dubey
18-23614-1 Astrology for You N. K. Sharma
22-68111-7 Fundamentals of Computers K. Ramesh
27-21675-2 C++ Programming R. P. Rajan
71606-214-0 Computer Networks A. N. Rai
89303-530-0 Database Systems P. N. Dixit
(c) Books data table

A report of overdue books as of 10-11-2020 from the
sample database of previous slide
List of overdue books as on 10-11-2020
Membership
No.
Member’s
Name
Member’s
Address
Due
Date
Book No. Book Title Book
Author
11348 P. K. Sen B-16,
Anand Park,
Pune-5
08-11 89303-530-0 Database
Systems
P. N. Dixit
32228 R. S. Gupta A-12,
Nandanvan,
Pune-2
10-11 13-201702-5 Concepts of
Physics
H. C. Verma
12859 R. Pandey D-18,
Vrindavan,
Pune-7
06-11 71606-214-0 Computer
Networks
A. N. Rai
Sample Report

Object-oriented Databases
 Some key features that several applications require for
effective modeling are:
 Ability to model complex nested entities
 Support for general data types found in object-oriented
 Support for frequently useful object-oriented concepts such as
object, class, inheritance, etc.
 Support for proper match between object-oriented programming
languages and database languages
 Object-oriented database is a collection of objects whose
behavior, state, and relationships are in accordance with
object-oriented concepts

Object-oriented Databases
 Object-oriented database management system allows
definition and manipulation of an object-oriented database
 It provides direct support for the definition and
manipulation of the relationships among objects

Object-Oriented Database
Length
Width
Height
Engine Type
Fuel Type
Fuel Tank Capacity
No. of Wheels
Vehicle VehicleSpecs
Other details
of the vehicle
like with/
without gear,
seating
capacity, etc.
TwoWheeler FourWheeler
Other details
of the vehicle
like no. of
doors, seating
capacity, etc.
Name
Location
President
Company
Id
Name
Age
Employee
Other details of
the company
DomesticCompany
Other details of
the company
ForeignCompany
Class/subclass link
Attribute/domain link
Id
Color
Specifications
Manufacturer

 DBMS allows users to organize, process and retrieve
selected data from a database without knowing about the
underlying database structure
 Four major components of a DBMS that enable this are:
 Data Definition Language (DDL): Used to define the
structure (schema) of a database
 Data Manipulation Language (DML): Provides
commands to enable the users to enter and manipulate
the data
Main Components of a DBMS

 Query Language: Enables users to define their
requirements for extracting the desired information
from the database in the form of queries
 Report generator: Enables the users of a database
to design the layout of a report so that it can be
presented in the desired format
Main Components of a DBMS

Creation of a database is a three step process:
 Defining its structure (schema)
 Designing forms (custom screens) for displaying and
entering data
 Entering the data into it
Creating a Database

EMPLOYEE DATABASE DATA ENTRY FORM
EMPLOYEE ID: 856392 SEX: M AGE: 42
LAST NAME:
FIRST NAME:
MIDDLE NAME:
SINHA
EMPLOYEE NAME:
PRADEEP
KUMAR
ADDRESS 1:
ADDRESS 2:
CITY:
STATE:
POSTAL CODE:
F/8, ANAND PARK
CONTACT ADDRESS:
SOCIETY, AUNDH
PUNE
MH
411007
TELEPHONE NO.: (020) 5680-489
ANY OTHER INFORMATION: IS FLUENT IN JAPANESE LANGUAGE
Sample Database Form

 All database systems provide commands to view,
modify, delete, or add records of an already established
database
 Many database systems also provide a facility to set up
a filter allowing user to browse through and view only
those records that meet some criterion
Viewing, Modifying, Deleting, and
Adding Records

Commonly supported features for enabling a user to
search for desired information in a database are:
 Find command: Used for simple database queries
 Query language: Used for more complex database
queries
 Query By Example (QBE): Provides a simple user
interface for specifying search criteria
Searching a Database

 Reports are generated by using report generator of a
database system to assemble the output of a database
query in desired format
 Report generator enables a user to specify layout of the
report, titles & subtitles for the report, column
headings for various fields, and other elements to
make the report appear more presentable
Creating Reports

The report is sorted in alphabetical order on last name of employee
LAST
NAME
FIRST
NAME
ADDRESS-1 ADDRESS-2 TELEPHONE
NUMBER
Gupta Rajiv A-12, Nandanvan M. G. Road 4623-4892
Murli Tapan A-11, Vrindavan Pashan Road 5863-4905
Pandey Rupa D-18, Vrindana Pashan Road 5865-3236
Raina Pushpa C-15, Sarita Vihar Aundh Road 5755-8328
Ray Suhas B-05, Royal Villa M. G. Road 4685-6356
Sen Prakash B-16, Anand Park Aundh Road 5762-3333
Singh Deepak A-22, Anand Park Aundh Road 5728-6287
LIST OF EMPLOYEES WHO BELONG TO PUNE
DATE: DECEMBER 17, 2020
Sample Output of Report

Key Words/Phrases
 Activity ratio
 Backup file
 Collision
 Copying
 Data
 Data Definition Language (DDL)
 Data dependence
 Data dictionary
 Data file
 Data integrity
 Data Manipulation Language
(DML)
 Data processing
 Data redundancy
 Data storage hierarchy
 Database
 Database administrator
 Database Management System
(DBMS)
 Database model
 Direct file
 Field
 File
 File Management System (FMS)
 File utilities
 Filter
 Hashing
 Hashing algorithm
 Hierarchical database
 Index file
 Indexed sequential file
 Information
 Master file
 Merging
 Network database
 Output file
 Peripheral Interchange Program
 Primary key

Key Words/Phrases
 Query By Example
 Query language
 Record
 Relational database
 Report file
 Report Generator
 Schema
 Searching
 Secondary key
 Sequential file
 Sorting
 Transaction file
 Tuple

Chapter 17: Data Communications & Computer Networks Slide 1/81
Chapter 17
Data Communications
& Computer Networks
Pradeep K. Sinha
Priti Sinha

Slide 2/81
Chapter 17: Data Communications & Computer Networks
 Basic elements of a communication system
 T
echniques, channels, and devices used to transmit data
between distant locations
 Types of computer networks
 Communication protocols and their use in computer
networks
 Internetworking tools and their use in building large
computer networks
 Wireless communications technologies and wireless
networks
 Characteristics and advantages of distributed computing
systems
Learning Objectives

Basic Concepts and
Terminologies

Data Communications and
Computer Networks
Ref. Page 357 Chapter 17: Data Communications & Computer Networks Slide 4/81
 A computer network is a network of computers
 It connects multiple computers in a manner to enable
meaningful transmission and exchange of data among them

Basic Elements of a Communication
System
 Communication is
from one point to another
the process of transferring a message
point to
 Electronic systems that transfer data from one
another are called data communication systems
Sender
(source)
Medium
Carries the
message
Creates and sends a
message
Receives the message
Receiver
(sink)

Data Transmission Modes
Sender
Sender
(or Receiver)
Sender
(and Receiver)
Receiver
Receiver
(or Sender)
Receiver
(and Sender)
(a) Simplex
OR
(b) Half-duplex
AND
(c) Full-duplex

 Bandwidth: Range of frequencies available for data
transmission. It refers to data transmission rate. Higher
the bandwidth, the more data it can transmit
 Baud: Unit of measurement of data transfer rate.
Measured in bits per second (bps)
Data Transmission Speed

 Narrowband: Sub-voice grade channels in range from
45 to 300 baud. Mainly used for telegraph lines and
low-speed terminals
 Voiceband: Voice grade channels with speed up to
9600 baud. Mainly used for ordinary telephone voice
communication and slow I/O devices
 Broadband: High speed channels with speed up to 1
million baud or more. Mainly used for high-speed
computer-to-computer communication or for
simultaneous transmission of data
Data Transmission Speed Category

Data Transmission Media

The most commonly used ones are:
 Twisted-pair wire (UTP cable)
 Coaxial cable
 Microwave system
 Communications satellite
 Optical fibers
Data Transmission Media

Unshielded Twisted-Pair (UTP) Cable

Coaxial Cable
Copper mesh
Outer PVC shield
PVC insulation
Central copper
wire

Microwave Communication System
Transmitting
station
In between
repeaters
Transmitting antennas Receiving antennas
Line of sight Line of sight Line of sight

Satellite Communication System
Transmitting
station on earth
6 GHz
Uplink
4 GHz
Downlink
Receiving
station on earth
Satellite in space

Optical Fiber Communication System
Electrical
signal
Optical fiber
Amplifier
Electrical
signal
Light-to-electrical-
wave converter
Electrical-to-light-
wave converter
Light waves
Sender
Receiver

Digital and Analog
Data Transmission

Digital and Analog Data Transmission
 Analog signal: Transmitted
continuous range. Example:
waves
power varies over a
sound, light, and radio
 Digital signal: Sequence of voltage pulses represented
in binary form
 Computer generated data signal is digital, whereas
telephone lines carry analog signals

 When digital data is to be sent over an analog facility,
digital signals must be converted to analog form
 Conversion of digital signal to analog form is known as
modulation
 Conversion of analog signal to digital form is known as
demodulation
 Digital transmission of data is preferred over analog
transmission of data due to lower cost, higher
transmission speeds, and lower error rate
Digital and Analog Data Transmission

Analog and Digital Signals
0 1/f 2/f
-v
(a) Analog signal
Voltage
+v
t
t
v
0 0
1 1
0 0
1 1
(b) Digital signal

Modulation Techniques
 Amplitude Modulation (AM): Two binary values (0 and
1) of digital data are represented by two different
amplitudes of the carrier signal, keeping frequency and
phase constant
 Frequency Modulation (FM): Two binary values of
digital data are represented by two different frequencies,
while amplitude and phase are kept constant
 Phase Modulation (PM): Two binary values of digital
data are represented by shift in phase of carrier signal

Modems
 Modem is short for MOdulator/DEModulator
 Special device used for conversion of digital data to
analog form (modulation) and vice-versa (demodulation)
 Essential piece of hardware where two digital devices
(say two computers) want to communicate over an
analog transmission channel (say a telephone line)

