Questions about initializing c++ member variables

#include "stdafx.h"
#include <iostream>
using namespace std;

class foam
{
public:
    int temp_c ;

    foam() 
    { 
     temp_a = 10;
     temp_b = 20;
    }

    int temp_a ;
    int temp_b ;



    void printdata()
    {
        cout << "temp_a : " << temp_a << endl;
        cout << "temp_b : " << temp_b << endl;
    }


};

int _tmain(int argc, _TCHAR* argv[])
{    
    foam exam = { 30 };
    exam.printdata();

    return 0;
}