Que: What is the difference between GetMessage and PeekMessage ?
Ans: GetMessage function waits for a message to be placed in the queue before returning where as PeekMessage function does not wait for a message to be placed in the queue before returning.
Que: What’s the difference between PostMessage and SendMessage?
Ans: The PostMessage function places (posts) a message in the message queue associated with the thread that created the specified window and then returns without waiting for the thread to process the message.
The SendMessage function sends the specified message to a window or windows. The function calls the window procedure for the specified window and does not return until the window procedure has processed the message.
Que: How to create a model less dialog?
Ans: m_pModeless is a variable of type CDialog or any of its descendants.
m_pModeless->Create(IDD_DIALOG1, this);
m_pModeless->ShowWindow(SW_SHOW);
this pointer as a paramter suggest we are creating a child dialog of the current dialog/window.
Que: How to setup a timer?
Ans: Use the SetTimer function
UINT_PTR SetTimer( HWND hWnd, UINT_PTR nIDEvent, UINT uElapse,
TIMERPROC lpTimerFunc );
To kill the timer use
BOOL KillTimer(int nIDEvent);
Where the nIDEvent is the ID returned by the SetTimer Function.
Que: Name the Synchronization objects ?
Ans: Following are the synchronization objects
1) Critical Section 2) Event 3) Mutex 4) Semaphore
Classes provided for above synchronization objects are:
1) CCriticalSection 2) CEvent 3) CMutex 4) CSemaphore
Que: What Is CMutex ?
Ans: An object of class CMutex represents a “mutex” — a synchronization object that allows one thread mutually exclusive access to a resource. Mutexes are useful when only one thread at a time can be allowed to modify data or some other controlled resource. For example, adding nodes to a linked list is a process that should only be allowed by one thread at a time. By using a CMutex object to control the linked list, only one thread at a time can gain access to the list.
To use a CMutex object, construct the CMutex object when it is needed. Specify the name of the mutex you wish to wait on, and that your application should initially own it. You can then access the mutex when the constructor returns. Call CSyncObject::Unlock when you are done accessing the controlled resource.
An alternative method for using CMutex objects is to add a variable of type CMutex as a data member to the class you wish to control. During construction of the controlled object, call the constructor of the CMutex data member specifying if the mutex is initially owned, the name of the mutex (if it will be used across process boundaries), and desired security attributes.
To access resources controlled by CMutex objects in this manner, first create a variable of either type CSingleLock or type CMultiLock in your resource’s access member function. Then call the lock object’s Lock member function (for example, CSingleLock::Lock). At this point, your thread will either gain access to the resource, wait for the resource to be released and gain access, or wait for the resource to be released and time out, failing to gain access to the resource. In any case, your resource has been accessed in a thread-safe manner. To release the resource, use the lock object’s Unlock member function (for example, CSingleLock::Unlock), or allow the lock object to fall out of scope
Que: What is thread & process?
Ans: Threads are similar to processes, but differ in the way that they share resources. Threads are distinguished from processes in that processes are typically independent, carry considerable state information and have separate address spaces. Threads typically share the memory belonging to their parent process.
Que: what is the use of AFX_MANAGE_STATE ?
Ans: By default, MFC uses the resource handle of the main application to load the resource template. If you have an exported function in a DLL, such as one that launches a dialog box in the DLL, this template is actually stored in the DLL module. You need to switch the module state for the correct handle to be used. You can do this by adding the following code to the beginning of the function:
AFX_MANAGE_STATE(AfxGetStaticModuleState( ));
This swaps the current module state with the state returned from AfxGetStaticModuleState until the end of the current scope. If all your resources lies in the single DLL you can even change the default handle to the DLL handle with the help of AfxSetResourceHandle function.
Ans: GetMessage function waits for a message to be placed in the queue before returning where as PeekMessage function does not wait for a message to be placed in the queue before returning.
Que: What’s the difference between PostMessage and SendMessage?
Ans: The PostMessage function places (posts) a message in the message queue associated with the thread that created the specified window and then returns without waiting for the thread to process the message.
The SendMessage function sends the specified message to a window or windows. The function calls the window procedure for the specified window and does not return until the window procedure has processed the message.
Que: How to create a model less dialog?
