Why std::cin doesn't prompt for user entry?

I'm trying to understand better the std::cin behavior.

Let's see the following code:

#include <iostream>                                                                                                                
int main()                                                                                                                         
{                                                                                                                                  
    char c, cin {'8'};                                                                                                             
    std::cin >> c; // enter '.'                                                                                                    
    std::cin.putback(c);                                                                                                           
    double d {88};                                                                                                                 
    std::cin >> d; // expected to fail.                                                                                            
    if (std::cin)                                                                                                                  
        std::cout << "double d = " << d << '\n';                                                                                   
    else                                                                                                                           
    {                                                                                                                              
        std::cin >> cin; // doesn't prompt user for entry neither put c into cin.                                                  
        std::cout << "cin = " << cin << '\n';                                                                                      
    }                                                                                                                              
    std::cout << "d = " << d << '\n'; // just to check.                                                                           
}

I wonder to get what explain the fact of std::cin >> cin; doesn't prompt for user entry neither attribute the value of c that was previously putted back into the std::cin stream to the variable cin.

Note:

• It's known that std:: cin >> skips whitespace (space, newline, tab, etc.)