C++ Introduction

C++ is a general-purpose, compiled programming language that builds on the C language by adding support for object-oriented programming, generic programming, and fine-grained control over memory and performance.

What Is C++ Used For?

C++ is a popular choice when a program needs to run fast and use system resources efficiently. You’ll find it powering operating systems, web browsers, video game engines, embedded devices, and performance-critical software like databases and trading systems.

Why Learn C++?

  • Performance: C++ code is compiled directly to machine code, making it one of the fastest languages available.
  • Control: You can manage memory manually, which gives you fine control over how your program uses resources.
  • Foundation: Many other languages (like C#, Java, and JavaScript) borrow ideas and syntax from C++, so learning it makes other languages easier to pick up.
  • Wide use: C++ is used across many industries, from game development to finance to robotics.

A First C++ Program

Let’s look at a simple C++ program that prints a message to the screen.

#include <iostream>

int main(void) {
    std::cout << "Hello, World!" << std::endl;
    return 0;
}

Output:

Hello, World!

How It Works

Here’s what each part of the program does:

  • #include <iostream> tells the compiler to include the input/output stream library, which lets your program read input and print output.
  • int main(void) defines the main function. Every C++ program starts running from main.
  • std::cout << "Hello, World!" << std::endl; sends the text "Hello, World!" to the console, followed by a new line. The << operator is called the insertion operator, and std::cout refers to the standard output stream.
  • return 0; ends the main function and tells the operating system the program finished successfully.

The std:: Prefix

cout and endl both belong to the C++ standard library’s std namespace. Writing std::cout tells the compiler exactly where to find cout. Later lessons will show how to avoid repeating std:: using a using statement.

Compiling and Running C++ Code

Unlike some languages, C++ code must be compiled into an executable file before it can run. If you save the program above as hello.cpp, you can compile and run it from a terminal using the GNU C++ compiler:

g++ hello.cpp -o hello
./hello

The first command compiles hello.cpp into an executable named hello. The second command runs it, printing Hello, World! to the screen.

Now that you’ve seen a complete C++ program, the next lesson will walk through setting up your environment and running C++ code on your own computer.