C++ Primer Plus полностью

C++ joins three separate programming categories: the procedural language, represented by C; the object-oriented language, represented by the class enhancements C++ adds to C; and generic programming, supported by C++ templates. This chapter looks into those traditions. But first, let’s consider what this heritage implies about learning C++. One reason to use C++ is to avail yourself of its object-oriented features. To do so, you need a sound background in standard C, for that language provides the basic types, operators, control structures, and syntax rules. So if you already know C, you’re poised to learn C++. But it’s not just a matter of learning a few more keywords and constructs. Going from C to C++ involves perhaps more work than learning C in the first place. Also if you know C, you must unlearn some programming habits as you make the transition to C++. If you don’t know C, you have to master the C components, the OOP components, and the generic components to learn C++, but at least you may not have to unlearn programming habits. If you are beginning to think that learning C++ may involve some mind-stretching effort on your part, you’re right. This book will guide you through the process in a clear, helpful manner, one step at a time, so the mind-stretching will be sufficiently gentle to leave your brain resilient.

C++ Primer Plus approaches C++ by teaching both its C basis and its new components, so it assumes that you have no prior knowledge of C. You’ll start by learning the features C++ shares with C. Even if you know C, you may find this part of the book a good review. Also it points out concepts that will become important later, and it indicates where C++ differs from C. After you have a good grounding in the basics of C, you’ll learn about the C++ superstructure. At that point, you’ll learn about objects and classes and how C++ implements them. And you will learn about templates.

This book is not intended to be a complete C++ reference; it doesn’t explore every nook and cranny of the language. But you will learn most of the major features of the language, including templates, exceptions, and namespaces.

Now let’s take a brief look at some of C++’s background.

The Origins of C++: A Little History

Computer technology has evolved at an amazing rate over the past few decades. Today a notebook computer can compute faster and store more information than the mainframe computers of the 1960s. (Quite a few programmers can recall bearing offerings of decks of punched cards to be submitted to a mighty, room-filling computer system with a majestic 100KB of memory—far less memory than even a smartphone uses today.) Computer languages have evolved, too. The changes may not be as dramatic, but they are important. Bigger, more powerful computers spawn bigger, more complex programs, which, in turn, raise new problems in program management and maintenance.

In the 1970s, languages such as C and Pascal helped usher in an era of structured programming, a philosophy that brought some order and discipline to a field badly in need of these qualities. Besides providing the tools for structured programming, C also produced compact, fast-running programs, along with the ability to address hardware matters, such as managing communication ports and disk drives. These gifts helped make C the dominant programming language in the 1980s. Meanwhile, the 1980s witnessed the growth of a new programming paradigm: object-oriented programming, or OOP, as embodied in languages such as SmallTalk and C++. Let’s examine these C and OOP a bit more closely.

The C Language

In the early 1970s, Dennis Ritchie of Bell Laboratories was working on a project to develop the Unix operating system. (An operating system is a set of programs that manages a computer’s resources and handles its interactions with users. For example, it’s the operating system that puts the system prompt onscreen for a terminal-style interface that manages the windows and mice for graphical interfaces and that runs programs for you.) For this work Ritchie needed a language that was concise, that produced compact, fast programs, and that could control hardware efficiently.

Traditionally, programmers met these needs by using assembly language, which is closely tied to a computer’s internal machine language. However, assembly language is a low-level language—that is, it works directly with the hardware (for instance, accessing CPU registers and memory locations directly). Thus, assembly language is specific to a particular computer processor. So if you want to move an assembly program to a different kind of computer, you may have to completely rewrite the program, using a different assembly language. It was a bit as if each time you bought a new car, you found that the designers decided to change where the controls went and what they did, forcing you to relearn how to drive.