The document summarizes key aspects of software engineering processes and lifecycles. It discusses: - The typical phases of the software development lifecycle including requirements, design, implementation, testing, deployment and maintenance. - The software engineering approach focuses on achieving high quality and productivity through effective software processes and managing process quality. - Effective processes are phased, with defined stages executed in order to better manage and control software projects. - The costs of software, including development costs which are a function of program size, productivity and salaries. Maintenance costs are higher than initial development. - Error correction becomes significantly more expensive in later stages, so earlier stages require more attention and error removal.

1. SE-381
Software Engineering
BEIT-V
Lecture no. 3
(Basis for Software Process)

2. Recap
• Definitions of Sw and SE
• Student’s and Industrial Strength Software
• Mini Test
– Retention Exercise
– Comprehension Exercise
• Goal
– Results
• Students Profiles’ Submission

3. What is common between the first two clips?
_____________________________________________________________
______________
In Grocery Store Clip
What two stores are compared? ______ and ________
QR Code is to __________________________________
TeSCo and E-Mart are the names for the same store (Yes/No)
-----------------------
Customers of E-Mart increased by 130% after this online shopping
campaign (Y/N) ____
Online Shopping Compaign
Exploited Koreans 2 habits
• ____________________________________
• ____________________________________
Exploited 3 widely available technologies
• __________________________________________
• __________________________________________
• __________________________________________
How many customers visited the store online during the compaign? _______
Did the store became number one in off-line shopping (Y/N)? __________
At which Institute, the Four Rotor Helicopter project was carried out?
__________________________
What Sw/Hw Project you can figure out from the first three clips
_____________________________
_____________________________
_____________________________

4. Answers to Mini Test

5. From Google Earth

6. North Tweaked

7. What is in Today’s Lecture
Covered till now
– Definitions
– Students’ Sw projects and Industrial Strength Sw
• Software Myths – Roger S Pressman (2005)
• Problem Domain
– Software is Expensive,
– Late and Unreliable,
– Maintenance and Rework
• Solution Domain – Software Engineering Challenges
– Scale,
– Quality & Productivity,
– Consistency and Repeatability,
– Change
• Software Engineering Approach
– Phased Development Process,
– Managing the Process to get quality software

8. Software Myths (‘Tonies or Ponies’)
• Management Myths ( Also see www.mhhe.com/pressman )
– We already have a book that’s full of standards and
procedures for building software. Won’t that provide
my people with everything they need to know?
– If we get behind schedule, we can add more
programmers and catch up
“Adding people to a late software project makes it later” – F
Brooks (1975)
– If I decide to outsource the software project to a 3rd
party, I can just relax and let that firm build it.
No substitute to misinformation

9. • Customer Myths
– A general statement of objectives is sufficient to begin writing
programs – we can fill the details later
• More information you have at start better equipped you are.
– Project requirements continually change, but change can be
easily accommodated because software is (not physical and)
flexible
• Practitioner’s Myths
– Once we write the program and get it to work, our job is done
• This is the start, not the end, 60% - 80% of effort will be
expended after the program is deployed. For every $ spent
on development needs 2 $s for its maintenance
– Until I get the program running, I have no way of assessing its
quality
• Quality is whole some, of each part, so quality filters need to
be inserted in the process for various phases of Sw
Development

10. – The only deliverable work product for a successful project is the
working program
• Documentation, data, rule base etc are all parts of software
– Software Engineering will make us create voluminous and
unnecessary documentation and will invariably slow us down.
• Will make things easy, and lead to quicker development and
easy and cost effective maintenance

11. Software is Expensive
• Bell 2005, quotes that US$ 500 B is spent
annually for software purchase and development
in USA and it is 1 % of her annual GNP (Gross
National Product)
• Globally US$ 1000 B is spent on Software
development
• Many countries exports like our neighbor’s have
significant fraction coming from Sw
• Pakistan currently generates 1.5 to 2 B US$
annually from Sw exports – Ref to Mr Saleem
Ghori, CEO, NetSol, 2009

