What is COM and DCOM?

Short Answer

1. COM (Component Object Model)

COM is like a rule book for how pieces of computer programs can talk to and understand each other. Imagine you have a LEGO set where each piece has a special way to connect with the others. COM ensures that these pieces fit together smoothly, no matter who made them or when. It’s used a lot in Windows computers to let different parts of programs work together, like fitting a puzzle piece into a big picture without worrying about who made the puzzle.

2. DCOM (Distributed Component Object Model)

DCOM is a super-charged version of COM. It’s like COM, but it can work over different computers connected by a network. Think of playing a game where you and your friends control different characters from your own houses. DCOM helps the game pieces (or program parts) work together smoothly, even though they’re on different computers. It makes sure everyone knows what’s happening in the game, keeping everything running fast and safe.

Detailed Answer

COM (Component Object Model)

The Component Object Model (COM) is a technology from Microsoft that lets different parts of computer programs communicate with each other. It’s a bit like how different apps on your phone can share information or work together, but for computer software. COM is special because it doesn’t matter what programming language was used to create these parts; they can still talk to each other. This makes building and updating software much easier because developers can use the best tools for each job.

Key Features:

  • Compatibility Across Languages: Developers can create components in any language that supports COM, like C++, and use them in other languages, such as Visual Basic.
  • Reusability: Once a component is made, it can be used in many different programs. This saves time and effort because developers don’t have to keep reinventing the wheel.


  • A text editor might use a spell check component made by someone else. Even if they’re made by different developers, COM ensures they work together seamlessly.

DCOM (Distributed Component Object Model)

DCOM takes COM’s ideas and extends them across networks, allowing components on different computers to interact as if they were on the same machine. It’s crucial for applications where parts of the software need to communicate over the internet or a local network, like in a big company.

Key Features:

  • Remote Procedure Calls: DCOM can call functions across the network. It’s like asking a friend in another city to check the weather there and tell you.
  • Security: DCOM has built-in ways to control who can access components and what they can do, which is vital for keeping data safe when sending it across networks.

Examples in Action:

  • An inventory system where stores in different locations update a central database in real-time. DCOM handles the communication, making sure updates are fast and secure.

Role of COM and DCOM in Modern Software

Even though newer technologies have emerged, COM and DCOM still play a role in many Windows-based systems today. They provide a robust way to build flexible, modular software. Plus, because so many existing applications use COM and DCOM, understanding them is crucial for maintaining and updating legacy systems.


COM and DCOM are like the glue and communication lines that hold and connect different software pieces, ensuring they work together smoothly, whether on the same machine or across a network. By making software components reusable and easier to integrate, COM and DCOM have had a lasting impact on how software is developed and maintained, demonstrating the power of well-designed component interaction in building complex systems.