Short for OLE Control Extension, an independent program module that can be accessed by other programs in a Windows environment. OCX controls end with a .ocx extension. OCX controls represent Microsoft's second generation of control architecture, the first being VBX controls written in Visual Basic.
A component software technology from Microsoft that enables a Windows program to add functionality by calling ready-made components. Generally called "OLE controls" or "OLE custom controls," they appear to the end user as just another part of the program.
OCXs are Microsoft's second-generation component architecture. Unlike first-generation 16-bit Visual Basic controls (VBXs), which were only written in Visual Basic, OCXs can be written in several languages and come in 16-bit and 32-bit versions. OCXs were renamed ActiveX controls and continue to use the .OCX file extension.
Both VBX and OCX controls have now been superseded by ActiveX controls.
However, ActiveX is backward compatible with OCX controls, which means that ActiveX containers, such as Microsoft's Internet Explorer, can execute OCX components.