12. Pak Software Exports
• Daily Express, Islamabad, dated Feb 21, 2011
quoted Federal Bureau of Statistics that for period
of July to December 2010
– Sw exports amounted to Rs 6.15 Billions, with an
increase of 13.13% from its last year figure
– Overseas Sw Consultancy services Rs 1.3 B
– Computers Repair and support Rs 0.05 B
– Computer related Auxiliary Services Rs 1.3B
• Total sw exports were Rs 8.8 B with an increase
of 8.37 % from previous year

13. Software is Expensive

14. Program Size

15. Program Size
C, C++40,000 KLOCWindows XP
C, c++30,000 KLOCLinux
C, sh100 KLOCAppache
C, perl, sh320 KLOCPerl
C, C++, yacc980KLOCGcc
C, C++40,000 KLOCWindows XP
C, c++30,000 KLOCLinux
C, sh100 KLOCAppache
C, perl, sh320 KLOCPerl
C, C++, yacc980KLOCGcc

16. Compute the Cost of a Software
A software of size say 100 KLOC, like
Apache web server, is to be developed by
a team of professional software
developers, having an average
productivity of 150 LOC per person-
month, and drawing an average salary of
Rs 30,000/- a month.

18. Program Size = 100 KLOC
Average Productivity = 150 LOC / Person-
Month
Duration = Program Size / Productivity
= 100 KLOC/150 LOC/Per-Mon
= 2/3 K Per-Mon
Rate = 30 K Rs / Per-Mon
Total Cost = Duration * Rate
= 2/3 K Per-Mon * 30 K Rs / Per-Mon
= 20 K * K Rs = 20 M Rs
= Rs 20,000,000

19. Software – Problems and
Prospects
Software is Open ended, complex and key
mechanism in providing the requisite
functionality of the system. It is of huge
size, needs 000s of people and millions of
$s of investment to develop.
The perceived problems in Sw development
and goals the Sw Development needs to
achieve are:

20. • Meeting Users’ Needs
• Low Cost of Production
• High Performance
• Portability – it works at various envisaged
platforms
• Low Cost of Maintenance
• High Reliability
• Scalability
• Delivery on Time
– Till to-date each of the above goals is partially
achieved, so it stays as a Sw dev problem. SE
seeks to provide the techniques to resolve these
problems i.e. to achieve these goals.

21. Software Engineering Challenges
• Scale

22. • Quality and Productivity

23. • Consistency and Repeatability
• Change

24. Software Engineering Approach
High Quality and Productivity (Q&P) is the
basic objective of Software Engineering.
The main three forces governing Q&P are:

25. Software Process
• Software Process is the way we produce
software, it starts with the concept
exploration and ends when the product is
decommissioned. During this product goes
through a series of phases like
Requirements, Specifications, Planning,
Design, Implementation, Testing, Integration,
Maintenance, Documentation and finally the
Retirement

26. Quality Product
• For a quality software product, both the
quality of product itself and quality of
software process is important.
• The cost of error recovery in the later
phases of software is many times more
than the earlier phases, so higher
attention should be paid in the earlier
phases, and these should be made error-
free.

27. Software Processes
– Software Process is comprised of a number of
processes working in Series and in parallel to
achieve the software product
– These processes can be Software Development
Process, Business Process, Training Process,
Human Resource Management or Social
Process, Quality Assurance Process, Software
Monitoring and Control Process, Inspection
Process and Software Management Process etc
– Process is execution of a number of steps in a
specified order

28. Process, Project and Product
– Process is a series of steps or activities
conducted in an orderly manner
– Project is execution of a Process, to achieve
or develop a product. It is an instance of
Process executed in specific time frame to get
the product that meets the needs of a user
– Product is the outcome of a successfully
executed project
– Process can be initiated on a number of
Projects, and a project can yield a number of
Products

29. – Process works as Check List and its pre-
defined stages are executed in the pre-
specified order
– The main objective of Software Engineering is
to develop Reliable, High Quality Software
that can be built within price and time budget,
hence we need to focus on Software Related
Processes and more precisely on Software
Development Process

