Difference Between COM
When it comes to understanding the differences between COM (Component Object Model) and COM+ (Component Services), it’s essential to delve into the nuances that set them apart. COM, a foundational technology in the Windows operating system, has been around for decades, while COM+ is an extension of COM that adds additional features and services. Let’s explore the differences from various dimensions to gain a comprehensive understanding.
Basic Definition and Purpose
COM is a software component architecture developed by Microsoft. It allows software components to interact with each other, regardless of the programming language, operating system, or hardware platform. The core of COM is the concept of interfaces, which define the methods and properties that a component can expose to other components.
On the other hand, COM+ is an extension of COM that provides additional services such as transaction management, security, and load balancing. It is designed to simplify the development of distributed applications by providing a higher-level programming model and a set of services that can be easily integrated into applications.
Component Model Architecture
COM is based on a client-server architecture, where the client requests services from the server. The communication between the client and server is done through interfaces, which are defined using the IDL (Interface Definition Language). This allows components to be written in different programming languages and still communicate with each other seamlessly.
COM+ extends the client-server architecture by introducing the concept of a container. A container is a runtime environment that manages the lifecycle of components, provides services such as transaction management and security, and ensures that components are scalable and reliable.
Programming Languages and Tools
COM supports a wide range of programming languages, including C++, Visual Basic, and JScript. Developers can create COM components using these languages and expose their functionality through interfaces.
COM+ builds upon the programming languages supported by COM and adds support for additional languages such as C and VB.NET. This allows developers to leverage the power of .NET Framework when developing COM+ applications.
Services and Features
COM provides a set of core services, including interface definition, object lifetime management, and type libraries. These services enable components to be created, managed, and communicated with other components.
COM+ adds several new services and features, including transaction management, security, and load balancing. These services make it easier to develop scalable and reliable distributed applications.
Performance and Scalability
COM is designed to be lightweight and efficient, which makes it suitable for a wide range of applications. However, due to its client-server architecture, COM may not be the best choice for high-performance, distributed applications.
COM+ addresses the performance and scalability concerns of COM by introducing the concept of a container. The container manages the lifecycle of components and provides services such as transaction management and load balancing, which help improve the performance and scalability of distributed applications.
Security and Reliability
COM provides basic security features, such as access control and authentication. However, these features are limited and may not be sufficient for complex security requirements.
COM+ extends the security features of COM by providing a more robust security model. This includes features such as role-based security, audit logging, and secure communication channels. These features help ensure that distributed applications are secure and reliable.
Conclusion
In conclusion, the difference between COM and COM+ lies in their architecture, services, and features. COM is a foundational technology that provides a basic set of services for component-based development, while COM+ extends these services and adds additional features to simplify the development of distributed applications. Depending on the requirements of your application, you may choose to use COM or COM+ to achieve the desired level of performance, scalability, and security.
| Feature | COM | COM+ |
|---|---|---|
| Architecture | Client-server | Container-based |
| Programming Languages | C++, Visual Basic, JScript | C++, Visual Basic, JScript, C, VB.NET |
| Services | Interface definition, object lifetime management, type libraries | Transaction management, security, load balancing |
| Security |
