Convert decimal to base 2 in C++

[Shervan360]

Hello,
I wrote a program to convert decimal to base 2 in C++ and work fine.
I use Array.
Can I write this program without any data structure or built-in function?

  #include <iostream>
using namespace std;

int main()
{
	{
		int num;
		cout << "Enter Number \n";
		cin >> num;
		int i = 0;
		int base[100];
		while (num / 2 !=0 )
		{
			base[i++] = num % 2;
			num /= 2;
		}
		base[i] = num;
		for(int j = i;  j >=0 ; j--)
		{
			cout << base[j];
		}
		cout << endl;
	}
		

}

[lastchance]

#include <iostream>
using namespace std;

void binary( int num )
{
   if ( num >= 2 ) binary( num / 2 );
   cout << num % 2;
}

int main()
{
   int num;
   cout << "Enter number: ";   cin >> num;
   binary( num );   cout << '\n';
}