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C++ Programming

C++ Programming

C++ is a popular programming language

C++ is used to create computer programs, and is one of the most used language in game development.

Examples in Each Chapter

Our “Try it Yourself” editor makes it easy to learn C++. You can edit C++ code and view the result in your browser.

Example

#include <iostream>
using namespace std;

int main() {
  cout << “Hello World!”;
  return 0;

Click on the “Run example” button to see how it works.

We recommend reading this tutorial, in the sequence listed in the left menu.

C++ is an object oriented language and some concepts may be new. Take breaks when needed, and go over the examples as many times as needed.


C++ Exercises

Test Yourself With Exercises

Exercise:

Insert the missing part of the code below to output “Hello World”.

int main() {
   << "Hello World!";
  return 0;
}

What exactly is C++?

C++ is a cross-platform programming language for developing high-performance applications.

Bjarne Stroustrup created C++ as an extension to the C programming language.

C++ gives programmers a lot of power over the system’s memory and resources.

C++11, C++14, and C++17 were the three main updates to the language in 2011, 2014, and 2017.

Why Should You Use C++?

C++ is one of the most widely used programming languages in the world.

Today’s operating systems, graphical user interfaces, and embedded systems all use C++.

C++ is an object-oriented programming language that offers programs a clear structure and permits code reuse, which reduces development costs.

C++ is a portable programming language that may be used to create applications that run on a variety of systems.

C++ Get Started

To start using C++, you need two things:

  • A text editor, like Notepad, to write C++ code
  • A compiler, like GCC, to translate the C++ code into a language that the computer will understand

There are many text editors and compilers to choose from. In this tutorial, we will use an IDE (see below).


C++ Install IDE

An IDE (Integrated Development Environment) is used to edit AND compile the code.

Popular IDE’s include Code::Blocks, Eclipse, and Visual Studio. These are all free, and they can be used to both edit and debug C++ code.

Note: Web-based IDE’s can work as well, but functionality is limited.

We will use Code::Blocks in our tutorial, which we believe is a good place to start.

You can find the latest version of Codeblocks at http://www.codeblocks.org/downloads/26. Download the mingw-setup.exe file, which will install the text editor with a compiler.


C++ Quickstart

Let’s create our first C++ file.

Open Codeblocks and go to File > New > Empty File.

Write the following C++ code and save the file as myfirstprogram.cpp (File > Save File as):

myfirstprogram.cpp

#include <iostream>
using namespace std;

int main() {
  cout << “Hello World!”;
  return 0;
}

Don’t worry if you don’t understand the code above – we will discuss it in detail in later chapters. For now, focus on how to run the code.

In Codeblocks, it should look like this:

code blocks

C++ Syntax

Let’s break up the following code to understand it better:

Example

#include <iostream>
using namespace std;

int main() {
  cout << “Hello World!”;
  return 0;
}

Example explained

Line 1: #include <iostream> is a header file library that lets us work with input and output objects, such as cout (used in line 5). Header files add functionality to C++ programs.

Line 2: using namespace std means that we can use names for objects and variables from the standard library.

Don’t worry if you don’t understand how #include <iostream> and using namespace std works. Just think of it as something that (almost) always appears in your program.

Line 3: A blank line. C++ ignores white space. But we use it to make the code more readable.

Line 4: Another thing that always appear in a C++ program, is int main(). This is called a function. Any code inside its curly brackets {} will be executed.

Line 5: cout (pronounced “see-out”) is an object used together with the insertion operator (<<) to output/print text. In our example it will output “Hello World”.

Note: Every C++ statement ends with a semicolon ;.

Note: The body of int main() could also been written as:
int main () { cout << "Hello World! "; return 0; }

Remember: The compiler ignores white spaces. However, multiple lines makes the code more readable.

Line 6: return 0 ends the main function.

Line 7: Do not forget to add the closing curly bracket } to actually end the main function.


