learncpp/ch_1/initialization/main.cpp

#include <iostream>

int main() {
    int x { 0 };
    double pi { 3.1415 };
    [[maybe_unused]] double tau { 6.2830 };

    std::cout << pi << std::endl;

    int y;

    std::cout << "y is uninitialized. it's value is " << y << "\n";

    return 0;
}