CSE-Kids

WHAT IS C++?

2011-08-04T08:45:00.001-07:00

You can see that the C programming language was developed first, C++
was developed later. You might be asking yourself what, exactly, is C++
and how does it relate to C? The answer is that C++ is essentially C taken
to the next level. The most obvious difference between the two is that
C++ supports object orientation (more on that in Chapters 10, 11, and 12).
However, C++ sports many other improvements over C. For example,
C++ handles strings better than C, and has a more robust exception handling.
(Exception handling refers to a program’s ability to handle unexpected
errors. What if the user inputs a zero then tries to divide by that
number? This is an exception, how your code handles it is exception handling.
Chapter 7 discusses this topic in depth.)
C code will compile fine in most C++ compilers, but the reverse is not
true. C++ code will not necessarily compile in a C compiler. You may be
wondering what is meant by the word code. Code is essentially the series
of programming commands that a programmer writes. All the commands
that make up a program are the source code for that program.
C++ supports all C commands and also has many additions. You may
frequently see old style C code mixed in with C++ code, especially in programs
written by programmers who originally started in C.
HOW TO

HISTORY OF C++

2011-08-04T08:44:00.000-07:00

C++, as the name implies, is essentially based on the C programming language.
Therefore, it seems prudent to begin with a brief history of C. The
C programming language was devised in the early 1970s at Bell Laboratories
by Dennis Ritchie. It was designed as a system implementation language
for the Unix operating system. The history of C and Unix are
closely intertwined. For this reason a lot of Unix programming is done
with C. To some extent, C was originally based on the typeless language
BCPL, however it grew well beyond that.
The C++ programming language was invented by Bjarne Stroustroup.
Work on what would become C++ began in 1979. The initial version was
called “C with Classes.” That name did not work out well, and was
replaced with C++. The first version of C++ was used internally in AT&T
in August 1983. The first commercial implementation was released in
1985. The C++ language standards are now handled by the American
National Standards Institute (ANSI), and the International Standards
Organization (ISO). This is why you often hear pure C++ referred to as
ANSI Standard C++, or ISO Standard C++.

HOW TO WRITE A C++ PROGRAM

2011-08-04T08:42:00.001-07:00

There are several ways to write a C++ program. You could simply open
your favorite text editor, such as notepad, write your program, save it, and
then use a command line compiler to compile the program. In fact, this is
the method that will be used in this book, until we get to Section IV, the
section on Visual C++. If you have a commercial development tool such
as Borland C++ Builder™ or Microsoft Visual C++,™then you must
follow the instructions for that particular software package. The examples
in this book will use the free downloadable version of the Borland
C++ compiler. The free Borland C++ compiler does not have the extra
development tools and IDE (Integrated Development Environment) that
Borland C++ Builder has. The Web address to go to and download this
free C++ compiler is listed in Appendix A. However, the free download
is simply a command line compiler. A command line compiler is one that
is executed from the command line. This, of course, begs the question of
what is a command line. When you enter commands at a DOS prompt
(Microsoft Windows™98), Command Prompt (Microsoft Windows
2000/XP), or Shell (Linux/Unix™) you are typing commands on a line,
thus the term “command line.” You literally type in commands one line
at a time. Figure 1.1 shows the basic DOS prompt for Windows 95/98™.
To use a command line compiler, like the free C++ compiler from Borland,
you simply type the code into a document in any text editor, then
save it with a .cpp extension (e.g., myprogram.cpp). That .cpp extension
stands for C Plus Plus. C files that are done in a text editor are saved with
the extension .c, as you might expect. Complete instructions for how to
download, install, configure, and use this compiler can be found in
Appendix D. You should use the instructions in Appendix D to make

sure you have the compiler properly installed on your PC before continuing
with this book.

C++ FUNDAMENTALS

2011-08-04T08:40:00.000-07:00

C++ is a programming language. As such, it shares a number of similarities
with other programming languages. First we may need to clarify
what a programming language is. A computer thinks in 1’s and 0’s. Various
switches are either on (1’s), or off (0’s). Most humans, however,
have trouble thinking in 1’s and 0’s. A programming language is a language
that provides a bridge between the computer and human beings.
A “low-level” language is one that is closer to a computer’s thinking
than to a human language. A prime example would be Assembly language.
A “high-level” language is one that is closer to human language.
COBOL and BASIC are prime examples of high-level language.

