C++: Example -- Convert to binary with bit ops

This program reads integers and prints them in binary, using the shift and "and" operators to extract the relevant bits. 
// Print binary representation of ints

#include <iostream>
using namespace std;

void main() {
   int n;
   while (cin >> n) {
      cout << "decimal: " << n << endl;

      // print binary with leading zeros
      cout << "binary : ";
      for (int i=31; i>=0; i--) {
         int bit = ((n >> i) & 1)
         cout << bit;
      }
      cout << endl;
   }//end loop
}

Problems

Here are some modifications that could be made to this code.
  1. It's difficult to read long sequences of digits. It's common to put a space after every 4 digits.
  2. Suppress leading zeros. This is done most easily by defining a bool flag, setting it to false at the beginning of each conversion, setting it to true when a non-zero bit is encountered, and printing zeros only when this flag is set to true. Then there's the case of all zeros that requires another test.