Intermediate C Programming

Preface

Why Is This Book Needed?

There are hundreds of books about programming, many of them about C programming.

Why do I write this book? Why should you spend time reading it? How is this book diﬀerent

from any other book? Like many authors, I wanted to write this book because I perceive a

need for it. Because I think the approach in this book is better.

I divide existing programming books into two types: introductory and advanced.In-

troductory books are written for beginners. These books assume readers have no back-

ground in programming and explain the basic concepts, sometimes starting with the “Hello

World!” program: a program that prints a “Hello World!” message on the computer screen.

These books explain language features step-by-step: keywords, data types, control struc-

tures, strings, ﬁle operations, and so on. These books have a common characteristic: Every

program is short, usually one or two pages. This works because a short program can serve

to explain one new concept about the programming language. If we think of learning a

computer language as learning a natural language like English, Chinese, French, or Korean,

these books teach us how to write sentences and short paragraphs.

The second type of book is written for people comfortable with programming. These

books describe programs solving real problems. Many books about computer games or

graphics belong to this second category. The examples in these books are usually quite

long, sometimes thousands of lines of code, and too long to print inside the books. As a

result, only sections of the programs are explained in the books, and the source code is

either included on a CD or can be downloaded from the Internet. These books do not talk

about how to write programs. Instead, they focus mostly on algorithms to solve particular

problems and, sometimes, include detailed information on performance. You deﬁnitely won’t

ﬁnd “Hello World!” examples anywhere in these books. Returning to the natural language

analogy, these books teach us how to write short novels, maybe a twenty-page story.

The problem is that it is diﬃcult to jump from writing a paragraph to writing a novel.

A Book for Intermediate-Level Students

There are very few books for intermediate-level students. These students know something

about programming already. They are not surprised when they see if or while. They know

how to create functions and call functions. They can write short programs, perhaps dozens

of lines of code, but they are not ready to handle thousand-line programs. They make

mistakes often but most books talk about how to write correct programs without much

help with avoiding common mistakes. The students are unfamiliar with many concepts and

tools that can help them write better programs. These students need a stepping stone to

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xxiv Preface

take them from being capable of writing short programs to being capable of writing real

programs.

Currently, the gap is partially ﬁlled by books that cover Data Structures and Algo-

rithms. These books provide programs that implement the data structures or algorithms.

However, this is not an ideal solution. These books focus on the subjects, Data Structures

and Algorithms, but rarely provide information that helps students write correct code. In

fact, they usually include the programs without much explanation. They do not explain

programming concepts—for example, why a function needs a pointer as an argument or

the diﬀerence between deep and shallow copy. As a result, students have to learn these

programming skills by themselves.

To ﬁll this need, I am writing this book for intermediate-level students. This book is

ideal as a second book on programming.

An Emphasis on Preventing Mistakes (“Bugs”) and Debugging

Most programming books talk about how to write programs. However, very few books

talk about how to develop software. Developing software is not simply typing code. Develop-

ing software requires much more knowledge and skill. To bridge this gap, it is useful to learn

by studying what is correct and what is wrong. Explaining how to write correct programs

is insuﬃcient. It is also important to explain common mistakes and compare them with

correct programs.

A careless mistake can make a program behave unexpectedly. Worse, the program may

be correct in some scenarios and wrong in others. Such bugs are diﬃcult to ﬁnd as well as

to correct. This book explains some common mistakes so that readers understand how to

prevent making these mistakes. Debugging is ignored in most books. Few books mention

the word “debugger” and sometimes readers simply do not know the existence of such tools.

Learning how to use a debugger takes less than thirty minutes and can save many hours.

Even fewer books talk about how to use debuggers and the strategies for debugging.

Integration of Programming and Discrete Mathematics

Programming and discrete mathematics are two important subjects in computing. How-

ever, most books treat these two topics independently. It is rare to see mathematical equa-

tions in programming books. It is rare to see code in books on discrete mathematics. I

believe that students can beneﬁt if they can see a closer connection between these two

subjects, as is shown in this book.

WhyDoesThisBookUseC?

C was invented in the late 1960s and early 1970s. Many languages were invented after

C and some of them were strongly inﬂuenced by C. Despite its age, the simplicity of C

Preface xxv

has ensured that it remains the foundation of computing on almost all modern platforms.

Like many operating systems, Linux is written in C. Android is mostly written in Java but

has an interface with C, called JNI (Java Native Interface). Most computer languages can

communicate with and through C. In fact, this is generally required for a programming

language to be useful, since most operating system interfaces use C. When a brand new

system is designed, C is often the ﬁrst (in many cases, the only) programming language

supported by the system.

C is a good choice for intermediate-level students because learning C requires knowing

many concepts about computers. The web site langpop.com compares the popularity of

programming languages and C is the most popular language, followed by Java. A report

in IEEE Spectrum [1] ranks popular programming languages. This report considers four

types of software: mobile, enterprise, embedded, and web. C is the most popular language

for embedded systems. When all four types are considered, the top ﬁve are:

1. Java (100%)

2. C (99.3%)

3. C++ (95.5%)

4. Python (93.4%)

5. C# (92.4%)

As you can see, three (C, C++, C#) of the top ﬁve languages are based on C. Java is

inﬂuenced by C++.

Who should read this book?

If you are a student in computer science, computer engineering, or electrical engineer-

ing, you should deﬁnitely read this book. This book covers many concepts essential for

understanding how programs work inside computers. If your major is engineering, science,

mathematics, or technology, you will very likely need to work with computers and this book

will be helpful. If your major is not engineering, science, mathematics, or technology, you

may still ﬁnd many concepts in this book (such as recursion) useful.

[1] Stephen Cass, Nick Diakopoulos, Joshua J. Romero, “Interactive: The Top Programming

Languages IEEE Spectrums 2014 Ranking”, July 1, 2014, http://spectrum.ieee.org/

static/interactive-the-top- programming-languages.

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Intermediate C Programming