1. An Introduction to
Software Engineering

2. Software engineering
Software engineering is concerned with theories, methods and tools for professional software development

3. Course Themes 1. Leadership of large software projects
 Software as a product
Clients and their needs
Quality
 Requirements and specification
Usability
Evolution
 Project management
Personnel management
Economic, legal, and social factors

4. Course Themes  Software design Software architecture
2. Large and very large systems
 Software design
Software architecture
Object-oriented design
 Dependable systems
Reliability
Verification

5. 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?
What is a software process?
What is a software process model?

6. FAQs about software engineering
What are the costs of software engineering?
What are software engineering methods?
What is CASE (Computer-Aided Software Engineering)
What are the attributes of good software?
What are the key challenges facing software engineering?

7. Computer programs and associated documentation
What is software?
Computer programs and associated documentation
Software products may be
Generic - developed to be sold to a range of different customers
Bespoke (custom) - developed for a single customer according to their specification
Embedded
Built into hardware
Hard to change

8. Software Applications
1. System software: such as compilers, editors, file management 2. Application software: stand-alone programs for specific needs. 3. Engineering/scientific software: such as automotive stress analysis, molecular biology, orbital dynamics etc 4. Embedded software resides within a product or system. (key pad control of a microwave oven, digital function of dashboard display in a car) 5. Product-line software focus on a limited marketplace to address mass consumer market. (word processing, graphics, database management) 6. WebApps (Web applications) network centric software :remote database and business applications. 7. AI software Robotics, expert system, pattern recognition game playing

9. Software Engineering Software Engineering is the science and art of
building significant software systems that are:
1) on time
2) on budget
3) with acceptable performance
4) with correct operation.

10. What is Software Engineering?
Some Definitions and Issues
“state of the art of developing quality software on time and within budget”
Trade-off between perfection and physical constraints
SE has to deal with real-world issues
State of the art!
Community decides on “best practice” + life-long education

11. What is Software Engineering?
“multi-person construction of multi-version software”
Team-work
Scale issue (“program well” is not enough) + Communication Issue
Successful software systems must evolve
Change is the norm, not the exception

12. Why Study Software Engineering?
To acquire skills to develop large programs.
Exponential growth in complexity and difficulty level with size.
The ad hoc approach breaks down when size of software increases

13. 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

14. 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
System engineers are involved in system specification, architectural design, integration and deployment

15. 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

16. 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
Data-flow perspective - information flow
Role/action perspective - who does what
Waterfall
Evolutionary development
Formal transformation
Integration from reusable components

17. Software Quality... Usability Efficiency Reliability Maintainability
Users can learn it and fast and get their job done easily
Efficiency
It doesn’t waste resources such as CPU time and memory
Reliability
It does what it is required to do without failing
Maintainability
It can be easily changed
Reusability
Its parts can be used in other projects, so reprogramming is not needed

18. Emergence of Software Engineering
Early Computer Programming (1950s):
Programs were being written in assembly language.
Programs were limited to about a few hundreds of lines of assembly code.

19. Early Computer Programming (50s)
Every programmer developed his own style of writing programs:
according to his intuition (exploratory programming).

20. High-Level Language Programming (Early 60s)
Software development style was still exploratory.
Typical program sizes were limited to a few thousands of lines of source code.

21. Control Flow-Based Design (late 60s)
Size and complexity of programs increased further:
exploratory programming style proved to be insufficient.
Programmers found:
very difficult to write cost-effective and correct programs.

22. Control Flow-Based Design (late 60s)
Programmers found:
programs written by others very difficult to understand and maintain.

23. Control Flow-Based Design (late 60s)
Using flow charting technique:
one can represent and design a program's control structure.
Usually one understands a program:
by mentally simulating the program's execution sequence.

24. Control Flow-Based Design (Late 60s)
It was found:
GO TO ) JUMP ( statements makes control structure of a program messy
GO TO statements alter the flow of control arbitrarily.
The need to restrict use of GO TO statements was recognized.

25. Control Flow-Based Design (Late 60s)
But, soon it was conclusively proved: A program is called structured
only three programming constructs are sufficient to express any programming logic:
sequence (e.g. a=0;b=5;)
selection (e.g.if(c=true) k=5 else m=5;)
iteration (e.g. while(k>0) k=j-k;)

26. Data Structure-Oriented Design (Early 70s)
Soon it was discovered:
it is important to pay more attention to the design of data structures of a program
than to the design of its control structure.

27. Data Flow-Oriented Design (Late 70s)
Data flow-oriented techniques advocate:
the data items input to a system must first be identified,
processing required on the data items to produce the required outputs should be determined.

28. Data Flow Model of a Car Assembly Unit
Engine Store
Door Store
Chassis with Engine
Partly Assembled Car
Fit
Engine
Fit
Doors
Fit
Wheels
Paint and
Test
Car
Assembled Car
Chassis Store
Wheel Store

29. Object-Oriented Design (80s)
Object-oriented technique:
an intuitively appealing design approach:
natural objects (such as employees, pay-roll-register, etc.) occurring in a problem are first identified.

30. Object-Oriented Design (80s)
Relationships among objects:
such as composition, reference, and inheritance are determined.
Each object essentially acts as
a data hiding (or data abstraction) entity.

31. Future Experience What will you be doing one year from now?
Ten years from now?

32. Principle Texts
Software Engineering (9th Edition), Ian Sommerville, 2010, ISBN-10: 
Software Engineering: A Practitioner's Approach, Roger Pressman, 2009

33. Projects  Project teams, about 3 to 5 people.
 Select your own project, any branch of software engineering
 Real project for real client who intends to use the software in production.
 Presentations:
requirements
design
final

34. Client (a.k.a Customer)
 The client provides resources and expects some product in return.
 Client satisfaction is the primary measurement of success.
Question: Who is the client for Microsoft Excel?