Lec1- Introduction.pptx

University of Science & Technology Faculty of Computer Science and Information Technology software Engineering I Dr. Ammar Mohamed Abdo 1 Lec1: Introduction to software Engineering 2  Soft...

University of Science & Technology Faculty of Computer Science and Information Technology software Engineering I Dr. Ammar Mohamed Abdo 1 Lec1: Introduction to software Engineering 2  Software engineering  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. 3 Lec1- Introduction  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. 4 Lec1- Introduction  Software project failure  Increasing system complexity  As new software engineering techniques help us to build larger, more complex systems, the demands change. Systems have to be built and delivered more quickly; larger, even more complex systems are required; systems have to have new capabilities that were previously thought to be impossible. 5 Lec1- Introduction  Software project failure (con…)  Failure to use software engineering methods  It is fairly easy to write computer programs without using software engineering methods and techniques. Many companies have drifted into software development as their products and services have evolved. They do not use software engineering methods in their everyday work. Consequently, their software is often more expensive and less reliable than it should be. 6 Lec1- Introduction  Professional software development 7 Lec1- Introduction  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 software Software specification, software development, software engineering activities? validation and software evolution. What is the difference between software Computer science focuses on theory and fundamentals; engineering and computer science? software engineering is concerned with the practicalities of developing and delivering useful software. What is the difference between software System engineering is concerned with all aspects of engineering and system engineering? computer-based systems development including hardware, software and process engineering. Software engineering is part of this more general process. Lec1- Introduction 8  Frequently asked questions about software engineering Question Answer What are the key challenges facing Coping with increasing diversity, demands for reduced software engineering? delivery times and developing trustworthy software. What are the costs of software Roughly 60% of software costs are development costs, engineering? 40% are testing costs. For custom software, evolution costs often exceed development costs. What are the best software engineering While all software projects have to be professionally techniques and methods? 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 The web has led to the availability of software services software engineering? 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. 9 Lec1- Introduction  Software products  Generic products  Stand-alone systems that are marketed and sold to any customer who wishes to buy them.  Examples – PC software such as graphics programs, project management tools; CAD software; software for specific markets such as appointments systems for dentists. 10 Lec1- Introduction  Software products  Customized products  Software that is commissioned by a specific customer to meet their own needs.  Examples – embedded control systems, air traffic control software, traffic monitoring systems. 11 Lec1- Introduction  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. 12 Lec1- Introduction  Essential attributes of good software Product characteristic Description Maintainability Software should be written in such a way so that it can evolve to meet the changing needs of customers. This is a critical attribute because software change is an inevitable requirement of a changing business environment. Dependability and Software dependability includes a range of characteristics security including reliability, security and safety. Dependable software should not cause physical or economic damage in the event of system failure. Malicious users should not be able to access or damage the system. Efficiency Software should not make wasteful use of system resources such as memory and processor cycles. Efficiency therefore includes responsiveness, processing time, memory utilisation, etc. Acceptability Software must be acceptable to the type of users for which it is designed. This means that it must be understandable, usable and compatible with other systems that they use. 13 Lec1- Introduction  Software engineering  Software engineering is an engineering discipline that is concerned with all aspects of software production from the early stages of system specification through to maintaining the system after it has gone into use.  Engineering discipline  Using appropriate theories and methods to solve problems bearing in mind organizational and financial constraints. 14 Lec1- Introduction  Software engineering (con…)  All aspects of software production  Not just technical process of development. Also project management and the development of tools, methods etc. to support software production. 15 Lec1- Introduction  Importance of software engineering  More and more, individuals and society rely on advanced software systems. We need to be able to produce reliable and trustworthy systems economically and quickly.  It is usually cheaper, in the long run, to use software engineering methods and techniques for software systems rather than just write the programs as if it was a personal programming project. For most types of system, the majority of costs are the costs of changing the software after it has gone into use. 16 Lec1- Introduction