Use of Modems in Data Communications
0
Sender
computer
0 1 1
0 1 0 0
0 1 1 0
Receiver
computer
0 1 0 0
Digital signals
Digital signals
Analog signals on
telephone line
Demodulator
Modulator
Modulator
Demodulator
A modem at
sender computer
end
A modem at receiver
computer end

Factors for Modem Selection
 Transmission speed
 Internal versus external
 Facsimile facility
 Error correction
 Data compression

Data Transmission
Services

Data Transmission Services
 Data transmission service providers are popularly
known as common carriers
 Various types of services offered by common carriers
are:
 Dial-up line: Operates in a manner similar to a
telephone line
 Leased line:
that directly
computers
Special conditioned
and permanently
telephone line
connects two
 Integrated Services Digital Network (ISDN):
Telephone system that provides digital (not analog)
telephone and data services

 Value Added Network (VAN): Provides value-added
data transmission service. Value added over and above
the standard services of common carriers may include
e-mail, data encryption/decryption, access to
for
commercial databases, and code conversion
communication between computers
Data Transmission Services

Multiplexing Techniques

Multiplexing
 Method of dividing physical channel into many logical
channels so that a number of independent signals may
be simultaneously transmitted
 Electronic device that performs multiplexing is known
as a multiplexer
 Multiplexing enables a single transmission medium to
concurrently transmit data between several
transmitters and receivers

A Multiplexed System
T1 T2 T3 T4
Multiplexer
Modem
Modem
Multiplexer
Computer

Two Basic Methods of Multiplexing
 Frequency-Division Multiplexing (FDM): Available
bandwidth of a physical medium is divided into several
smaller, disjoint logical bandwidths. Each component
bandwidth is used as a separate communication line
 Time-Division Multiplexing (TDM): Total time
available in a channel is divided among several users,
and each user of the channel is allotted a time slice
during which he/she may transmit a message

Frequency-Division Multiplexing
40 KHz
50 KHz
60 KHz
70 KHz
80 KHz
Signal-1
Signal-2
Signal-3
Signal-4
Signal-5
40 KHz
50 KHz
60 KHz
70 KHz
80 KHz
Signal-1
Signal-2
Signal-3
Signal-4
Signal-5
Sender end Receiver end
Modulator Demodulator
Channel

Time-Division Multiplexing
A3 A2 A1
B3 B2 B1
C3 C2 C1
Signal A
Signal B
Signal C C3 C2 C1
B3 B2 B1
A3 A2 A1
C2 B2 A21 C1 B1 A1
…
Time sliced
signals
Reassembled
signals
Sender
end
Receiver
end
Demulti-
plexer
Channel

Asynchronous and
Synchronous Transmission

Asynchronous and Synchronous
Transmission
 Two modes of data transmission on a communication
line are asynchronous and synchronous
 Asynchronous transmission
 Sender can send data at any convenient time and
the receiver will accept it
 Data is transmitted character by character at
irregular intervals
 Well suited to many keyboard type terminals

 Synchronous transmission
 Sender and receiver must synchronize with each
other to get ready for data transmission before it
takes place
 Entire blocks of characters are framed and
transmitted together
 Well suited to remote communication between a
computer and such devices as buffered terminals
and printers
Asynchronous and Synchronous
Transmission

Irregular time intervals
between two characters
Each character framed by
start and stop bits
Character Character Character
Asynchronous Transmission

Synchronous Transmission
Char Char Char Char Char Char
Indefinite time interval
between two blocks of data
A block of characters may consist
of hundreds of characters
Trailer containing
end of block indication
Header containing
synchronizing and other
information

Switching & Routing
Techniques

Switching Techniques
 Data is often transmitted from source to destination
through a network of intermediate nodes
 Switching techniques deal with the methods of
establishing communication links between the sender
and receiver in a communication network
 Three commonly used switching techniques are:
 Circuit switching: Dedicated physical path is
established between sending and receiving stations
through nodes of the network for the duration of
communication

 Message switching: Sender appends receiver’s
destination address to the message and it is
transmitted from source to destination either by
store-and-forward method or broadcast method
 Packet switching: Message is split up into fixed size
packets and each packet is transmitted independently
from source to destination node. Either store-and-
forward or broadcast method is used for transmitting
the packets. All the packets of a message are re-
assembled into original message at the destination
node
Switching Techniques

Circuit Switching Method
Source node
Destination
node
Switching nodes
Dotted lines and shaded
balls indicate the circuit
established

Store-and-Forward Method of
Message Switching
Either path 1-2-3-4 or 1-5-4 may be used to
transmit a message from A to B.
D
A
B
C
1
3
2
4
5

Broadcast Method of Message Switching
Nodes 1 2 3
Message
Broadcast channel
n

Routing Techniques
 In a WAN, when multiple paths exist between the source
and destination nodes of a packet, any one of the paths
may be used to transfer the packet
 Selection of path to be used for transmitting a packet is
determined by the routing technique used

Routing Techniques
 Three popularly used routing algorithms are:
 Source routing: Source node selects the entire path
before sending the packet
 Hop-by-hop routing: Each node along the path
decides only the next node for the path
 Hybrid routing: Source node specifies only a few
major intermediate nodes of the complete path, and
hop-by-hop routing method is used to decide the
subpaths between any two of the specified nodes.

Network Topologies
and Types

Network Topology
 A network’s topology refers to the way in which the network
links its nodes
 It determines the various data paths available between any
pair of nodes in the network
 Choice of a topology depends on a combination of factors
such as:
 Desired performance
 Desired reliability
 Size of the system
 Expandability
 Cost of components and services
 Availability of communication lines
 Acceptable delays in routing

Network Topologies
 Although number network topologies are possible, four
major ones are:
 Star network
 Ring network
 Completely connected network
 Multi-access bus network

Star Network
Host node

Ring Network

Completely Connected Network

Multi-Access Bus Network
Computers (nodes)
Single communication line shared by all nodes

Hybrid Network
Ring Star Completely connected

Network Types
 Five types of networks in common use are:
 Personal-area networks (PANs)
 Local-area networks (LANs)
 Campus-area networks (CANs)
 Metropolitan-area networks (MANs)
 Wide-area networks (WANs)

Communication Protocols

Communication Protocols
 A protocol is a set of formal operating rules, procedures, or
conventions that govern a given process
 Communication or network protocol, therefore, describes
rules that govern transmission of data over communication
networks

Roles of a Communication Protocol
 Data sequencing
 Breaking a long message into smaller packets of fixed size
 Rules define method of numbering packets to detect loss or
duplication of packets, and to identify packets
 Data routing
 Decide the path between source and destination
 Data formatting
 Define which group of bits or characters within a packet
constitutes data, control, addressing, or other information
 Flow control
 Prevent a fast sender from flooding a slow receiver with data by
regulating flow of data on communication lines

 Error control
 Detect errors in messages to ensure transmission of correct
messages
 Precedence and order of transmission
 Ensure that all nodes get a chance to use communication lines
and other resources
 Connection establishment and termination
 How connections are established, maintained, and terminated
 Data security
 Mechanisms for providing security and privacy of messages
sent/received
 Log information
 What types of log information the system should maintain for all
jobs and data communications tasks
Roles of a Communication Protocol

Concept of Layered Protocols in
Network Design
 Networks have modular design for easy and efficient handling of
the system
 Consist of several modules, which are grouped into layers
logically
 Each layer offers certain services to higher layers, shielding those
layers from implementation details of services offered by lower
layers
 Each layer has its own set of protocols
 Main reasons for using layered protocols are:
 Layers makes their implementation more manageable
 Provides well-defined interfaces between layers
 Allows interaction between functionally paired layers in different
locations
 Protocol suite, protocol family, or protocol stack are terms used to
refer to a collection of protocols of a network system

Network Interface Card (NIC)
 Network Interface Card (NIC or network card) is a hardware
device that connects a computer to a network, both
functionally and physically
 It is an add-on card that is connected directly to a computer’s
I/O bus
 NIC’s ROM has the network’s physical-layer communication
protocol

The OSI Model
 The Open System Interconnection (OSI) model is
framework for defining standards for linking
heterogeneous computers in a packet switched network
 Standardized OSI protocol makes it possible for any two
heterogeneous computer systems, located anywhere in
the world, to easily communicate with each other
 Separate set of protocols is defined for each layer in its
seven-layer architecture. Each layer has an independent
function

Layers, Interfaces, and Protocols
in the OSI Model
Layer 7 (application)
Layer 6 (presentation)
Layer 5 (session)
Layer 4 (transport)
Layer 3 (network)
Layer 2 (data link)
Layer 1 (physical)
Application protocol
Presentation protocol
Session protocol
Transport protocol
Network protocol
Data-link protocol
Physical protocol
Layer 7 (application)
Layer 6 (presentation)
Layer 5 (session)
Layer 4 (transport)
Layer 3 (network)
Layer 2 (data link)
Layer 1 (physical)
Node 1 Node 2
Process A Process B
Network
Interface
Interface
Interface
Interface
Interface
Interface Interface
Interface
Interface
Interface
Interface
Interface

An example illustrating transfer of message M from sending node to the
receiving node in the OSI model: Hn, header added by layer n:Tn, trailer
added by layer n.
H7 M
H2 H3 H4 H5 H6 H7 M1 T2
H3 H4 H5 H6 H7 M1
H4 H5 H6 H7 M1
H6 H7 M
H4 H5 H6 H7 M2
H3 H4 H
5
H6 H7 M2
H2 H3 H4 H5 H6 H7 M2 T2
H5 H6 H7 M
H7 M
Sender node Receiver node
Process A Process B
H2 H3 H4 H5 H6 H7 M1 T2
H3 H
4
H5 H6 H7 M1
H4 H5 H6 H7 M1
H6 H7 M
H4 H5 H6 H7 M2
H3 H
4
H5 H6 H7 M2
H2 H3 H4 H5 H6 H7 M2 T2
H5 H6 H7 M