Ans: m_pModeless is a variable of type CDialog or any of its descendants.
m_pModeless->Create(IDD_DIALOG1, this);
m_pModeless->ShowWindow(SW_SHOW);
this pointer as a paramter suggest we are creating a child dialog of the current dialog/window.
Que: How to setup a timer?
Ans: Use the SetTimer function
UINT_PTR SetTimer( HWND hWnd, UINT_PTR nIDEvent, UINT uElapse,
TIMERPROC lpTimerFunc );
To kill the timer use
BOOL KillTimer(int nIDEvent);
Where the nIDEvent is the ID returned by the SetTimer Function.
Que: Name the Synchronization objects ?
Ans: Following are the synchronization objects
1) Critical Section 2) Event 3) Mutex 4) Semaphore
Classes provided for above synchronization objects are:
1) CCriticalSection 2) CEvent 3) CMutex 4) CSemaphore
Que: What Is CMutex ?
Ans: An object of class CMutex represents a “mutex” — a synchronization object that allows one thread mutually exclusive access to a resource. Mutexes are useful when only one thread at a time can be allowed to modify data or some other controlled resource. For example, adding nodes to a linked list is a process that should only be allowed by one thread at a time. By using a CMutex object to control the linked list, only one thread at a time can gain access to the list.
To use a CMutex object, construct the CMutex object when it is needed. Specify the name of the mutex you wish to wait on, and that your application should initially own it. You can then access the mutex when the constructor returns. Call CSyncObject::Unlock when you are done accessing the controlled resource.
An alternative method for using CMutex objects is to add a variable of type CMutex as a data member to the class you wish to control. During construction of the controlled object, call the constructor of the CMutex data member specifying if the mutex is initially owned, the name of the mutex (if it will be used across process boundaries), and desired security attributes.
To access resources controlled by CMutex objects in this manner, first create a variable of either type CSingleLock or type CMultiLock in your resource’s access member function. Then call the lock object’s Lock member function (for example, CSingleLock::Lock). At this point, your thread will either gain access to the resource, wait for the resource to be released and gain access, or wait for the resource to be released and time out, failing to gain access to the resource. In any case, your resource has been accessed in a thread-safe manner. To release the resource, use the lock object’s Unlock member function (for example, CSingleLock::Unlock), or allow the lock object to fall out of scope
Que: What is thread & process?
Ans: Threads are similar to processes, but differ in the way that they share resources. Threads are distinguished from processes in that processes are typically independent, carry considerable state information and have separate address spaces. Threads typically share the memory belonging to their parent process.
Que: what is the use of AFX_MANAGE_STATE ?
Ans: By default, MFC uses the resource handle of the main application to load the resource template. If you have an exported function in a DLL, such as one that launches a dialog box in the DLL, this template is actually stored in the DLL module. You need to switch the module state for the correct handle to be used. You can do this by adding the following code to the beginning of the function:
AFX_MANAGE_STATE(AfxGetStaticModuleState( ));
This swaps the current module state with the state returned from AfxGetStaticModuleState until the end of the current scope. If all your resources lies in the single DLL you can even change the default handle to the DLL handle with the help of AfxSetResourceHandle function.
Ans:- Threads are similar to processes, but differ in the way that they share resources. Threads are distinguished from processes in that processes are typically independent, carry considerable state information and have separate address spaces. Threads typically share the memory belonging to their parent process.
Q:- what is the use of AFX_MANAGE_STATE ?
Ans:- By default, MFC uses the resource handle of the main application to load the resource template. If you have an exported function in a DLL, such as one that launches a dialog box in the DLL, this template is actually stored in the DLL module. You need to switch the module state for the correct handle to be used. You can do this by adding the following code to the beginning of the function:
AFX_MANAGE_STATE(AfxGetStaticModuleState( ));
This swaps the current module state with the state returned from AfxGetStaticModuleState until the end of the current scope. If all your resources lies in the single DLL you can even change the default handle to the DLL handle with the help of AfxSetResourceHandle function.
Q:- Why wizards generate enum IDD for dialogs?
Ans:- It's good programming practice to do it this way, as from the client code you can always refer to the CMyDlg::IDD without worrying what the actual constant is.
Q:- What is CArchive class does?
