First C++ Program

Now that your system is set up, it is time to write and run your first C++ program.

In this lesson, you will learn the basic structure of a C++ program and understand what each part does.

Writing Your First Program

Every C++ program follows a specific structure. Even complex programs are built on the same basic foundation.

Let us start with a simple program that prints a message on the screen.

#include <iostream>
using namespace std;

int main() {
    cout << "Hello, C++!" << endl;
    return 0;
}
  

When you run this program, it displays:

Hello, C++!

Understanding Each Part of the Program

Let us break this program into smaller pieces and understand what each line means.

The #include <iostream> Line

This line tells the compiler to include the input-output stream library.

It allows the program to use features like printing text on the screen and reading input from the user.

The using namespace std; Line

This line allows us to use standard C++ features without writing the full namespace every time.

Without this line, we would need to write std::cout instead of cout.

The main() Function

Every C++ program starts execution from the main() function.

It is the entry point where the operating system begins running your program.

Printing Output with cout

The cout statement is used to display output on the screen.

The symbols << are called insertion operators. They send data to the output stream.

The return 0; Statement

This line tells the operating system that the program finished successfully.

Returning zero usually indicates that there were no errors.

Compiling and Running the Program

After writing the program, it must be compiled before it can run.

Open your terminal or command prompt, navigate to the file location, and use the following command:

g++ first.cpp -o first
  

This command creates an executable file from your C++ source code.

To run the program:

./first
  

Common Beginner Mistakes

When writing the first program, beginners often make small mistakes.

• Forgetting to include <iostream>
• Missing semicolons at the end of statements
• Spelling main incorrectly
• Using cout without the correct namespace

These errors are normal and will reduce with practice.

Mini Practice

Try the following small changes on your own:

• Change the message inside quotes
• Add another cout statement
• Remove endl and observe the output

This will help you understand how output works in C++.

Key Takeaways

• Every C++ program starts with the main() function
• cout is used to print output
• Programs must be compiled before running
• Small syntax details are very important in C++

What’s Next

In the next lesson, we will learn how to take input from the user using cin.