Esoft Metro Campus - Diploma in Information Technology - (Module VII) Software Engineering (Template - Virtusa Corporate) Contents: What is software? Software classification Attributes of Software What is Software Engineering? Software Process Model Waterfall Model Prototype Model Throw away prototype model Evolutionary prototype model Rapid application development Programming styles Unstructured programming Structured programming Object oriented programming Flow charts Questions Pseudo codes Object oriented programming OOP Concepts Inheritance Polymorphism Encapsulation Generalization/specialization Unified Modeling Language Class Diagrams Use case diagrams Software testing Black box testing White box testing Software documentation

1. Diploma in Information Technology
Module VII: Software Engineering
Rasan Samarasinghe
ESOFT Computer Studies (pvt) Ltd.
No 68/1, Main Street, Pallegama, Embilipitiya.

2. Contents
1. What is software?
2. Software classification
3. Attributes of Software
4. What is Software Engineering?
5. Software Process Model
6. Waterfall Model
7. Prototype Model
8. Throw away prototype model
9. Evolutionary prototype model
10. Rapid application development
11. Programming styles
12. Unstructured programming
13. Structured programming
14. Object oriented programming
15. Flow charts
16. Questions
17. Pseudo codes
18. Object oriented programming
19. OOP Concepts
20. Inheritance
21. Polymorphism
22. Encapsulation
23. Generalization/specialization
24. Unified Modeling Language
25. Class Diagrams
26. Use case diagrams
27. Software testing
28. Black box testing
29. White box testing
30. Software documentation

3. What is software?
A software is a collection of instructions that
enables a user to interact with the computer
or have the computer perform special task for
them.

4. Software classification
• System Software
– Directly controlling the hardware resources and
supports the operation of application software.
• Application Software
– Serves the user requirements in a particular
application domain.

5. Software classification
• Generic Software (off the shelf)
– Available on open market to any customer who is
able to buy it.
• Custom Software (bespoke)
– Developed specially for a customer requirement.

6. Generic Software vs Custom Software
Less expensive
More reliable
Immediate installation
More user friendly
User requirements are
not completely satisfied
Cannot accommodate
future changes
More expensive
Less reliable
Delay due to high
development time
Less user friendly
Completely satisfied
Can easily
accommodate future
changes
Generic Software Custom Software

7. Attributes of Software
• Maintainability
• Dependability
• Efficiency
• Usability
• Security
• Reliability
• Robustness
• Customizability
• Scalability
• Accessibility
• Extensibility

8. What is Software Engineering?
Software engineering is concerned with application
of theories, methods and tools to develop and
maintain software systems that behave reliably and
efficiently, are affordable to develop and maintain,
and satisfy all the requirements that customers
have defined for them.

9. Software Engineering Process ModelA software process model is a set of predicted
procedures or set of stages to be use to
develop a fully tested software system timely.
Software Process Model

10. • Waterfall model
• Prototyping model
• Rapid application development model
• Spiral model
• V-model
• Join application development model
• Incremental development model
Software Process Models

11. Waterfall Model

12. Waterfall Model
• A linear sequential development model.
• Because of the cascade form one stage to another it
is known as waterfall model.
• Divided project activities into isolated stages and
each stage should complete before next started.
• Concurrent activities are not possible.
• Need to wait until end of the life cycle to see the
outcome.
• Suitable for develop systems which has stable
requirements.

13. Waterfall Model Stages
Stage 1: Requirement Definition
• The system services, constraints and goals are
established by consulting with the system
users.
• They are define in a manner which is
understandable by both users and the
development staff.

14. Waterfall Model Stages
Stage 2: System and Software designing
• Partitions the requirements either hardware or
software.
• Involves representing the software system
functions in a form that may be transformed into
executable programs.
• Identifying and describing fundamental software
system abstraction and there relationships.

15. Waterfall Model Stages
Stage 3: Implementation and unit testing
• Implementation consists of converting the
physical designing into set of actual programs
and a set of database tables.
• The software is realized as a set of programs
or program units.
• Unit testing involves verifying that each unit
meets it’s requirements.