Ans:- The CArchive class allows you to save a complex network of objects in a permanent binary form (usually disk storage) that persists after those objects are deleted. Later you can load the objects from persistent storage, reconstituting them in memory. This process of making data persistent is called “serialization.”
Q:- How to handle command line arguements from simple MFC application ?
Ans:- m_lpCmdLine Corresponds to the lpCmdLine parameter passed by Windows to WinMain. Points to a null-terminated string that specifies the command line for the application. Use m_lpCmdLine to access any command-line arguments the user entered when the application was started. m_lpCmdLine is a public variable of type LPTSTR.
BOOL CMyApp::InitInstance()
{
// ...
if (m_lpCmdLine[0] == _T('\0'))
{
// Create a new (empty) document.
OnFileNew();
}
else
{
// Open a file passed as the first command line parameter.
OpenDocumentFile(m_lpCmdLine);
}
// ...
}
Q:- What is the base class for MFC Framework ?
Ans:-CObject
Q:- If I derive a new class from CObject what are the basic features my derived will get?
Ans:-Searialization, Debugging support, Runtime time class information, compatibility with collection classes.
Q:- What is the use of CCmdTarget ?
Ans:- It is the base class for the MFC library message map architecture.Which maps commands/messages to the member functions to handle them. Classes derived from this are CWnd,CWinApp,CFrameWnd,CView, CDocument
Q:- What is document-view architecture ? Give me one real time example for SDI ?
Ans:- Document/view architecture, which defines a program structure that relies on document objects to hold an application's data and on view objects to render views of that data. MFC provides the infrastructure for documents and views in the classes CDocument and CView. example of SDI is a wordpad application
Q:- Can you explain the relashionship between document,frame and view ?
Ans:- The frame window is the application's top-level window. It's normally a WS_OVERLAPPEDWINDOW-style window with a resizing border, a title bar, a system menu, and minimize, maximize, and close buttons.
The view is a child window sized to fit the frame window so that it becomes the frame window's client area.
The application's data is stored in the document object, a visible representation of which appears in the view.
For an SDI application, the frame window class is derived from CFrameWnd, the document class is derived from CDocument, and the view class is derived from CView or a related class such as CScrollView.
Q:- How to access document object from view ?
Ans:- Using GetDocument() function within a CView class.
Q:- What is the entry point for window based applications ?
Ans:- WinMain() is the entry point for window based applications.
Q:- Explain the flow for a simple win32 based application ?
Ans:- Starting point for win32 based applications is WinMain()
WinMain begins by calling the API function RegisterClass to register a window class. The window class(WNDCLASS) defines important characteristics of a window such as its window procedure address, its default background color, and its icon. Once the WNDCLASS is registered, WinMain calls the all-important CreateWindow function to create the application's window. WinMain follows CreateWindow with calls to ShowWindow and UpdateWindow, which make the window visible and ensure that its WM_PAINT handler is called immediately. Next comes the message loop. In order to retrieve and dispatch messages, WinMain executes a simple while loop that calls the GetMessage, TranslateMessage, and DispatchMessage API functions repeatedly. GetMessage checks the message queue. If a message is available, it is removed from the queue and copied to msg; TranslateMessage converts a keyboard message denoting a character key to an easier-to-use WM_CHAR message, and DispatchMessage dispatches the message to the window procedure. The message loop executes until GetMessage returns 0, which happens only when a WM_QUIT message is retrieved from the message queue. When this occurs, WinMain ends and the program terminates.
Q:- What is model and modeless dialog box ? Give some examples?
Ans:- When we create Modal Dialog Box we can't move to other windows until this dialog is closed. For eg: MessageBox, where we can't move to the other window until we press ok or cancel.
When we create Modeless Dilaog Box we can swap to the other windows. For eg: like a conventional window.
Q:- How to create open & save dialogs ?
Ans:- In CommonDialogs class we have to use CFileDialog class where the first parameter TRUE for open dialog and FALSE for Save dialog.
For file open:
CFileDialog SampleDlg(TRUE,NULL,NULL,OFN_OVERWRITEPROMPT,"Text Files (*.txt)|*.txt|Comma Separated Values(*.csv)|*.csv||");
int iRet = SampleDlg.DoModal();
Q:- What is CSingleDocTemplate?
