Overview

The Story of C++

C++ is a strong statement, but it is not an exaggeration. C++ is the center of gravity around which all of modern programming revolves. Its syntax and design philosophy define the essence of object-oriented programming. Moreover, C++ charts the course for future language development. For example, both Java and C# are directly descended from C++. C++ is also the universal language of programming; it is the language in which programmers share ideas with one another.

To be a professional programmer today implies competency in C++. It is that fundamental and that important. C++ is the gateway to all of modern programming. Before beginning your study of C++, it is important for you to know how C++ fits into the historical context of computer languages.

Understanding the forces that drove its creation, the design philosophy it represents, and the legacy that it inherits makes it easier to appreciate the many innovative and unique features of C++. With this in mind, this chapter presents a brief history of the C++ programming language, its origins, and its relationship to its predecessor (C), its uses, and the programming philosophies that it supports. It also puts C++ into perspective relative to other programming languages.

The Origins of C++

The story of C++ begins with C. The reason for this is simple: C++ is built upon the foundation of C. In fact, C++ is a superset of C. (Indeed, all C++ compilers can also be used to compile C programs!) Specifically, C++ is an expanded and enhanced version of C that embodies the philosophy of object-oriented programming (which is described\ later in this chapter). C++ also includes several other improvements to the C language, including an extended set of library routines. However, much of the spirit and flavor of C++ is inherited directly from C. To fully understand and appreciate C++, you need to understand the “how and why” behind C.

The Creation of C

The C language shook the computer world. Its impact should not be underestimated

Because it fundamentally changed the way programming was approached and thought

About. C is considered by many to be the first modern “programmer’s language.” Prior

to the invention of C, computer languages were generally designed either as academic

Exercises or by bureaucratic committees. C is different. C was designed, implemented,

and developed by real, working programmers, and it reflected the way they approached

the job of programming. Its features were honed, tested, thought about, and rethought

by the people who actually used the language.

The result of this process was a language that programmers liked to use. Indeed, C quickly attracted many followers who had near-religious zeal for it, and it found wide and rapid acceptance in the programmer community. In short, C is a language designed by and for programmers. C was invented and first implemented by Dennis Ritchie on a DEC PDP-11 using the UNIX operating system. C is the result of a development process that started with an older language called BCPL, which was developed by Martin Richards. BCPL influenced language called B, invented by Ken Thompson, which led to the development of C in the 1970s.

For many years, the de facto standard for C was the one supplied with the UNIX

operating system and described in The C Programming Language, by Brian Kernighan and Dennis Ritchie (Prentice-Hall, 1978). However, because no formal standard existed, there were discrepancies between different implementations of C. To alter this situation, a committee was established in the beginning of the summer of 1983 to work on the creation of an ANSI (American National Standards Institute) standard that would define—once and for all—the C language. The final version of the standard was a dopted in December 1989, the first copies of which became available in early 1990. This version of C is commonly referred to as C89, and it is the foundation upon which C++ is built.

NOTE:

The C standard was updated in 1999 and this version of C is usually referred to as C99. This version contains some new features, including a few borrowed from C++, but, overall, it is compatible with the original C89 standard. At the time of this writing, no widely available compiler supports C99 and it is still C89 that defines what is commonly thought of as the C language. Furthermore, it is C89 that is the basis for C++. It is possible that a future standard for C++ will include the features added by C99, but they are not part of C++ at this time.

It may seem hard to understand at first, but C is often called a “middle-level” computer

Language. As it is applied to C, middle-level does not have a negative connotation; it does not mean that C is less powerful, harder to use, or less developed than a “high-level” language, or that it is as difficult to use as assembly language. (Assembly language, or assembler, as it is often called, is simply a symbolic representation of the actual machine code that a computer can execute.) C is thought of as a middle-level language because it combines elements of high-level languages, such as Pascal, Modula-2, or Visual Basic, with the functionality of assembler.

From a theoretical point of view, a high-level language attempts to give the programmer everything he or she could possibly want, already built into the language. A low-level language provides nothing other than access to the actual machine instructions. A middle-level language gives the programmer a concise set of tools and allows the programmer to develop higher-level constructs on his or her own. A middle-level language offers the programmer built-in power, coupled with flexibility. Being a middle-level language, C allows you to manipulate bits, bytes, and addresses—the basic elements with which a computer functions. Thus, C does not attempt to buffer the hardware of the machine from your program to any significant extent. For example, the size of an integer in C is directly related to the word size of the CPU. In most high-level languages there are built-in statements for reading and writing disk files. In C, all of these procedures are performed by calls to library routines and not by keywords defined by the language. This approach increases C’s flexibility. C allows—indeed, needs—the programmer to define routines for performing high-level operations. These routines are called functions, and they are very important to the C language. In fact, functions are the building blocks of both C and C++. You can easily tailor a library of functions to perform various tasks that are used by your program. In this sense, you can personalize C to fit your needs.

