What is a busy loop?

Question

Can it be a loop with or without statements?

while (1)
{
   //Empty
}

OR

int i = 0;

while (1)
{
   i++;
}

Answer 1

To me, a busy loop is a loop that never blocks.

Blocking is a behavior provided by the operating system that allows a thread to consume NO cpu cycles until some condition is met (a condition variable is signaled, or perhaps just data arriving on a socket (as recv() will block)).

In a traditional Win32 main loop, you potentially block every time your thread calls GetMessage(). All event driven windowing system are similar in this way.