Ans:- It’s a document template class used to create single document interface SDI applications. Only one document can be opened at a time. It identifies the document class used to manage the application's data, the frame window class that encloses views of that data, and the view class used to draw visual representations of the data. The document template also stores a resource ID that the framework uses to load menus, accelerators, and other resources that shape the application's user interface.
Q:- What is the difference between hinstance and hprevinstance in WinMain function?
Ans:- hInstance is used for things like loading resources and any other task which is performed on a per-module basis. A module is either the EXE or a DLL loaded into your program. hPrevInstance used to be the handle to the previously run instance of your program (if any) in Win16. It is always NULL for Win32 programs.
Q:- Explain about MDI and CMultiDocTemplate ?
Ans:- MDI applications are designed using the doc-view architectures in which there could be many views associated with a single document object and an application can open multiple docuements at the same time for eg:WORD.
In MDI terms, your main window is called the Frame, this is probably the only window you would have in a SDI (Single Document Interface) program. In MDI there is an additional window, called the MDI Client Window which is a child of your Frame window. CMultiDocTemplate is the document template class used to create MDI applications..The document template also stores a resource ID that the framework uses to load menus, accelerators, and other resources that shape the application's user interface.
Q:- Which are the different controls in MFC ?
Ans:- CAnimateCtrl, CButton, CEdit, CListBox, CComboBox, CRichEditCtrl, CStatic, TreeCtrl, ToolTipCtrl, IPAddressCtrl, TabCtrl,CDa teTimeCtrl, HeaderCtrl, ListCtrl, MonthCalCtrl, OleCtrl, ProgressCtrl, ScrollBar, SliderCtrl, StatusBarCtrl, TollBarCtrl etc.,
Q:- What is the use of OnInitDialog ?
Ans:- This message is sent to the dialog box during the Create, CreateIndirect, or DoModal calls, which occur immediately before the dialog box is displayed. This can be used to intialize the dialog controls or show/hide the controls etc.,
Q:- What is the functioning of UpdateData() funciton ?
Ans:- This is to initialize data in a dialog box, or to retrieve and validate dialog data.
The framework automatically calls UpdateData with bSaveAndValidate set to FALSE when a modal dialog box is created in the default implementation of CDialog::OnInitDialog. The call occurs before the dialog box is visible. The default implementation of CDialog::OnOK calls this member function with bSaveAndValidate set to TRUE to retrieve the data, and if successful, will close the dialog box. If the Cancel button is clicked in the dialog box, the dialog box is closed without the data being retrieved.
Q:- How to update all the views whenever document got updated ?
Ans:- call UpdateAllViews()- which updates all views associated with the document by calling OnUpdate() function of all the views.
Q:- How to handle RTTI in MFC ?
Ans:- Run-Time Type Information is a mechanism that allows the type of an object to be determined during the program execution. 3 main elements to RTTI in MFC are
1. Dynamic_cast operator Used for conversion of polymorphic types.
2. typeid - used for identifying the exact type of an object
3. type_info classused to hold the type information returned by typeid.
Q:- What is serialization ?which function is responsible for serializing data ?
Ans:- Searialization is the process of streaming the object data to or from a persistent storage medium. It's useful in Doc-View Architecture. CObject :: Serialize() function is used to do serialization.
Q:- what is the use of Mutex and critical section ?
Ans:- Mutex as the name suggest allows a mutullay exclusive access to a shared resource among the threads. Critical section is a piece of code that can be executed safely to be accessed by two or more threads. Criticalsection provides synchronization means for one process only, while mutexes allow data synchronization across processes. Means two or more threads can share the common resources among more than one application or process boundaries in mutex.
Ans:- When we create Modal Dialog Box we can't move to other windows until this dialog is closed. For eg: MessageBox, where we can't move to the other window until we press ok or cancel.
When we create Modeless Dilaog Box we can swap to the other windows. For eg: like a conventional window.
Q:- How to create open & save dialogs ?
Ans:- In CommonDialogs class we have to use CFileDialog class where the first parameter TRUE for open dialog and FALSE for Save dialog.
For file open:
CFileDialog SampleDlg(TRUE,NULL,NULL,OFN_OVERWRITEPROMPT,"Text Files (*.txt)|*.txt|Comma Separated Values(*.csv)|*.csv||");
int iRet = SampleDlg.DoModal();
Q:- What is CSingleDocTemplate?