30. Software Process
• Software should be
– Reliable (high quality)
– Affordable (Cheap, low cost)
– Small Time Cycle (so that the software could
be developed speedily)
• For better management and control
software process should be
– Phased i.e. consist of multiple stages

31. Software Development Process
Software Development
Process
Requirements Software Product
In fact, this SD Process consists of:
Analysis Design
Implementa-
tion
Deployment

32. And each one of these is further
divided into sub phases, like
Analysis Requirements Analysis Specification
Design Architectural
Design
Lower Level or
Detailed Design
Implement-
ation
Coding
Testing Unit Testing
Sub-system
Testing
System
Testing
Acceptance Tst
=
=
=
=
Higher Level
Design

33. Software Process
• Software Process is the way we produce
software, it starts with the concept
exploration and ends when the product is
decommissioned or retired. During this life,
the product goes through a series of
phases like
Requirements, Specifications, Planning,
Design, Implementation, Testing, Integration,
Maintenance, Documentation and finally the
Retirement

34. Software Development Life Cycle
• Life Cycle
• All what is done on a product from its conception to its
physical realization and retirement is called its Life Cycle
• Software Development Life Cycle Model
• It is a description of all the stages/phases that should be
performed when building a software product. Number of
stages differ from author to author, from 4 to 10 or even
more, but in general the Classical Software Development
Life Cycle model has eight (highlighted) stages

35. Different Phases of SDLC
Authors partition the SDLC activities differently, Eg
[Jal98] mentions the following 4 stages
• Requirement Analysis
• Design (further divided into System Design & Detailed Des, or Jal05
mentions them as Architectural Des, High Level Des and Low Level Des)
• Coding and
• Testing (including Unit Testing, Integration Testing and Acceptance Testing)
– Towards over-all Effort/Cost, each one of them contributed 10%, 20%,
30% and 40% respectively, and
– Error distribution among the first three phases was 20%, 30% and 50%
respectively

36. Software Development Life Cycle
(SDLC) Stage or Phases
1. Requirements Phase
2. Analysis (Specification) Phase
3. Planning Phase
4. Design Phase
a. Architectural Design
b. High Level Design
c. Detailed Design
5. Implementation Phase
6. Integration Phase
7. Testing
8. Documentation
9. Post delivery Maintenance Phase
Corrective, Perfective, Adaptive
10. Retirement Phase

37. Comparative Effort Spent in
Different Stages of SDLC

38. Different types of Maintenance
Post-delivery Maintenance
• Done after deployment at the clients premises
This is of two types:
Corrective Maintenance or Software Repair
Removal of Residual faults leaving the Specifications unchanged
Enhancement or Software Update
Consists of changes to specification and implementation of those
changes. It further consists of two types:
Perfective Maintenance
The changes which client thinks will improve the effectiveness of
the product, such as Additional Functionality, Decreased
response time, or Optimal memory usage
Adaptive Maintenance
Changes made in response to changes in the environment in
which the product operates, such as, a new hardware, OS or new
government regulations or conformance to new standard like
UNICODE

39. Stage-wise Cost of SD

41. Relative Costs of the Stages of SD

43. Cost of Error Recovery / Correction
• The cost of error recovery in the later
phases of software is many times more
than the earlier phases, so higher attention
should be paid in the earlier phases, and
respective stages/phases errors be
identified and eradicated, making these
phases error-free.

44. Stage-wise Number of Errors

45. Cost of Fixing of Errors

49. Reading Assignment
1. Ch-1 Problems and Prospects, pp 3-22
From Douglas Bell (2005); Software Engineering for
Students; Pearson Education Limited
2. Ch – 1 Introduction, pp 1-20 + Ch-2
From Pankaj Jalote (2005); An Integrated Approach to
Software Engineering, 3rd Edition, Narosa
Publishing House, New Delhi
3. Ch – 1 Introduction to Software Engineering,
pp 33-50
From Roger S Pressman (2005); Software Engineering
– A Practitioner’s Approach, 6th Edition, McGraw Hill
Higher Education, Boston