Lecture-01

An Introduction to
Software Engineering

Instructor: Inam Ul Haq

(Assistant Professor)
Inam.ul.haq@uo.edu.pk
Subject: Software Engineering
BSCS-5th
Book: Software Engineering by Ian Sommerville

1 Lecture-1: Introduction to SE, University of Okara

 Objectives
• To introduce software engineering and to explain
its importance
• To set out the answers to key questions about
software engineering
• To introduce ethical and professional issues and to
explain why they are of concern to software
engineers

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 Some Facts

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 Some Facts

4 Lecture-1: Introduction to SE, University of Okara

 Software engineering (economy)
• The economies of ALL developed nations are
dependent on software.
• More and more systems are software controlled
• Software engineering is concerned with theories,
methods and tools for professional software
development.
– Expenditure on software represents a
significant fraction of GNP in all developed countries.

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 Software costs
• Software costs often dominate computer system costs.
• The costs of software on a PC are often greater than the
hardware cost.
• Software costs more to maintain than it does to develop.
• For systems with a long life, maintenance costs may be several
times development costs.
• Software engineering is concerned with cost-effective and
reliable software development.(definition)

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 FAQs about software engineering
• What is software?
• What is software engineering?
• What is the difference between software engineering and
computer science?
• What is the difference between software engineering and system
engineering?[yourself]
• What is a software process?
• What is a software process model?

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 FAQs about software engineering
• What are the costs of software engineering?(current
scenario?)
• What are software engineering methods?
• What is CASE (Computer-Aided Software Engineering) [explore case
tools?-assignment]
• What are the attributes of good software?
• What are the key challenges facing software engineering?

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 What is software?
• Computer programs and associated documentation such as
requirements, design models and user manuals.
• Software products may be developed for a particular customer or may
be developed for a general market.
• Software products may be
– Generic - developed to be sold to a range of different customers e.g. PC software
such as Excel or Word.
– Bespoke (custom) - developed for a single customer according to their
specification.
• New software can be created by developing new programs,
configuring generic software systems or reusing existing software.

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 What is software engineering?
• Software engineering is an engineering discipline that is concerned with
all aspects of software production.
• Software engineers should adopt a systematic and organised approach to
their work and use appropriate tools and techniques depending on the
problem to be solved, the development constraints and the resources
available.

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 What is the difference between software
engineering and computer science?
• Computer science is concerned with theory and fundamentals;
software engineering is concerned with the practicalities of
developing and delivering useful software.
• Computer science theories are still insufficient to act as a complete
underpinning for software engineering (unlike e.g. physics and
electrical engineering).

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 What is the difference between software
engineering and system engineering?
• System engineering is concerned with all aspects of computer-based
systems development including hardware, software and process
engineering.

• Software engineering is part of this process concerned with developing

the software infrastructure, control, applications and databases in the
system.
• System engineers are involved in system specification, architectural
design, integration and deployment.

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 What is a software process?
• A set of activities whose goal is the development or evolution of
software.
• Generic activities in all software processes are:
• Specification - what the system should do and its development constraints
• Development - production of the software system
• Validation - checking that the software is what the customer wants
• Evolution - changing the software in response to changing demands.

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 What is a software process model?
• A simplified representation of a software process, presented from a
specific perspective.
• Examples of process perspectives are
• Workflow perspective - sequence of activities; (sequence diagram)
• Data-flow perspective - information flow; (dfd diagram)
• Role/action perspective - who does what. (use case diagram)
• Generic process models
• Waterfall;
• Iterative development;
• Component-based software engineering.

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 What are the costs of software engineering?

• Roughly 60% of costs are development costs, 40% are testing costs. For
custom software, evolution costs often exceed development costs.
• Costs vary depending on the type of system being developed and the
requirements of system attributes such as performance and system
reliability.
• Distribution of costs depends on the development model that is used.

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 Activity cost distribution
Waterfall model
0 25 50 75 100

Specification Design Development Integ ration and testing

Iterative development

0 25 50 75 1 00

Specification Iterative development System tes ting

Component-based software eng ineering

0 25 50 75 1 00

Specification Development Integ ration and testing

Development and evolution costs fo r long-lifetime syst ems

0 10 200 30 400

System development System evolution

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 Product development costs

0 25 50 75 100

Specification Development System tes ting

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 What are software engineering methods? (optional)

• Structured approaches to software development which include

system models, notations, rules, design advice and process guidance.
• Model descriptions
• Descriptions of graphical models which should be produced;
• Rules
• Constraints applied to system models;
• Recommendations
• Advice on good design practice;
• Process guidance
• What activities to follow.