Ans:- It’s a document template class used to create single document interface SDI applications. Only one document can be opened at a time. It identifies the document class used to manage the application's data, the frame window class that encloses views of that data, and the view class used to draw visual representations of the data. The document template also stores a resource ID that the framework uses to load menus, accelerators, and other resources that shape the application's user interface.
Q:- What is the difference between hinstance and hprevinstance in WinMain function?
Ans:- hInstance is used for things like loading resources and any other task which is performed on a per-module basis. A module is either the EXE or a DLL loaded into your program. hPrevInstance used to be the handle to the previously run instance of your program (if any) in Win16. It is always NULL for Win32 programs.
Q:- Explain about MDI and CMultiDocTemplate ?
Ans:- MDI applications are designed using the doc-view architectures in which there could be many views associated with a single document object and an application can open multiple docuements at the same time for eg:WORD.
In MDI terms, your main window is called the Frame, this is probably the only window you would have in a SDI (Single Document Interface) program. In MDI there is an additional window, called the MDI Client Window which is a child of your Frame window. CMultiDocTemplate is the document template class used to create MDI applications..The document template also stores a resource ID that the framework uses to load menus, accelerators, and other resources that shape the application's user interface.
Q:- Which are the different controls in MFC ?
Ans:- CAnimateCtrl, CButton, CEdit, CListBox, CComboBox, CRichEditCtrl, CStatic, TreeCtrl, ToolTipCtrl, IPAddressCtrl, TabCtrl,CDa teTimeCtrl, HeaderCtrl, ListCtrl, MonthCalCtrl, OleCtrl, ProgressCtrl, ScrollBar, SliderCtrl, StatusBarCtrl, TollBarCtrl etc.,
Q:- What is the use of OnInitDialog ?
Ans:- This message is sent to the dialog box during the Create, CreateIndirect, or DoModal calls, which occur immediately before the dialog box is displayed. This can be used to intialize the dialog controls or show/hide the controls etc.,
Q:- What is the functioning of UpdateData() funciton ?
Ans:- This is to initialize data in a dialog box, or to retrieve and validate dialog data.
The framework automatically calls UpdateData with bSaveAndValidate set to FALSE when a modal dialog box is created in the default implementation of CDialog::OnInitDialog. The call occurs before the dialog box is visible. The default implementation of CDialog::OnOK calls this member function with bSaveAndValidate set to TRUE to retrieve the data, and if successful, will close the dialog box. If the Cancel button is clicked in the dialog box, the dialog box is closed without the data being retrieved.
Q:- How to update all the views whenever document got updated ?
Ans:- call UpdateAllViews()- which updates all views associated with the document by calling OnUpdate() function of all the views.
Q:- How to handle RTTI in MFC ?
Ans:- Run-Time Type Information is a mechanism that allows the type of an object to be determined during the program execution. 3 main elements to RTTI in MFC are
1. Dynamic_cast operator Used for conversion of polymorphic types.
2. typeid - used for identifying the exact type of an object
3. type_info classused to hold the type information returned by typeid.
Q:- What is serialization ?which function is responsible for serializing data ?
Ans:- Searialization is the process of streaming the object data to or from a persistent storage medium. It's useful in Doc-View Architecture. CObject :: Serialize() function is used to do serialization.
Q:- what is the use of Mutex and critical section ?
Ans:- Mutex as the name suggest allows a mutullay exclusive access to a shared resource among the threads. Critical section is a piece of code that can be executed safely to be accessed by two or more threads. Criticalsection provides synchronization means for one process only, while mutexes allow data synchronization across processes. Means two or more threads can share the common resources among more than one application or process boundaries in mutex.
Q:- What is socket?
Ans:- A "socket" is an endpoint of communication: an object through which your application communicates with other Windows Sockets applications across a network.The two MFC Windows Sockets programming models are supported by the following classes: CAsyncSocket and CSocket
Q:- What is the difference between Synchronous sockets and asynchronous sockets?
Ans:- Consider a server application that is listening on a specific port to get data from clients. In synchronous receiving, while the server is waiting to receive data from a client, if the stream is empty the main thread will block until the request for data is satisfied. Hence, the server cannot do anything else until it receives data from the client. If another client attempts to connect to the server at that time, the server cannot process that request because it is blocked on the first client. This behavior is not acceptable for a real-world application where we need to support multiple clients at the same time.
