The Power Manager controls power to the internal hardware devices of battery-powered Macintosh computers (such PowerBook computers). The Power Manager automatically shuts off power to internal devices to conserve power whenever the computer has not been used for a predetermined amount of time. In addition, the Power Manager allows your application or other software to
• install a procedure that is executed when power to internal devices is about to be shut off or when power has just been restored
• set a timer to wake up the computer at some time in the future
• set or disable the wakeup timer and read its current setting
• enable, disable, or delay the CPU idle feature
• read the current CPU clock speed
• control power to the internal modem and serial ports
• read the status of the internal modem
• read the state of the battery charge and the status of the battery charger
Most applications do not need to know whether they are executing on a battery-powered Macintosh computer because the transition between power states is largely invisible. As a result, most applications do not need to use Power Manager routines. You need Power Manager only if you are writing a program--such as a device driver--that must control power to some subsystem of a battery-powered Macintosh computer or that might be affected by the idle or sleep state.