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RCW is used for making a NET compnent talk to a COM component. CCW is used for Com to .NET communication.

RCW is used for making a NET compnent talk to a com component. CCW is used for Com to .NET communication.

Queued Components, a key feature of COM+ and based on Microsoft MESSAGE Queuing SERVICES (MSMQ), provides an easy way to invoke and execute components asynchronous. Processing can occur without regard to the availability or accessibility of either the sender or receiver. A HOME SHOPPING network is an example of the type of application that might benefit from asynchronous processing. In this asynchronous, disconnected scenario where viewers phone in to several operators, orders are taken en masse and are then queued for later retrieval and processing by the server.

Queued Components, a key feature of COM+ and based on Microsoft Message Queuing Services (MSMQ), provides an easy way to invoke and execute components asynchronous. Processing can occur without regard to the availability or accessibility of either the sender or receiver. A home shopping network is an example of the type of application that might benefit from asynchronous processing. In this asynchronous, disconnected scenario where viewers phone in to several operators, orders are taken en masse and are then queued for later retrieval and processing by the server.

QueryInterface to A will delegate request to B which, in turn, will delegate request for the INTERFACE to C. This POINTER will be RETURNED to the CLIENT.

QueryInterface to A will delegate request to B which, in turn, will delegate request for the interface to C. This pointer will be returned to the client.

While accessing the DCOM COMPONENT you have to PROVIDE COSERVERINFO STRUCTURE. This structure is having the information about where the component is.

While accessing the DCOM component you have to provide COSERVERINFO structure. This structure is having the information about where the component is.

There are two KIND components:

1. InProc

2. OutProc

We can use both as DCOM SERVERS, its upto our DESIGN.

There are two kind components:

1. InProc

2. OutProc

We can use both as DCOM servers, its upto our design.

• No COMPATIBILITY
• PROJECT Compatibility
• BINARY Compatibility

Object references in COM is accounted USING TWO methods of IUnknown INTERFACE (AddRef and Release).

AddRef: Increments a reference count WHEREAS "Release" DECREMENTS the count. When the count of the reference is zero the DLL is unloaded from memory.

Object references in COM is accounted using two methods of IUnknown Interface (AddRef and Release).

AddRef: Increments a reference count whereas "Release" decrements the count. When the count of the reference is zero the DLL is unloaded from memory.

In order to call your DLL as COM dll, you have to follow some RULES to develop the dll. If those rules are there then only your DLL will be called as COM dll.

COM is a SPECIFICATION SET of rules to develop BINARIES, COM is not a language.

In order to call your DLL as COM dll, you have to follow some rules to develop the dll. If those rules are there then only your DLL will be called as COM dll.

COM is a specification set of rules to develop binaries, COM is not a language.

COM (COMPONENT Object MODEL) technology in the Microsoft WINDOWS-family of Operating Systems enables software components to communicate. COM is used by DEVELOPERS to create re-usable software components, LINK components together to build applications, and take advantage of Windows services.

COM (Component Object Model) technology in the Microsoft Windows-family of Operating Systems enables software components to communicate. COM is used by developers to create re-usable software components, link components together to build applications, and take advantage of Windows services.

COM Dll exposes Interface on the contrary to normal DLL that exports functions. Clients create the POINTER to COMDLL's interface to call the methods defined by the COMPONENT that implements the interface. 

That results in isolation of IMPLEMENTATION and definition of method in the interface. Client doesnt need to RELINK or recompile the CODE if method in the com dll changes as far as the definition of the interface remains same.

COM Dll exposes Interface on the contrary to normal DLL that exports functions. Clients create the pointer to COMDLL's interface to call the methods defined by the component that implements the interface. 

That results in isolation of implementation and definition of method in the interface. Client doesnt need to relink or recompile the code if method in the com dll changes as far as the definition of the interface remains same.

CoInitialize will initialize the COM library and will move the executing thread to a STA or SINGLE Threaded Apartment Apartment is the LOGICAL entity where threads LIVE.

CoInitialize will initialize the COM library and will move the executing thread to a STA or Single Threaded Apartment Apartment is the logical entity where threads live.

