Chapter 1: Introduction

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. In this definition, there are two key phrases

Engineers make things work. They apply theories, methods, and tools where these are appropriate, but use them selectively. They always try to discover solutions to problems even when there are no applicable theories and methods. Engineers also recognize that they must work within organizational and financial constraints, so they look for solutions within these constraints.

Software engineering is not just concerned with the technical processes of software development. It also includes activities such as software project management and the development of tools, methods, and theories to support software production.

Different types of systems require different development processes depending on their purpose and complexity. For instance, real-time systems like aircraft software need full specification before development, while e-commerce systems evolve as they're built. Software engineering is closely related to both computer science and systems engineering — computer science provides the theoretical foundations, while software engineering focuses on practical application in building reliable systems. Systems engineering, on the other hand, deals with the broader integration of hardware, software, and processes to create complete, complex systems.

As I discuss in the next section, there are many different types of software. There is no universal software engineering method or technique that is applicable for all of these. However, there are three general issues that affect many different types of software:

1. Heterogeneity: Modern systems must work across diverse devices and platforms, including legacy systems. The challenge is to build flexible and dependable software that can handle this diversity.
2. Business and Social Change: Rapid technological and societal shifts demand faster software development. Traditional methods must adapt to deliver value more quickly and efficiently.
3. Security and Trust: As software becomes part of daily life, ensuring protection against attacks and maintaining user trust and data security is crucial.

Software engineering is a systematic approach to software production that balances cost, schedule, dependability, and customer needs. The methods used vary depending on the organization, software type, and development team. There are no universal techniques suitable for all cases — instead, various methods and tools have evolved over the years.

The type of application being developed largely determines which techniques are most important. Below are the main categories of software applications:

1. Stand-alone Applications: Run on a local computer without network connections, such as office suites, CAD programs, and photo editors.
2. Interactive Transaction-Based Applications: Operate remotely and are accessed via PCs or browsers. Examples include e-commerce sites, business systems, and cloud-based services.
3. Embedded Control Systems: Control and manage hardware devices, such as car braking systems, phone software, or microwave controls.
4. Batch Processing Systems: Process large sets of data periodically, such as billing or payroll systems.
5. Entertainment Systems: Designed mainly for personal enjoyment—mostly games where user interaction quality is key.
6. Modeling and Simulation Systems: Used by scientists and engineers to simulate complex physical processes, often requiring high-performance computing.
7. Data Collection Systems: Gather data from sensors in real-world environments and transmit it for processing, often operating in harsh conditions.
8. Systems of Systems: Combine multiple software systems—some generic, some custom-built—to work together in one environment.

Software engineering techniques differ depending on the system type. For instance, embedded systems prioritize safety and stability, while web-based systems emphasize speed and iterative updates.

Despite these differences, all software systems share common fundamentals:

• They must follow a managed and well-understood development process.
• Dependability, performance, and security are essential for every system.
• Clear understanding and management of requirements are crucial.
• Existing resources and reusable components should be used effectively.

These principles—process management, dependability, requirements, and reuse—apply to all forms of professional software development, regardless of implementation differences.

The rise of the World Wide Web transformed how software is developed and used. Initially, the Web was mainly for information sharing, but as browsers became more powerful, web-based systems emerged—allowing software to run on servers instead of local computers. This made upgrades easier and cheaper.

The evolution continued with web services and cloud computing, where software is accessed online rather than installed locally. Businesses shifted from monolithic systems to distributed, component-based architectures.

Key changes in web-based software engineering include:

1. Software Reuse: Web-based systems are now built by assembling pre-existing software components and services, promoting efficiency and consistency in development.
2. Incremental Development: Since it's often impossible to define all requirements in advance, web systems are developed and delivered in iterative phases to adapt to changing needs.
3. Browser-Constrained Interfaces: User interfaces are limited by browser capabilities, so most web apps rely on web forms and scripts rather than fully customized designs.

Despite these shifts, the core principles of software engineering—such as process management, dependability, and requirements control—remain essential.

Like other engineering disciplines, software engineering operates within a social and legal framework that limits professional freedom. As a software engineer, you must recognize that your work involves responsibilities beyond technical expertise. Ethical and moral behavior is essential to maintaining respect as a professional. You must uphold honesty, integrity, and avoid actions that could harm others or the reputation of the profession.

1. Confidentiality: Always respect the confidentiality of your employers or clients, even if no formal agreement has been signed.
2. Competence: Do not misrepresent your skills or accept tasks beyond your level of expertise.
3. Intellectual Property Rights: Be aware of laws related to patents, copyrights, and other intellectual property. Protect the rights of your employers and clients.
4. Computer Misuse: Never use your technical knowledge to harm or exploit others' systems. This includes both minor misuse and serious offenses such as spreading malware.

Figure 1.3 The ACM/IEEE Code of Ethics (© IEEE/ACM 1999)

Professional organizations like the ACM and IEEE establish codes of ethics to guide software engineers in responsible and professional behavior. The ACM/IEEE Code of Ethics outlines eight key principles emphasizing public interest, client and employer responsibility, product quality, independent judgment, ethical management, professional integrity, fairness to colleagues, and lifelong learning.

Software engineers must recognize their power to do good or harm through their work and act ethically to protect public welfare. Ethical dilemmas often arise, such as conflicts with management, handling unsafe practices, or working on military systems. These situations require careful judgment, balancing professional responsibility, honesty, and respect for employers.

Overall, ethics in software engineering are best understood through practical codes of conduct rather than abstract philosophy, as real-world examples make ethical issues more relatable and actionable.