1) Explain COM?

1) Explain COM?

 component object module is com.It defines standard binary

 interface between object modules.this interface defines the

 function calling methodology standardised structure.

        COM is used by developers to create re-usable software components.

2) What is Moniker?

An object that implements the IMoniker interface. A moniker 

acts as a name that uniquely identifies a COM object. In 

the same way that a path identifies a file in the file 

system, a moniker identifies a COM object in the directory 

namespace.

3)What is In – proc?

In-proc server is a COM component, when instance is the 

server is loaded into the caller process space. In-Proc 

server can be easily identified by .dll extension.

Out-of-Proc server is a COM component that run in its own 

process space and for any instances created by the users, a 

proxy is created within the users process space. Proxy is 

responsible for interacting with the server to carry out 

operation on behalf of the client. (.exe extension).

There are two kind of components: in-process and out-of-

process. This is identified by where the component runs 

when it is invoked. That is, (i) if a component sits inside 

the calling process's address space, it is an in-process 

component and (ii) if a component runs in its own address 

space when invoked, it is an out-of-process component.

The data transmission between out-of-process component and 

the calling process must be carried out by some IPC 

mechanism while it is not required for the other one.

4) What is IUnknown? What methods are provided by IUnknown?

Iunknow is the base interface for any com component.

it supports three methods

addref()

release()

queryinterface()

5) What is the difference, if any, between OLE and COM?

OLE is a set of technologies to support linking and 

embedding. COM lies in OLE as one of the technologies. COM 

defines a binary standard / set of rules for developing 

reusable components.

6) QueryInterface?

Every interface derived from IUnknown, so every interface implementation of Queryinterface. this method queries an object using the IID of the interface to which the caller wants a pointer.

QueryInterface retrieves a pointer to the interface, while also calling AddRef. Otherwise, it returns the E_NOINTERFACE error code.