8.1. What are the LED's left side of the machine for?

	This is from John Milton's HwNotes series #1.

	0 RED:	  This is the "user LED". It can be turned on and off
		  with the syslocal(2) call. It is not used by any
		  existing applications.
	1 GREEN:  This is the one most people get wrong. This LED
		  toggles every time there is a process context
		  change, and is cleared on the whole second.
	2 YELLOW: This is the idle LED. When it is on, there are no
		  processes in the ready to run state.
	3 RED:    Heart beat LED. This is toggled on the whole second.

	This and other interesting information is available in the
HwNote series 1-15 that are archived on OSU.