[MSDN]Visual C++ Libraries as Shared Side-by-Side Assemblies

In Visual C++ 2005, the ATL, MFC, Standard C++, and CRT libraries support the new deployment model available on Windows XP, Windows Server 2003, and Windows Vista. The DLLs corresponding to all Visual C++ libraries have been grouped into several shared side-by-side assemblies and are installed into the native assembly cache, also called the WinSxS folder, under the operating system root directory. Similarly, while building a C++ application using Visual C++ 2005, by default the compiler and the linker generate a manifest file that describes runtime dependencies of this application on Visual C++ libraries.

Visual C++ libraries cannot be used by a C/C++ application without a manifest binding the application to these libraries. If a C/C++ application that depends on a Visual C++ library does not use a manifest, then an attempt to load the Visual C++ library as a dependent DLL from the application-local folder will result in an error message indicating that this is an unsupported way of loading a Visual C++ library.

Note:

On versions of Windows that do not support deployment of shared side-by-side assemblies, such as Windows 98 and Windows 2000 Server, the Visual C++ libraries are installed in the System32 folder and WinSxS folder under the operating system root directory. This setup enables running Visual C++ applications on these operating system versions because they do not support manifest-based binding of applications to dependent DLLs. On these operating systems, when an application is loaded, the corresponding manifest file is ignored and the operating systems searches for dependent DLLs using paths set in the current running environment. However, on upgrading the operating system to a version that support manifest-based binding, such as Windows XP, Windows Server 2003, or Windows Vista, applications built with manifests start using the DLLs installed in the WinSxS folder.

This change to the deployment model of Visual C++ libraries prevents the problem of version conflicts between DLLs that occur when you add updates or configurations to a machine, and will allow support of side-by-side installation of two different Visual C++ toolsets. It will also allow you to produce reliable, self-describing applications and components that will not conflict with existing components. For more information on the advantages of new deployment model, please see Concepts of Isolated Applications and Side-by-side Assemblies. To learn about how this may impact deployment of existing native C++ applications, please refer to Redistributing Visual C++ Files.

Visual C++ libraries have been packaged in several shared side-by-side assemblies with corresponding manifest files.

Assembly Name	DLLs included in the assembly	Visual C++ Library
Microsoft.VC90.ATL	atl90.dll	Active Template Library
Microsoft.VC90.CRT	msvcr90.dll msvcp90.dll msvcm90.dll	C Runtime Library, release DLLs
Microsoft.VC90.DebugCRT	msvcr90d.dll msvcp90d.dll msvcm90d.dll	C Runtime Library, debug DLLs
Microsoft.VC90.MFC	mfc90.dll mfcm90.dll mfc90u.dll mfcm90u.dll	Microsoft Foundation Classes, release DLLs
Microsoft.VC90.DebugMFC	mfc90d.dll mfcm90d.dll mfc90ud.dll mfcm90ud.dll	Microsoft Foundation Classes, debug DLLs
Microsoft.VC90.MFCLOC	mfc90chs.dll mfc90deu.dll mfc90esp.dll mfc90ita.dll mfc90kor.dll mfc90cht.dll mfc90enu.dll mfc90fra.dll mfc90jpn.dll	Microsoft Foundation Classes, localized resources
Microsoft.VC90.OpenMP	vcomp.dll	OpenMP Library, release DLLs
Microsoft.VC90.DebugOpenMP	Vcompd.dll	OpenMP Library, debug DLLs

When you build applications with Visual C++ 2008, you may need to redistribute Visual C++ libraries and deploy the corresponding DLLs to customers' desktops. For more information please see Deployment (C++).