Definition of Advanced Configuration and Power Interface (ACPI) in Network Encyclopedia.
What is ACPI?
ACPI, or Advanced Configuration and Power Interface, is an open industry specification that enables software designers to integrate features for power management throughout a computer system, including the hardware, operating system, and application software.
Advanced Configuration and Power Interface (ACPI) is supported by the Microsoft Windows family and enables the operating system to handle all the power-management resources for computer subsystems and peripherals.
ACPI works with subsystems and peripherals for a wide range of mobile, desktop, and server platforms. ACPI is also the foundation for the OnNow industry initiative that enables computers to start at the touch of the keyboard.

ACPI is in part a response to global concerns about energy conservation and environmental control. ACPI replaces Intel’s SL technology and the more recent APM (Advanced Power Management) technology. Based on the collaborative effort of Hewlett-Packard, Intel, Microsoft, Phoenix, and Toshiba, ACPI moves away from power management that simply times out during inactivity to a more sophisticated demand-based power management. ACPI components collect information about power consumption from the computer and give that information to the operating system.
The operating system then distributes power to the different computer components on an as-needed basis. With ACPI, the computer can power itself down to a deep sleep state but still be capable of responding to an incoming phone call or a timed backup procedure. Another feature of ACPI is the “hibernation” mode. Before the computer goes into a deep sleep or hibernation, the contents of RAM are written to an image file and saved on the hard drive. When the computer is turned back on, the image file is reloaded, eliminating the need to reboot the system and open applications.