What is the full form of APM


APM: Advanced Power Management

APM stands for Advanced Power management. APM is an application programming interface developed by Microsoft and Intel to achieve power management. It makes Operating system to run on the personal computer to interact with any basic input/output system and attain power management. It controls the power usage of the system until the system is brought into the suspended state.

How it works

It uses a layered approached to manage the device. It contains a device driver to talk to OS specific APM driver. APM communicate with BIOS and the BIOS sends power management to APM driver. So the APM driver works as a mediator between the BIOS and operating system.

States of Power Control

There are five power states in APM:

  • Full on State: This state specifies that high power consumption is on. No power management is done in this state.
  • APM Enabled State: APM system is enabled and doing work in this state but no power management is done in some unused devices.
  • APM Standby State: This state specifies that APM is inactive for a short time and the system comes into that state.
  • APM Suspend State: This state specifies that APM is inactive for a long time and system comes into that state. It takes too much time to come in enabled state from the suspended state.
  • OFF State: This state specifies that CPU clock is stopped.