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 What is CASE (Computer-Aided Software Engineering)

• Software systems that are intended to provide automated support for

software process activities.
• CASE systems are often used for method support.
• Upper-CASE
• Tools to support the early process activities of requirements and
design;
• Lower-CASE
• Tools to support later activities such as programming, debugging and
testing.

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 What are the attributes of good software?

• The software should deliver the required functionality and performance to

the user and should be maintainable, dependable and acceptable.
• Maintainability
• Software must evolve to meet changing needs;
• Dependability
• Software must be trustworthy;
• Efficiency
• Software should not make wasteful use of system resources;
• Acceptability
• Software must accepted by the users for which it was designed. This means
it must be understandable, usable and compatible with other systems.

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 What are the key challenges facing software
engineering?
• Heterogeneity
• Developing techniques for building software that can cope with
heterogeneous platforms and execution environments;
• Delivery
• Developing techniques that lead to faster delivery of software;
• Trust
• Developing techniques that demonstrate that software can be trusted
by its users.

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 Professional and ethical responsibility
• Software engineering involves wider responsibilities than simply the
application of technical skills.
• Software engineers must behave in an honest and ethically responsible
way if they are to be respected as professionals.
• Ethical behaviour is more than simply upholding the law.
• I’ll teach about “Social & Ethical Perspective of Information System”

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 Issues of professional responsibility
• Confidentiality
Engineers should normally respect the confidentiality of their employers
or clients irrespective of whether or not a formal confidentiality
agreement has been signed.
• Competence
Engineers should not misrepresent their level of competence. They
should not knowingly accept work which is outwith their competence.

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 Issues of professional responsibility
• Intellectual property rights
– Engineers should be aware of local laws governing the use of intellectual
property such as patents, copyright, etc. They should be careful to ensure that
the intellectual property of employers and clients is protected.
• Computer misuse
– Software engineers should not use their technical skills to misuse other people’s
computers. Computer misuse ranges from relatively trivial (game playing on an
employer’s machine, say) to extremely serious (dissemination of viruses).

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 ACM/IEEE Code of Ethics
• The professional societies in the US have cooperated
to produce a code of ethical practice.
• Members of these organisations sign up to the code
of practice when they join.
• The Code contains eight Principles related to the
behaviour of and decisions made by professional
software engineers, including practitioners,
educators, managers, supervisors and policy makers,
as well as trainees and students of the profession.

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 Code of Ethics - Principles
• PUBLIC
– Software engineers shall act consistently with the public interest.
• CLIENT AND EMPLOYER
– Software engineers shall act in a manner that is in the best interests of their
client and employer consistent with the public interest.
• PRODUCT
– Software engineers shall ensure that their products and related modifications
meet the highest professional standards possible.

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 Code of Ethics - Principles
• JUDGMENT
– Software engineers shall maintain integrity and independence in their
professional judgment.
• MANAGEMENT
– Software engineering managers and leaders shall subscribe to and promote an
ethical approach to the management of software development and
maintenance.
• PROFESSION
– Software engineers shall advance the integrity and reputation of the profession
consistent with the public interest.

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 Code of Ethics - Principles
• COLLEAGUES
– Software engineers shall be fair to and supportive of their
colleagues.
• SELF
– Software engineers shall participate in lifelong learning
regarding the practice of their profession and shall
promote an ethical approach to the practice of the
profession.

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 Ethical Dilemmas
• Disagreement in principle with the policies of senior
management.
• Your employer acts in an unethical way and releases
a safety-critical system without finishing the testing
of the system.
• Participation in the development of military
weapons systems or nuclear systems.

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 Exercise
• What is Software Engineering World Economy?
• BS Software Engineering syllabus?
• Software Engineering terms.
• CASE tools? (https://www.geeksforgeeks.org/computer-aided-software-engineering-case/)
• Explore UML Tools (https://en.wikipedia.org/wiki/List_of_Unified_Modeling_Language_tools)
• Requirement Management Software (https://www.g2.com/products/casecomplete/competitors/alternatives)
• What happens if we do not use S.E. Methods?
• What are top 5 reasons of software project failure?
• What are fundamental S.E. Activities?
• What are key challenges that S.E. is facing?
• General cost of S.E.?
• What are best S.E. Techniques and Methods?
• What is ERP system?

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