Internetworking Tools

Internetworking
 Interconnecting two or more networks to form a single
network is called internetworking, and the resulting
network is called an internetwork
 Goal of internetworking is to hide details of different
physical networks, so that resulting internetwork
functions as a single coordinated unit
 Tools such as bridges, routers, brouters, and gateways
are used for internetworking
 The Internet is the best example of an internetwork

Bridges
 Operate at bottom two layers of the OSI model
 Connect networks that use the same communication
protocols above data-link layer but may use different
protocols at physical and data-link layers

Routers
 Operates at network layer of the OSI model
 Used to interconnect those networks that use the same
high-level protocols above network layer
 Smarter than bridges as they not only copy data from
one network segment to another, but also choose the
best route for the data by using routing table

Gateways
 Operates at the top three layers of the OSI model
(session, presentation and application)
 Used for interconnecting dissimilar networks that use
different communication protocols
 Since gateways interconnect dissimilar networks,
protocol conversion is the major job performed by
them

Wireless Networks

Wireless Computing Systems
 A wireless computing system uses wireless
communication technologies for interconnecting computer
systems
 It enhances functionality of computing equipment by
freeing communication from location constraints of wired
computing systems
 Wireless computing systems are of two types:
 Fixed wireless systems: Support little or no
mobility of the computing equipment associated with
the wireless network
 Mobile wireless systems: Support mobility of the
computing equipment to access resources associated
with the wireless network

Issues in Wireless Computing Systems
 Lower bandwidth
 Variable bandwidth
 Higher error rate
 Increased security concern
 Dynamically changing network
 Lost or degraded connection
 Support for routing and location
management functions
 Limited power

Wireless Applications
 Interesting and important applications include:
 Mobile e-commerce applications (m-commerce)
 Web surfing
 Access to corporate data by employees while they are
traveling
 Mobile video-on-demand
 Location-sensitive services such as finding nearby movie
theaters or restaurants

 1G, 2G, 3G, 4G and 5G
 Wireless LAN
 WiMAX (Worldwide Interoperability for
Microwave Access)
 Wireless Local Loop (WLL)
 Radio-router
 Multihop Wireless Network
 Wireless Application Protocol (WAP)
Wireless Technologies

 The era of mobile wireless communication started in
1980.
 The five generations of mobile wireless communication
technologies since then are 1G, 2G, 3G, 4G and 5G.
 Every new generation made mobile wireless
communication faster than before and had improved or
new features than earlier generation technologies
Mobile Wireless Communication Technologies

S. No. Features 1G 2G 3G 4G 5G
1. Year of launch 1980 1991 2000 2010 2020 (expected)
2.
Maximum
communication
speed
2.4
Kbps
64 Kbps,
384 Kbps
with 2.5G
2 Mbps 1 Gbps 35.46 Gbps
3. Technology Analog Digital,
GSM,
CDMA
CDMA
2000,
UMTS,
EDGE
LTE,
MIMO,
OFDM
WWWW,
Massive MIMO,
Millimeter Wave Mobile
Communications

S. No. Features 1G 2G 3G 4G 5G
4. Key Services Analog
phone
calls
Digital
phone
calls, and
Messaging
(SMS,
MMS)
Digital phone
calls, True
multimedia
messaging
including
video, Video
conferencing,
Mobile TV,
Video games,
Web-based
applications
IP-based
services
including
phone calls,
Multimedia
messaging,
Web access,
HDTV, Video
conferencing,
IP telephony,
High-end
mobile
gaming,
Mobile cloud
computing
IP-based services
including phone calls,
Multimedia messaging,
Web access, HDTV,
Video conferencing,
High-end mobile
gaming, Mobile cloud
computing, Interactive
multimedia
applications, Mobile
applications based on
device-to-device
communication (IoT
applications), etc. with
far better experience
than before.

Distributed Computing
Systems

Distributed Computing Systems
 It is a configuration, which consists of many independent
computer systems interconnected by a communication
network
 It enables sharing of many hardware and software resources,
as well as information, among several users who may be far
away from each other
 It is more complex to build because its design must:
 Enable it to use and manage a very large number of distributed
resources effectively
 Enable various nodes of the system to communicate with each
other reliably
 Include special security mechanisms to protect distributed
shared resources and services against intentional or accidental
security violations

Main Advantages of Distributed
Computing Systems
 Inherently distributed applications
 Information sharing among distributed users
 Resource sharing
 Better price-performance ratio
 Shorter response times and higher throughput
 Higher reliability
 Extensibility and incremental growth
 Better flexibility in meeting users’ needs

 1G technology
 2G technology
 3G technology
 4G technology
 5G technology
 Amplifier
 Amplitude Modulation (AM)
 Application layer
 ARPANET
 Asynchronous transmission
 Bandwidth
 Baud
 Bridge
 Broadband
 Broadcast
 Campus Area Network (CAN)
 C-band transmission
 Circuit switching
 Coaxial cable
 Common Carriers
 Communication protocol
 Communications satellite
 Completely connected network
 Computer network
 Data-link layer
 Demodulation
 Dial-up line
 Distributed Computing System
 Ethernet
 Fax modem
 File Transfer Protocol (FTP)
 Frequency Modulation (FM)
 Frequency-Division Multiplexing (FDM)
 Full duplex
 Gateway
 Half duplex
 Hop-by-hop routing
 Hybrid network
 Internet Protocol (IP)
 Internetworking
 ISDN (Integrated Services Digital Network)
 Ku-band transmission
 Leased line
 Local Area Network (LAN) (Continued on next slide)
Keywords/Phrases

 Message switching
 Metropolitan Area Network (MAN)
 Microwave system
 Mobile computing
 Modem
 Modulation
 Multi-access Bus network
 Multiplexer
 Narrowband
 Network Interface Card (NIC)
 Network layer
 Network topology
 Nomadic computing
 Optical fibers
 OSI Model
 Packet switching
 Phase Modulation (PM)
 Physical layer
 POTS (Plain Old Telephone Service)
 Presentation layer
 Protocol family
 Protocol stack
 Protocol suite
 Repeater
 Ring network
 Router
 Session layer
 Simplex
 Source routing
 Star network
 Store-and-forward
 Synchronous transmission
 Time-Division Multiplexing (TDM)
 Transport Control Protocol (TCP)
 Transport layer
 Twisted-pair
 Unshielded twisted-pair (UTP)
 User Datagram Protocol (UDP)
 Value Added Network (VAN)
 Voiceband
 VSAT (Very Small Aperture Terminals)
 Wireless Application Protocol (WAP)
 Wide Area Network (WAN)
 WiMax
 Wireless LAN
 Wireless Local Loop (WLL)
 Wireless network
Keywords/Phrases

Chapter 18: The Internet and Internet of Things Slide 1/29
Pradeep K. Sinha
Priti Sinha
Chapter 18
The Internet and
Internet of Things

Slide 2/29
Chapter 18: The Internet and Internet of Things
Learning Objectives
 Definition and history of the Internet
 Its basic services
 The World Wide Web (WWW)
 WWW browsers
 Internet search engines
 Uses of the Internet
 Internet of Things (IoT)
 Benefits and Uses of IoT
 Challenges in Adoption of IoT

Definition and History

Slide 4/23
Chapter 18: The Internet
Ref. Page 396
 The Internet is a network of computers, which links many
different types of computers all over the world
 It is a network of networks sharing a common mechanism for
addressing computers, and a common set of communication
protocols
 The Internet has its root in the ARPANET system of the
Advanced Research Project Agency of the U.S. Department of
Defense
 ARPANET was the first WAN and had only four sites in 1969
 The Internet evolved from basic ideas of ARPANET for
interconnecting computers

 In 1989, the U.S. Government lifted restrictions on the use of
the Internet, and allowed its usage for commercial purposes
as well
 It now interconnects more than 50 Billion devices, and more
than 5 Billion users around the world to communicate with
each other
 The Internet continues to grow at a rapid pace
Slide 5/23
Ref. Page 396

Chapter 18: The Internet Slide 6/23
Its Basic Services

Basic Services of the Internet
Ref. Page 398
 Electronic Mail (e-mail): Allows a user to send a mail
(message) to another Internet user in any part of the
world in a near-real-time manner
 File Transfer Protocol (FTP): Allows a user to move a
file from one computer to another on the Internet
 Telnet: Allows a user to log in to another computer
somewhere on the Internet
 Usenet News: Allows a group of users to exchange
their views/ideas/information

Electronic Mail
Ref. Page 398
 E-mail is a rapid and productive communication tool
because:
 It is faster than paper mail
 Unlike telephone, the persons communicating with
each other need not be available at the same time
 Unlike fax documents, e-mail documents can be
stored in a computer and be easily edited using
editing programs

File Transfer Protocol
Ref. Page 398
 Moving a file from a remote computer to ones own
computer is known as downloading
 Moving a file from ones own computer to a remote
computer is known as uploading
 Anonymous ftp site is a computer allowing a user to log in
with a username of anonymous and password that is
user’s e-mail address.
 Anonymous ftp sites are called publicly accessible sites
because they can be accessed by any user on the Internet

Telnet
Ref. Page 398
Some common uses of telnet service are:
 Using the computing power of the remote computer
 Using a software on the remote computer
 Accessing remote computer’s database or archive
 Logging in to ones own computer from another computer

Usenet News
Ref. Page 398
 Several usenet news groups exist on the Internet and
are called newsgroups
 In a moderated newsgroup only selected members have
the right to directly post (write) a message to the virtual
notice board. Other members can only read the posted
messages
 In a nonmoderated newsgroup any member can directly
post a message to the virtual notice board
 A moderated newsgroup ensures quality of posted
messages
 Netiquette (network etiquette) deals with rules of
framing messages that will not hurt others

The World Wide Web
(WWW)

The World Wide Web (WWW)
Slide 13/23
Ref. Page 399
 World Wide Web (WWW or W3) is the most popular and
promising method of organizing and accessing information on
the Internet
 Hypertext is a new way of information storage and retrieval
that enables authors to structure information in novel ways
 A properly designed hypertext document can help users
locate desired type of information rapidly
 Hypertext documents enable this by using a series of links
 A link is a special type of item in a hypertext document
connecting the document to another document
 Hypertext documents on the Internet are known as Web
Pages

