C++ · Basics: compiling and hello world

I started phase 2 today. After three months of Python, the biggest change is the build step. Python runs source code through an interpreter. C++ is compiled ahead of time into a native executable:

hello.cpp --(preprocess, compile)--> hello.o --(link)--> hello.exe
g++ -std=c++17 -Wall hello.cpp -o hello
./hello

• #include <iostream> is a preprocessor directive. It pastes in the declarations for input and output.
• Execution always starts at int main(). Returning 0 tells the operating system the program succeeded.
• std::cout << ... prints. std:: is the standard library’s namespace.
• -Wall turns on warnings. I’m keeping it on from day one.

#include <iostream>

int main() {
    std::cout << "Hello, C++!" << '\n';
    std::cout << "C++ standard: " << __cplusplus << '\n';
    std::cout << "sizeof(int) = " << sizeof(int) << " bytes\n";
    return 0;
}

Output:

Hello, C++!
C++ standard: 201703
sizeof(int) = 4 bytes

__cplusplus printing 201703 confirms the compiler is in C++17 mode.