COM - Component Object Model

🧩 What COM Is

COM = Component Object Model

A Microsoft technology from the 1990s.
It defines how software components can talk to each other on Windows, even if they’re written in different languages (C++, VB6, .NET, etc.).
Think of it as Windows’ plug-in system for applications and the OS.

Office add-ins: Excel, Word, Outlook — when you load a "COM Add-in," it’s literally a DLL that exposes COM interfaces.
Windows Shell extensions: The right-click menus, thumbnail providers, property sheets in Explorer → these are COM objects registered in the registry.
ActiveX controls: Old but still around — embeddable components in IE, Excel forms, etc.
System APIs: A lot of Windows internals (DirectX, WMI, Shell.Application, etc.) are exposed as COM objects.

A COM component is identified by a CLSID (a GUID like {00024500-0000-0000-C000-000000000046} for Excel).
Programs ask Windows: “Give me the object for this CLSID”.
Windows loads the DLL/EXE that implements it.
The program then calls methods on it via interfaces (kind of like abstract base classes).

If you want Excel context menu integration beyond VBA, you’d write a COM add-in (usually in C# or C++).
If you want Explorer text/context menu extensions that go deeper than the registry, you’d write a COM shell extension.
Python can consume COM objects (e.g., import win32com.client; excel = win32com.client.Dispatch("Excel.Application")), but writing a COM component in Python is possible only with extra libraries (pywin32), and it’s awkward compared to C#/.NET.

✅ In short:
COM is Windows’ old but still critical "component glue system."

Next steps:

Map out what a COM add-in for Excel would look like (C# example)
simpler VBA approach: adding a pipeline-eds right-click action Python and VBA