What is COM?

If you develop Windows applications, you will often encounter COM (Component Object Model). COM provides a standard way for software components to communicate with each other.

A COM component exposes one or more interfaces:

Application > Interface > COM Component

Applications interact with interfaces rather than the internal implementation of the component. This allows components to be reused across different programming languages and applications. This concept might be familiar to you from OOP (Object-Oriented Programming)

Many Microsoft technologies are built on COM, including ActiveX controls, ADO, Microsoft Office automation, and Microsoft Transaction Server.

COM components are typically registered in the system registry before use. Understanding COM is necessary if you are going to working with many enterprise applications or Windows automation.