 Web page designers create Web Pages by using a special
language called HyperText Markup Language (HTML)
 HTML is a subset of a more generalized language called
Standard Generalized Markup Language (SGML)
 HTML is now a de-facto industrial standard for creating Web
Pages
 The WWW uses client-server model, and an Internet Protocol
called HyperText Transport Protocol (HTTP)
 Any computer on the Internet using the HTTP protocol is
called a Web Server
 Any computer accessing that server is called a Web Client
The World Wide Web (WWW)
Slide 14/23
Ref. Page 400

Example of Hypertext Document
Pradeep K. Sinha has been involved in the research and
development of distributed systems for more than three
decades. In addition to being the founding Vice
Chancellor and Director of IIIT-Raipur, Dr. Sinha has
worked with the Centre for Development of
Advanced Computing (C-DAC), Pune, India and the
Multimedia Systems Research Laboratory (MSRL)
of Panasonic in Tokyo, Japan.
Links
Ref. Page 399

WWW Browsers
Slide 16/23
Ref. Page 400
 To use a computer as a web client, a user needs to load on it
a special software tool known as WWW browser (browser)
 Browsers provide following navigation facilities:
 Do not require a user to log in to a server computer
 Enable a user to visit a server computer’s site directly and
access information on it by specifying its URL (Uniform
Resource Locator)
 Enable a user to create and maintain a personal hotlist of
favorite URL
 Maintain a history of server computers visited by a user in a
surfing session
 Enable a user to download information in various formats

Chapter 18: The Internet Slide 17/23
Internet Search Engines

Internet Search Engines
Slide 18/23
Ref. Page 401
 Internet search engine is an application, which helps users
locate web sites containing useful information and references
 To search information:
 A user types the description of the information using the user
interface of the search engine
 The search engine then searches the requested information on
the WWW and returns the results to the user
 Results enable the user to locate the requested information
quickly from the vast ocean of information available on the
Internet

Major Elements of Internet Search Engines
Slide 19/23
Ref. Page 401
 Search Request Interface
 Enables users to provide description of desired information to
the search engine
 Search engine may allow specifications of simple keywords and
phrases, combination of keywords and phrases using Boolean
operators and exclusion/inclusion operators, and title and URL
limiters
 Information Discoverer
 Discovers information from the WWW and creates a database
for the search engine
 Search engine uses the database to locate useful information
during the search process
 Information discoverer accrues this information in two-ways:
 In manual method, authors provide information about their
websites (Continued on next slide…)

 In automatic method, information discoverer collects the
information using programs, such as web crawlers, spiders, robots
 Presenter of Search Results
 Returns search results, ranking them in an order
 Search engines often list search results in accordance to a
relevance score
 Relevance scores reflect the number of times a search term
appears in a web page
 Some search engines also allow users to control relevance
score by giving different weights
Major Elements of Internet Search Engines
Slide 20/23
Ref. Page 401

Some Popular Internet Search Engines
Slide 21/23
Ref. Page 401
 Google (www.google.com)
 Yahoo (www.yahoo.com)
 Lycos (www.lycos.com)
 Infoseek (www.infoseek.com)
 HotBot (www.hotbot.com)
 Inference Find (www.infind.com)
 Ixquick (www.ixquick.com)

Slide 22/29
Uses of the Internet
Some important current strategic uses of the Internet are:
 On-line communication
 Software sharing
 Exchange of views on topics of common interest
 Posting of information of general interest
 Organization promotion
 Product promotion and feedback about products
 Customer support service
 On-line journals, magazines, encyclopedia, and
dictionary
 On-line shopping
 World-wide video conferencing
 World-wide web casting
Ref. Page 401

Internet of Things

What It Is?
Ref. Page 403
IoT is enhanced form of the Internet, in which the enhancement
takes care of the following two objectives:
1. Interconnection of things, in addition to computing
devices, and
2. Automatic collection and transfer of data, without any help
from human being

Things in IoT?
Ref. Page 403
• Refers to any object (device) with any kind of built-in sensors
and having the ability to collect and transfer data over a
network without manual intervention
• Also known as Smart Objects

Benefits of IoT
Ref. Page 403
• Increased accuracy
• Increased efficiency
• Reduced wastage
• Improved customer satisfaction

IoT Applications (Uses of IoT)
Ref. Page 403
• IoT is used in many sectors with millions of applications
• A few examples of IoT applications are:
 Smart home
 Smart city
 Smart healthcare
 Smart energy management
 Smart transportation system
 Smart agriculture/farming
 Smart manufacturing/industry (Industry 4.0)

Challenges in Adoption of IoT
Ref. Page 403
1. Interoperability issue
2. Issue of designing smart “things”
3. Unstructured data handling issue
4. Security and privacy issue
5. Reliability issue

Slide 29/29
Keywords/Phrases
 Anonymous ftp site
 Browser
 Download
 Electronic mail (e-mail)
 File Transfer Protocol (FTP)
 Hypertext
 Hypertext Transport Protocol (HTTP)
 Industry 4.0
 Internet
 Internet of Things (IoT)
 Internet search engine
 Netiquette
 Newsgroup
 On-line shopping
 Publicly accessible sites
 Smart agriculture/farming
 Smart city
 Smart energy management
 Smart healthcare
 Smart home
 Smart manufacturing
 Smart objects
 Smart transportation system
 Standard Generalized Markup
Language (SGML)
 Telnet
 Things
 Uniform Resource Locator (URL)
 Upload
 Usenet
 Video conferencing
 Web casting
 Web client
 Web crawler
 Web Server
 World Wide Web (WWW)

Chapter 19: Multimedia Slide 1/36
Pradeep K. Sinha
Priti Sinha
Chapter 19
Multimedia

Slide 2/36
Chapter 19: Multimedia
Learning Objectives
 What is multimedia?
 What is a multimedia computer system?
 Main components of multimedia and their associated
technologies
 Common multimedia applications
 Media center computer

What is Multimedia?

Multimedia
Ref. Page 410
 A medium (plural media) is something that a presenter can
use for presentation of information
 Two basic ways to present information are:
 Unimedium presentation: Presenter uses a single
medium to present information
 Multimedia presentation: Presenter uses more than one
medium to present information
 Multimedia presentation of any information enhances
comprehension capability of its user because it involves use of
multiple senses by the user

Common Media
Ref. Page 411
 Common media for storage, access, and transmission of
information are:
 Text (alphanumeric characters)
 Graphics (line drawings and images)
 Animation (moving images)
 Audio (sound)
 Video (Videographed real-life events)
 Multimedia in information technology refers to use of more
than one of these media for information presentation to
users

Multimedia Computer System
Ref. Page 411
 Multimedia computer system is a computer having
capability to integrate two or more types of media (text,
graphics, animation, audio, and video)
 In general, data size for multimedia information is much
larger than plain text information
 Hence, multimedia computer systems require:
 Faster CPU
 Larger storage devices (for storing large data files)
 Larger main memory (for large data size)
 Good graphics terminals
 I/O devices to play any multimedia

Multimedia Components

Text Media
Ref. Page 412
 Alphanumeric characters are used to present information
in text form. Computers are widely used for text
processing
 Keyboards, electronic writing pads, OCRs, terminal
screens, and printers are some commonly used
hardware devices for processing text media
 Text editing, text searching, hypertext, and text
importing/exporting are some highly desirable features
of a multimedia computer system for better presentation
and use of text information

Graphics
Ref. Page 413
 Computer graphics deals with tools and technologies for
generating, representing, manipulating, and displaying
pictures with a computer
 Graphics is an important component of multimedia
applications because a picture is a powerful way to illustrate
information

Graphics Types
Ref. Page 413
 Line drawings
 Drawings are illustrations in the form of 2D and 3D pictures
created from mathematical representation of simple objects like
lines, circles, arcs, etc.
 Area of computer graphics that deals with this type of pictures is
known as generative graphics
 Images
 Computers store pixels of an image as a two-dimensional matrix
 This two-dimensional representation is called image resolution
 Each pixel is composed of three components: red (R), green (G),
blue (B)
 On a display screen, each component of a pixel corresponds to a
phosphor

 Phosphor glows when excited by an electron gun
 Number of bits used to represent a pixel is called color depth
 Color depth in turn is determined by the size of video buffer in
display circuitry
 Resolution and color depth determine the presentation quality
and size of image storage
 Applications use image compression techniques to compress
images to reduce their size before storing or transmitting them
 Area of computer graphics that deals with this type of pictures
is known as cognitive graphics
Graphics Types
Chapter 19: Multimedia Slide 11/
Ref. Page 413

An Image Composition
A pixel composition
Image sample Divided into pixels
R G
B
Ref. Page 414

Graphics: Hardware Requirements
Ref. Page 414
 Locating device with a video display terminal and
drawing software
 Flatbed or rectangular coordinate digitizer
 Scanners
 Digital camera or frame-capture hardware
 Computer screens with graphics display capability
 Laser printers
 Plotters

Graphics: Software Requirements
Ref. Page 414
 Drawing and painting software
 Screen-capture software
 Clip art
 Graphics importing
 Software support for high resolution

Animation Media
Ref. Page 415
 Computer animation deals with generation, sequencing,
and display (at a specified rate) of a set of images
(called frames) to create an effect of visual change or
motion, similar to a movie film (video)
 Animation is commonly used in those instances where
videography is not possible or animation can better
illustrate the concept than video
 Animation deals with displaying a sequence of images at
a reasonable speed to create an impression of
movement. For a jerk-free full motion animation, 25 to
30 frames per second is required

Animation: Hardware Requirements
Ref. Page 415
 Image generation tools and devices such as scanners, digital
cameras, and video capture board
 Computer monitor with image display capability and a
graphics accelerator board

Animation: Software Requirements
Ref. Page 415
 Animation-creation software
 Screen-capture software
 Animation clips
 Animation file importing
 Software support for high resolution
 Recording and playback capability
 Transition effects

Virtual Reality
Ref. Page 415
 Virtual reality is a relatively new technology using
which the user can put a pair of goggles and a glove
and tour a three-dimensional world that exists only in
the computer, but appears realistic to the user
 Virtual reality applications use animation extensively

