How to Write Your First C++ Program: Detailed Explanation

Before we begin, ensure you have the following:

• A C++ Compiler:Other examples include GCC, Clang, or MSVC. IDEs like Code::Blocks, Dev-C++, or Visual Studio are great options as they include a compiler.
• A Text Editor or IDE: Tools like Visual Studio Code or JetBrains CLion work well for writing and debugging C++ code.

Steps to Write Your First C++ Program

1. Create a New File

Open your IDE or text editor and create a new file. Save it with the extension .cpp (e.g., hello_world.cpp).

2. Write the Code

Here’s a simple C++ program that prints "Hello, World!" to the console:

#include <iostream>

// The main function: Entry point of the program
int main() {
    std::cout << "Hello, World!" << std::endl; // Print message to the console
    return 0; // Indicate that the program ended successfully
}

Explanation:

• #include <iostream>: Includes the library to use input and output features like std::cout.
• int main(): The starting point of every C++ program.
• std::cout: Used to print output to the console.
• <<: The insertion operator, directs data to std::cout.
• std::endl: Ends the line and flushes the output buffer.
• return 0: Indicates that the program was executed successfully.

3. Compile the Program

Using a Command Line (GCC Example):

1. Open a terminal or command prompt.
2. Navigate to the directory containing your file (hello_world.cpp).
3. Compile the program using:

   g++ hello_world.cpp -o hello_world

This generates an executable file named hello_world.

In an IDE: Click on the Build or Compile button. The IDE will handle the compilation process for you.

4. Run the Program

Using the Command Line:

./hello_world

In an IDE: Click on the Run button, and the program output will appear in the console window of the IDE.

Expected Output

Hello, World!

Begin your 1st C++ Program

• Again, Open any text editor or IDE and create a new file with any name and a .cpp extension. e.g. HelloWorld.cpp
• Open the file and enter the below code in the C++ Compiler:

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

  Run Code >>
• Compile and run the code

Output

Hello, World!

• With the help of cout, our program printed the sentence “Hello world” on the screen. There can be as many cout statements as you want in your program.

  
  #include <iostream>
  using namespace std;
  int main() {
   cout << "Hello, World!" << endl;
   cout << "This is my first program" << endl;
   return 0;
  } 

  Run Code >>

  Output

  Hello, World!
  This is my first program
  

• The endl manipulator is used to insert a new line. That's why each output is displayed in a new line.
• The << operator can be used more than once if we want to print different variables, strings, and so on in a single statement.
• return 0 indicates the end of the main() function.
• The closing curly bracket }is used to end the main() function.
• Have you noticed ; after each line of code in the main() function? It is necessary to put it after each line of code. In C++ every line ends with a ;. If you forget to put a ;, it will show you a compile-time error.
• C++ ignores white spaces but we use it to make the code more readable.

User Input in C++

Example of User Input in C++

#include <iostream>
using namespace std;

int main() {
 int a;
 cout << "Enter a number: ";
 cin >> a; // Taking input
 cout << "The number is: " << a;
 return 0;
}

The above C++ code is usedcin to take an integer input from the user. The input is stored in the variable a.

You will see variables and data types in the upcoming tutorials, Variables in C++ Programming and Data Types in C++

Output

Enter a number: 85
The number is: 85

• You can even use std::cin instead of cin if you don't want to use the statement, using namespace std;.

  
  #include <iostream>
  int main() {
   int a;
   std::cout << "Enter a number: ";
   std::cin >> a; // Taking input
   std::cout << "The number is: " << a;
   return 0;
  } 

• You can even take multiple inputs using a single cin statement

  
  #include <iostream>
  int main() {
   int a, b;
   std::cout << "Enter two numbers: ";
   std::cin >> a >> b; // Taking inputs
   std::cout << "The numbers are: " << a << "," << b;
   return 0;
  }
  

Output

Enter two numbers: 10 20
The numbers are: 10, 20

Top 5 Programs to Practice C++ As a Fresher

1. Program to Add Two Numbers

#include <iostream>
using namespace std;

int main() {
    int num1, num2, sum;
    
    cout << "Enter the first number: ";
    cin >> num1;
    cout << "Enter the second number: ";
    cin >> num2;

    sum = num1 + num2;

    cout << "The sum of " << num1 << " and " << num2 << " is " << sum << "." << endl;

    return 0;
}

Sample Output

#include <iostream>
using namespace std;

int main() {
    int a, b, temp;

    cout << "Enter the first number: ";
    cin >> a;
    cout << "Enter the second number: ";
    cin >> b;

    // Swapping using a temporary variable
    temp = a;
    a = b;
    b = temp;

    cout << "After swapping, first number: " << a << ", second number: " << b << endl;

    return 0;
}

Sample Output

#include <iostream>
using namespace std;

int main() {
    int num;

    cout << "Enter an integer: ";
    cin >> num;

    if (num % 2 == 0) {
        cout << num << " is even." << endl;
    } else {
        cout << num << " is odd." << endl;
    }

    return 0;
}

Sample Output

#include <iostream>
using namespace std;

int main() {
    int n, sum = 0;

    cout << "Enter a positive integer: ";
    cin >> n;

    for (int i = 1; i <= n; ++i) {
        sum += i; // Add current number to the sum
    }

    cout << "The sum of the first " << n << " natural numbers is " << sum << "." << endl;

    return 0;
}

#include <iostream>
using namespace std;

int main() {
    int year;

    cout << "Enter a year: ";
    cin >> year;

    if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)) {
        cout << year << " is a leap year." << endl;
    } else {
        cout << year << " is not a leap year." << endl;
    }

    return 0;
}