people consider C and C++ to be high-level languages, but actually C
and C++ are both somewhat of a bridge between the low-level languages
and high-level languages. You might think of them as mid-level
languages. The level of a language, in this context, essentially refers to
how far it is removed from actual machine language. It has no relationship
to either the power of the programming language, or the difficulty
of learning and using it. Various languages, with their basic level indicated,

are shown in Figure 1.2.
Each programming language has various strengths and weaknesses.
Some, like BASIC, are easy to use but are neither flexible nor powerful.
Others, such as Assembly, are powerful, but difficult to use. C and C++
are somewhere in the middle. C++ is quite powerful, but relatively easy
to use (easier than Assembly but more difficult than BASIC). Some languages
are also written with specific purposes in mind. Fortran was
written specifically for mathematical programming, BASIC was
designed simply for teaching programming, and COBOL was designed

for business applications. C++ was designed as a general purpose language.
It is used in business applications, telecommunications programming,
artificial intelligence programming, games programming, and
much more. This is one reason why it is the language that many teachers
choose to teach students. Once you have learned C++, you can use it in a
wide variety of situations.
Programs are written to handle data. This is why the industry as a
whole is often referred to as data processing, information technology,
computer information systems, and so on. That data might be information
about employees, parts to a mathematical computation, scientific
data, or even the elements of a game. No matter what programming language
or techniques you use, the ultimate goal of programming is to
store, manipulate, and retrieve data. Data must be temporarily stored in
the program, in order to be manipulated. This is accomplished via variables.
A variable is simply a place in memory set aside to hold data of a
particular type. It is a specific section of the computer’s memory that has
been reserved to hold some data. It is called a variable because its value
or content can vary. When you create a variable, you are actually setting
aside a small piece of memory for storage purposes. The name you give
the variable is actually a label for that address in memory. For example,
you might declare a variable in the following manner.
int j;
Then, you have just allocated four bytes of memory; you are using the
variable j to refer to those four bytes of memory. You are also stating that
the only type of data that j will hold, is whole numbers. (The int is a data
type that refers to integers, or whole numbers.) Now, whenever you reference
j in your code, you are actually referencing the contents being
stored at a specific address in memory.
With that said, you might now be asking what is meant by “data of a
particular type”? Data comes in different types. Some data consists of letters
and some consists of numbers. Any programming language will recognize
only certain types or categories of data. The basic data types that
C++ recognizes, and what they hold, are shown in Table 1.1. In addition,
there are a few other data types that will be introduced later in the book.
When you are deciding what type of variable to create, you need to
think about what kind of data you might wish to store in that variable. If
you want to store a person’s age, then an int is a good choice. The int
data type will hold whole numbers, and will, in fact, hold numbers much
larger than you might need for a person’s age. The long data type will

STATEMENTS AND EXPRESSIONS

2011-08-04T08:35:00.001-07:00

As you have already seen, a statement is simply a single line of code that
performs some action. Remember that another word for a statement is an
expression. In C++, a single expression does some type of action. That
action might be to declare a variable, add two numbers, compare two
values, or just about anything at all. It is also important to remember that
all statements/expressions end with a semicolon. Another of the most
common mistakes that beginners make is leaving off semicolons. Let’s
look at a few simple statements.
int i_acctnum;
i_acctnum = 555555;
i_acctnum = i_acctnum + 5;
Each statement performs a different action—but it does perform some
action—and it ends with a semicolon. The first statement/expression
simply declares a variable. The second statement/expression sets that
variable equal to some value. Finally, the last statement/expression performs
addition and puts the answer in the variable that was previously
declared.
Operators
You saw, at the end of the last section, the use of the + sign. This is an
operator. An operator is simply some symbol that performs some action,
usually a mathematical action, such as addition or subtraction. C++ supports
a number of important operators that you will need to get

with. Let’s begin examining C++ operators, starting with the basic math
operators, shown in Table 1.4.
TABLE 1.4 Operators
Operator Purpose Example
+ To add two numbers int answer;
answer = 5 +6;
- To subtract two numbers int answer;
answer = 10 –3;
* To multiply two numbers int answer;
answer = 4 * 5;
/ To divide two numbers int answer;
answer = 7/3;
++ This is a special operator that simply int answer;
increments the value by 1. You will see answer++;
this used later in this book when loops
are discussed.
-- This is also a special operator that simply int answer;
decrements the value by 1. answer--;
= The single equals sign is an assignment answer = 16;
operator. It states “make what’s on
the left equal to what’s on the right”
== The double equals is an equality operator. if(answer==5)
It asks “is what’s on the left equal to what’s
on the right?” This is frequently used in
if statements (which you will see in a
later chapter!)
!= Not equal to if (x !=3)
+= Add then assign x += 1;
-= Subtract then assign x -=1;
|| This is the logical OR operator. if(j == 5 || j ==10)
&& This is the logical AND operator if(j > 5 && j<10)
>> Bitwise shift to the right 3<<2;
<< Bitwise shift to the left 3>>2;
& Bitwise And 3&2;
| Bitwise Or 3|

