Hello C++

This chapter gets you to a minimal C++ program: one that uses the C++20 standard library module and prints a line of text. If you can build and run this, your environment is ready for the rest of the book.

Your first C++ program

In modern C++ with modules, the program can be very small. Here is the full program from the FirstModule project (IntroToCpp/FirstModule/main.cpp):

import std;

int main()
{
	std::println("{}:{}: hello!", __FUNCTION__, __LINE__);
}

• import std; — Imports the C++20 standard library as a module. Your project must be set up to use the standard library module (e.g. MSVC with /std:c++20 or later and the std module enabled).
• int main() — Program entry point, same idea as in C.
• std::println("{}:{}: hello!", __FUNCTION__, __LINE__); — Prints a line. The {} placeholders are filled by the following arguments. __FUNCTION__ and __LINE__ are preprocessor macros that expand to the current function name and line number, so you get output like main:5: hello!.

Run the FirstModule project from IntroToCpp/FirstModule/ to see this in action. Once this builds and runs, you’re ready for variables, pointers, and references in the next chapter.