8. Standard Input – Modern C++ for Absolute Beginners: A Friendly Introduction to C++ Programming Language and C++11 to C++20 Standards

© Slobodan Dmitrović 2020
S. DmitrovićModern C++ for Absolute Beginnershttps://doi.org/10.1007/978-1-4842-6047-0_8

8. Standard Input

Slobodan Dmitrović1 
(1)
Belgrade, Serbia
 
C++ provides facilities for accepting input from a user. We can think of the standard input as our keyboard. A simple example accepting one integer number and printing it out is:
#include <iostream>
int main()
{
    std::cout << "Please enter a number and press enter: ";
    int x = 0;
    std::cin >> x;
    std::cout << "You entered: " << x;
}

The std::cin is the standard input stream, and it uses the >> operator to extract what has been read into our variable. The std::cin >> x; statement means: read from a standard input into a x variable. The cin object resides inside the std namespace. So, std::cout << is used for outputting data (to a screen) and std::cin >> is used for inputting the data (from the keyboard).

We can accept multiple values from the standard input by separating them with multiple >> operators:
#include <iostream>
int main()
{
    std::cout << "Please enter two numbers separated by a space and press enter: ";
    int x = 0;
    int y = 0;
    std::cin >> x >> y;
    std::cout << "You entered: " << x << " and " << y;
}
We can accept values of different types:
#include <iostream>
int main()
{
    std::cout << "Please enter a character, an integer and a double: ";
    char c = 0;
    int x = 0;
    double d = 0.0;
    std::cin >> c >> x >> d;
    std::cout << "You entered: " << c << ", " << x << " and " << d;
}