The Win32 application programming interface (API) defines the 32-bit members of the Windows operating system family from the programmer's point of view. Some members of the Windows family use the entire Win32 API, while others use subsets.
The Microsoft Foundation Class Library (MFC) encapsulates or "wraps" most (but not all) of the Win32 API. MFC and earlier versions 2.x encapsulated the 16-bit Windows API. In general, MFC provides classes that represent key Windows objects, such as windows, dialog boxes, brushes, pens, and fonts. The member functions of these classes wrap most of the important Win32 API functions associated with the encapsulated object. That is, the MFC class member function calls the Win32 API function (you can do other things as well).
Microsoft Windows SDK and its predecessors Platform SDK and .NET Framework SDKs are Microsoft Software Development Kits (SDKs) that contain documentation, header files, libraries, samples, and tools necessary to develop applications for Microsoft Windows and the .NET Framework . Platform SDK specializes in developing applications for Windows 2000, XP and Windows Server 2003. .NET Framework SDK is dedicated to developing applications for the .NET Framework 1.1 and .NET Framework 2.0. Windows SDK is the successor of the two and supports the development of applications for Windows XP and later, as well as .NET Framework 3.0 and later.
Platform SDK is the successor to the original Microsoft Windows SDK for Windows 3.1 and Microsoft Win32 SDK for Windows 9x. It was released in 1999 and is the oldest SDK. Platform SDK contains compilers, tools, documentation, header files, libraries and samples needed for software development in IA-32, x64 and IA-64 CPU architectures. However, the .NET Framework SDK came to be with the .NET Framework. Starting with Windows Vista, the Platform SDK, .NET Framework SDK, Tablet PC SDK, and Windows Media SDK are replaced with a new unified kit called the Windows SDK. However, the .NET Framework 1.1 SDK is not included because the .NET Framework 1.1 is not included with Windows Vista. (Windows Media Center SDK for Windows Vista ships separately). DirectX SDK was merged into the Windows SDK with the Windows 8 version.
Windows SDK allows the user to specify the components to be installed and where to install them. It integrates with Visual Studio so that multiple copies of the components they have are not installed; However, there are compatibility warnings if either is not from the same time. The information displayed may be filtered by content, such as displaying only new Windows Vista content, .NET Framework content only, or displaying content for a specific language or technology.
Windows SDK available for free; They were once available in the Microsoft Download Center, but were moved to MSDN in 2012.
A developer may want to use an older SDK for a particular reason. For example, the Windows Server 2003 Platform SDK released in February 2003 was the last SDK to provide full Visual Studio 6.0 support. Some earlier versions of PSDK can still be downloaded from the Microsoft Download Center; Others can be ordered on CD / DVD.