KMain() includes ::/StartOS.CC includes ~/MakeHome.CC includes ~/HomeSys.CC calls StartUpTasks() includes ~/Once.CC calls OnceExe(). ZOnce() appends src code to ~/Registry.CC Once/System tree, executed at next boot by System. Once() appends src code to ~/Registry.CC Once/User tree, executed at next boot by first User term. At boot, OnceExe(), executes Once/System tree, ZOnceFlush()s it, executes Once/User tree and OnceFlush()s.