A Resource-Not a Straightjacket Early Classes Flexibility in Topic Ordering Summary Boxes Support Material Acknowledgments
This book is meant to be used in a first course in programming and computer science using the C++ language. It assumes no previous programming experience and no mathematics beyond high school algebra. It could also be used as a text for a course designed to teach C++ to students who have already had some other programming course, in which case the first few chapters can be assigned as outside reading.
A Resource-Not a Straightjacket
Most introductory textbooks that use C++ have a very detailed agenda that an instructor must follow in order to use the book in a class. If you are an instructor, this book adapts to the way you teach, rather than making you adapt to the book. This book explains C++ and basic programming techniques in a way suitable for beginning students, but it does not tightly prescribe the order in which your course must cover topics and does not prescribe the specialized libraries, if any, that must be used in your course. You can easily change the order in which chapters and sections are covered without loss of continuity in reading the book. The details about rearranging material are explained in the section of this preface on flexibility. Although this book uses libraries and teaches students the importance of libraries, it requires no special libraries. It was designed to be used with a "standard" C++ implementation and only uses libraries that are provided with essentially all C++ implementations. Instructors who wish to do so may use additional libraries of their own choosing.
Early Classes
There are at least two ways that a book can introduce classes early. A book can teach students how to design their own classes early in the book or it can merely teach them how to use classes early without defining them. This book teaches students to design and define their own classes early and does not merely teach them how to use classes early. In order to effectively design classes, a student needs some basic tools such as some simple control structures and function definitions. This book thus starts out covering these basics in chapters 2, 3, and 4. It then moves immediately to classes. In Chapter 5 file I/O streams are used to teach students how to use classes. In Chapter 6 students learn how to write their own classes.
This book uses a measured approach to classes. It teaches students to write some very simple classes, then adds constructors, then overloading simple operators, then overloading the I/O operators >, and so forth. This measured approach keeps the student from being overwhelmed with a long list of complicated constructions and concepts. However, one goal of this book is to get students writing realistic class definitions as soon as possible, and not to have them spending time writing classes that are artificially simple. By the end of Chapter 8, they are writing essentially the same kinds of classes that they will be writing when they finish the course.
There are a few topics related to classes that are not introduced at the beginning. Destructors, templates, and sophisticated use of inheritance are not introduced early.
Destructors are not introduced until dynamic data structures are covered. Introducing them before dynamic data structures would be pointless, since they would have no purpose.
Templates are not introduced early for three reasons: First, many compilers still do not handle them gracefully. With many compilers, class templates require special care if they are to be compiled separately. Often separate compilation of class templates has restrictions that make separate compilation impractical. Second, a template is a schema that generates numerous nontemplate classes. Thus, before one can understand what a template class is, one needs to know what a nontemplate class is. Once a student is comfortable with nontemplate classes, template classes are an easy and natural generalization. Third, many of the examples that benefit most from templates are data structures, like stacks and queues, which are usually not covered until the second programming course. However, if an instructor wishes to cover templates earlier, the material on templates was written so that it can be moved to earlier in the course.
Inheritance is covered briefly in Chapter 5 so that students become aware of the concept. However, this book does not teach students how to write their own derived classes. The reason for this is that the examples that strongly motivate inheritance and derived classes often do not arise until the second course. One can make a point of introducing examples that use derived classes in the first course, but it is difficult for students to get much realistic utility out of derived classes until they are more sophisticated programmers. These more advanced topics can easily be introduced later, and even without these topics students have a sophisticated and realistic concept of classes. Brief coverage of how to write derived classes is given in an appendix.
Even though we postpone the discussion of destructors and templates, the classes that are used early in the book are very sophisticated and many would argue that they are too complicated to be covered so early in a first programming course. After all, in addition to the basic notions of member variables and member functions, beginning students reading this book will learn all of the following topics very early: public and private members, function overloading, operator overloading, friend functions, returning a reference so that they can overload the I/O operators >, constructors for automatic initialization, constructors for type conversion, and a number of smaller issues. Many would argue that this is too much to give students so early. We have class tested this material and found that the examples become unrealistic or poorly behaved if we omit any of these topics. Moreover, in class testing we found that students respond to early classes in basically the same way that they respond to early functions. Certainly the material presents some problems. However, they are as capable of learning it early in the course as they will be later in the course. Moreover, covering classes early leaves students with a better working knowledge of classes. Students have a strong loyalty to the first technique they learn for solving a problem. So, if you want them to really use a technique, then you need to teach it early. Moreover, classes are not the hardest topic the students encounter. For example, classes are more intuitive and better behaved than ordinary (C style) arrays, which they learn later in the course.
Having made the case for early classes, we are still aware that not everybody wants to introduce classes as early as we do and so we have written the book to allow instructors to move coverage of classes to later in the course. This is discussed in the section of this preface on flexibility.
Flexibility in Topic Ordering
This book was written to allow instructors wide latitude in reordering the material. Our goal was to write the book so that an instructor making the transition to teaching the introductory course in C++ could, if she or he desired, start with a course that is essentially an ANSI C course, change the course slightly each term it is taught, and quickly be teaching a course that is a full-blown C++ course with students defining their own classes early in the course. We would urge instructors to move along this path quickly, but that decision is up to each instructor. To illustrate this flexibility we give a number of alternative orderings of topics after this paragraph. There is no loss of continuity when the book is read in any of these orders. In order to ensure this continuity when you rearrange material you do need to sometimes move sections rather than entire chapters. However, only large sections in convenient locations are moved. Under any of these orderings, whenever a chapter is first introduced the chapter is covered without interruption up to some point. One cut point is inserted into the chapter and all the material before the cut is moved as a unit and all the material after the cut is moved as another unit. To help customize an ordering to any particular class's needs, the dependency charts, which follow this preface, describe many more possible orders in which the chapters and sections can be covered without loss of continuity.
Reordering 1: Late Classes
This version essentially covers all of an ANSI C course before going on to cover classes. The only thing that is very C++ like before the introduction of classes is the use of streams for I/O:
Basics: Chapters 1, 2, 3, 4, 5, and 7 (omitting Chapter 6 on defining classes). This material covers all of control structures, function definitions, and basic file I/O.
Arrays: Chapters 9 omitting the last section (section 9.4), which uses classes. Chapter 10 omitting the last section (sectio
