freeCodeCamp/guide/english/cplusplus/index.md

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C++

Hello World! - Your First C++ Program

What is C++?

• C++ is a general purpose programming language which has been used since the 1990's

• It was designed by Bjarne Stroustrup under the name "C with classes".

• It is a version of C that includes Object-Oriented elements, including classes and functions.

• It is considered one of the biggest programming languages, as you can see in the following image: source: Github

Your First Program in C++

#include <iostream>
using namespace std;
int main()
{
    cout << "Hello World" << endl;
    return 0;
}

The Output of this program will be:

Hello World!

Now, let's break down the code:

Lines 1 and 2

#include <iostream>
using namespace std;

• The first line tells the computer to use the "iostream" header file for this specific program. A header file is a separate file with prewritten C++ code. There are many other header files which are required for a specific program to run properly. For example, math, vector, string, etc. Header files are generally represented by a ".h" extension, when including standard library header files you don't include the ".h" extension.
• The iostream header contains the public interface for the input-output stream from the standard library. The "iostream" file contains code for allowing the computer to take input and generate an output, using the C++ language.
• The second line tells the computer to use the standard namespace which includes features of standard C++. You could write this program without this line, but you'd have to use std::cout instead of cout and std::endl instead of endl on line 4. It makes the code more readable and our lives as programmers easier.

Line 3 and 4

int main()
{

• C++ starts execution of a program from the -main function- int main() . During execution, the computer starts running the code from every line from {(opening bracket) till }(closing bracket) NOTE : Every function starts with an opening curly brace "{" and ends with a closing curly brace "}".
• Line 4 indicates the start of the main() function.

Lines 5, 6 & 7

    cout << "Hello World" << endl;
    return 0;
}

• The word cout in C++ is used to stream data to standard output.
• It is followed by << , the insertion operator.
• Whatever is in the double quotes "" is printed. Certain special characters have a different syntax for print statements
• Now to print any other kind of data, you have to add <<.

Challenge: Change Hello World to another sentence. What will be the output?

• endl is another symbol from the iostream library which means to end this line and go to the next line during output . - cout stands for "console output"
• Finally, finish the statement with a semicolon ;.

NOTE : Every statement except the main function definition and the #include directive needs to be ended by the semicolon. Without a ";", you may encounter a compiler error.

• return 0; safely terminates the current function i.e. 'main()' in this case and since no function follows after 'main()' the program is terminated.
• Don't forget to tell the computer that this is end of the main() function. To do this , you add the closing curly brace "}". You will encounter compiler error before program execution if you do not include the } .

The code should look something like this:

Programmers use a Hello World program (like this one) as a ritual on using a new programming language. It is a symbol of good luck.
You have finished coding your first C++ program and have understood most of the code you have written/typed. CONGRATULATIONS!

Good Luck to all of you and happy coding! :)

Happy Coding ! :)

Feel free to ask any questions on FreeCodeCamp's GitHub page or FreeCodeCamp's Forum.

Try it yourself ! :)

You need software to write and execute C++ code, download from one of the links below:

Codeblocks
Xcode
Eclipse