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The Plug and Play Manager maintains a device tree, viewable through Device
Manager, which keeps track of the active devices in the system and information
about those devices. The Plug and Play Manager updates the device tree as
devices are added and removed or as resources are reallocated. The device tree is
hierarchical, with devices on a bus represented as children of the bus adapter or
controller. The registry is the central repository for static hardware information. Plug
and Play system components and drivers build, maintain, and access new and
existing subtrees in the registry .
During enumeration, data for each device is stored under a new
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Enum key in the registry
(this is the enum tree). Plug and Play makes decisions about which device drivers
are loaded based on the results of enumeration. Thus, there is an important
connection between the enum tree and the services list in
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services.
Figure 2 shows a Plug and Play device tree for a hypothetical ACPI system
configuration. In practice, a device tree would consist of many additional devices,
but Figure 2 shows only the devices needed in this discussion.
Windows 2000 White Paper
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