Unraveling the Jargon: What is the Definition of Component Object Model?

It’s no secret that technology continues to evolve, bringing about new ways of working and increasing efficiency within the IT industry. The Component Object Model (COM) is a pivotal technology in the world of software development that has significantly impacted the creation of high-quality, reusable software components. According to studies, as of 2004, more than 70% of all new commercial software development in the Windows environment utilized COM. This system has drastically facilitated collaboration, interoperability, and code reuse for developers.

“Component Object Model (COM) is the DNA of the software world: a fundamental building block for creating reusable software components.” – Bill Gates

What is the Component Object Model? Definition of Microsoft COM

Component Object Model is a binary-interface standard that allows developers to create reusable software components that can be integrated into applications, regardless of the programming language used in their creation. It was developed by Microsoft initially for the OLE (Object Linking and Embedding) technology and has now evolved into a popular standard in software development.

The primary goal of COM is to enable communication between different software components at runtime using binary interfaces, allowing developers to build their applications in a modular way. To do this, COM essentially provides a foundation for creating, using, and managing software components in a language-agnostic manner.

ℹ️ Synonyms: COM, Microsoft COM, ActiveX, OLE, Object Linking and Embedding, Microsoft Component Object Model

How it Works

COM operates by facilitating communication between software components through a contract known as an interface. Each interface has a unique identifier called the Interface Identifier (IID), which serves as a contract for what functionality the component provides. When a client communicates with a component, it does so through its interfaces, which in turn helps ensure that the components can be reused across different programming languages.

When a client wants to utilize a specific COM object, it issues a request to the object handler or, in some cases, directly to the object’s server. Regardless of the communication method, the client receives an interface pointer, allowing it to interact with the COM object’s methods and properties as defined by the interface.

Innovatively, COM manages cross-process or remote procedure calls for developers, handling the complexities of marshaling and unmarshaling of data automatically. This allows the clients and components to communicate seamlessly, even when they reside in different processes or on separate machines.

Benefits of Using Component Object Model

• Reusability: Software components in COM can be used repeatedly, which reduces development time and cost.
• Language Independence: COM components can be written in different programming languages, allowing developers to work with their language of choice.
• Modularity: The usage of interfaces in COM allows for clear separation of concerns in complex software applications, making them easier to maintain.
• Versioning: COM supports binary compatibility, allowing new components to replace older ones without breaking the overall system.
• Scalability: COM offers robust support for distributed computing, communication, and deployment in distributed environments, making it an excellent choice for large-scale applications.

Component Object Model Use Cases

Some common use cases for COM include:

1. Automation: COM is widely used to automate tasks and expose application functionality to other applications through scripting languages such as VBScript and JavaScript.
2. Interoperability: COM facilitates the integration of components written in various programming languages, allowing developers to reuse codebases and create modular, dynamic applications.
3. Plugin or add-on support: COM components can serve as plugins or add-ons for applications, extending their functionality without modifying the original code.

Code Examples

#include <iostream>
#include <objbase.h>
#include <atlbase.h>
#include <atlcom.h>
#import "Component.dll"

using namespace std;
using namespace Component;

int main()
{
    CoInitialize(NULL);

    {
        CComPtr<IMyComponent> pComponent;
        HRESULT hr = pComponent.CoCreateInstance(CLSID_MyComponent);

        if (SUCCEEDED(hr))
        {
            BSTR result;
            pComponent->MyMethod(L"Hello", L"World", &result);

            wcout << L"Result: " << result << endl;
            SysFreeString(result);
        }
        else
        {
            cout << "Error: Failed to create COM instance" << endl;
        }
    }

    CoUninitialize();

    return 0;
}

Best Practices

When working with COM, it’s essential to adhere to best practices to ensure the efficient and effective development of software components. Some best practices include creating lean components with a single responsibility, implementing consistent error handling, and adhering to the principles of interface-based programming. Properly planning, designing, and documenting components will also make the process smoother, allowing other developers to reuse and understand them easily. Furthermore, paying attention to binary compatibility can prevent potential issues when updating or replacing components in a system.

Most Recommended Books About Component Object Model

To further understand and effectively use COM in your software development process, consider exploring the following books:

1. “Inside COM” by Dale Rogerson
2. “ATL Internals” by Chris Tavares, Kirk Fertitta, and Brent E. Rector
3. “Understanding ActiveX and OLE” by David Chappell
4. “COM and .NET Component Services” by Juval Lowy
5. “Professional COM Applications with ATL” by Sing Li and Panos Economopoulos

Conclusion

The Component Object Model has made a significant impact on software development by allowing developers to create reusable components in various programming languages. It has facilitated interoperability, modularity, and extensibility in software applications, ultimately reducing development time and costs. By understanding COM and adhering to best practices, developers can harness its power to create efficient, scalable, and maintainable systems.

Tags: architecture, component, definition, interface, jargon.