Hello World Program in C++

In this tutorial we will write and understand the first program in C++ programming. We are writing a simple C++ program that prints “Hello World!” message. Lets see the program first and then we will discuss each and every part of it in detail.

Hello World Program in C++

/*
* Multiple line
* comment
*/
#include<iostream>

//Single line comment
using namespace std;

//This is where the execution of program begins
int main()
{
   // displays Hello World! on screen
   cout<<"Hello World!";

   return 0;
}

(code-box)

Output:
Hello World! (code-box)



Let’s discuss each and every part of the above program.
1. Comments – You can see two types of comments in the above program
// This is a single line comment
/* This is a multiple line comment
* suitable for long comments
*/
Comments as the names suggests are just a text written by programmer  during code development. Comment doesn’t affect your program logic in  any way, you can write whatever you want in comments but it should be  related to the code and have some meaning so that when someone else look  into your code, the person should understand what you did in the code  by just reading your comment.
For example:
/* This function adds two integer numbers 
 * and returns the result as an integer value
 */
int sum(int num1, int num2) {
   return num1+num2;
}
Now if someone reads my comment he or she can understand what I did  there just by reading my comment. This improves readability of your code and when you are working on a project with your team mates, this  becomes essential aspect.
2. #include<iostream> – This statements tells  the compiler to include iostream file. This file contains pre defined  input/output functions that we can use in our program.
3. using namespace std; – A namespace is like a  region, where we have functions, variables etc and their scope is  limited to that particular region. Here std is a namespace name, this  tells the compiler to look into that particular region for all the  variables, functions, etc. I will not discuss this in detail here as it  may confuse you. I have covered this topic in a separate tutorial with  examples. Just follow the tutorial in the given sequence and you would  be fine.
4. int main() – As the name suggests this is the  main function of our program and the execution of program begins with  this function, the int here is the return type which indicates to the  compiler that this function will return a integer value. That is the  main reason we have a return 0 statement at the end of main function.
5. cout << “Hello World!”; – The cout object  belongs to the iostream file and the purpose of this object is to  display the content between double quotes as it is on the screen. This  object can also display the value of variables on screen(don’t worry, we  will see that in the coming tutorials).
6. return 0; – This statement returns value 0 from  the main() function which indicates that the execution of main function  is successful. The value 1 represents failed execution.