Audio
Ref. Page 415
 Computer audio deals with tools and technologies for
synthesizing, recording, and playing of audio or sound with a
computer

Analog and Digital Audio
Ref. Page 415
 Audio information travels in natural medium in the form of
sound waves that are analog
 To enable a computer to deal with audio information, a device
must convert sound waves from analog to digital form
 Transducer is a device that converts signals from one form to
another
 Microphone is a transducer that converts sound waves to
electrical signals, and loudspeaker is a transducer that
converts electrical signals to sound waves
 Analog signals are continuous tone of smooth fluctuations,
while digital signals are discrete values in the form of
numbers

 A/D conversion transforms an analog input into a series of
numeric representation by digitization
 D/A conversion is the reverse process of transforming a
sequence of discrete numbers back into continuous analog
signal
Analog and Digital Audio
Ref. Page 415

Secondary
storage
Network
I/O
A
A/D
converter
D
Memory
Analog data
output device
Analog data
input device
Data in analog form
Data in digital form
D
D/A
converter
A
Roles of A/D and D/A Converters
Ref. Page 415

Audio Processing
Ref. Page 415
 Audio processing requires a sound-board which has:
 A/D and D/A converters
 Connector for a speaker or headphone
 MIDI input port to input sound from an external MIDI device
 MIDI output port
device
 MIDI synthesizer
 Volume control
to output recorded sound to the MIDI

Audio: Hardware Requirements
Ref. Page 415
 Sound-board with A/D and D/A converters
 Input device for audio input to record sound
 Output device to listen audio output
 Computer may use MIDI devices
 Computer may also enable generation of
sound by using keyboard
synthesized
 Sound editors enable cut and paste of sound sequences
 Audio mixers enable combining of multiple channels of
sound with controls like synchronization points

Audio: Software Requirements
Ref. Page 415
 Audio clips
 Audio file importing
 Software support for high quality sound
 Text-to-speech conversion software
 Speech-to-text conversion software
 Voice recognition software

Video
Ref. Page 415
 Video deals with tools and technologies for recording and
displaying a sequence of images (frames) at a reasonable
speed to create an impression of motion
 For jerk-free full motion video, the display device must
display 25 to 30 frames per second
 Video is an important component of multimedia
applications because it is useful for illustrating concepts
involving movement

Analog and Digital Video
Ref. Page 415
 Video information travels in natural medium in the form of
light waves that are analog
 To enable a computer to deal with video information, a device
must convert light waves from analog to digital form
 Video camera is a transducer that converts light waves to
electrical signals, and monitor is a transducer that converts
electrical signals to light waves
 Analog-to-digital conversion of video also involves sampling
and quantization of analog video signals

Video: Hardware Requirements
Ref. Page 415
 Video camera
 Video monitor
 Video board with A/D and D/A converters, and
connectors for video camera and video monitor
 Video editors

Video: Software Requirements
Ref. Page 415
 Video clips
 It is a library of video clips
 A user can import a video clip directly from this library for
use in a multimedia application
 Enables users to control recording and display of a video
sequence

Multimedia Applications

Multimedia Applications
Ref. Page 420
 Multimedia books and e-Books
 Digital library
 Multimedia presentation
 Foreign language learning
 Video games
 Special effects in movies
 Animation films
 Animated advertisements
 Multimedia kiosk
 Virtual shops and shopping malls
 Multimedia conferencing
 Smart/Interactive TV

A Video-on-Demand System
Disks
T
ransport
network
Switch Switch
Customer’s home
Set-top box
Remote
control
TV monitor
Ref. Page 420
Video server
Tapes

Media Center Computer

 There is a growing trend of owning a personal computer
(PC) at home like other electronic equipment
 New terminologies like “infotainment” and “edutainment”
have evolved to refer to computers as versatile tools
 Media center PC provides following functionalities:
 Server as PC, TV, radio, and music system
 Serve as digital photo album and digital library
 Server as Game station and DVD/CD Player
 Allows play, pause, and record of TV programs
 Provides Electronic Programming Guide (EPG)
Ref. Page 423

 Any PC with good graphics display card, multimedia
components, and a TV tuner card can serve as a media
center PC by installing media center applications on it
 Some operating systems provide features of media centre
applications integrated into OS itself
 Such operating systems are called media center OS
High-resolution display screen
System unit
Remote control
Mouse
Keyboard
Ref. Page 424

Slide 36/36
Chapter 19: Multimedia
Keywords/Phrases
 Animation
 Audio
 Clip art
 Cognitive graphics
 Computer Aided Design (CAD)
 Computer Aided Manufacturing (CAM)
 Digital library
 Frames
 Generative graphics
 Graphics
 Interactive TV
 Multimedia
 Media Center Computer
 Pixel
 Refresh rate
 Text
 Transducer
 Transition effects
 Unimedia presentation
 Video
 Virtual reality

Chapter 20: Classification of Computers Slide 1/33
Pradeep K. Sinha
Priti Sinha
Chapter 20
Classification of
Computers

Slide 2/33
Chapter 20: Classification of Computers
Learning Objectives
 Classifications of computers
 Common types of computers used today
 Characteristic features of various types of
computers in use today

Computer Classification
 Traditionally, computers were classified by their size,
processing speed, and cost
 Based on these factors, computers were classified as
microcomputers, minicomputers, mainframes, and
supercomputers
 However, with rapidly changing technology, this
classification is no more relevant
 Today, computers are classified based on their mode
of use

Types of Computers
Based on their mode of use, computers are classified as:
 Notebook computers (Laptops)
 Personal computers (PCs)
 Workstations
 Mainframe systems
 Supercomputers
 Client and server computers
 Handheld computers

Notebook Computers
(Laptops)

Notebook Computers
 Portable computers mainly meant for use by people who
need computing resource wherever they go
 Approximately of the size of an 8½ x 11 inch notebook and
can easily fit inside a briefcase
 Weigh only around 2 kg or less.
 Comfortably placed on ones lap while being used. Hence,
they are also called laptop PCs.
 Lid with display screen is foldable in a manner that when
not in use it can be folded to flush with keyboard to
convert the system into notebook form

 Designed to operate with chargeable batteries
 Mostly used for word processing, spreadsheet
computing, data entry, and power point presentations
 Normally run MS-DOS, MS WINDOWS Mac OS, or Linux
operating system
 Some manufacturers are also offering models with
GNU/Linux or its distributions
 Each device of laptop is designed to use little power and
remain suspended if not used
Notebook Computers

Notebook Computers
Keyboard, trackball, hard
disk, I/O ports, etc. are in
this unit
Foldable flat screen

Personal Computers (PCs)

Personal Computers (PCs)
 Non-portable, general-purpose computer that fits on a
normal size office table
 Designed to meet personal computing needs of individuals
 Often used by children and adults for education and
entertainment also
 Generally used by one person at a time, supports
multitasking
 Two common models of PCs are desktop model and tower
model
 Popular OS are MS-DOS, MS-Windows, Windows-NT
, Mac
OS, Linux, and UNIX

(a) Desktop model
Keyboard
Mouse
System
Unit
Mouse
Monitor
(b) Tower model
Common PC Models

Workstations

Slide 13/33
Workstations
 Powerful desktop
computing needs
professionals
computer designed to
of engineers, architects,
meet the
and other
 Provides greater processing power
, larger storage, and
better graphics display facility than PCs
 Commonly used for computer-aided design, multimedia
applications, simulation of complex scientific and
engineering problems, and visualization
 Generally run server version of Windows, Mc OS, Linux, or
UNIX operating system
 Operating system is generally designed to support
multiuser environment
Ref. Page 431

Mainframe Systems

Mainframe Systems
 Mainly used by large organizations as banks, insurance
companies, hospitals, railways, etc.
 Used for data handling and information processing
requirements
 Used in such environments where a large number of
users need to share a common computing facility
 Oriented to input/output-bound applications

Mainframe Systems
 Typically consist of a host computer, front-end
computer, back-end computer, console terminals,
magnetic disk drives, tape drives, magnetic tape library,
user terminals, printers, and plotters
 Typical mainframe system looks like a row of large file
cabinets and needs a large room
 Smaller configuration (slower host and subordinate
computers, lesser storage space, and fewer user
terminals) is often referred to as a minicomputer
system

Mainframe Computer Systems
USERS ROOM
(Entry restricted to authorized users)
SYSTEM ROOM
(Entry restricted to system administrators and maintenance staff)
Magnetic
disk drives
Host processor
Front-end processor
User terminal User terminal User terminal
Console
Printer
Magnetic tape
drive
Magnetic tape library
Back end processor
Plotter

Supercomputers

Supercomputers
 Most powerful and most expensive computers available at
a given time.
 Primarily used for processing complex scientific
applications that require enormous processing power
 Well known supercomputing applications include:
 Analysis of large volumes of seismic data
 Simulation of airflow around an aircraft
 Crash simulation of the design of an automobile
 Solving complex structure engineering problems
 Weather forecasting
 Creating special effects for movies and TV programs

 Supercomputers also support multiprogramming
 Supercomputers primarily address processor-bound
applications
Supercomputers

 Use multiprocessing and parallel processing
technologies to solve complex problems faster
 Also known as parallel computers or parallel processing
systems
 Modern supercomputers employ hundreds of processors
and are also known as massively parallel processors
Parallel Processing Systems

C-DAC’s PARAM Yuva Supercomputer

Client and Server
Computers

Client and Server Computers
 Client-server computing environment has multiple
clients, one/more servers, and a network
 Client is a PC/workstation with user-friendly interface
running client processes that send service requests to
the server
 Server is generally a relatively large computer that
manages a shared resource and provides a set of
shared user services to the clients
 Server runs the server process that services client
requests for use of managed resources
 Network may be a single LAN or WAN or an internet
work

 Involves splitting an application into tasks and putting
each task on computer where it can be handled most
efficiently
 Computers and operating systems of a client and a
server may be different
 Common for one server to use the services of another
server, and hence act both as client and server
 Concept of client and server computers is purely role-
based and may change dynamically as the role of a
computer changes
Client-Server Computing

