If that function is really supposed to return the square of a number, you took a wrong turn somewhere. Because it says the square of 16 is 56. Now here's a mo

If that function is really supposed to return the square of a number, you took a wrong turn somewhere. Because it says the square of 16 is 56. Now here's a more efficient algorithm which does produce the currect result: int square(int num) { int a = 0; for (int x = 1, n = num; x <= num; x+=x, n+=n) { if( num & x) { a += n; } } return a; } It would be nice if this site allowed us to run/step through the code, to see exactly what it is doing.