1. Defines a BINARY STANDARD for COMPONENT interoperability 
2. Is programming language-independent 
3. Is provided on multiple platforms (Microsoft® Windows®, 
4. Microsoft Windows NT™, Apple® Macintosh®, UNIX®) 
5. PROVIDES for ROBUST evolution of component-based applications and systems 
6. Is extensible

Open the dll in dependency walker APPLICATION(depends.exe).

If the dll is having FOLLOWING FUNCTIONS:

• DLLRegisterServer
• DLLUnRegisterServer
• DLLCanUnloadNow
• DLLGetClassObject

It is a COM DLL OTHERWISE it is not.

Open the dll in dependency walker application(depends.exe).

If the dll is having following functions:

It is a COM DLL otherwise it is not.

NO.

NO.

USE DCOMCONFIG.EXE

use DCOMCONFIG.EXE

Query Interface METHOD is used to get the pointer to the interface specified in one of the parameters of this method. Client then USES this pointer to call the method of the component. 

ADDREF and Release are used to increase and decrease the count of the instance of component LOADED in MEMORY respectively. when the count reaches zero the component is unloaded.

Query Interface method is used to get the pointer to the interface specified in one of the parameters of this method. Client then uses this pointer to call the method of the component. 

AddRef and Release are used to increase and decrease the count of the instance of component loaded in memory respectively. when the count reaches zero the component is unloaded.

IUnknown is a type of COM Interface.

Every COM class implements an interface NAMED IUnKnown.

IUnKnown contains three methods:

1. HRESULT QueryInterface()
2. ULONG ADDREF()
3. ULONG RELEASE()

IUnknown is a type of COM Interface.

Every COM class implements an interface named IUnKnown.

IUnKnown contains three methods:

RETURNS a pointer to the current interface if SUCCESSFUL or 

E_NOINTERFACE otherwise.

Returns a pointer to the current interface if successful or 

E_NOINTERFACE otherwise.

• Reads RootClassesProgId for the matching ProgID
• Reads RootClassesProgId for the matching CLSID. The CLSID is READ from the above step.
• From the CLSID key, the server type and image filename is known.
• Depending UPON the server type, it starts the server.
• Calls CoGetClassObject FUNCTION to get a HANDLE to the FACTORY object.
• Then calls createinstance on the factory interface to get the pointer to the derived object.

To CREATE the instance of COM componet use the following 

WIN32 APIs

To access the component that was there in local SYSTEM use following API

COCREATEINSTANCE(clsid,NULL(used for 

AGGREGATION),CLSCTX_ALL,Interface_GUID,(void**)

&pRequestedInterface );

To access the COM componet remotely use the following API

CoCreateInstanceEx

(CLSID,NULL,CLSCTX_ALL,COSERVERINFO,Interface_GUID,MULTI_QI*

);

To create the instance of COM componet use the following 

WIN32 APIs

To access the component that was there in local system use following API

CoCreateInstance(clsid,NULL(used for 

aggregation),CLSCTX_ALL,Interface_GUID,(void**)

&pRequestedInterface );

To access the COM componet remotely use the following API

CoCreateInstanceEx

(CLSID,NULL,CLSCTX_ALL,COSERVERINFO,Interface_GUID,MULTI_QI*

);

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.

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.

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.

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.

For the first QUESTION, Yes, we can since the QueryInterface () RULES of thumb suggest that if we can query an interface of C from B, we should be able to query the viceversa.The IUnknown implementation of both the objects has to do the 'magic'.

For the second question, Aggregation bounds outer and inner objects together and gives the user the interface pointers of either objects to access it directly so that the user never knows the objects are aggregated. 

But when containment is used, the interface of inner object never exposed to the client directly rather the outer object receives the calls and forwards internally. Here ALSO, the user doesn't KNOW the objects are contained.

For the first question, Yes, we can since the QueryInterface () rules of thumb suggest that if we can query an interface of C from B, we should be able to query the viceversa.The IUnknown implementation of both the objects has to do the 'magic'.

For the second question, Aggregation bounds outer and inner objects together and gives the user the interface pointers of either objects to access it directly so that the user never knows the objects are aggregated. 

But when containment is used, the interface of inner object never exposed to the client directly rather the outer object receives the calls and forwards internally. Here also, the user doesn't know the objects are contained.

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).

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).