Omitting Namespace

You might see some C++ programs that runs without the standard namespace library. The using namespace std line can be omitted and replaced with the std keyword, followed by the :: operator for some objects:

Example

#include <iostream>

int main() {
std::cout << “Hello World!”;
  return 0;
}

C++ Output (Print Text)

The cout object, together with the << operator, is used to output values/print text:

Example

#include <iostream>
using namespace std;

int main() {
cout << “Hello World!”;
  return 0;
}

You can add as many cout objects as you want. However, note that it does not insert a new line at the end of the output:

Example

#include <iostream>
using namespace std;

int main() {
cout << “Hello World!”;
cout << “I am learning C++”;
  return 0;
}

New Lines

To insert a new line, you can use the \n character:

Example

#include <iostream>
using namespace std;

int main() {
  cout << “Hello World! \n“;
  cout << “I am learning C++”;
  return 0;
}

Tip: Two \n characters after each other will create a blank line:

Example

#include <iostream>
using namespace std;

int main() {
  cout << “Hello World! \n\n“;
  cout << “I am learning C++”;
  return 0;
}

Another way to insert a new line, is with the endl manipulator:

Example

#include <iostream>
using namespace std;

int main() {
  cout << “Hello World!” << endl;
  cout << “I am learning C++”;
  return 0;
}

Both \n and endl are used to break lines. However, \n is used more often and is the preferred way.

C++ Comments

Comments can be used to explain C++ code, and to make it more readable. It can also be used to prevent execution when testing alternative code. Comments can be singled-lined or multi-lined.


Single-line Comments

Single-line comments start with two forward slashes (//).

Any text between // and the end of the line is ignored by the compiler (will not be executed).

This example uses a single-line comment before a line of code:

Example

// This is a comment
cout << “Hello World!”;

This example uses a single-line comment at the end of a line of code:

Example

cout << “Hello World!”; // This is a comment


C++ Multi-line Comments

Multi-line comments start with /* and ends with */.

Any text between /* and */ will be ignored by the compiler:

Example

/* The code below will print the words Hello World!
to the screen, and it is amazing */
cout << “Hello World!”;

Single or multi-line comments?

It is up to you which you want to use. Normally, we use // for short comments, and /* */ for longer.

C++ Variables

Variables are containers for storing data values.

In C++, there are different types of variables (defined with different keywords), for example:

  • int – stores integers (whole numbers), without decimals, such as 123 or -123
  • double – stores floating point numbers, with decimals, such as 19.99 or -19.99
  • char – stores single characters, such as ‘a’ or ‘B’. Char values are surrounded by single quotes
  • string – stores text, such as “Hello World”. String values are surrounded by double quotes
  • bool – stores values with two states: true or false

Declaring (Creating) Variables

To create a variable, specify the type and assign it a value:

Syntax

typevariableName = value;

Where type is one of C++ types (such as int), and variableName is the name of the variable (such as x or myName). The equal sign is used to assign values to the variable.

To create a variable that should store a number, look at the following example:

Example

Create a variable called myNum of type int and assign it the value 15:int myNum = 15;
cout << myNum;

You can also declare a variable without assigning the value, and assign the value later:

Example

int myNum;
myNum = 15;
cout << myNum;

Note that if you assign a new value to an existing variable, it will overwrite the previous value:

Example

int myNum = 15;  // myNum is 15
myNum = 10;  // Now myNum is 10
cout << myNum;  // Outputs 10

Other Types

A demonstration of other data types:

Example

int myNum = 5;               // Integer (whole number without decimals)
double myFloatNum = 5.99;    // Floating point number (with decimals)
char myLetter = ‘D’;         // Character
string myText = “Hello”;     // String (text)
bool myBoolean = true;       // Boolean (true or false)

You will learn more about the individual types in the Data Types chapter.


Display Variables

The cout object is used together with the << operator to display variables.

To combine both text and a variable, separate them with the << operator:

Example

int myAge = 35;
cout << “I am ” << myAge << ” years old.”;


Add Variables Together

To add a variable to another variable, you can use the + operator:

Example

int x = 5;
int y = 6;
int sum = x + y;
cout << sum;


C++ Exercises

Test Yourself With Exercises

Exercise:

Create a variable named myNum and assign the value 50 to it.

C++ User Input

You have already learned that cout is used to output (print) values. Now we will use cin to get user input.

cin is a predefined variable that reads data from the keyboard with the extraction operator (>>).

In the following example, the user can input a number, which is stored in the variable x. Then we print the value of x:

Example

int x; 
cout << “Type a number: “; // Type a number and press enter
cin >> x; // Get user input from the keyboard
cout << “Your number is: ” << x; // Display the input value

Good To Know

cout is pronounced “see-out”. Used for output, and uses the insertion operator (<<)

cin is pronounced “see-in”. Used for input, and uses the extraction operator (>>)


Creating a Simple Calculator

In this example, the user must input two numbers. Then we print the sum by calculating (adding) the two numbers:

Example

int x, y;
int sum;
cout << “Type a number: “;
cin >> x;
cout << “Type another number: “;
cin >> y;
sum = x + y;
cout << “Sum is: ” << sum;

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