Re: How does this C segment work?

The WDTCSR is the WatchDog Timer Control Register. Each of it's eight named bits means something different. WDE is the WatchDog Enable bit, and WDP0, WDP1, WDP2 and WDP3 are the WatchDog Prescale bits. They are used to select (effectively) the time-out on the WatchDog. The combination of WDP1 and WDP0 indicate that the timeout should be about half a second.