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The '''Windows registry''' stores configuration information for a user's copy of the [[Microsoft]] [[Windows (operating system)|Windows]] operating system in a centralized, hierarchical [[database]]; it is often referred to as ''"brains of your computer"''.<ref name="asknerd">[http://www.registryonwindows.com What is the Windows Registry]</ref> Since the introduction of Windows 95, this database model has almost completely replaced the text-based .INI files that previous versions of Windows had utilized to store configuration information. The registry was designed to make the storage of this information more compact, logical, and efficient overall.<ref name="Windows 2000 Registry: Latest Features and APIs Provide the Power to Customize and Extend Your Apps" http://msdn.microsoft.com/msdnmag/issues/1100/Registry/ >Windows 2000 Registry: Latest Features and APIs Provide the Power to Customize and Extend Your Apps</ref>

The '''Windows registry''' stores configuration information for a user's copy of the [[Microsoft]] [[Windows (operating system)|Windows]] operating system in a centralized, hierarchical [[database]]; it is often referred to as ''"brains of your computer"''.<ref name="asknerd">[http://www.registryonwindows.com What is the Windows Registry]</ref> Since the introduction of Windows 95, this database model has almost completely replaced the text-based .INI files that previous versions of Windows had utilized to store configuration information. The registry was designed to make the storage of this information more compact, logical, and efficient overall.<ref name="Windows 2000 Registry: Latest Features and APIs Provide the Power to Customize and Extend Your Apps">[http://msdn.microsoft.com/msdnmag/issues/1100/Registry Windows 2000 Registry: Latest Features and APIs Provide the Power to Customize and Extend Your Apps]</ref>

== Advantages ==

== Advantages ==

The design of the Windows registry provides several major advantages over the text-based .INI files used in the predecessors of Windows 95. Because of the relatively primitive and simplistic specifications that govern text-based items like .INI files, these files are often limited to basic [[ASCII]] text in their content. This normally excludes all Unicode characters that fall outside the standard ASCII character set. The registry, however, can store strongly typed data, which includes non-ASCII characters, thus giving it a distinct advantage in that non-Latin characters, specialized symbols, and escape characters can all be incorporated into settings.<ref name="Registry Structure, from Microsoft Technet" http://technet.microsoft.com/en-us/library/cc776231%28WS.10%29.aspx>Registry Structure, from Microsoft Technet</ref>

The design of the Windows registry provides several major advantages over the text-based .INI files used in the predecessors of Windows 95. Because of the relatively primitive and simplistic specifications that govern text-based items like .INI files, these files are often limited to basic [[ASCII]] text in their content. This normally excludes all Unicode characters that fall outside the standard ASCII character set. The registry, however, can store strongly typed data, which includes non-ASCII characters, thus giving it a distinct advantage in that non-Latin characters, specialized symbols, and escape characters can all be incorporated into settings.<ref name="Registry Structure, from Microsoft Technet">[http://technet.microsoft.com/en-us/library/cc776231%28WS.10%29.aspx Registry Structure, from Microsoft Technet]</ref>

The registry also allows multiple users to log in and use a workstation. Because program settings can be stored on a per-user basis in each user's respective location in the registry, a program can call that specific group of settings when a user executes a program. Text-based .INI files, however, were often stored in a program's installation directory, thus limiting that program to one configuration. The ability of the registry to allow for multiple users has led in part to the development and increased adoption of multiple user workstations and environments, such as [[Active Directory]] domains in the corporate environment and family PCs in the home.

The registry also allows multiple users to log in and use a workstation. Because program settings can be stored on a per-user basis in each user's respective location in the registry, a program can call that specific group of settings when a user executes a program. Text-based .INI files, however, were often stored in a program's installation directory, thus limiting that program to one configuration. The ability of the registry to allow for multiple users has led in part to the development and increased adoption of multiple user workstations and environments, such as [[Active Directory]] domains in the corporate environment and family PCs in the home.

The centralized nature of the registry also makes backups and restoration of system and user configuration information significantly easier than for .INI files. Although the registry does technically consist of multiple files that can be stored in radically different locations on the local machine or even across the network, the Windows operating system is traditionally capable of working with these different locations as if they were combined.<ref name="The Windows Registry" http://www.tech-pro.net/intro_reg.html> The Windows Registry </ref>

The centralized nature of the registry also makes backups and restoration of system and user configuration information significantly easier than for .INI files. Although the registry does technically consist of multiple files that can be stored in radically different locations on the local machine or even across the network, the Windows operating system is traditionally capable of working with these different locations as if they were combined.<ref name="The Windows Registry"> [http://www.tech-pro.net/intro_reg.html The Windows Registry ]</ref>

