Chapter One_Introduction to SE_Phoenix PDF

# Chapter 1 - Introduction ## Topics covered - Professional software development - What is meant by software engineering. ## The Need for Software Engineering - We can't run the modern world without software: - National infrastructures and utilities are controlled by computer-based systems...

# Chapter 1 - Introduction ## Topics covered - Professional software development - What is meant by software engineering. ## The Need for Software Engineering - We can't run the modern world without software: - National infrastructures and utilities are controlled by computer-based systems - Most electrical products include a computer and controlling software. - Industrial manufacturing and distribution is completely computerized, as is the financial system. - Entertainment, including the music industry, computer games, and film and television, is software intensive. - Therefore, software engineering is essential for the functioning of national and international societies. ## Software engineering - The economies of ALL developed nations are dependent on software. - More and more systems are software controlled. ## History of software engineering The notion of 'software engineering' was first proposed in 1968 at a conference held to discuss what was then called the ‘software crisis' (Naur and Randell, 1969). It became clear that individual approaches to program development did not scale up to large and complex software systems. These were unreliable, cost more than expected, and were delivered late. Throughout the 1970s and 1980s, a variety of new software engineering techniques and methods were developed, such as structured programming, information hiding and object-oriented development. Tools and standard notations were developed and are now extensively used. **[Link](http://www.SoftwareEngineering-9.com/Web/History/)** ## Software engineering - Software engineering is intended to support professional software development, rather than individual programming. It includes techniques that support program specification, design, and evolution, none of which are normally relevant for personal software development. ## A professionally developed software system is often: - More than a single program. The system usually consists of a number of separate programs and configuration files that are used to set up these programs. - It may include system documentation, which describes the structure of the system; user documentation, which explains how to use the system, and websites for users to download recent product information. ## Software engineering - Software engineering is concerned with theories, methods and tools for professional software development. ## 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. - Advanced courses in SwE will be taught to students that cover professional development viewpoint of SWs. ## Software products - Software engineers are concerned with developing software products (i.e., software which can be sold to a customer). There are two kinds of 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; (Computer Aided Design) CAD software; software for specific markets (Specific purpose) such as appointments systems for dentists. ### Customized products (Bespoke products) - Software that is commissioned by a specific customer to meet their own needs. - Examples – embedded control systems (for electronic devices), air traffic control software, traffic monitoring systems. ## Product specification **One important difference:** ### Generic products - The specification of what the software should do is owned by the software developer (or the organization that developed it) 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. ## 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 is software engineering? | Software engineering is an engineering discipline that is concerned with all aspects of software production. | | What are the fundamental software engineering activities? | Software specification, software development, software validation and software evolution. | | 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. | | 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. | ## 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 security | Software dependability includes a range of characteristics 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. | ## 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, methods and tools to solve problems bearing in mind organizational and financial constraints. ### All aspects of software production - Software Engineering is *Not just technical process of software development*. Also *software project management and the development of tools, methods etc. to support software production*. ## Importance of Software Engineering 1. 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. (*With related Qualities*). 2. 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. ## General issues that affect most types of software 1. **Heterogeneity** - Increasingly, systems are required to operate as distributed systems across networks that include different types of computer and mobile devices. The challenge here is to develop techniques for building dependable software that is flexible enough to cope with heterogeneity. 2. **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. 3. **Security and trust** - As software is intertwined with all aspects of our lives, it is essential that we can trust that software. We have to make sure that malicious users cannot attack our software and information security is maintained. ## 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. - A diverse set of software engineering methods and tools have evolved over the past 50 years. - 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. (*Also, Practical costs, Schedule, etc.*) - Most significant factor affecting the choice is the type of the application. ## Application types ### Stand-alone applications - These are application systems that run on a local computer, such as a PC. They include all necessary functionality and do not need to be connected to a network. E.g. Office Applications on PC, Photo manipulation software, etc. ### Interactive transaction-based applications - Applications that execute on a remote computer and are accessed by users from their own PCs or terminals. These include web applications such as e-commerce applications. - This class of application also includes business systems, where a business provides access to its systems through a web browser or special-purpose client program and cloud-based services, such as mail and photo sharing. Interactive applications often incorporate a large data store that is accessed and updated in each transaction. ### Embedded control systems - These are software control systems that control and manage hardware devices. Numerically, there are probably more embedded systems than any other type of system. - E.g. Software in a mobile (cell) phone, software that control the anti-lock braking in a car, and software in a microwave to control the cooking process. ### Batch processing systems - These are business systems that are designed to process data in large batches. They process large numbers of individual inputs to create corresponding outputs. - E.g. Periodic billing systems, such as phone billing systems and salary payment systems ### Entertainment systems - These are systems that are primarily for personal use and which are intended to entertain the user. - Most of these systems are games of one kind or another. The quality of the user interaction offered is the most important distinguishing characteristic of entertainment systems. ### Systems for modelling and simulation - These are systems that are developed by scientists and engineers to model physical processes or situations, which include many, separate, interacting objects. - Some examples of computer simulation modeling familiar to most of us include: weather forecasting, flight simulators used for training pilots, and car crash modeling. ### Data collection systems - These are systems that collect data from their environment using a set of sensors and send that data to other systems for processing. ### Systems of systems - These are systems that are composed of a number of other software systems. ## Some Software engineering fundamental principles apply to all types of software system, irrespective of the development techniques used: 1. Systems should be developed using a managed and understood development process. The organization developing the software should plan the development process and have clear ideas of what will be produced and when it will be completed. Of course, different processes are used for different types of software. 2. Dependability and performance are important for all types of systems. Software should behave as expected, without failures and should be available for use when it is required. It should be safe in its operation and, as far as possible, should be secure against external attack. The system should perform efficiently and should not waste resources. 3. Understanding and managing the software specification and requirements (what the software should do) are important. You have to know what different customers and users of the system expect from it and you have to manage their expectations so that a useful system can be delivered within budget and to schedule. 4. You should make as effective use as possible of existing resources. This means that, where appropriate, you should reuse software that has already been developed rather than write new software