File
Server
LAN or WAN or an
Internet of Networks
Database
Server
Workstation
(Client)
Workstation
(Client)
PC (Client)
PC (Client)
PC (Client)
Client-Server Computing Environment

Handheld Computers

Handheld Computers
 Small computing device that can be used by holding in
hand, also known as palmtop
 Size, weight, and design are such that it can be used
comfortably by holding in hand
 Types of Handheld are:
 Tablet PC: Miniaturized laptop with light weight, screen
flip, handwriting and voice recognition
 PDA/Pocket PC: Acts as PIM device with LCD touch
screen, pen for handwriting recognition, PC based
synchronization, and optionally mobile phone services
 Smartphone: Fully functional mobile phone with
computing power, voice centric, do not have a touch
screen and are smaller than PDA

Handheld Computers
(a) Tablet PC
(b) PDA/Pocket PC (c) Smartphone

Key features
Types of
computers
Notebook
Personal
Computer
Workstation
Mainframe
system
Super
compute
r
Client Server Handheld
Size Very small
(can be
placed
on ones lap)
Small
(can be placed
on an office
table)
Medium
(Slightly larger
than PC)
Large
(needs a
large room)
Large
(needs a
large
room)
Generally
small
(may be
large if it
also plays
the role of a
server)
Generally
large
Very small (can
be placed on
ones palm)
Processing power Low Low High Higher Highest Generally
low
Generally high Low
Main memory
capacity
Low Low High Higher Highest Generally
low
Generally high Low
Hard disk storage
capacity
Low Low High Highest Higher Generally
low
Generally high Low
Has its own
monitor, keyboard,
and mouse for
user interface
Yes Yes Yes Generally
no
Generally
no
Yes Generally no No
Comparison of Different Types of
Computers

Key features
Types of
computers
Notebook
Personal
Computer
Workstation
Mainframe
system
Super
compute
r
Display facility Foldable
flat screen
small
display
Medium size
display screen
Large-screen
display that can
display high-
resolution
graphics
Generally
not
available
Generally
not
available
Medium to
large
screen
display
Generally not
available
Small display
Single/multiple
processors
Single Generally
single
Generally multiple Multiple Multiple Generally
single
Generally
multiple
Single
Single/multiple
- User oriented
Single Single Generally single Multiple Multiple Single Multiple Single
Popular
operating
systems
MS-DOS,
MS-
Windows,
Mac OS,
Linux
MS-DOS,
MS-Windows,
Windows-NT,
Mac OS,
Linux,
Unix
Server version of
Windows, Mac OS,
Linux or Unix
A variant of
Unix, or
proprietary
A variant
of Unix,
or
proprieta
ry
MS-DOS,
MS-
Windows,
Windows-
NT,
Mac OS,
Linux,
Unix
Server
version of
Windows,
Mac OS,
Linux or Unix
MS-Wndows
Mobile, iOS,
Palm OS,
Symbian OS,
Linux,
Blackbery OS
Computers

Key features
Types of
computers
Notebook
Personal
Computer
Workstation
Mainframe
system
Super
computer
Popular usage Word
processing;
Spreadsheet;
Data Entry;
Preparing
presentation
materials;
and Making
presentations
Personal
computing
needs of
individuals
either at
their work
places or at
their homes;
and
Education
and
entertainme
nt of
children and
adults
Computing needs
of engineers,
architects,
designers;
Simulation of
complex scientific
and engineering
problems and
visualizing the
results of
simulation; and
Multimedia
applications
Processing
of I/O-
bound
applications
Large
processor-
bound
applica-
tions like
complex
scientific
simulations
Provide
highly user-
friendly
interface in
a client-
server
computing
environment
Manage a
shared
resource
and
provide a
set of
shared
user
services in
a client-
server
computing
environm
ent
Computing,
Personal
Information
Management
(PIM), cell
phone, digital
camera
Major vendors IBM,
Compaq,
Siemens,
Apple,
Toshiba
IBM, Apple,
Compaq,
Dell,
Siemens,
Toshiba,
Hewlett-
Packard,
Lenovo
Sun
Microsystems,
IBM, DEC,
Hewlett-Packard,
Silicon Graphics
IBM, DEC Cray, IBM,
Silicon
Graphics,
Fujitsu,
Intel,
C-DAC
Same as PC
and
Workstation
vendors
Same as
Workstati
on,
Mainframe
System,
and
Supercom
puter
vendors
Nokia, Sony,
Apple,
Samsung,
Motorola, Dell,
Hawlett-
Packard
Computers

Slide 33/33
Key Words/Phrases
 Back-end computer
 Client computer
 Client process
 Front-end computer
 Host computer
 Handheld
 I/O-bound application
 Laptop PC
 Mainframe system
 Massively parallel processors
 Minicomputer
 Notebook computer
 Parallel computers
 Parallel processing system
 Personal Computer (PC)
 Processor-bound application
 Server computer
 Server process
 Supercomputer
 System board
 Workstation

Chapter 21: Introduction to C Programming Languages Slide 1/76
Pradeep K. Sinha
Priti Sinha
Chapter 21
Introduction to C
Programming
Language

Slide 2/76
Chapter 21: Introduction to C Programming Languages
Learning Objectives
 Features of C
 Various constructs and their syntax
 Data types and operators in C
 Control and Loop Structures in C
 Functions in C
 Writing programs in C

Basic Features and Rules

Features of C
Ref. Page 442 Chapter 21: Introduction to C Programming Languages Slide 4/76
 Reliable, simple, and easy to use
 Has virtues of high-level programming language with
efficiency of assembly language
 Supports user-defined data types
 Supports modular and structured programming concepts
 Supports a rich library of functions
 Supports pointers with pointer operations
 Supports low-level memory and device access
 Small and concise language
 Standardized by several international standards body

C Character Set
Category Valid Characters Total
Uppercase alphabets A, B, C, …, Z 26
Lowercase alphabets a, b, c, …, z 26
Digits 0, 1, 2, …, 9 10
Special characters
~ `!@ # % ^ & * ( ) _ 
  | {}[ ] : ; " '   , . ? /
31
93

Constants
 Constant is a value that never changes
 Three primitive types of constants supported in C are:
 Integer
 Real
 Character

Rules for Constructing Integer
Constants
 Must have at least one digit
 + or – sign is optional
 No special characters (other than + and – sign) are
allowed
 Allowable range is:
 -32768 to 32767 for integer and short integer
constants (16 bits storage)
 -2147483648 to 2147483647 for long integer
constants (32 bits storage)
 Examples are: 8, +17, -6

Rules for Constructing Real
Constants in Fractional Form
 Must have at least one digit
 Must have one and only one decimal point
 + or – sign is optional
 No special characters (other than + and – sign) are
allowed
 Examples are: 5.3, +18.59, -0.46

Rules for Constructing Real Constants
in Exponential Form
 Has two parts – mantissa and exponent - separated by
‘e’ or ‘E’
 Mantissa part is constructed by the rules for constructing
real constants in fractional form
 Exponent part is constructed by the rules for
constructing integer constants
 Allowable range is -3.4e38 to 3.4e38
 Examples are: 8.6e5, +4.3E-8, -0.1e+4

Rules for Constructing Character
Constants
 Single character from C character set
 Enclosed within single inverted comma (also
called single quote) punctuation mark
 Examples are: ’A’ ’a’ ’8’ ’%’

Variables
 A C variable is an entity whose value may vary during
program execution
 It has a name and type associated with it
 Variable name specifies programmer given name to
the memory area allocated to a variable
 Variable type specifies the type of values a variable
can contain
 Example: In i = i + 5, i is a variable

Rules for Constructing Variable Names
 Can have 1 to 31 characters
 Only alphabets, digits, and underscore (as in last_name)
characters are allowed
 Names are case sensitive (nNum and nNUM are different)
 First character must be an alphabet
 Underscore is the only special character allowed
 Keywords cannot be used as variable names
 Examples are: I saving_2007 ArrSum

Data Types Used for Variable Type
Declaration
Data
Type
Minimum Storage
Allocated
Used for Variables that can contain
int 2 bytes (16 bits) integer constants in the range
-32768 to 32767
short 2 bytes (16 bits) integer constants in the range
-32768 to 32767
long 4 bytes (32 bits) integer constants in the range
-2147483648 to 2147483647
float 4 bytes (32 bits) real constants with minimum 6 decimal digits
precision
double 8 bytes (64 bits) real constants with minimum 10 decimal
digits precision
char 1 byte (8 bits) character constants
enum 2 bytes (16 bits) Values in the range -32768 to 32767
void No storage allocated No value assigned

int
short
long
float
double
char
count;
index;
principle;
area;
radius;
c;
Variable Type Declaration Examples

Standard Qualifiers in C
Category Modifier Description
Lifetime auto
register
static
extern
Temporary variable
Attempt to store in processor register, fast access
Permanent, initialized
Permanent, initialized but declaration elsewhere
Modifiability const
volatile
Cannot be modified once created
May be modified by factors outside program
Sign signed
unsigned
+ or –
+ only
Size short
long
16 bits
32 bits

Lifetime and Visibility Scopes of
Variables
 Lifetime of all variables (except those declared as static) is
same as that of function or statement block it is declared in
 Lifetime of variables declared in global scope and static is
same as that of the program
 Variable is visible and accessible in the function or
statement block it is declared in
 Global variables are accessible from anywhere in program
 Variable name must be unique in its visibility scope
 Local variable has access precedence over global variable of
same name

Keywords
 Keywords (or reserved words) are predefined words whose
meanings are known to C compiler
 C has 32 keywords
 Keywords cannot be used as variable names
auto double int struct
break else long switch
case enum register typedef
char extern return union
const float short unsigned
continue for signed void
default goto sizeof volatile
do if static while

Comments
 Comments are enclosed within / and  /
 Comments are ignored by the compiler
 Comment can also split over multiple lines
 Example: / This is a comment statement  /

