I'm newer to c++ and today I looked at a game engine main render loop which looked like this:

```
for (register unsigned long long i = 0xaull; engine_tick(); kRuntimeStatistics::INSTANCE.FramesSinceStart++, ++ i); 

```

Why did it have any body and when it is exiting? I thought for loops are for numbers only? And what does 0xaull mean behind the long i?