C++ User Input

In C++, programs can interact with users by receiving input from the keyboard. While cout is used to display output, cin allows the program to capture input using the extraction operator (>>).

Reading User Input

To prompt a user to enter a value, use cin along with a variable to store the input.

Example

#include <iostream>
using namespace std;

int main() {
    int engineCC;  
    cout << "Enter engine capacity (cc): "; // Asking for user input
    cin >> engineCC; // Storing the input
    cout << "Your engine capacity is: " << engineCC;
    return 0;
}

#include <iostream>

using namespace std;

​

int main() {

    int engineCC;  

    cout << "Enter engine capacity (cc): "; // Asking for user input

    cin >> engineCC; // Storing the input

    cout << "Your engine capacity is: " << engineCC;

    return 0;

}

​

Explanation:

• cout displays a message asking the user to enter a number.
• cin >> engineCC; stores the user’s input in the variable engineCC.
• The value entered is then displayed using cout.

Understanding cout and cin

• cout (pronounced “see-out”) → Displays information using the insertion operator (<<).
• cin (pronounced “see-in”) → Captures input using the extraction operator (>>).

Creating a Simple Calculator

Let’s build a program that asks the user for two numbers, adds them, and displays the result.

Example

#include <iostream>
using namespace std;

int main() {
    int speedA, speedB;
    int totalSpeed;

    cout << "Enter first speed: ";
    cin >> speedA;
    cout << "Enter second speed: ";
    cin >> speedB;

    totalSpeed = speedA + speedB;
    cout << "Total combined speed is: " << totalSpeed;

    return 0;
}

#include <iostream>

using namespace std;

​

int main() {

    int speedA, speedB;

    int totalSpeed;

​

    cout << "Enter first speed: ";

    cin >> speedA;

    cout << "Enter second speed: ";

    cin >> speedB;

​

    totalSpeed = speedA + speedB;

    cout << "Total combined speed is: " << totalSpeed;

​

    return 0;

}

​

Explanation:

• The user enters two values (speedA and speedB).
• The program adds them and displays the result.