code not working to the end

hi,

Anything to improve for someone learning in the code below...

/* 1- Compute a n*2 value for 64 iterations */
/* 2- Maximum integer variable iterations for n*2 */
/* 3- Computer the number of iteration needed to reach the value in
question 1 */
int main()
try
{
        long double var_long_double = 1 ;
        long double var_long_double2 = 1 ;
        unsigned int var_integer = 1 ;
        unsigned int var_integer2 = 1 ;
        int i = 1 ;
        int nb = 1 ;
        // QUESTION 1
        while (i < 64)
        {
                var_long_double *= 2 ;
                i++ ;
        }
        cout << "\n1- Value for 64 iteration : " << var_long_double ;
        //QUESTION 2
        while (var_integer > 0)
        {
                cout << "\n" << nb << "\tvar_int : " << var_integer ;
                var_integer *= 2 ;
                nb++ ;
                if (var_integer > 0)
                        var_integer2 = var_integer ;
        }
        cout << "\n\n2- Number as integer variable for " << nb << "
incrementations : " << var_integer2 ;
        // QUESTION 3
        i = 1 ;
        while (var_long_double >= 0)
        {
                var_long_double /= 2 ;
                if (var_long_double >= 0)
                        var_long_double2 = var_long_double ;
                else
                        break ;
                i++ ;
        }
        cout << "\n3-Number of maximum iteration for i as int " << i
<<
"\n" ;
        cout << "\n\n" ;
        system("pause") ;
        return 0 ;
}

catch (runtime_error e)
{
        cout << e.what() << '\n' ;
        keep_window_open("~") ;
}

catch(...)
{
        cout << "Exiting\n" ;
        keep_window_open("~") ;
}

I am running this on a 64 bits computer using Windev.
Above the fact that I don't see the code above very reliable, I don't
understand why I get to -2 147 483 648 with an unsigned int variable.
From my understanding it should be 4 294 967 295...