!!! Overview
[{$pagename}] is a [hierarchical] [Data Store|DataStore] that stores low-level settings for the [Microsoft Windows] [Operating System] and for [applications] that opt to use the [{$pagename}]. The [Microsoft Windows] [kernel], device drivers, services, [Security Account Manager] ([SAM]), and user interface can all use the [{$pagename}]. \\
[{$pagename}] also allows access to counters for profiling system performance.

!! Keys and values
[{$pagename}] contains two basic elements: 
* keys are [Containers] objects similar to folders. 
* values are non-container objects similar to files. 
Keys may contain values and subkeys. Keys are referenced with a syntax similar to [Microsoft Windows]' [File System] path names, using backslashes to indicate levels of hierarchy. Keys must have a [Case-insensitive] name without backslashes.The hierarchy of registry keys can only be accessed from a known root key handle (which is anonymous but whose effective value is a constant numeric handle) that is mapped to the content of a registry key preloaded by the kernel from a stored "hive", or to the content of a subkey within another root key, or mapped to a registered service or DLL that provides access to its contained subkeys and values.

There are seven predefined root keys, traditionally named according to their constant handles defined in the Win32 API, or by synonymous abbreviations (depending on applications)
%%zebra-table
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||[HIVE]||[ABBR|Abbreviation]||File(s)
|[HKEY_CURRENT_CONFIG]|[HKCC]|System, System.alt, System.log, System.sav
|[HKEY_CURRENT_USER]|[HKCU]|Ntuser.dat, Ntuser.dat.log
|[HKEY_LOCAL_MACHINE]\[SAM]|[HKLM]|Sam, Sam.log, Sam.sav
|[HKEY_LOCAL_MACHINE]\Security|[HKLM]| Security, Security.log, Security.sav
|[HKEY_LOCAL_MACHINE]\Software|[HKLM]|Software, Software.log, Software.sav
|[HKEY_LOCAL_MACHINE]\System|[HKLM]|System, System.alt, System.log, System.sav
|[HKEY_CLASSES_ROOT]|[HKCR]| contains information about registered applications, such as file associations and OLE Object Class IDs, tying them to the applications used to handle these items.
|[HKEY_USERS]|[HKU]|contains subkeys corresponding to the [HKEY_CURRENT_USER] keys for each [user] actively loaded on the machine, user hives are usually only loaded for currently logged-in users.
|[HKEY_USERS].DEFAULT|[HKU]|Default, Default.log, Default.sav
|[HKEY_PERFORMANCE_DATA]| |__only in [Windows Server NT]__, but invisible in the Windows Registry Editor)
|[HKEY_DYN_DATA]| |__only in [Windows 95],[Windows 98],[Windows ME]__, and visible in the Windows Registry Editor)
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!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]
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* [#1] - [Windows_Registry|Wikipedia:Windows_Registry|target='_blank'] - based on information obtained 2018-10-18- 
* [#2] - [Registry|https://docs.microsoft.com/en-us/windows/desktop/sysinfo/registry|target='_blank'] - based on information obtained 2018-10-18-