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.
Both VBX and OCX controls have now been superseded by ActiveX controls.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.