An application must open a key before it can add data to the registry. To open
a key, an application must supply the handle of another key in the registry
that is already open. The system defines standard handles that are always open.
An application can use these predefined handles as entry points to the registry.
The system provides two predefined keys at the root of the registry: HKEY_LOCAL_MACHINE
. In addition, the system defines two subkeys: HKEY_CLASSES_ROOT
(a subkey of HKEY_LOCAL_MACHINE
) and HKEY_CURRENT_USER
(a subkey of HKEY_USERS
). These registry handles are valid for all Win32 implementations of the
registry, although the use of the handles may vary from platform to platform.
Predefined keys help an application navigate in the registry and make it
possible to develop tools that allow a system administrator to manipulate categories
of data. Applications that add data to the registry should always work within
the framework of predefined keys, so administrative tools can find and use the
These predefined keys are used as entry points to the registry.
||Registry entries subordinate to this key define types (or classes) of
documents and the properties associated with those types. Data stored under this key is
used by Windows shell applications and by object linking and embedding (OLE)
||Registry entries subordinate to this key define the preferences of the current
user. These preferences include the settings of environment variables, data
about program groups, colors, printers, network connections, and application
||Registry entries subordinate to this key define the physical state of the
computer, including data about the bus type, system memory, and installed hardware
||Registry entries subordinate to this key define the default user configuration
for new users on the local computer and the user configuration for the current
The use of HKEY_CURRENT_USER
, and HKEY_USERS
varies depending on the implementation of the registry. In addition, other
predefined handles have been defined for specific Windows platforms.
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