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Encyclopedia > WOW64

WoW64 (Windows-on-Windows 64-bit) is a subsystem of the Windows operating system that is capable of running 32-bit applications and is included on all 64-bit versions of Windows — including Windows XP 64-bit Editions, Windows Server 2003 x64 Edition and Windows Vista 64-bit Editions. WOW64 takes care of all the differences between 32-bit Windows and 64-bit Windows, particularly involving structural changes to Windows itself. Windows redirects here. ... // An operating system (OS) is the software that manages the sharing of the resources of a computer. ... 32-bit is a term applied to processors, and computer architectures which manipulate the address and data in 32-bit chunks. ... This does not cite any references or sources. ... Windows Server 2003 is a server operating system produced by Microsoft. ... Windows Vista is a line of graphical operating systems used on personal computers, including home and business desktops, notebook computers, Tablet PCs, and media centers. ...

Contents

Translation libraries

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. For the Macintosh operating system, which was called System up to version 7. ... DLL is an abbreviation which can commonly mean: Data link layer, a layer in the OSI network architecture model Dynamically Linked Library, a binary application library file format in Microsoft Windows and IBM OS/2 (see the Dynamic linking section of the Library (computer science) article) Doubly Linked List, a... Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. ... A kernel connects the application software to the hardware of a computer. ... It has been suggested that Software pointer be merged into this article or section. ... In computer science, a call stack is a special stack which stores information about the active subroutines of a computer program. ...


Architectures

Despite its outwardly similar appearance on all versions of 64-bit Windows, WOW64's implementation varies depending on the target processor architecture. For example, the version of 64-bit Windows developed for the Intel Itanium 2 processor (known at Microsoft as IA-64 architecture) uses Wow64win.dll to set up the emulation of x86 instructions within the Itanium 2's unique instruction set. That's a more computationally expensive task than the Wow64win.dll's functions on the x64 architecture, which switches the processor hardware from its 64-bit mode to compatibility mode when it's time to execute a 32-bit thread, and then handles the switch back to 64-bit mode. No emulation is required for WOW64 on x64. To a large extent, the design of a CPU, or central processing unit, is the design of its control unit. ... Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is an American multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ... Itanium 2 logo The Itanium 2 is an IA-64 64-bit microprocessor developed jointly by Hewlett-Packard (HP) and Intel, and introduced on July 8, 2002. ... Microsoft Corporation, (NASDAQ: MSFT, HKSE: 4338) is a multinational computer technology corporation with global annual revenue of US$44. ... x86 or 80x86 is the generic name of a microprocessor architecture first developed and manufactured by Intel. ... It has been suggested that some sections of this article be split into a new article entitled instruction set architecture. ... x64 is Microsoft Corporations marketing designation for the Advanced Micro Devices AMD64 and Intel EM64T 64-bit Instruction Set Extensions to the x86 architecture, which were substantially similar as of 2004. ... For the form of code consisting entirely of subroutine calls, see Threaded code. ...


The registry and the file system

The WOW64 subsystem also handles other key aspects of running 32-bit applications. For example, it's involved in managing the interaction of 32-bit apps with the Windows registry, which is somewhat different in 64-bit versions of the OS, and in providing an interface to the storage subsystem.


The operating system uses the %SystemRoot%system32 directory for its 64-bit library and executable files. This is done for backwards compatibility reasons as many legacy applications are hardcoded to use that path. When executing 32-bit applications, WOW64 redirects requests for DLLs from that directory to %SystemRoot%sysWOW64, which contains legacy libraries and executables. The %SystemRoot% variable is a special system-wide environment variable found on Microsoft Windows NT and its derivatives. ... ...


See also

x64 is Microsoft Corporations marketing designation for the Advanced Micro Devices AMD64 and Intel EM64T 64-bit Instruction Set Extensions to the x86 architecture, which were substantially similar as of 2004. ... In computing, IA-64 (short for Intel Architecture-64) is a 64-bit processor architecture developed cooperatively by Intel Corporation and Hewlett-Packard (HP), and implemented in the Itanium and Itanium 2 processors. ... Windows on Windows, commonly referred to as Wow, is an abstraction component of Microsoft Windows operating system. ...

External links

  • Windows On Windows 64
  • Windows 64-bit and Visual Basic Scripting
  • Do you really need Windows x64 ??

  Results from FactBites:
 
WOW64 - Wikipedia, the free encyclopedia (409 words)
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 Windows—including Windows XP 64-bit Editions, Windows Server 2003 x64 Edition and Windows Vista 64-bit Editions.
The WOW64 subsystem is a lightweight translation layer that has similar interfaces on all 64-bit versions of Windows.
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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