Operators

Operators
 Operators in C are categorized into data access,
arithmetic, logical, bitwise, and miscellaneous
 Associativity defines the order of evaluation when
operators of same precedence appear in an expression
 a = b = c = 15, ‘=’ has R  L associativity
 First c = 15, then b = c, then a = b is evaluated
 Precedence defines the order in which calculations
involving two or more operators is performed
 x + y  z , ‘’ is performed before ‘+’

Arithmetic Operators
Operator Meaning with Example Associativity Precedence
+ Addition; x + y L  R 4
- Subtraction; x - y L  R 4
 Multiplication; x  y L  R 3
/ Division; x / y L  R 3
% Remainder (or Modulus); x % y L  R 3
++ Increment;
x++ means post-increment (increment
the value of x by 1 after using its value);
L  R 1
++x means pre-increment (increment the
value of x by 1 before using its value)
R  L 2

Operator Meaning with Example
Associativit
y
Precedence
-- Decrement;
x-- means post-decrement (decrement
the value of x by 1 after using its value);
L  R 1
--x means pre-decrement (decrement
the value of x by 1 before using its value)
R  L 2
= x = y means assign the value of y to x R  L 14
+= x += 5 means x = x + 5 R  L 14
-= x -= 5 means x = x - 5 R  L 14
 = x = 5 means x = x  5 R  L 14
/= x /= 5 means x = x / 5 R  L 14
%= x %= 5 means x = x % 5 R  L 14

Logical Operators
Logical Operators
! Reverse the logical value of a single variable;
!x means if the value of x is non-zero, make it
zero; and if it is zero, make it one
R  L 2
> Greater than; x > y L  R 6
< Less than; x < y L  R 6
>= Greater than or equal to; x >= y L  R 6
<= Less than or equal to; x <= y L  R 6
== Equal to; x == y L  R 7
!= Not equal to; x != y L  R 7
&& AND; x && y means both x and y should be
true (non-zero) for result to be true
L  R 11
|| OR; x || y means either x or y should be true
(non-zero) for result to be true
L  R 12
z?x:y If z is true (non-zero), then the value returned
is x, otherwise the value returned is y
R  L 13

Bitwise Operators
~ Complement; ~x means
All 1s are changed to 0s and 0s to 1s
R  L 2
& AND; x & y means x AND y L  R 8
| OR; x | y means x OR y L  R 10
^ Exclusive OR; x ^ y means x
 y L  R 9
<< Left shift; x << 4 means shift all bits in x
four places to the left
L  R 5
>> Right shift; x >> 3 means shift all bits
in x three places to the right
L  R 5
&= x &= y means x = x & y R  L 14
|= x |= y means x = x | y R  L 14
^= x ^= y means x = x ^ y R  L 14
<<= x <<= 4 means shift all bits in x four places
to the left and assign the result to x
R  L 14
>>= x >>= 3 means shift all bits in x three
places to the right and assign the result to x
R  L 14
Bitwise Operators

Data Access Operators
x[y] Access yth element of array x; y starts
from zero and increases monotically up
to one less than declared size of array
L  R 1
x.y Access the member variable y of
structure x
L  R 1
x –›y Access the member variable y of
structure x
L  R 1
&x Access the address of variable x R  L 2
*x Access the value stored in the storage
location (address) pointed to by pointer
variable x
R  L 2
Data Access Operators

Operator Meaning with Example
Associativit
y
Precedenc
e
Miscellaneous Operators
x(y) Evaluates function x with argument y L  R 1
sizeof (x) Evaluate the size of variable x in bytes R  L 2
sizeof (type) Evaluate the size of data type “type”
in bytes
R  L 2
(type) x Return the value of x after converting
it from declared data type of variable
x to the new data type “type”
R  L 2
x,y Sequential operator (x then y) L  R 15
Miscellaneous Operators

Statements

Statements
 C program is a combination of statements written
between { and } braces
 Each statement performs a set of operations
 Null statement, represented by “;” or empty {} braces,
does not perform any operation
 A simple statement is terminated by a semicolon “;”
 Compound statements, called statement block, perform
complex operations combining null, simple, and other
block statements

Examples of Statements
 a = (x + y)  10; / simple statement /
 if (sell > cost) / compound statement follows /
{
profit = sell – cost;
printf (“profit is %d”, profit);
}
/* null statement follows /
else
{
}

I/O Operations

Simple I/O Operations
 C has no keywords for I/O operations
 Provides standard library functions for performing all I/O
operations

Basic Library Functions for I/O
Operations
I/O Library
Functions
Meanings
getch() Inputs a single character (most recently typed) from standard input (usually
console).
getche() Inputs a single character from console and echoes (displays) it.
getchar() Inputs a single character from console and echoes it, but requires Enter key to be
typed after the character.
putchar() or
putch()
Outputs a single character on console (screen).
scanf() Enables input of formatted data from console (keyboard). Formatted input data
means we can specify the data type expected as input. Format specifiers for
different data types are given in Figure 21.6.
printf() Enables obtaining an output in a form specified by programmer (formatted
output). Format specifiers are given in Figure 21.6. Newline character “n” is
used in printf() to get the output split over separate lines.
gets() Enables input of a string from keyboard. Spaces are accepted as part of the input
string, and the input string is terminated when Enter key is hit. Note that although
scanf() enables input of a string of characters, it does not accept multi-word
strings (spaces in-between).
puts() Enables output of a multi-word string

Basic Format Specifiers for
scanf() and printf()
Format
Specifiers
Data Types
%d integer (short signed)
%u integer (short unsigned)
%ld integer (long signed)
%lu integer (long unsigned)
%f real (float)
%lf real (double)
%c character
%s string

Formatted I/O Example
/ A portion of C program to illustrate formatted input and output /
int maths, science, english, total;
float percent;
clrscr();
printf ( “Maths marks = ” );
scanf ( “%d”, &maths);
/ A C library function to make the screen clear /
/ Displays “Maths marks = ” /
/ Accepts entered value and stores in variable “maths” /
printf ( “n Science marks = ” ); / Displays “Science marks = ” on next line because of n /
scanf ( “%d”, &science); / Accepts entered value and stores in variable “science” /
printf ( “n English marks = ” ); / Displays “English marks = ” on next line because of n /
scanf ( “%d”, &english); / Accepts entered value and stores in variable “english” /
total = maths + science + english;
percent = total/3; / Calculates percentage and stores in variable “percent” /
printf ( “n Percentage marks obtained = %f”, percent);
/ Displays “Percentage marks obtained = 85.66” on next line
because of n /

Formatted I/O Example
Output:
Maths marks = 92
Science marks = 87
English marks = 78
Percentage marks obtained = 85.66

Preprocessor Directives

Preprocessor Directives
 Preprocessor is a program that prepares a program for
the C compiler
 Examples of some common preprocessor directives in C
are:
Preprocessor
directive
Use
#include
Used to look for a file and place its
contents at the location where this
preprocessor directives is used
#define Used for macro expansion
#ifdef..#endif
Used for conditional compilation of
segments of a program

Examples of Preprocessor Directives
#include <stdio.h>
#define PI 3.1415
#define AND &&
#define ADMIT printf (“The candidate can be admitted”);
#ifdef WINDOWS
.
.
.
Code specific to windows operating system
.
.
.
#else
.
.
.
Code specific to Linux operating system
.
.
.
#endif
.
.
.
Code common to both operating systems

Standard Preprocessor
Directives in C
Preprocessor Directive Meaning Category
# Null directive
Simple
#error message Prints message when processed
#line linenum filename Used to update code line number and filename
#pragma name Compiler specific settings
#include filename Includes content of another file File
#define macro/string Define a macro or string substitution
Macro
#undef macro Removes a macro definition
#if expr Includes following lines if expr is true
Conditional
# elif expr Includes following lines if expr is true
#else Handles otherwise conditions of #if
#endif Closes #if or #elif block
#ifdef macro Includes following lines if macro is defined
#ifndef imacro Includes following lines if macro is not defined
# String forming operator
Operators
## Token pasting operator
defined same as #ifdef

Pointers, Arrays and
Strings

Pointers
 C pointers allow programmers to directly access
memory addresses where variables are stored
 Pointer variable is declared by adding a ‘’ symbol
before the variable name while declaring it.
 If p is a pointer to a variable (e.g. int i, *p = i;)
 Using p means address of the storage location of
the pointed variable
 Using p means value stored in the storage location
of the pointed variable
 Operator ‘&’ is used with a variable to mean variable’s
address, e.g. &i gives address of variable i

Illustrating Pointers Concept
1000 i
62
Location
address
Address of i = 1000
Value of i = 62
Location
contents
Location
name
int i = 62;
int p;
int j;
p = &i;
j = p;
j = 0;
j = (&i)
/ p becomes 1000 /
/ j becomes 62 /
/ j becomes zero /
/ j becomes 62 /

Array
 An array is a collection of fixed number of elements in
which all elements are of the same data type
 It is a homogeneous, linear, and contiguous memory
structure
 Its elements can be referred to by using their subscript
or index position that is monotonic in nature
 First element is always denoted by subscript value of 0
(zero), increasing monotonically up to one less than
declared size of array
 Before using an array, its type and dimension must be
declared
 An array can also be declared as multi-dimensional such
as Matrix2D[10][10]

Illustrating Arrays Concept
1010
1008
1006
1004
1002
1000
int marks[6];
Each element
being an int
occupies 2 bytes
marks[0] = 45
marks[1] = 84
.
.
.
marks[5] = 92
(a) An array of
integers having
6 elements
float price[4];
Each element
being a float
occupies 4 bytes
price[0] = 82.75
price[1] = 155.50
.
.
price[3] = 10.25
(b) An array of
real numbers
having 4 elements
char city[6];
Each element
being a char
occupies 1 byte
city[0] = ‘B’
city[1] = ‘O’
.
..
.
city[5] = ‘Y’
(c) An array of
characters
having 6 elements
92
63
82
66
84
45
10.25
250.00
155.50
82.75
1012
1008
1004
1000
1005
1004
1003
1002
1001
1000
Y
A
B
M
O
B

