a portable computer in which a single switch is positioned to be closed when the case is closed , and also to be readily operable by the user &# 39 ; s finger . software polls the switch . if the switch is briefly depressed , the software detects that the user is requesting entry into standby mode , and accordingly powers down certain input / output functions until new stimulus is received . if the switch is held down for a long time by the user closing the case cover , or manually holding the button down for a long time , the software causes the system to enter sleep mode .