WOW64 (Windows-on-Windows 64-bit) is a Microsoft Operating system subsystem capable of running 32 - bit applications and is included on all 64-bit versions of Microsoft Windos.  WOW64 takes care of all the differences between 32-bit Windows and 64-bit Windows, particularly involving structural changes to Windows itself.

The WOW64 subsystem is a lightweight translation layer that has similar interfaces on all 64-bit versions of Windows. Its primary purpose is to create a 32-bit environment that provides the interfaces required to allow 32-bit Windows apps to run unmodified in the 64-bit system. Technically, WOW64 is implemented using three dynamic-link libraries (DLLs): Wow64.dll, which is the core interface to the NT kernel that translates between 32-bit and 64-bit calls, including pointer and stack manipulations; Wow64win.dll, which provides the appropriate entry points for 32-bit apps; and Wow64cpu.dll, which takes care of switching the processor from 32-bit to 64-bit mode.

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