16. Waterfall Model Stages
Stage 4: integration and system testing
• Individual program units are integrated and
tested as a complete system.
• Ensure the software requirements have been
met.
• After testing the software system is delivered
to the customer.

17. Waterfall Model Stages
Stage 5: Operation and maintenance
• The system installed and put into practical use.
• Involved correcting errors which were not
discovered in earlier stages.
• Improving implementation as new requirements
are discovered.
• Normally this is the longest life cycle phase.

18. Extended Waterfall Model
• Due to the above discussed disadvantages, the
waterfall model was modified with the
concept of backtracking.
• As a result, the Extended Waterfall Model
introduced.

19. Extended Waterfall Model

20. Prototype Model
Prototype is a working model of the actual
System
There are two types of prototype model.
1. Throw away prototype model
2. Evolutionary prototype model

21. Throw away prototype model

22. Throw away prototype model
• Prototype is use to gather requirements and
there after it will be thrown away.
• Further designing, construction and
implementation will be done using the normal life
cycle stages.
• Requirements gathering can be exactly done by
using the prototype
• Even to develop prototype consumes lot of time
and effort , therefore once a prototype is thrown
away it’s a waste of time and money.

23. Evolutionary prototype model
System
Complete
System
Architecture
Identify
Prototype Quick Design
Construct
And Use The
System
Revise
Prototype
Deliver
System
Yes
No

24. Evolutionary prototype model
• Prototype is use to gather requirements and it
will become the final system.
• Both the prototyping process as well as the
development process will be combine
together.
• Prototype will not be thrown away and it is
not wasting effort and cost like throw away
prototype.

25. Rapid Application Development (RAD)

26. Rapid application development model (RAD)
• This is a software process model which uses to
develop applications rather quickly.
• The entire system is broken down into several
manageable stages and each stage analyzed,
designed, developed, tested and implemented
simultaneously
Rapid Application Development (RAD)

27. Stages in the RAD
1. Business modeling
• The information flow among business
functions is modeled.
• Find answers for the following questions:
What information drives the business process?
What information is generated?
Who generate it?
Where does information go?
Who process it?

28. Stages in the RAD
2. Data modeling
• The information flows are refined into set of
data objects.
• The attributes of each objects and
relationships between these objects defined.

29. Stages in the RAD
3. Process modeling
• The data objects are transformed to achieve
the information flow necessary to implement
the business function.
• Processes are created for adding, modifying,
deleting and retrieving data objects.

30. Stages in the RAD
4. Application generation
• Using fourth generation techniques rather
than using conventional third generation
programming languages.
• In possible cases automated tools/reusable
components are use to facilitate construction
of the software. (Ex: DB query tools, reports,
graphics manipulation, interface designs)

31. Stages in the RAD
5. Testing and turnover
• Since the RAD process use many reusable
components that have been tested, it reduces
the overall testing time.
• How ever the new components should be
tested.

32. Programming Styles
There are 3 main programming styles
1. Unstructured Programming
2. Structured Programming
3. Object Oriented Programming

33. Unstructured Programming
• Unstructured programming is the historically
earliest programming paradigm.
• It is a procedural program, the statements are
executed in sequence as written.
• This type of programming uses the goto
statement. A goto statement allows control to
be passed to any other place in the program.
• Difficult to understand the logic of the
program.
Ex: Machine language, Cobol

34. Structured Programming
• Structured programming is a subset of procedural
programming that enforces a logical structure to
make it more efficient and easier to understand
and modify.
• Use of the goto statement is discouraged.
• Structured programming using 3 controls
constructs:
– Sequence
– Selection
– repetition
Ex: C, Pascal, Ada

35. Object Oriented Programming
• Object-oriented programming (OOP) is a
programming model organized around objects
rather than actions and data rather than logic.
• It is becoming more popular as a designing
technique, because it has an ability to
represent complex relationships, data and data
processing with suitable notations.
Ex: Java, C++, C#

36. Flow Charts
A flowchart is a diagrammatic representation
of the process involved in arriving at a solution
to a problem.