String
 A string is a one-dimensional
terminated by a null character (‘0)’
array of characters
 It is initialized at declaration as
char name[] = “PRADEEP”;
 Its individual elements can be accessed in the same way
as we access array elements such as name[3] = ‘D’
 Strings are used for text processing
 C provides a rich set of string handling library functions

Library Functions for String Handling
Library Function Used To
strlen Obtain the length of a string
strlwr Convert all characters of a string to lowercase
strupr Convert all characters of a string to uppercase
strcat Concatenate (append) one string at the end of another
strncat Concatenate only first n characters of a string at the end of another
strcpy Copy a string into another
strncpy Copy only the first n characters of a string into another
strcmp Compare two strings
strncmp Compare only first n characters of two strings
stricmp Compare two strings without regard to case
strnicmp Compare only first n characters of two strings without regard to case
strdup Duplicate a string
strchr Find first occurrence of a given character in a string
strrchr Find last occurrence of a given character in a string
strstr Find first occurrence of a given string in another string
strset Set all characters of a string to a given character
strnset Set first n characters of a string to a given character
strrev Reverse a string

User Defined Data Types

User Defined Data Types (UDTs)
 UDT is composite data type whose composition is not
included in language specification
 Programmer declares them in a program where they are
used
 Two types of UDTs are:
 Structure
 Union

Structure
 It is a UDT containing a number of data types grouped
together
 Its constituents data types may or may not be of different
types
 It has continuous memory allocation and its minimum size
is the sum of sizes of its constituent data types
 All elements (member variable) of a structure are publicly
accessible
 Each member variable can be accessed using “.” (dot)
operator or pointer (EmpRecord.EmpID or EmpRecord 
EmpID)
 It can have a pointer member variable of its own type,
which is useful in crating linked list and similar data
structures

struct Employee
{
int EmpID;
char EmpName[20];
} EmpRecord;
struct Employee
{
int EmpID;
char EmpName[20];
};
Struct Employee EmpRecord;
Struct Employee pempRecord = &EmpRecord;
Structure (Examples)

Union
 It is a UDT referring to same memory location using several
data types
 It is a mathematical union of all constituent data types
 Each data member begins at the same memory location
 Minimum size of a union variable is the size of its largest
constituent data types
 Each member variable can be accessed using “,
” (dot)
operator
 Section of memory can be treated as a variable of one type
on one occasion, and of another type on another occasion

unionNum
{
int intNum;
unsigned
unsNum’
};
union Num Number;
Union Example

Difference Between Structure and
Union
 Both group a number of data types together
 Structure allocates different memory space contiguously
to different data types in the group
 Union allocates the same memory space to different
data types in the group

Control Structures

Control Structures
 Control structures (branch statements) are decision
points that control the flow of program execution based
on:
 Some condition test (conditional branch)
 Without condition test (unconditional branch)
 They ensure execution of other statement/block or
cause skipping of some statement/block

Conditional Branch Statements
 if is used to implement simple one-way test. It can be in
one of the following forms:
 if..stmt
 if..stmt1..else..stmt2
 if..stmt1..else..if..stmtn
 switch facilitates multi-way condition test and is very
similar to the third if construct when primary test object
remains same across all condition tests

Examples of “if” Construct
 if (i <= 0)
i++;
 if (i <= 0)
i++;
else
j++;
 if (i <= 0)
i++;
else if (i >= 0)
j++;
else
k++;

Same thing can be written also using if
construct as:
if (ch == ‘A’ || ch == ‘B’ || ch == ‘C’)
printf(“Capital”);
else if (ch == ‘a’ || ch == ‘b’ || ch == ‘c’)
printf(“Small”);
else
printf(“Not cap or small”);
Example of “switch” Construct
switch(ch)
{
case ‘A’:
case ‘B’:
case ‘C’:
printf(“Capital”);
break;
case ‘a’:
case ‘b’:
case ‘c’:
printf(“Small”);
break;
default:
printf(“Not cap or small”);
}

Unconditional Branch Statements
 Break: Causes unconditional exit from for, while, do,
or switch constructs. Control is transferred to
the statement immediately outside the block
in which break appears.
 Continue: Causes unconditional transfer to next
iteration in a for, while, or do construct. Control is
transferred to the statement beginning the block in
which continue appears.
 Goto label: Causes unconditional transfer to statement
marked with the label within the function.

 Return [value/variable]: Causes immediate termination of
function in which it appears and
transfers control to the statement
that called the function. Optionally,
it provides a value compatible to
the function’s return data type.
Unconditional Branch Statements

Loop Structures

Loop Structures
 Loop statements are used to repeat the execution of
statement or blocks
 Two types of loop structures are:
 Pretest: Condition is tested before each iteration to
check if loop should occur
 Posttest: Condition is tested after each iteration to
check if loop should continue (at least, a single
iteration occurs)

Pretest Loop Structures
 for: It has three parts:
 Initializer is executed at start of loop
 Loop condition is tested before iteration to
decide whether to continue or terminate the
loop
 Incrementor is executed at the end of each
iteration
 While: It has a loop condition only that is
tested before each iteration to decide whether to
continue or terminate the loop

Examples of “for” and “while”
Constructs
 for (i=0; i < 10; i++)
printf(“i = %d”, i);
 while (i < 10)
{
i++;
}

Posttest Loop Construct
“do…while”
 It has a loop condition only that is tested after each
iteration to decide whether to continue with next
iteration or terminate the loop
 Example of do…while is:
do {
i++;
} while (i < 10) ;

Functions

Functions
 Functions (or
program
subprograms) are building blocks of a
 All functions must be declared and defined before use
 Function declaration requires function name, argument
list, and return type
 Function definition requires coding the body or logic of
function
 Every C program must have a main function. It is the
entry point of the program

Example of a Function
int myfunc ( int Val, int ModVal )
{
unsigned temp;
temp = Val % ModVal;
return temp;
}
This function can be called from any other place using
simple statement:
int n = myfunc(4, 2);

Sample C Program (Program-1)
/ Program to accept an integer from console and to display
whether the number is even or odd /
# include <stdio.h>
void main()
{
int number, remainder;
clrscr(); / clears the console screen /
printf (“Enter an integer: ”);
scanf (“%d”, &number);
remainder = number % 2;
if (remainder == 0)
printf (“n The given number is even”);
else
printf (“n The given number is odd”);
getch();
}

/ Program to accept an integer in the range 1 to 7 (both inclusive) from
console and to display the corresponding day (Monday for 1, Tuesday for
2, Wednesday for 3, and so on). If the entered number is out of range,
the program displays a message saying that /
# include <stdio.h>
# include <conio.h>
#define MON printf (“n
#define TUE printf (“n
#define WED printf (“n
#define THU printf (“n
Entered number is 1 hence day is MONDAY”);
Entered number is 2 hence day is TUESDAY”);
Entered number is 3 hence day is WEDNESDAY”);
Entered number is 4 hence day is THURSDAY”);
#define FRI printf (“n Entered number is 5 hence day is FRIDAY”);
#define SAT printf (“n Entered number is 6 hence day is SATURDAY”);
#define SUN printf (“n Entered number is 7 hence day is SUNDAY”);
#define OTH printf (“n Entered number is out of range”);
void main()
{
int day;
clrscr();
printf (“Enter an integer in the range 1 to 7”);
scanf (“%d”, &day);

switch(day)
{
Case 1:
MON;
break;
Case 2:
TUE;
break;
Case 3:
WED;
break;
Case 4:
THU;
break;
Case 5:
FRI;
break;
Case 6:
SAT;
break;
Case 7:
SUN;
break;
default:
OTH;
}
getch();
}

/ Program to accept the radius of a circle from console and to calculate
and display its area and circumference /
# include <stdio.h>
# include <conio.h>
# define PI 3.1415
void main()
{
float radius, area, circum;
clrscr();
printf (“Enter the radius of the circle: ”);
scanf (“%f”, &radius);
area = PI  radius  radius;
circum = 2  PI  radius;
printf (“n Area and circumference of the circle are %f
and %f respectively”, area, circum);
getch();
}

/ Program to accept a string from console and to display the number of
vowels in the string /
# include <stdio.h>
# include <conio.h>
# include <string.h>
void main()
{
char input_string[50]; / maximum 50 characters /
int len;
int i = 0, cnt = 0;
clrscr();
printf (“Enter a string of less than 50 characters: n”);
gets (input_string);
len = strlen (input_string);
for (i = 0; i < len; i++)
{
switch (input_string[i])

{
case ‘a’:
case ‘e’:
case ‘i’:
case ‘o’:
case ‘u’:
case ‘A’:
case ‘E’:
case ‘I’:
case ‘O’:
case ‘U’:
cnt++
}
}
printf (“n Number of vowels in the string are: %d”, cnt);
getch();
}

/ Program to illustrate use of a user defined function. The program initializes an array of n elements
from 0 to n-1 and then calculates and prints the sum of the array elements. In this example n = 10 /
#include <stdio.h>
#define SIZE 10
int ArrSum(int *p, int n);
{
int s, tot = 0;
for(s = 0; s < n; s++)
{
tot += *p;
p++;
}
return tot;
}
int main()
{
int i = 0, sum = 0;
int nArr[SIZE] = {0};
while(i < SIZE)
{
nArr[i] = i;
i++
}
sum = ArrSum(nArr, SIZE);
printf("Sum of 0 to 9 = %dn", sum);
return 0;
}

Slide 76/76
Chapter 21: Introduction to C Programming Languages
Key Words/Phrases
 Arithmetic operators
 Arrays
 Assignment operators
 Bit-level manipulation
 Bitwise operators
 Branch statement
 Character set
 Comment statement
 Compound statement
 Conditional branch
 Conditional compilation
 Constants
 Control structures
 Format specifiers
 Formatted I/O
 Function
 Keywords
 Library functions
 Logical operators
 Loop structures
 Macro expansion
 Main function
 Member element
 Null statement
 Operator associativity
 Operator precedence
 Pointer
 Posttest loop
 Preprocessor directives
 Pretest loop
 Primitive data types
 Reserved words
 Simple statement
 Statement block
 Strings
 Structure data type
 Unconditional branch
 Union data type
 User-defined data types
 Variable name
 Variable type declaration
 Variables

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