Training
Module
Explore Windows architecture - Training
This module provides information about the operating system’s architecture and supported devices. It also describes the desktop support environment and troubleshooting terminology.
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The registry redirector isolates 32-bit and 64-bit applications by providing separate logical views of certain portions of the registry on WOW64. The registry redirector intercepts 32-bit and 64-bit registry calls to their respective logical registry views and maps them to the corresponding physical registry location. The redirection process is transparent to the application. Therefore, a 32-bit application can access registry data as if it were running on 32-bit Windows even if the data is stored in a different location on 64-bit Windows.
Windows 10 on ARM: In addition to the 32-bit logical view for x86 applications, Windows 10 on ARM includes a separate logical view for 32-bit ARM applications.
A subset of keys under redirected registry paths are shared. 32-bit registry calls to shared keys are not redirected. Instead, one physical copy of the key is mapped into each logical view of the registry. For a list of redirected keys and shared keys, see Registry Keys Affected by WOW64.
Windows Server 2008, Windows Vista, Windows Server 2003 and Windows XP: To enable application interoperability through COM and other mechanisms, a subset of redirected registry keys are also reflected. The process of registry reflection copies registry keys and values between two registry views to keep them synchronized. Registry reflection was removed starting with Windows 7 and Windows Server 2008 R2. For more information, see Registry Reflection.
The following scenario illustrates the use of these logical views:
Redirected keys are mapped to physical locations under Wow6432Node. For example, HKEY_LOCAL_MACHINE\Software is redirected to HKEY_LOCAL_MACHINE\Software\Wow6432Node. However, the physical location of redirected keys should be considered reserved by the system. Applications should not access a key's physical location directly, because this location may change. For more information, see Accessing an Alternate Registry View.
Windows 10 on ARM: Redirected 32-bit ARM keys are mapped to physical locations under WowAA32Node.
To help 32-bit applications that write REG_SZ or REG_EXPAND_SZ data containing %ProgramFiles% or %commonprogramfiles% to the registry, WOW64 intercepts these write operations and replaces them with "%ProgramFiles(x86)%" and "%commonprogramfiles(x86)%". For example, if the Program Files directory is on the C drive, then "%ProgramFiles(x86)%" expands to "C:\Program Files (x86)". The replacement occurs only if the following conditions are met:
Windows Server 2008, Windows Vista, Windows Server 2003 and Windows XP: The KEY_WOW_64_64KEY flag does not affect whether a key is replaced. This flag affects replacement starting with Windows 7 and Windows Server 2008 R2.
In addition, REG_SZ or REG_EXPAND_SZ keys containing system32 are replaced with syswow64. The string must begin with the path pointing to or under %windir%\system32. The string comparison is not case-sensitive. Environment variables are expanded before matching the path, so all of the following paths are replaced: %windir%\system32, %SystemRoot%\system32, and C:\windows\system32. This patch is applied only to the keys that were reflected prior to Windows 7.
For more information, see the following topics:
Training
Module
Explore Windows architecture - Training
This module provides information about the operating system’s architecture and supported devices. It also describes the desktop support environment and troubleshooting terminology.
Documentation
Registry Keys Affected by WOW64 - Win32 apps
Under WOW64, certain registry keys are redirected.
Example of Registry Redirection on WOW64 - Win32 apps
The following example code demonstrates the separate views of the registry provided by the registry redirector on 64-bit Windows.
Registry Reflection - Win32 apps
The registry redirector isolates 32-bit and 64-bit applications by providing separate logical views of certain portions of the registry on WOW64. However, the values of some registry keys must be the same in both the 32-bit and 64-bit views.