37. Flow Chart Notations
Start / End of the program
Input / Output
Process
Decision / Repetition
Flow
Connector

38. Flow Charts
• Question 1:
Draw a flowchart to develop a program to
input the student index number, name and
total marks scored in three modules and
display the students index number, name and
average marks on the screen.

39. Flow Charts
• Question 2:
Draw a flowchart to develop a program to
input student number, name, module 1 marks
and module 2 marks and display student
number, name, average marks and total
marks.

40. Flow Charts
• Question 3:
A student has sat for an exam and following
details were entered through the keyboard:
student number, name, and average marks.
If he average is greater than 50 student will be
graded as “Pass” otherwise graded as “Fail”.
Draw a flowchart to display the student name,
average and grade.

41. Flow Charts
• Question 4:
Draw a flowchart to input two numbers from
the keyboard and evaluate and display the
maximum value.

42. Flow Charts
• Question 5:
Draw a flowchart to develop a program to
input student no, name, module 1 marks and
module 2 marks by keyboard. Calculate and
display student no, average and the grade. The
grading system is as follows. Average > 75
grade is “distinction”, 50 - 75 grade is “credit”,
25 - 50 grade is “Pass” and less than 25 is
“Fail”.

43. Flow Charts
• Question 6:
Draw a flowchart to calculate and display the
sum of first five natural numbers.

44. Flow Charts
• Question 7:
Draw a flowchart to input a number from
keyboard, and there after calculate and
display the factorial number.

45. Pseudo Codes
Pseudo code consists of short, English phrases
used to explain specific tasks within a
program's algorithm. Pseudo code should not
include keywords in any specific computer
languages. It should be written as a list of
consecutive phrases.

46. Pseudo Codes
One of the concepts in programming is…
PROGRAM = DATA + ALGORITHM
Data
 Data types: String, Integer, Real
 Data usage: Variable, Constant
 Data scope: Global data, Local data
Algorithm
 Sequence
 Selection
 Repetition

47. Object Oriented Programming
• Object-oriented programming (OOP) is a
programming language model organized
around objects rather than actions and data
rather than logic.
• Object oriented programming becoming more
popular as a designing technique, because it
has an ability to represent complex
relationships, data and data processing with
suitable notations.

48. Object Oriented Programming
Male Female
Son
Father Mother Daughter
Family system
Objects

49. Object and Class
An object is person,
place or thing which
consist of data and
behaviors. The data of
an object is its
properties (attributes)
and behaviors
represent how an
object acts and reacts.
A class is simply a
representation of a
type of object. It is the
blueprint / template
that describe the
details of an object.
Class is composed of
three things: a name,
attributes, and
operations.

50. Object Instance
Object instance is uniquely identified
occurrence of an object
Book
Book_id
Title
Author
Lending
Reservation
Reading
Book
001 – A
Science
Peter
Lending
Reservation
Reading
Object instance

51. Object Oriented Programming Concepts
 Inheritance
 Polymorphism
 Encapsulation
 Generalization
 Specialization

52. Inheritance
Inheritance is sharing of attributes and operations
among classes based on a hierarchical relationship.
Vehicle
v-no
Model
color
Drive
Stop
Bus
v-no
Model
color
Drive
Stop
Car
v-no
Model
color
Drive
Stop
Super class
operations and
attributes are
inherited to the
sub classes

53. Polymorphism
• Polymorphism is simply the ability for an
object behaves differently depending on its
type.
• Ex: both cat and dog are animals which has
the same method called makeNoise(). But
they are making noise in different ways.

54. Polymorphism

55. Encapsulation
• According to encapsulation attributes and
operations are encapsulated (hidden) within
the object.
• The outside world know what the object can
do but don’t know how it does or where data
is stored. These features are hidden from the
user.

