Lecture 01 A Brief Overview of Software Engineering

Lecture 01: A Brief Overview of Software Engineering Mamuna Fatima

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.

Topics covered • FAQs about software engineering • Professional and ethical responsibility

FAQs about software engineering • • • What is software? What is software engineering? How Software domain is different from other engineering domains? Apply Engineering approach to software development What is a software process? What is a software process model? What are the costs of software engineering? What are the attributes of good software? What are the key challenges facing software engineering? What are the professional and ethical responsibilities of software engineering practitioners?

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.

Product specification Generic Products • The specification of what the software should do is owned by the software developer and decisions on software change are made by the developer. Customized Products • The specification of what the software should do is owned by the customer for the software and they make decisions on software changes that are required. Chapter 1 Introduction 6

What is Software engineering? • Def 1: Software engineering is an engineering discipline that is concerned with all aspects of software production. • Def 2: Software engineering is the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software, and the study of these approaches; that is, the application of engineering to software. • 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.

How software domain is different from other engineering domains? • Nature of software projects • Engineering approaches

Frequently asked questions about software engineering Question Answer 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. What are the attributes of good software? Good software should deliver the required functionality and performance to the user and should be maintainable, dependable and usable. What is software engineering? Software engineering is an engineering discipline that is concerned with all aspects of software production. What are the fundamental engineering activities? software Software specification, software development, software validation and software evolution. What is the difference between software engineering and computer science? Computer science focuses on theory and fundamentals; software engineering is concerned with the practicalities of developing and delivering useful software. 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 more general process. Chapter 1 Introduction 9

Frequently asked questions about software engineering Question Answer What are the key challenges facing software engineering? Coping with increasing diversity, demands for reduced delivery times and developing trustworthy software. What are the costs of software engineering? Roughly 60% of software costs are development costs, 40% are testing costs. For custom software, evolution costs often exceed development costs. What are the best software engineering techniques and methods? While all software projects have to be professionally managed and developed, different techniques are appropriate for different types of system. For example, games should always be developed using a series of prototypes whereas safety critical control systems require a complete and analyzable specification to be developed. You can’t, therefore, say that one method is better than another. What differences has the web made to software engineering? The web has led to the availability of software services and the possibility of developing highly distributed service-based systems. Web-based systems development has led to important advances in programming languages and software reuse. Chapter 1 Introduction 10

Software Systems Used in variety of applications • Business, Engineering, Scientific • Simple to complex, internal to public. Single function to enterprise wide, one location to distributed. Batch wise or real time, informational to mission critical

Challenge in large projects Developing large /complex software app is very challenging • Effort intensive • High cost • Long development time • Changing needs for user • High risk of failure, user acceptance, performance, maintainability • Quite different from one time program where user and author is same

Successful Software System § Software development projects have not always been successful § When we do consider a software application successful? ‗ Development completed ‗ It is useful and ‗ It is usable, and ‗ It is used Cost effectiveness, maintainability applied.

Failure Reasons • • • Schedule slippage Cost over-runs Does not solve user ‘s problems Poor quality of software Poor Maintainability

Failure Reasons • Ad hoc software development lead to such problems —No planning of developing work(e. g. no milestones are defined) —Deliverables to user are not identified —Poor Understanding of user requirements —No control or review —Technical incompetence of developers

Engineering: Other Disciplines • Building, bridges, dams, • Power plants • Aircrafts Engineering : a solution —To design , develop (build) an artifact that meets specification efficiently and Cost effectively and ensuring quality —Using scientific principles

Engineering approach • Requires well defined approach, repeatable and predictable • Large projects requires managing the project itself Manage People, money (cost), equipment, schedule • Scale makes big difference , compared a small hut , two storeyed house • Quality extremely important, relates to failures, efficiency and usability

Large projects • Involve different type of people • Large Building: Architect , civil engineers, electrical engineers, workers( masons, carpenters) • Continuous supervision of quality assurance • On site supervisors check ( cement /steel quality , ensuring proper mix of sand cement…)

Large Projects • Many deliverables, architecture plans, models, structural diagrams, electrical cabling etc. • Standards , regulations and conventions need to be followed • Steps, milestones defined and reviews are carried out, progress is visible

Software Projects Software is different from other projects • Cost of production is concentrated in development • Maintenance consists of making corrections, enhancing or adding functions • Progress in development is difficult to measure

Apply Engineering Approach • • • Hence Planning and control is even more important in software development-> Engineering approach: Attempt to estimate cost/effort Plan and schedule work Involve user in defining requirements Identify stages in development Define clear milestones so that progress can be measured Schedule review both for Control and quality Define Deliverables Plan extensive Testing

Job of software developer is difficult • Dealing with users • Dealing with technical people • Dealing with Management

• For success in large software development, it is important to follow engineering approach. Consisting of a well defined process.

Software Process • Process consists of activities/steps to be carried out in a particular order • Deals with both technical and management issues • Consists of different type of processes 1. Process for software development • Produces software as end result • Multiple such processes may exits • A project follow a particular process

Process types 2. Process for managing the project • Defining project planning and control • Effort estimations made and schedule prepared • Resources are provided • Feedback is taken fro quality assurance • Monitoring done

Process Types 3. Process for change & Configuration Mgt • Resolving request for changes • Defining versions, their compositions 4. Process for managing the above processes themselves • Improving the processes based on new techniques • Standardization and certifications (CMMI, ISO)

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 software development.

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 whom it was designed. This means it must be understandable, usable and compatible with other systems.

What are the key challenges facing software engineering? • Heterogeneity, delivery and trust. • 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.

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.

Issues of professional responsibility • Confidentiality • Engineers should 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 out of proportion with their competence.

Issues of professional responsibility • Intellectual property rights • Engineers should be aware of 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).

Key points • Software engineering is an engineering discipline that is concerned with all aspects of software production. • Software products consist of developed programs and associated documentation. Essential product attributes are maintainability, dependability, efficiency and usability. • The software process consists of activities that are involved in developing software products. Basic activities are software specification, development, validation and evolution. • Software engineers have responsibilities to the engineering profession and society. They should not simply be concerned with technical issues.