Porting and Upgrading OCXs and VBXs
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As of Visual C++ 4.0, the Microsoft OLE Control Development Kit (CDK) became fully integrated with the Microsoft Foundation Class Library (MFC). For development of 32-bit ActiveX controls (formerly OLE controls), use the ActiveX Template library (ATL) or the MFC library.
You can use 16-bit controls only in 16-bit containers and 32-bit controls only in 32-bit containers. However, you can write 32-bit controls, then port them to 16 bits. (Some control features are not available in 16-bit controls.)
You can use Visual Basic controls in your Visual C++ projects, and vice versa.
To port or upgrade your ActiveX controls and Visual Basic controls, see these in-depth articles: