The Essentials of Modern Software Engineering. Ivar Jacobson

to the relationship between programming und software engineeering. The important issue is that software engineering is much more than just programming. Of course, the running system created by an act of programming is an essential and rewarding ingredient of what the right system will become, and it is important that the reader is actually able to use and apply a programming language to create a program, at least a small one. But is it by no means everything. Thus, this chapter

      • introduces the notion of software development and that it is more than just putting a program together;

      • shows what additionally is needed beyond programming, i.e., shows the differences between programming, software development, and software engineering;

      • shows the motivations for the discipline of software engineering;

      • introduces some important elements of software engineering that actually show the differences between software engineering and programming, and shows how they relate to each other.

      What is fascinating about this aspect of software development is that it is more than just programming. Rather, it is to learn the whole picture and as a software engineer to solve a problem or exploit an opportunity that the users may have.

      As a new student, understanding what software engineering is about is not easy, because there is no way we can bring its realities and complexities into the student’s world. Nevertheless, it is a student’s responsibility to embark on this journey of learning and discovery into the world of software engineering.

      Throughout this entire book, we will trace the journey of a young chap, named Smith, from his days in school learning about programming through to becoming a software engineering professional and continuing his on-going learning process in this ever-changing and growing field. In a way, we are compressing time into the pages of this book. If you are a new student, you are considered to be the primary audience for this book. Smith will be your guide to the software engineering profession, to help you understand what software engineering is about. If you are already a software engineer by profession, or you teach and coach software engineering, you can reflect on your own personal journey in this exciting profession. As an experienced developer you will observe an exicting and fundamentally new way to understand and practice software engineering. Regardless of your current personal level of experience, through Smith’s experiences we will distill the essence of software engineering.

Sidebar 1.1 Programming

      Programming is used here as a synonym for implementation and coding. From Wikipedia we quote: “Related tasks include testing, debugging, and maintaining the source code,…. These might be considered part of the programming process, but often the term software development is used for this larger process with the term programming, implementation, or coding reserved for the actual writing of source code.”

1.1 Beginning with Programming

      The focus of our book is not about programming (see Sidebar 1.1), but about software engineering. However, understanding programming is an obvious place to start. Before we delve deeper into it, we should clarify the relation of programming to software development and to software engineering. Thus we have chosen the following.

      • Programming stands for the work related to implementation or coding of source code.

      • Software development is the larger process which, apart from programming, includes working with requirements, design, test, etc.

      • “Software engineering combines engineering techniques with software development practices” (from Wikipedia). Moving from development to engineering means more reliance on science and less on craft, which typically manifests itself in some form of description of a designated way of working and higher-level automation of work. This allows for repeatability and consistency from project to project. Engineering also means that teams, for example, learn as they work and continuously improve their way of working. Thus, stated in simple terms, software engineering is bringing engineering discipline to software development.

      Going forward, when introducing software engineering we will mean the larger subject of “software development + engineering,” implicitly understood without specifically separating out the two parts. This will be so even if in many cases the discussion is more about the development aspect, because the approach we take is chosen to facilitate the other aspect—engineering. When we sometimes talk about software development we want to be specific and refer to the work: the activities or the practices we use. We will not further try to distinguish these terms, so the reader can in many cases see them as synonyms.

      As a frequent user of applications like Facebook, Google, Snapchat, etc., whether on his laptop or his mobile, Smith knew that software forms a major component in these products. From this, Smith became strongly interested in programming and enrolled in a programming course where he started to understand what program code was and what coding was all about. More importantly, he knew that programming was not easy. There were many things he had to learn.

      The very first thing Smith learned was how to write a program that displays a simple “Hello World” on his screen, but in this case, we have a “Hello Essence!”, as in Figure 1.1. Through that he learned about programming languages, programming libraries, compilers, operating systems, processes and threads, classes, and objects. These are things in the realm of computer technology. We expect that you, through additional classes, will have learned about these things. We also expect you as a student to have some knowledge of these things as a prerequisite to reading this book. We expect that you have some knowledge of programming languages like Java and JavaScript.

Figure 1.1 Hello Essence.

       1.2 Programming Is Not Software Engineering

      However, Smith quickly learned that programming on its own is not software engineering. It is one thing to develop a small program, such as the “Hello Essence” program; it is a different thing to develop a commercial product.

      It is true that some fantastic products such as those that gave birth to Apple, Microsoft, Facebook, Twitter, Google, and Spotify once were developed by one or a few individuals with a great vision but by just using programming as a skill. However, as the great vision has been implemented, be sure that these companies are today not relying on heroic programmers. Today, these companies have hired the top people with long experience in software engineering including great programming skills.

      So, what is software engineering? Before we answer this question, we must first make it very clear that there is a remarkable difference between hacking versus professional programming. Professional programming involves clear logical thinking, beginning with the objective of the program, and refining the objective into logically constructed expressions. Indeed, the expressions are a reflection of the programmers’ thinking and analysis. Hacking on the other hand is an ad hoc trial and error to induce the desired effect. When the effect is achieved, the hacker marvels without really understanding why it worked. Professional programmers understand why and how it worked.

      As such, professional programming is highly disciplined. Software engineering takes this discipline to software teams working on complex software. A typical software development endeavor involves more than one person working on a complex problem over a period of time to meet some objectives. Throughout Smith’s introductory software engineering course, he worked on several assignments, which frequently required him to work with his fellow students, and which included tasks, such as:

      1. brainstorming what an event calendar app would look like;

      2. writing code for a simple event calendar in a small group;

      3. writing code for the event calendar app, and hosting the app on the cloud;

      4. reviewing a given piece of code to