1. Introduction to Software Engineering

2. What is software? Computer programs and associated documentation
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
Custom - developed for a single customer according to their specification

3. What is Good Software?
Software has number of attributes which decide whether it is a good or bad . The definition of a good software changes with the person who evaluates it. The software is required by the customer , used by the end users of an organization and developed by software engineer . Each one will evaluate the different attributes differently in order to decide whether the software is good.

4. 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 usable.
Maintainability
Software must evolve to meet changing needs
Dependability
Software must be trustworthy
Efficiency
Software should not make wasteful use of system resources
Usability
Software must be usable by the users for which it was designed

5. Software - Characteristics
Software has a dual role. It is a product, but also a vehicle for delivering a product.
Software is a logical rather than a physical system element.
Software has characteristics that differ considerably from those of hardware.
- Software is developed or engineered, it is not manufactured in the classical sense.
- Software doesn’t “wear out”.
- Most software is custom-built, rather than being assembled from existing components.

6. Types of Software
System Software- A collection of programs written to service other programs at system level.
For example, compiler, operating systems.
Real-time Software- Programs that monitor/analyze/control real world events as they occur.
Business Software- Programs that access, analyze and process business information.
Engineering and Scientific Software - Software using “number crunching” algorithms for different science and applications. System simulation, computer-aided design.

7. Types of Software Embedded Software-:
Embedded software resides in read-only memory and is used to control products and systems for the consumer and industrial markets. It has very limited and esoteric functions and control capability.
Artificial Intelligence (AI) Software:
Programs make use of AI techniques and methods to solve complex problems. Active areas are expert systems, pattern recognition, games

8. Types of Software Internet Software :
Programs that support internet accesses and applications. For example, search engine, browser, e-commerce software, authoring tools.
Software Tools and CASE environment :
Tools and programs that help the construction
of application software and systems. For example, test tools, version control tools.

9. Importance of software
Software can have a huge
impact in any aspect of
society.

10. Where can you find software?

11. Some popular ones…

12. Some popular ones…

13. Some popular ones…

14. And even in…

15. Conclusion
Software is Almost
Everywhere.

16. General issues that affect most software
Heterogeneity
Increasingly, systems are required to operate as distributed systems across networks that include different types of computer and mobile devices
Business and social change
Business and society are changing incredibly quickly as emerging economies develop and new technologies become available. They need to be able to change their existing software and to rapidly develop new software
Security and trust
As software is intertwined with all aspects of our lives, it is essential that we can trust that software
Chapter 1 Introduction

17. Common issues
The final Software doesn´t fulfill the needs of the customer.
Hard to extend and improve: if you want to add a functionality later is mission impossible.
Bad documentation.
Bad quality: frequent errors, hard to use, ...
More time and costs than expected

18. i. The final Software doesn´t fit the needs of the customer
ii. Hard to extend and improve: if you want to add a functionality later is mission impossible
Bad documentation, bad software design
iii. Bad quality: frequent errors, hard to use...
iv. More time and costs than expected

19. But
That never
happens,
right?

20. Wrong!

21. Problems in software
development

22. Limitations of Non-engineered Software
Requirements
Here is the problem!!
One of the problems with complex system design is that you cannot foresee the requirements at the beginning of the project. In many cases, where you think you can start with a set of requirements, that specifies the completely the properties of your system you end up with....
Software

23. Software Production has a Poor Track Record Example: Space Shuttle Software
Cost: $10 Billion, millions of dollars more than planned
Time: 3 years late
Quality: First launch of Columbia was cancelled because of a synchronization problem with the Shuttle's 5 onboard computers.
Error was traced back to a change made 2 years earlier when a programmer changed a delay factor in an interrupt handler from 50 to 80 milliseconds.
The likelihood of the error was small enough, that the error caused no harm during thousands of hours of testing.
Substantial errors still exist.
Astronauts are supplied with a book of known software problems "Program Notes and Waivers".

24. Ariane 5 Flight 501
Cause: design errors in the software

25. 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

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

27. Solution

28. Software Engineering The study of approaches as in
Application of a systematic, disciplined, quantifiable approach to the development, operation and maintenance of software; that is, the application of engineering to software.
(IEEE 93)

29. By “Systematic” we mean
Following a well-defined sequence of activities, in which desired outputs (deliverables) are well-defined by using well-defined inputs (i.e. documented syntax, semantics, context and other relevant properties of the input) in a well-defined process (e.g. using organizational standards for interprocess communication, data formats, error handling etc.) whose outputs are in turn used similarly as inputs in subsequent process(es), until the final output is achieved, and where the correctness of the output is verifiable. Note: The “inputs” and “outputs” most often refer to requirements, software specifications, the software itself, documentation, test inputs/outputs and similar software artifacts. Back

30. By “disciplined” we mean:
Each process is followed using organizational principles (e.g. who manages whom, who is responsible for what?),
Intermediate results are carefully documented, as well as final results,
Actions are traceable as to their causes, individuals involved, time of occurrence and circumstances.
Back
Software Engineering - Introduction

31. By “quantifiable” we mean:
The size and extent of the required effort (size of output code, data, documentation, manpower, duration, budget for development, expected error rate and user support) are predictable within justifiable and acceptable bounds
Software Engineering - Introduction

32. Software Engineering Objective To produce software that is:
On time: is deliver at the established date.
Reliable: doesn´t crash.
Complete: good documentation, fulfill customer needs.
On time: deliver at the established date
Reliable: doesn´t crash often, etc
Complete: good documentation, fulfill customer needs

33. Requirements Analysis
Stages for software development
Requirements Analysis
Software Design
Implementation
Testing
Maintenance

34. 1. Requirements Analysis
Find out what the client want the software to do
Find out what the client want the software to do

35. 2. Design Planning the software solution
How are you going to build your application and how will it be
Planning the software solution

36. 3. Implementation
Code!!!
Code!!!

37. 4. Testing Executing the application trying to find software bugs
Try everything to make sure is working correctly
Test techniques include, but are not limited to, the process of executing a program or application with the intent of finding software bugs
Executing the application trying to find software bugs

38. 5. Maintenance
Any activity oriented to change an existing software product.
Maintenance and enhancing software to cope with newly discovered problems or new requirements can take far more time than the initial development of the software. It may be necessary to add code that does not fit the original design to correct an unforeseen problem or it may be that a customer is requesting more functionality and code can be added to accommodate their requests. It is during this phase that customer calls come in and you see whether your testing was extensive enough to uncover the problems before customers do.
Software maintenance activities include any software engineering activity oriented to change an existing software product or to improve or plan for future changes.

39. Why Software Engineering?
Major Goals:
- To increase software productivity and quality.
- To effectively control software schedule and planning.
- To reduce the cost of software development.
- To meet the customers’ needs and requirements.
- To enhance the conduction of software engineering process.
- To improve the current software engineering practice.
- To support the engineers’ activities in a systematic and efficient manner.

40. Computer Science Software Engineering
What is the difference between software engineering and computer science?
Computer Science
Software Engineering
is concerned with
theory
fundamentals
the practicalities of developing
delivering useful software
Computer science theories are currently insufficient to act as a complete underpinning for software engineering, BUT it is a foundation for practical aspects of software engineering

41. What is the difference between software engineering and system engineering?
Software engineering is part of System engineering
System engineering is concerned with all aspects of computer-based systems development including
hardware,
software and
process engineering
System engineers are involved in
system specification
architectural design
integration and deployment

42. Software engineering ethics
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 but involves following a set of principles that are morally correct
Chapter 1 Introduction

43. 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
Chapter 1 Introduction

44. 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).
Chapter 1 Introduction