In asynchronous communication, while the server is listening or receiving data from a client, it can still process connection requests from other clients as well as receive data from those clients. When a server is receiving asynchronously, a separate thread (at the OS level) listens on the socket and will invoke a callback function when a socket event occurs. This callback function in turn will respond and process that socket event.
Q:- Have you ever used win32 APIs ?
Ans:- MFC is a wrapper around win32 API, It provides classes which uses the win32 API, Some of the API's we usually work with are : GetDlgItemInt,GetDlgItemText,GetWindowTextA,Messag eBoxA,CreateFile,CreateMutex,CreateEvent,WaitForSi ngleObject,CreateWindow,ShowWindow etc.,
Q:- What is the difference between ANSI Code and UNICODE ?
Ans:- ANSI code represents 8bytes data where UNICODE represents 16bytes data for supporting universal languages. One major draw back to ASCII was you could only have 256 different characters. However, languages such as Japanese and Arabic have thousands of characters. Thus ASCII would not work in these situations. The result was Unicode which allowed for up to 65,536 different character
Q:- What is the difference between regular dlls and extended dlls?
Ans:- Regular dlls wraps only the c/c++ functions. Where extention dlls include c++ interfaces where we can create the objects of it and use in our classes. Extended dlls support object oriented concepts.Regural dlls uses mfc internally and exported functions can be used by any mfc or non-mfc applications.Extention dlls implements reusable classes derived from mfc library,built using dll version of mfc.Only mfc executables(applications/dll-shared version of mfc) can use extention dlls.extention dlls used for passing mfc derived objects b/w applications and dlls. Regulardlls linked both statically and dynamically but extended dlls links dynamically.
Q:- What is a message map, and what is the advantage of a message map over virtual function ?
Ans:- MessageMap is a logical table that maps the windows messages to the member functions of the class. We use message maps over virtual function because of lots of overhead. If every windows message had a virtual function associated with it , there would be several hundred bytes per window class of vtable. Message maps means we only pay for the messages we use.
Q:- Given two processes, how can they share memory?
Ans:- Processes and thread are very similar but they differ in the way they share their resources. Processes are independent and have its own address space. If two independent processes want to communicate they do this by using the following techniques 1.Message Passing 2.Sockets 3. named pipes
Or
Use memory-mapped files to share data memory between processes
Q:- How to restrict only one instance of a class object to be created?
Ans:- Create a Named Mutex.
HANDLE hMutex=CreateMutex(TRUE,_T(“NamedMutex”))
And check the Mutex existence for each of your instance launch and dont allow it to launch if it exists.
Q:- How do I dynamically change the mainframe menu?
Ans:- CMenu newMenu;
newMenu.LoadMenu (IDR_MENU1);
AfxGetMainWnd()->SetMenu( &newMenu );
AfxGetMainWnd()->DrawMenuBar();
newMenu.Detach ()
Ans:- A "socket" is an endpoint of communication: an object through which your application communicates with other Windows Sockets applications across a network.The two MFC Windows Sockets programming models are supported by the following classes: CAsyncSocket and CSocket
Q:- What is the difference between Synchronous sockets and asynchronous sockets?
Ans:- Consider a server application that is listening on a specific port to get data from clients. In synchronous receiving, while the server is waiting to receive data from a client, if the stream is empty the main thread will block until the request for data is satisfied. Hence, the server cannot do anything else until it receives data from the client. If another client attempts to connect to the server at that time, the server cannot process that request because it is blocked on the first client. This behavior is not acceptable for a real-world application where we need to support multiple clients at the same time.
In asynchronous communication, while the server is listening or receiving data from a client, it can still process connection requests from other clients as well as receive data from those clients. When a server is receiving asynchronously, a separate thread (at the OS level) listens on the socket and will invoke a callback function when a socket event occurs. This callback function in turn will respond and process that socket event.
Q:- Have you ever used win32 APIs ?
Ans:- MFC is a wrapper around win32 API, It provides classes which uses the win32 API, Some of the API's we usually work with are : GetDlgItemInt,GetDlgItemText,GetWindowTextA,Messag eBoxA,CreateFile,CreateMutex,CreateEvent,WaitForSi ngleObject,CreateWindow,ShowWindow etc.,
Q:- What is the difference between ANSI Code and UNICODE ?
