Snippets

// Iterate through non-empty proper subsets. Doesn't include mask
for(int a = (mask - 1) & mask; a ; a = (a - 1) & mask){
   printf("%d is a non-empty proper subset of %d", a,n);
}

// Iterate through all subsets
for(int a = mask; true ; a = (a - 1) & mask){
   printf("%d is a subset of %d", a,n);
   if(a == 0) break;
}