OCX是什么英文的缩写？

It's a computer term, used with Microsoft Windows:

OCX = OLE Custom Control
OCX = OLE Control eXtension (computer term ActiveX file extension)

Object Linking and Embedding (OLE) is a distributed object system and protocol developed by Microsoft.

OLE allows an editor to "farm out" part of a document to another editor and then reimport it. For example, a desktop publishing system might send some text to a word processor or a picture to a bitmap editor using OLE. The main benefit of using OLE, next to reduced file size, is the ability to create a master file. References to data in this file can be made and the master file can then have changed data which will then take effect in the referenced document.

Its primary use is for managing compound documents, but it is also used for transferring data between different applications using drag and drop and clipboard operations. The concept of "embedding" is also central