Abstract: An uninterruptable power supply system is connected to motherboard and hard disk respectively. An interrupt signal is sent to power management circuit to command power management circuit to control the power switching circuit to switch the power of motherboard and hard disk to battery when a power interrupt is detected in a running computer by power detecting circuit. At the same time, central processing unit (CPU) on motherboard is commanded to save running programs and data in the hard disk. As such, CPU on motherboard can read the stored programs and data from hard disk when computer is turned on again. Thus computer may recover to the previous normal state. This can effectively avoid data lost once blackout occurred.