Now using the expression,
answer = num++;
the value of num will first be put in answer, THEN incremented. In
other words, the value of answer will be set to 5, and then the value of num
will be incremented. If you want num to be incremented BEFORE you
assign the value to answer then you must put the increment operator first,
as shown in the following example.
answer = ++num;
The operators shown in Table 1.4 are your basic math operators and
logical operators. There are several other operators you will also see in
C++. These will be introduced in later chapters because they are pertinent
to topics that will be covered in those chapters. Most of the operators
in Table 1.4 should be familiar to you. The math operators represent
simple math operations. All math operators occur with a specific order.
The order is pretty much the same as the order of operations defined in
mathematics. First is * (multiplication), next / (division), then + (addition),
and, finally, – (subtraction). The increment ++ and decrement –
operators precedence is determined by what side of the variable they are
on. You can alter the order of operations by using parentheses, just as you
do in mathematics. An example follows.
answer = x * 3 + 4;
First, x and 3 would be multiplied, and then 4 would be added to that
product. If, instead, you wanted to add 3 and 4, then multiply by x, you
could simply use parentheses to denote that.

BASIC STRUCTURE OF A C++ PROGRAM

2011-08-04T08:30:00.001-07:00

Now that you have seen variable declaration, C++ expressions, and the
basic math operators, let’s take a quick look at the basic structure of a
C++ program. All C++ programs must have a main function. This is
where the program begins. Chapter 4 goes into greater detail regarding
functions. For now, suffice it to say that a function is one or more statements
grouped together in a logical manner to accomplish some goal
under a common name. Chapter 4 covers all the intricacies of C++ functions.
The following is a basic C++ program.
int main()
{
return 0;
}
Now, this program will not do much—in fact, it won’t do anything
useful at all. It is, however, a valid C++ program. It has a main function
that returns an integer value. The main function is where all C++ programs
start. This is the starting point for your entire program. All main functions
are required by the ANSI (American National Standards Institute) standards
to return an integer. The integer is a 0 if the program executes fine,
and a 1 if some problem is encountered. This was originally done because
some operating systems require any program to return a value telling the
operating system that everything is OK. You will see a lot of Windows programmers
use a main function that returns a void like the following.
void main()
This will work in some cases, but it is not technically correct. This book
endeavors to conform to the ANSI standards and use return 0.
The next thing to notice about our sample program is the presence of
brackets. These brackets are C++’s way of establishing borders around
any block of code. (Incidentally, C, Java, and JavaScript™ do the same
thing. Learning it here will help you learn other languages as well.).
Every time you see an opening bracket, {there must be a matching}
closing bracket. You will see a lot more about this when we discuss loops,
decision structures, and functions. For now, suffice it to say that brackets
form borders around blocks of code.
With all that said, let’s look at a program that has a few statements.
int main()
{
int j;
j = 5;
j++;
return 0;
}
This simple program creates a variable named j, sets the value of that
variable to 5, then increments that value by one. This is still not a particularly
exciting piece of code, but it does illustrate the basic structure of a
C++ program. Three statements are executed, a 0 is returned to indicate
that everything is OK, and there are brackets surrounding the main function.
If you carefully examine this code, and follow this template in all
your programming, then you will do well!

Header Files

2011-08-04T08:28:00.000-07:00

There is only one more item that needs to be discussed regarding the
basic structure of a C++ program. That item is header files. Header files are
files that contain the definitions for functions and/or classes. Basically, if
you have a lot of functions or variables that you might want to use in several
programs, you can put them in a header file, then include that header
file anywhere you need to use it. After creating a header file you can then
include a reference to a header file in your program and use the functions
and/or classes defined in that header file. The real intricacies of header
files are discussed in a later chapter, in which you will actually create
some header files. However, you should realize that there are a lot of
these files built into C++ that you can use! Well, “built in” is not exactly
accurate. They are actually installed with your compiler and you can
include them in your programs. One of which you will use in Chapter 2 is
the iostream header file. It gives you functions to handle input and
output from the screen. The way you include any header file is simple. At
the beginning of your file, you reference the header file. This is demonstrated
in the following
example.
#include <iostream>
int main()
{
return 0;
}
You now have access to all the classes and functions defined in the
iostream header file. In the following chapters, you will see several different
header files, each providing a different set of functions for you to
use. For now, all that is important is that you realize that you include a
header file using the # sign and the word include. If the header file is one
that is part of C++, then you simply use the <headerfilename>. Make
sure that this is the first thing you do in your file! Remember that you use
.cpp to indicate a C++ source file and .c to indicate a C source file, while
the .h indicates a header source file. A source file is simply a plain text file
that has the source code for your C++ program. Source code is the basic
lines of programming language that you write, and that the compiler will
later use as a source to create an executable program.

