Your First C++ Program

C++ is compiled directly to machine code. That makes it fast, and it means you need a compiler before you can run anything.

The Program

Every C++ program starts at main. #include brings in declarations from the standard library.

#include <iostream>

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

Compile and Run

Compile to an executable, then run it. Turn on warnings; they catch many bugs before they happen.

g++ -std=c++20 -Wall -Wextra main.cpp -o hello
./hello

Reading the Pieces

• #include <iostream> adds input and output.
• std::cout writes to the console.
• << sends a value to the stream.
• return 0 tells the operating system the program succeeded.

Practice

1. Print your name and school on separate lines.
2. Explain what return 0 means.
3. Compile with -Wall and fix any warning.

Hands-on exercise

Write a program that prints:
1. Your name.
2. Your favourite subject.
3. A closing line.
Each on its own line.

Recap

C++ is compiled, main is the entry point and the standard library is included with headers.