#include <stdio.h>
#define ISSET(x,k) ((x & (1 << k)) != 0)

void printBits(int x)
{
   for (int k = 31; k >= 0; k--)
   {
       if ( ISSET(x,k) )
          printf("1");
       else
          printf("0");
   }
}

int main( int argc, char* argv[] )
{
   int a = 7;

   printf("a = %d, in binary: ", a);
   printBits(a);
   printf("\n\n");
}