In classic COM and Visual Basic, what is a key difference between an ActiveX EXE component and an ActiveX DLL component?

Introduction / Context:
In classic COM and Visual Basic development, reusable components can be built as ActiveX DLLs or ActiveX EXEs. Choosing the correct server type affects performance, isolation, deployment, and scalability. This question checks whether you understand the fundamental architectural difference between an ActiveX EXE and an ActiveX DLL in terms of process boundaries and how the client interacts with the component.

Given Data / Assumptions:

• The technologies in focus are ActiveX EXE components and ActiveX DLL components.
• Both are COM based and can expose public classes and interfaces.
• We want to compare where they execute relative to the client process.
• We assume a Windows environment with COM registration and Visual Basic style projects.

Concept / Approach:
An ActiveX DLL is an in process COM server. It is loaded into the client process memory space as a dynamic link library. This gives better performance because calls are direct function calls without crossing process boundaries, but it also means that a crash in the DLL can crash the client. An ActiveX EXE is an out of process COM server. It runs as a separate executable process, and calls are marshaled between the client and the server. This improves isolation and can support remote access or multi client scenarios but adds overhead.

Step-by-Step Solution:
1. Recall that in process COM servers (DLLs) are loaded into the client application process. 2. Note that out of process COM servers (EXEs) run in their own process, separate from the client. 3. Remember that ActiveX DLL components are of the in process type, and ActiveX EXE components are out of process. 4. Understand that this difference affects performance, isolation, threading, and deployment strategies. 5. Compare the options and select the one that clearly describes this in process versus out of process distinction.

Verification / Alternative check:
To verify, think of how Visual Basic configures project types. When you create an ActiveX DLL project, the compiled output is a DLL and the client references it as an in process component. When you create an ActiveX EXE project, the output is an executable that can run alone and host COM classes. When a client activates a class from that EXE, the COM runtime starts the executable and marshals calls across processes. This mental model aligns with the correct option.

Why Other Options Are Wrong:

• Option B is wrong because both component types can be called by other applications; the difference is how they are hosted, not whether they are callable.
• Option C is wrong because crossing process boundaries introduces overhead, so ActiveX EXEs are usually slower than in process DLLs.
• Option D is wrong because the technologies differ significantly in process model and are not just file extension variants.

Common Pitfalls:
A common pitfall is assuming that ActiveX EXE is always better because it allows multiple clients, while ignoring the performance cost of cross process calls. Another mistake is using an ActiveX DLL for everything, even when isolation and remote access are required. Developers need to understand the trade off between performance and robustness when choosing component types. Also, misconfiguring registration and security for out of process servers can lead to subtle runtime issues.

Final Answer:
The correct statement is An ActiveX EXE runs as an out of process server in its own executable, while an ActiveX DLL runs in process inside the client application, because this describes the key architectural difference between these two COM component types.