know what the input data is whether integer or not

To determine whether the input data is an integer or not in C++, you can use a combination of the cin input stream and the >> extraction operator. Here is an example code snippet that demonstrates this process:

#include <iostream>

int main() {
    int num;

    std::cout << "Enter a number: ";
    std::cin >> num;

    if (std::cin.fail()) {
        std::cout << "Invalid input. You did not enter an integer." << std::endl;
    } else {
        std::cout << "You entered the integer: " << num << std::endl;
    }

    return 0;
}

Let's break down the code and explain each step:

1. We start by including the <iostream> header, which provides input/output stream functionality in C++.

2. In the main() function, we declare an integer variable num that will store the user input.

3. We prompt the user to enter a number using std::cout and the << insertion operator.

4. We read the user input using std::cin and the >> extraction operator, and store it in the num variable.

5. We use the std::cin.fail() function to check if the input was successful. If it fails, it means the user did not enter a valid integer.

6. If the input fails, we display an error message saying that the input was invalid.

7. If the input is successful, we display the entered integer using std::cout and the << insertion operator.

8. Finally, we return 0 to indicate successful program execution.

By using std::cin.fail(), we can check if the input data is an integer or not. If the extraction fails, it means the user did not enter a valid integer, and we can handle it accordingly.