## Input/Output Device Driver Reference

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### OS/2 APM Software Components

There are four major software components defined in the OS/2 Power Management Architecture:

Power Object manages and tracks power consumption in battery-powered computers that support the APM standard. This component is provided in OS/ 2 but might be extended by APM-aware device drivers or APM BIOS vendors.

APM Subsystem interacts with the APM BIOS, APM-aware device drivers, and the Power object to process power management state changes. This component is provided in OS/2.

APM-Aware Device Drivers manage specific device details across power management state changes. There are numerous device drivers that can fit into this component category. Some of the OS/2-provided device drivers are APM-aware (such as MOUSE.SYS). Other OS/2 APM-aware device drivers are provided by OEM hardware manufacturers that produce power managed add-on devices (such as data/fax modems).

APM BIOS encapsulates the underlying hardware characteristics and provides a consistent industry-wide function base for higher layers of software ( such as OS/2). The APM BIOS component is provided by the Personal Computer Manufacturer (PCM) if the system is meant to provide power management capabilities. A machine's APM BIOS will support a given version of the APM Specification. OS/2 currently supports the Advanced Power Management Specification. Older machines may only support APM 1.0. Older versions of the APM Specification will not support all of the features of newer versions, and the following discussion makes note of these cases.