©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 1 An Introduction to Software Engineering

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 2 What is software? l Computer instructions or data. Anything that can be stored electronically is software. The storage devices and display devices are hardware. Computerinstructionsdatastoredstoragedeviceshardware l Computer programs and associated documentation such as requirements, design models and user manuals. l Software products may be developed for a particular customer or may be developed for a general market. l 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. l New software can be created by developing new programs, configuring generic software systems or reusing existing software.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 3 Classes of Software Software is classified into two classes: l Generic Software : is designed for broad customer market whose requirements are very common, fairly stable and well understood by the software engineer. l Customized Software: is developed for a customer where domain, environment and requirements are being unique to that customer and cannot be satisfied by generic products.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 4 Types of software System Software- Software used to control the computer and develop and run applications. 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. 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(posheeda) 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 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.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 5 l Examples of real time software l Real-time software programs can be found in various applications. Some of them are known as anti-virus programs, which perform scheduled maintenance checks, as well as database applications like airline database controls, and 24-hour transaction facilities. Real-time software programs are also found in security systems and imaging as parts of a database application, as well as consumer appliances and in graphic editing tools used by multimedia artists. l Read more: Real-Time Software Definition | eHow.com _real_time-software- definition.html#ixzz1q44J5uDbReal-Time Software Definition | eHow.comhttp:// _real_time-software- definition.html#ixzz1q44J5uDb

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 6 What is software engineering? l Software engineering is the technologies and practices that are used to create computer software.Software Engineering is the application of science and mathematics by which the capabilities of computer are made useful to man via computer programs, procedures and associated documentation. l Software engineering is an engineering discipline that is concerned with all aspects of software production. l 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.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 7 Why Software Engineering? Objectives: - Identify new problems and solutions in software purodction. - Study new systematic methods, principles, approaches for system analysis, design, implementation, testing and maintenance. - Provide new ways to control, manage, and monitor software process. - Build new software tools and environment to support software engineering.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 8 Goals of Software Engineering? l 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.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 9 What is the difference between software engineering and computer science? Computer ScienceSoftware Engineering is concerned with Computer science theories are currently insufficient to act as a complete underpinning for software engineering, BUT it is a foundation for practical aspects(roop) of software engineering  theory  fundamentals  the practicalities of developing  delivering useful software

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 10 What is the difference between software engineering and system engineering? l 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. l System engineers are involved in system specification, architectural design, integration and deployment.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 11 Components of Software Engineering SE approach has two components, namely systems engineering approach and development engineering approach. The software and its quality depends upon the system in which it is installed. The system here has a broad meanings. The understanding of the system can be achieved by the System study and Analysis. the System study and Analysis is carried out through SEM( Systems Engineering and Methodology). The SEM steps are as under: l Define the Objective of the system l Define the boundaries of the system

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 12 Components of Software Engineering l Define relationship in terms of inputs, outputs and processes l Understand the relationship between various components l Understand the role of hardware and software l Discuss the system with the customer l Factories the system into different components l Model the system for analysis and development l Identify the key operational and functional requirements

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 13 Components of Software Engineering Development Engineering methodology has responsibility of translating the system requirements as software system goal, and proceeds to achieve it through a series of steps. The development engineering steps are l Requirement definition and specification l Design solution to deliver the requirements l Determine the architecture for the delivery of solution l Customer development and planning l Software testing components l Integration of system components l Implementation

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 14 Components of Software Engineering Software development engineering is carried out in two ways l Structured System Analysis and Design ( SSAD) l Object Oriented System Analysis and Design ( OOSAD) Structured System Analysis and Design ( SSAD) The SSAD approach in which the system and its requirements are decomposed in structured manner. Software development is carried out using sub-system structure, tested and integrated and implemented.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 15 Components of Software Engineering l Object Oriented System Analysis and Design ( OOSAD) In contrast, the OOSAD development approach recommended the analysis of domain and builds objects of model independent of the system under consideration. The object could represents a function, process or document evolved for the organization. Each object has attributes that describes the methods to perform and relationship to other objects.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 16 Comparison between SSAD And OOSAD l In SSAD the focus is on the functions and the data structure designed for those functions. Functions, data and processing methods are closely coupled. In OOSAD, however, objects and processing methods are decoupled from the data. l In SSAD, skill lies in decomposing the system whereas in OOSAD skill lies in modeling the organization and its business in the objects. l SSAD and OOSAD are dissimilar in focus but similar in that both propose a problem solving methodology and a set of techniques and tools to assist the S/W engineer analyze, model,design and develop the system.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 17 What is a software process? l A set of activities whose goal is the development or evolution of software. l 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.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 18 What is a software process model? l A simplified representation of a software process, presented from a specific perspective. l Examples of process perspectives are Workflow perspective - sequence of activities; Data-flow perspective - information flow; Role/action perspective - who does what. l Generic process models Waterfall; Iterative development; Component-based software engineering.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 19 What is CASE (Computer-Aided Software Engineering) l Software systems that are intended to provide automated support for software process activities. l CASE systems are often used for method support. l Upper-CASE Tools to support the early process activities of requirements and design; l Lower-CASE Tools to support later activities such as programming, debugging and testing.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 20 What are the attributes of good software? l The software should deliver the required functionality and performance to the user and should be maintainable, dependable and acceptable. l Maintainability Software must evolve to meet changing needs; l Dependability Software must be trustworthy; l Efficiency Software should not make wasteful use of system resources; l Acceptability Software must accepted by the users for which it was designed. This means it must be understandable, usable and compatible with other systems.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 1 Slide 21 What are the key challenges facing software engineering? l Heterogeneity, delivery and trust. l Heterogeneity Developing techniques for building software that can cope with heterogeneous platforms and execution environments; l Delivery Developing techniques that lead to faster delivery of software; l Trust Developing techniques that demonstrate that software can be trusted by its users.