FUNCTION BASICS

2011-08-04T08:25:00.001-07:00

What are functions? In simple terms, a function is a block of code that is
identified by some name and can take zero or more parameters and can
return some value. That definition probably does little to clarify the issue
for you! Let’s look at a function and its parts to help clarify this issue. To
begin with, consider the following function, which squares a number.
float square(float num)
{
float answer = num * num;
return answer;
}
The first line of the function is called its declaration line. It has three parts.
The first part is its return type. The return type tells you what kind of data
the function will give you back. If it returns nothing, then its return type
would be void. In the previous example, the function will return the answer
to our math problem, and that is a float. The second thing is the name of the
function. Function names follow the same guidelines as variable names. It is
a good idea to have the function name reflect what the function will do.
Next, inside the parenthesis, we have parameters. A parameter is some
value you pass to the function in order for it to work. For example, in this
case, to square a number, we have to give it the number to square. Students
often ask: “What do we need to put as parameters? Do we even need any
parameters for this function?” There is a simple way to answer this question
for any function you write. Ask yourself this question: If you wanted some
person to do this task for you, would you need to give them anything? And,
if so, what? If you wanted a person to square a number for you, you would
have to give them that number. However, if you just wanted them to say
hello, you would not have to give them anything. Therefore, a function that
squares a number should take one parameter, and a function that displays
hello on the screen might not take any parameters. There will be a lot more
in-depth discussion on functions in Chapter 4.

VARIABLE SCOPE

2011-08-04T08:24:00.001-07:00

In the beginning of this chapter, you were introduced to the concept of
variables. You saw the various data types, how to declare a variable, and
what proper names you could use for variables (as well as ones you
could not). There is one more topic concerning variables. This had to be
left until after the discussion about the structure of a C++ program, and
you will see why shortly. The topic at hand concerns WHERE you
declare a variable. This is called variable scope. Consider the following

example.
int main()
{
int j;
return 0;
}

This variable is declared inside the main function. That means it is only
usable within that function. If you create other functions, they will not be
able to access the variable j. This is referred to as a local variable. A local
variable is a variable that is declared within a function, or within any
block of code. Now let’s look at another example.
int j;
int main()
{
j++;
return 0;
}
Notice that j was NOT declared inside the main function. It was
declared outside of any function. This means that it can be used
throughout your code. A variable declared outside of any function can be
used in any function, and is referred to as a global variable. This is referred
to as variable scope. Scope defines the range within which a variable can
be used. If the variable has local scope, then its range is restricted to the
function in which it was declared. It is essential to pay attention to the
scope of your variables. It is not uncommon for a beginner to declare a
variable inside one function, and then forget that it is only usable within
that function.

COMPILING

2011-08-04T08:23:00.001-07:00

When you write a program you are typing in code. You might be simply
typing code into a basic text editor or into a commercial IDE (Integrated
Development Editor) such as Borland C++ Builder or Microsoft Visual
C++. But you will not be distributing what you are typing to end-users.
What do you distribute to them? First of all, what you type is the source
code. It is not an executable program. Remember that the source code is
simply all the programming commands that you write. The process of
taking your source code and creating an executable is called compiling.
The purpose of a compiler (whether it’s a command line compiler, or
one built into some commercial IDE) is to translate the specific programming
language code you wrote into standard machine instructions that
the computer can understand and run. That code is in a binary data file
(1’s and 0’s) that the machine can understand and execute (thus, the
term executable).
The specifics about how you compile a program depend on the compiler
you are using. Commercially available development kits such as
C++ Builder and Visual C++ usually have a button to press, or a dropdown
menu to select. Command line compilers require you to type in
compilation instructions at the command line. The specifics for using the
free Borland C++ compiler used in the examples in this book are given in
Appendix D.

REVIEW QUESTIONS

2011-08-04T08:22:00.001-07:00

1. What is a variable?
2. What is a statement?
3. Which of the following are legal names for variables in C++?
a. firstname
b. &salary
c. x
d. y
e. first@name
4. All valid C++ statements end with a what?
5. What type of value must the main function return?
6. What is the purpose of brackets?
7. What is a local variable?
8. What is a global variable?
9. If a function does not return anything, then what do you put for its
return type?
10. What is a parameter?