1. CS385T Software Engineering Dr.Doaa Sami
An Introduction to Software Engineering

2. 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

3. 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?
What are the attributes of good software?
What are the key challenges facing software engineering?

4. What is software?
Computer programs and associated documentation (such as requirements, design models and user manuals) and configuration data needed to make programs operate correctly
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 e.g., embedded control systems, air traffic control software, traffic monitoring systems etc.
New software can be created by developing new programs, configuring generic software systems or reusing existing software
Software system

5. The Nature of Software Software is intangible
Hard to understand development effort
Software is easy to reproduce
Cost is in its development
in other engineering products, manufacturing is the costly stage
Untrained people can hack something together
Quality problems are hard to notice
Software is easy to modify
People make changes without fully understanding it

6. The Nature of Software Software does not ‘wear out’ Conclusions
It deteriorates by having its design changed:
erroneously, or
in ways that were not anticipated, thus making it complex
Conclusions
Much software has poor design and is getting worse
Demand for software is high and rising
We are in a perpetual ‘software crisis’
We have to learn to ‘engineer’ software

7. 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 be accepted by the users for which it was designed. This means it must be understandable, usable and compatible with other systems

8. Software Failures
There is a  long list of failed software projects and software failures

9. Software’s chronic crisis
Development of large software systems  is a 
challenging task as large software systems often
Do not provide the desired functionality
Take too long to build
Cost too much to build
Require too much resources (time, space) to run
Cannot evolve to meet changing needs
Software engineering  focuses on addressing challenges that arise in development of large software systems using a systematic, disciplined, quantifiable  approach

10. What is Software Engineering?
The process of
solving customers’ problems by the
systematic development and evolution of
large, high-quality software systems within
cost, time and other constraints

11. What is Software Engineering?
Solving customers’ problems
This is the goal of software engineering
Sometimes the solution is to buy, not build
Adding unnecessary features does not help solve the problem
Software engineers must communicate effectively to identify and understand the problem

12. What is Software Engineering?
Systematic development and evolution
An engineering process involves applying well understood techniques in a organized and disciplined way
Many well-accepted practices have been formally standardized
e.g. by the IEEE or ISO
Most development work is evolution

13. What is Software Engineering?
Large, high quality software systems
Software engineering techniques are needed because large systems cannot be completely understood by one person
Teamwork and co-ordination are required
Key challenge: Dividing up the work and ensuring that the parts of the system work properly together
The end-product must be of sufficient quality

14. What is Software Engineering?
Cost, time and other constraints
Finite resources
The benefit must outweigh the cost
Others are competing to do the job cheaper and faster
Inaccurate estimates of cost and time have caused many project failures

15. 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
CS310 Software Engineering

16. 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

17. 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.

18. 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.
Generic process models
Waterfall;
Iterative development;
Component-based software engineering.

19. 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.

20. Software engineering diversity
There are many different types of software system and there is no universal set of software techniques that is applicable to all of these.
The software engineering methods and tools used depend on the type of application being developed, the requirements of the customer and the background of the development team.

21. Professional and ethical responsibility
There are various things that may drive one to consider ethical issues
Laws in areas such as intellectual property
Professional bodies such as the ASCM, IEEE and BCS also have their own codes of professional practice
As individuals we also bring our own sets of values which may determine what kinds of work we will accept

22. Recommended Reading
Chapter 1 of the textbook