== Disadvantages ==

== Disadvantages ==

The Windows registry does possess several disadvantages as well. Although it is relatively easy to back up and restore the database to the same Windows installation, moving per-program settings to a different machine is difficult because so many programs use settings that are dependent on the local machine. <ref name="The Windows Registry"/>

The Windows registry does possess several disadvantages as well. Although it is relatively easy to back up and restore the database to the same Windows installation, moving per-program settings to a different machine is difficult because so many programs use settings that are dependent on the local machine. <ref name="The Windows Registry"/>

The entire registry database must be processed upon every boot for the operating system to function, which can create performance delays during startup. Critics have also labeled the Windows registry as a single point of failure, because its centralized and hierarchical structure, while providing the many benefits discussed above, also makes it a weak link in the system and an easy target for both malicious and unintentional damage by users. <ref name="Forensic Analysis of the Windows Registry" http://www.docstoc.com/docs/2381418/Forensic-Analysis-of-the-Windows-Registry-Computer-Forensics>Forensic Analysis of the Windows Registry</ref>

The entire registry database must be processed upon every boot for the operating system to function, which can create performance delays during startup. Critics have also labeled the Windows registry as a single point of failure, because its centralized and hierarchical structure, while providing the many benefits discussed above, also makes it a weak link in the system and an easy target for both malicious and unintentional damage by users. <ref name="Forensic Analysis of the Windows Registry">[http://www.docstoc.com/docs/2381418/Forensic-Analysis-of-the-Windows-Registry-Computer-Forensics Forensic Analysis of the Windows Registry]</ref>

Applications that store their settings in the registry are irreducibly tied to the local machine, meaning that transitioning users from one computer to another very often requires a complete re-installation of the program. <ref name="Was the Windows Registry a Good Idea?" http://www.codinghorror.com/blog/2007/08/was-the-windows-registry-a-good-idea.html>Was the Windows Registry a Good Idea?</ref>

Applications that store their settings in the registry are irreducibly tied to the local machine, meaning that transitioning users from one computer to another very often requires a complete re-installation of the program. <ref name="Was the Windows Registry a Good Idea?">[http://www.codinghorror.com/blog/2007/08/was-the-windows-registry-a-good-idea.html Was the Windows Registry a Good Idea?]</ref>

== Structure==

== Structure==

'''Abbreviation'''

'''Abbreviation'''

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'''Description'''<ref name="Windows Registry Information for Advanced Users" http://support.microsoft.com/kb/256986>Wndows Registry Information for Advanced Users</ref>

'''Description'''<ref name="Windows Registry Information for Advanced Users">[http://support.microsoft.com/kb/256986 Windows Registry Information for Advanced Users]</ref>

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HKU

HKU

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Contains the configuration information for all users currently active on a computer. HKEY_CURRENT_USER is a subset of this key. Because HKEY_USERS can store information for multiple users simultaneously, it allows for multiple user environments, as well as specialized user accounts utilized internally by Windows (like the ASP.NET user account in Windows XP and the TrustedInstaller account in Windows Vista/7).  

Contains the configuration information for all users currently active on a computer. HKEY_CURRENT_USER is a subset of this key. Because HKEY_USERS can store information for multiple users simultaneously, it allows for multiple user environments, as well as specialized user accounts utilized internally by Windows (like the ASP.NET user account in Windows XP and the TrustedInstaller account in Windows Vista and Windows 7).  

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HKDD

HKDD

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This key is only used in Windows 95, Windows 98, and Windows 98 Second Edition (SE). Like HKEY_CURRENT_CONFIG, it stores information on specific aspects of a computer's hardware, and details for Plug and Play drivers.<ref name="Description of the HKEY_DYN_DATA Registry Key in Windows 95, Windows 98, and Windows 98 Second Edition" http://support.microsoft.com/kb/250568>Description of the HKEY_DYN_DATA Registry Key in Windows 95, Windows 98, and Windows 98 Second Edition</ref> With support for all versions of Windows 98 SE now ended, this key is now officially deprecated.

This key is only used in Windows 95, Windows 98, and Windows 98 Second Edition (SE). Like HKEY_CURRENT_CONFIG, it stores information on specific aspects of a computer's hardware, and details for Plug and Play drivers.<ref name="Description of the HKEY_DYN_DATA Registry Key in Windows 95, Windows 98, and Windows 98 Second Edition">[http://support.microsoft.com/kb/250568 Description of the HKEY_DYN_DATA Registry Key in Windows 95, Windows 98, and Windows 98 Second Edition]</ref> With support for all versions of Windows 98 SE now ended, this key is now officially deprecated.

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