What Is C?

C is a popular computer programming language, often used to write language compilers and operating systems. I examine C here because its
development (and its relationship to the UNIX operating system) is directly relevant to the Internet's development.

Nearly all applications designed to facilitate communication over the Internet are written in C. Indeed, both the UNIX operating system (which forms the underlying structure of the Internet) and TCP/IP (the suite of protocols used to traffic data over the Net) were developed in C. It is no exaggeration to say that if C had never emerged, the Internet as we know it would never have existed at all.

For most non-technical users, programming languages are strange, perplexing things. However, programming languages (and programmers) are the very tools by which a computer program (commonly called an application) is constructed. It may interest you to know that if you use a personal computer or workstation, better than half of all applications you now use were written in the C language. (This is true of all widely used platforms, including Macintosh.) In this section, I want to briefly discuss C and pay some homage to those who helped develop it. These folks, along with Paul Baran, Ken Thompson, and a handful of others, are the grandparents of the Internet.

C was created in the early 1970s by Dennis M. Ritchie and Brian W. Kernighan. These two men are responsible for many technological advancements that formed the modern Internet, and their names appear several times throughout this book.

Let's discuss a few basic characteristics of the C programming language. To start, C is a compiled as opposed to an interpreted language. I want to take a moment to explain this critical distinction because many of you may lack programming experience.



Advantages of C

One primary advantage of the C language is that it is smaller than many other languages. The average individual can learn C within a reasonable period of time. Another advantage is that C now conforms to a national standard. Thus, a programmer can learn C and apply that knowledge on any platform, anywhere in the country.

C has direct relevance to the development of the Internet. As I have explained, most modern TCP/IP implementations are written in C, and these form the basis of data transport on the Internet. More importantly, C was used in the development of the UNIX operating system. As I will explain in the next section of this chapter, the UNIX operating system has, for many years, formed the larger portion of the Internet.

C has other advantages: One is portability. You may have seen statements on the Internet about this or that program being ported to another operating system or platform, and many of you might not know exactly what that means. Portability refers to the capability of a program to be re-worked to run on a platform other than the one for which it was originally designed (that is, the capability to take a program written for Microsoft Windows and port it to the Macintosh platform). This aspect of portability is very important, especially in an environment like the Internet, because the Internet has many different types of systems running on it. In order to make a program available networkwide, that program must be easily conformable to all platforms.

Unlike code in other languages, C code is highly portable. For example, consider Visual Basic. Visual Basic is a wonderful rapid application development tool that can build programs to run on any Microsoft-based platform. However, that is the extent of it. You cannot take the raw code of a VB application and recompile it on a Macintosh or a Sun Sparcstation.

In contrast, the majority of C programs can be ported to a wide variety of platforms. As such, C-based programs available for distribution on the Internet are almost always distributed in source form (in other words, they are distributed in plain text code form, or in a form that has not yet been compiled). This allows the user to compile the program specifically for his or her own operating system environment.

Limitations of C and the Creation of C++

Despite these wonderful features, C has certain limitations. C is not, for example, an object-oriented language. Managing very large programs in C (where the code exceeds 100,000 lines) can be difficult. For this, C++ was created. C++ lineage is deeply rooted in C, but works differently. Because this section contains only brief coverage of C, I will not discuss C++ extensively. However, you should note that C++ is generally included as an option in most modern C compilers.

C++ is an extremely powerful programming language and has led to dramatic changes in the way programming is accomplished. C++ allows for encapsulation of complex functions into entities called objects. These objects allow easier control and organization of large and complex programs.

In closing, C is a popular, portable, and lightweight programming language. It is based on a national standard and was used in the development of the UNIX operating system.

 

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