Input/Output and streams

In C++, standard input and output are managed via streams (data flows) defined in the <iostream> standard library.

The two main objects you will use are:

• std::cout: the output stream (associated with the screen).
• std::cin: the input stream (associated with the keyboard).

Printing with std::cout

To send data to the screen, we use the insertion operator <<:

#include <iostream>

int main() {
    std::cout << "Hello!" << " Welcome to C++." << std::endl;
    return 0;
}

• << can be chained to print different texts and variables consecutively.
• std::endl inserts a newline character (\n) and flushes the stream (ensures that the output is immediately displayed on the screen).

Reading with std::cin

To read values entered by the user, we use the standard input stream std::cin combined with the extraction operator >>:

#include <iostream>

int main() {
    int age;
    std::cout << "Enter your age: ";
    std::cin >> age; // Extracts user input and saves it into age
    std::cout << "You are " << age << " years old." << std::endl;
    return 0;
}

Try it yourself