56. Generalization / Specialization
Generalization and specialization both refer to
inheritance but the approach in which they
are implemented are different.
If many similar existing
classes are combined
to form a super class
to do common job of
its subclass, then it is
known as
Generalization.
If some new
subclasses are created
from an existing super
class to do specific job
of the super class,
then it is known as
Specialization.

57. Generalization / Specialization
Vehicle
v-no
Model
Color
Drive
Stop
Motorbike
v-no
Model
color
Drive
Stop
Car
v-no
Model
Color
Airbag
Drive
Stop
Reverse
Specialization
Generalization
Car and Motorbike specialize Vehicle to their
own sub-type.
Vehicle Generalize what is
common between Car and
Motorbike

58. Unified Modeling Language (UML)
• UML is a general purpose visual modeling
language to visualize, specify and document
software systems.
• The most important goal for developing UML
is to define some general purpose modeling
language which all modelers can use and it
also needs to be simple to understand and
use.

59. Unified Modeling Language (UML)
• Class Diagrams
• Use Case Diagrams

60. Class Diagrams
• A class diagram shows the static structure of
an object oriented model.
• Also it shows object classes and their internal
structures (attributes and operations) and
their relationships.

61. Class Diagrams
Student
Name
Address
Phone
Display
Add
Edit
Delete
Class Name
Attributes
Operations
Structure of a Class

62. Relationships
• Association
• Aggregation
• Composition
• Generalization

63. Association
• An association is a relationship among classes
or objects.
• Ex: Student follows Course, Lecturer teaches
Student, Manager manages company.
manager company

64. Aggregation
• When an object has an another object, then
you have got an aggregation between them.
• Ex: Library has Students
Student Library

65. Composition
• When an object contains the other object, if
the contained object cannot exist without the
existence of container object, then it is called
composition.
• Ex: University consist from Buildings, Shirt
consist from Collar, buttons, etc.

66. Generalization
Person
Employer Customer

67. Multiplicity
Multiplicity indicates the number of instance
of one class linked to instance of another
class.
One to One
1 1
One to Many
1 *
Many to Many
* *

68. A Sample Class Diagram
A sample class diagram

69. Use Case Diagrams
A use case diagram is a graphical
representation of a user's interaction with the
system.
The purpose of use case diagram is to capture
the dynamic aspect of a system.

70. Use Case Diagram Notations
Actor
Use Case
Communication Extend/include
System
Boundary

71. A Sample Use Case Diagram

72. A Sample Use Case Diagram

73. Software Testing
• The objective of testing is uncover errors in a
program as much as possible
• In testing a series of steps such as
– Unit Testing
– Integration Testing
– Validation Testing
– System Testing
Are planned and executed…

74. Unit Testing
Unit Testing focuses verification effort of the
smallest unit of the software component or
module.

75. Integration Testing
Verifies the incorporation of components into
a program structure.

76. Validation Testing
Validation Testing is testing traceability to the
software requirements.

77. System Testing
Validates software once it has been
incorporated into a large system. (hardware,
people, information)

78. Testing Approaches
There are two main testing approaches
1. Black Box Testing
2. White Box Testing

79. Black Box Testing
• The program is considered as a black box
which the internal logic is cannot seen by the
testers.
• The expected output is checking against the
input given to the program.

80. White Box Testing
• Program is assumed as a transparent box
where the internal logic is seen by the testers.
• The flows of every logical pathway are tested
in a systematic approach.

81. Software Documentation
Documentation are two types
1. Documents for programmers
2. Documents for users

82. Documents for Programmers
• Internal
Used in coding
– Meaningful names for variables
– Comments
– Using standard style and format
• External
These are the documents which carried out by
designers, analysts and programmers to
communicate
– Requirements Specification
– Design Specification
– Feasibility Report

83. Documents for Users
There are user manuals which is giving
instructions and support for end users for using
the software systems.
Explaining the purpose of the system
Detailed, descriptions and examples by screen
shots.
Step by step guide for operating the system
Troubleshooting support

84. The End
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