software engg

1. IT – 3901-3
Software Engineering
for BS(IT)
Lecture 1: Introduction
Hareem Aslam
Hareem.aslam@pucit.edu.pk
Punjab University College of Information Technology (PUCIT)

2. 2
Course Objectives
 Importance and need of software engineering
 To discuss software development models appropriate for the development
and maintenance of software products
 To introduce basic project management concepts
 To impart comprehensive knowledge regarding software development
lifecycle
 To demonstrate, with justification, an appropriate set of tools to support the
development of a range of software projects

3. Scope of Software
Engineering:
Definition Motivation and Need, Software characteristics and
Applications.
Software Process: Intro to SDLC, Software Process Models.
Project Management
Concepts
Essentials, 4P’s(Product, People, Project, Process).
Software Measurement
concepts:
Project, process and product and software Quality metrics.
Software Cost Estimation techniques
Project Scheduling: Gantt chart, Critical Path Method.
Requirement Engineering: Definition, Requirement Elicitation, Requirement Traceability ,
Requirement Analysis and Specification.
Course Outline

4. 4
Course Outline
Software Designing: elementary concepts, data design, software Architecture,
Functional Independence, Interface Design, Component-level
Design, Coding Standards.
Software Testing: Fundamentals, Verification & Validation, Testing Plan, Testing
Techniques, White Box Testing and Black Box Testing, Test Case
Design, Unit Testing, Integration Testing, Validation Testing,
System Testing, Debugging practices

5. 5
Course Material
 Course Book
 Roger Pressman, Software Engineering, 7th Edition, Mcgraw Hill.

6. Motivation

7. Software can have huge impact
in any aspect of our society

8. Where can we find software?

9. Some popular ones…

10. Some popular ones…

11. And even in…

12. Conclusion
Software is almost everywhere!!!

13. Problems in software development
 Common issues
 The final software does not fulfill the needs of the
customer
 Hard to extend and improve: if you want to add a
functionality later its mission impossible
 Bad documentation
 Bad quality: frequent errors, hard to use, ...
 More time and costs than expected

14. http://www.projectcartoon.com

15. But…
that never
happens?
right?

16. Wrong!

17. Ariane 5 Flight 501
 Cause: design
errors in the
software
 https://www.youtube.com/watc
h?v=5tJPXYA0Nec

18. Conclusion
 Programming is NOT enough!
It is not enough to do your best: you must Know what to do, and
THEN do your best. -- W. Edwards Deming

19. And Since…
A clever person solves a problem.
A wise person avoids it.
- Albert Einstein

20. Solution
Software Engineering

22. Software Engineering: Basic Definitions
22
 Software:
 A product that is built by computer professionals that
encompasses programs that execute within a computer of
any size.
 The textbook description of software is
 Instructions that when executed provide desired function and
performance
 Data structures that enable the programs to adequately
manipulate information

23. 23
Software Engineering Defined
 Engineering:
 A set of practices followed to build a product using the
knowledge of Basic Science. For example, mechanical
engineering and electrical engineering use the knowledge of
Physics.
 Software Engineering:
 It’s a process, a collection of methods (practice) and an array
of tools that allow professionals to build high quality computer
software.

24. Software Engineering
 IEEE [IEEE93]: Software Engineering:
 (1) The application of systematic, disciplined, quantifiable
approach to the development, operation, and maintenance of
software; that is, the application of engineering to software

25. Software Engineering
Objective is to produce software that is:
 On-time: is deliver at the established date.
 Reliable: does not crash.
 Complete: good documentation, fulfill customer needs.

26. Nature of Software
 “Software is developed or engineered; it is not manufactured
in the classical sense”
 “Software doesn’t wear out”
 Why software deteriorate?(due to changes)
 Software is complex
 Software is expensive
 Software is risky
 Component based construction.
 Well Engineered Software
26

27. Failure curve for hardware
(bathtub curve)
S/W characteristics different from H/W
( high failure rate in the beginning,
then drop to steady state, then
cumulative effects of dust, vibration,
abuse occurs).

28. 28
Failure curve for software
(every failure indicate error in design)
S/W characteristics different from H/W

29. Software poses challenges
 How do we ensure the quality of the software
that we produce?
 How do we meet growing demand and still
maintain budget control?
 How do we upgrade an aging "software
plant?"
 How do we avoid disastrous time delays?
 How do we successfully institute new
software technologies?
29

30. Software Application Domains
 System software
 Application software
 Scientific software
 Embedded software
 Legacy software
 Web/Mobile Apps
 AI software
30
Provides platform for other s/w to run e.g, OS, compiler
Serve a particular purpose e.g, payroll s/w, MS word
Solve scientific problems like Genetic analysis
Induce human like intelligence in machines e.g, Robotics
Run on browser or mobile
Provide limited features and functionalities e.g,
Microwave ovens
Very old & traditional software MS-DOS

31. Attributes of a good software
 What is a well Engineered Software?
Product
Characteristics
Description
Maintainability Software should be written in such a way that it may evolve to meet the changing
needs of customers. This is a critical attribute because software change is an
inevitable consequence of a changing business environment.
Dependability Software dependability has a range of characteristics, including reliability, security
and safety. Dependable software should not cause physical or economic damage
in the event of system failure.
Efficiency Software should not make wasteful use of system resources such as memory and
processor cycles. Efficiency therefore includes responsiveness, processing time,
memory utilization, etc.
Usability Software must be usable, without undue effort, by the type of user for whom it is
designed. This means that it should have an appropriate user interface and
adequate documentation.

32. Software Engineering Practice
 Understand the problem
 Plan the Solution
 Carry out the Plan
 Examine the result
32

33. Professional and Legal Responsibility
Organizations put trust in software developers:
 Competence: Software that does not work effectively can destroy an
organization.
 Confidentiality: Software developers and systems administrators may
have access to highly confidential information (e.g., trade secrets,
personal data).
 Legal environment: Software exists in a complex legal environment
(e.g., intellectual property, obscenity).
 Acceptable use and misuse: Computer abuse can paralyze an
organization (e.g., the Internet worm).
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34. 34
Legacy Software
 Developed decades ago and have been
continually modified to meet changes
 Issues
 Non existent documentation
 Inextensible code
 Test cases and results missing
 Poorly managed changed history

35. 35
Software Myths
 Management
 We have standards
 We have new computers
 We’ll add more people to catch up
 I outsourced it, I’m done
 Customer
 We have general objectives, let’s start
 Change is easily accommodated

36. 36
Software Myths
 Practitioner
 We’ll write it and be done
 I can’t assess quality until it is running
 The only deliverable is the working code
 Software engineering is about meaningless
documents