0/ Reading.  Chapter 3 by friday.
  HW: Ex: 3.2 3.4, 3.6 Due by Monday in class.
1. How a procedure call works.
   Save context
   Create new context
   Execute
   Restore context
   
   
   
2. Where does it happen
   On the stack.
   
2a. DANGER situation  DaNGER
    main()
	
   
3. How a transition to the OS works
   Change Mode to Kernel
   Save Context
   Create new Context in kernel mode
	      - Kernel-mode Stack
	      - Execute
	      
4. PROCESSES