There is another aspect of C that you must understand, because it is also important

to C++: C is a structured language. The most distinguishing feature of a structured language is that it uses blocks. A block is a set of statements that are logically connected. For example, imagine an IF statement that, if successful, will execute five discrete statements. If these statements can be grouped together and referenced as an indivisible unit, then they form a block. A structured language supports the concept of subroutines with local variables. A local variable is simply a variable that is known only to the subroutine in which it is defined. structured language also supports several loop constructs, such as while, do-while, and for. The use of the go to statement, however, is either prohibited or discouraged, and is not the common form of program control in the same way that it is in traditional BASIC or FORTRAN. A structured language allows you to indent statements and does not require a strict field concept (as did early versions of FORTRAN).Finally, and perhaps most importantly, C is a language that stays out of the way. The underlying philosophy of C is that the programmer, not the language, is in charge. Therefore, C will let you do virtually anything that you want, even if what you tellit to do is unorthodox, highly unusual, or suspicious. C gives you nearly complete control over the machine. Of course, with this power comes considerable responsibility, which you, the programmer, must shoulder.

Understanding the Need for C++

Given the preceding discussion of C, you might be wondering why C++ was invented.Since C is a successful and useful computer programming language, why was therea need for something else? The answer is complexity. Throughout the history of programming, the increasing complexity of programs has driven the need for better ways to manage that complexity. C++ is a response to that need. To better understand this correlation, consider the following. Approaches to programming have changed dramatically since the invention of the computer. The primary reason for change has been to accommodate the increasing complexity of programs. For example, when computers were first invented, programming was done by toggling in the binary machine instructions using the computer’s front panel.

As long as programs were just a few hundred instructions long, this approach worked. As programs grew, assembly language was invented so that programmers could deal with larger, increasingly complex programs by using symbolic representations of the machine instructions. As programs continued to grow, high-level languages were developed to give programmers more tools with which to handle complexity. The first widespread language was, of course, FORTRAN. While FORTRAN was a very impressive first step, it is hardly a language that encourages clear, easy-to-understand programs. The 1960s gave birth to structured programming. This is the method of programming supported by languages such as C.

With structured languages, it was, for the first time, possible to write moderately complex programs fairly easily. However, even with structured programming methods, once a project reaches a certain size, its complexity exceeds what a programmer can manage. By the late 1970s, many projects were near or at this point. To solve this problem, a new way to program began to emerge. This method is called object-oriented programming (OOP for short). Using OOP, a programmer could handle larger programs.

The trouble was that C did not support object-oriented programming. The desire for an object-oriented version of C ultimately led to the creation of C++. In the final analysis, although C is one of the most liked and widely used professional programming languages in the world, there comes a time when its ability to handle complexity reaches its limit. The purpose of C++ is to allow this barrier to be broken and to help the programmer comprehend and manage larger, more complex programs.

C++ Is Born

In response to the need to manage greater complexity, C++ was born. It was invented by Bjarne Stroustrup in 1979 at Bell Laboratories in Murray Hill, New Jersey. He initially called the new language “C with Classes.” However, in 1983 the name was changed to C++. C++ contains the entire C language. As stated earlier, C is the foundation upon which C++ is built. C++ includes all of C’s features, attributes, and benefits. It also adheres to C’s philosophy that the programmer, not the language, is in charge. At this point, it is critical to understand that the invention of C++ was not an attempt to create a new programming language. Instead, it was an enhancement to an already highly successful language.

Most of the additions that Stroustrup made to C were designed to support object-oriented programming. In essence, C++ is the object-oriented version of C. By building upon the foundation of C, Stroustrup provided a smooth migration path to OOP. Instead of havingto learn an entirely new language, a C programmer needed to learn only a few new features to reap the benefits of the object-oriented methodology. But C is not the only language that influenced C++. Stroustrup states that some ofits object-oriented features were inspired by another object-oriented language called Simula67. Therefore, C++ represents the blending of two powerful programming methods.

When creating C++, Stroustrup knew that it was important to maintain the original spirit of C, including its efficiency, flexibility, and philosophy, while at the same time adding support for object-oriented programming. Happily, his goal was accomplished. C++ still provides the programmer with the freedom and control of C, coupled with the power of objects. Although C++ was initially designed to aid in the management of very large programs, is in no way limited to this use. In fact, the object-oriented attributes of C++ can be effectively applied to virtually any programming task. It is not uncommon to see C++ used for projects such as compilers, editors, programmer tools, games, and networking programs. Because C++ shares C’s efficiency, much high-performance systems software is constructed using C++. Also, C++ is frequently the language of choice for Windows programming. One important point to remember is this: Because C++ is a superset of C, once you can program in C++, you can also program in C! Thus, you will actually be learning two programming languages at the same time, with the same effort that you would use to learn only one.

The Evolution of C++

Since C++ was first invented, it has undergone three major revisions, with each revision adding to and altering the language. The first revision was in 1985 and the second occurred in 1990. The third revision occurred during the C++ standardization process. In the early 1990s, work began on a standard for C++. Towards that end, a joint ANSI and ISO (International Standards Organization) standardization committee was formed. The first draft of the proposed standard was created on January 25, 1994. In that draft, the ANSI/ISO C++ committee (of which I was a member) kept the features first defined by Stroustrup and added some new ones as well. But, in general, this initial draft reflected the state of C++ at the time.

Soon after the completion of the first draft of the C++ standard, an event occurred that caused the standard to expand greatly: the creation of the Standard Template Library (STL) by Alexander Step a now. As you will learn, the STL is a set of generic routines that you can use to manipulate data. It is both powerful and elegant. But the STL is also quite large. Subsequent to Therefore, the code and information in this book is fully applicable to all modern C++ environments.