Ans:- ANSI code represents 8bytes data where UNICODE represents 16bytes data for supporting universal languages. One major draw back to ASCII was you could only have 256 different characters. However, languages such as Japanese and Arabic have thousands of characters. Thus ASCII would not work in these situations. The result was Unicode which allowed for up to 65,536 different character
Q:- What is the difference between regular dlls and extended dlls?
Ans:- Regular dlls wraps only the c/c++ functions. Where extention dlls include c++ interfaces where we can create the objects of it and use in our classes. Extended dlls support object oriented concepts.Regural dlls uses mfc internally and exported functions can be used by any mfc or non-mfc applications.Extention dlls implements reusable classes derived from mfc library,built using dll version of mfc.Only mfc executables(applications/dll-shared version of mfc) can use extention dlls.extention dlls used for passing mfc derived objects b/w applications and dlls. Regulardlls linked both statically and dynamically but extended dlls links dynamically.
Q:- What is a message map, and what is the advantage of a message map over virtual function ?
Ans:- MessageMap is a logical table that maps the windows messages to the member functions of the class. We use message maps over virtual function because of lots of overhead. If every windows message had a virtual function associated with it , there would be several hundred bytes per window class of vtable. Message maps means we only pay for the messages we use.
Q:- Given two processes, how can they share memory?
Ans:- Processes and thread are very similar but they differ in the way they share their resources. Processes are independent and have its own address space. If two independent processes want to communicate they do this by using the following techniques 1.Message Passing 2.Sockets 3. named pipes
Or
Use memory-mapped files to share data memory between processes
Q:- How to restrict only one instance of a class object to be created?
Ans:- Create a Named Mutex.
HANDLE hMutex=CreateMutex(TRUE,_T(“NamedMutex”))
And check the Mutex existence for each of your instance launch and dont allow it to launch if it exists.
Q:- How do I dynamically change the mainframe menu?
Ans:- CMenu newMenu;
newMenu.LoadMenu (IDR_MENU1);
AfxGetMainWnd()->SetMenu( &newMenu );
AfxGetMainWnd()->DrawMenuBar();
newMenu.Detach ()
1. Which controls can not be placed in MDI ?
2. List out controls which does not have events
3. Which property of textbox cannot be changed at runtime. What
is the max size of textbox?
4. How many system controls are available
5. ___,_____ and ____ container objects.
6. strech___ Property is to compress a image in image control.
7. ___,___ and __ are difference between image and picture
controls.
8. Is it possible to set a shortcut key for label.
9. What is the default property of data control?
10. ___,__,___ are the type of combo box?
11. __ no of controls in form.
12. OLE is used for _______
13. What is the need of tabindex property is label control.
14. ___ is the control used to call a windows application.
15. Clear property is available in ____,___ control.
16. ___ Property is used to count no. of items in a combobox.
17. ___ is a property to resize a label control according to your
caption.
18. Which controls have refresh method.
19. ___ property is used to change to ___ value to access a
identity column in datacontrols.
20. _____ is the property to ___,____,____ are valid for
recordsource property of dat control.
21. To find the current record position in data control.
22. Timer control contains ________ no. of events.
23. ____ property is used to lock a textbox to enter data.
24. What is the need of z-order method?
25. ____ is the difference between Listindex and Tab index.
26. ____ property of menu cannot be set at run time.
27. Can you create a tabletype of recordset in Jet - connected
ODBC dbengine.
28. Difference between listbox and combo box.
29. What are the new events in textbox that has been included in
VB
30. 0
31. Can you create a Updatecascade, Deletecascade relation in Ms-
Access? If no, give on eample.
32. _____ collection in recordset used to assign a value from
textbox to table columns without making abinding in datacontrol.
33. ____ argument can be used to make a menu item into bold.
34. What is the difference between Msgbox Statement and MsgboxQ
function?
35. What is.the difference between queryunload and unload in
form?
36. ___,___ arguments will be used to run a executable program in
shell function
37. ___ property used to add a menus at runtime.
38. What is the difference between modal and module-less window?
39. ___ VB constant make the menu item in centre.
40. ___ method used to move a recordset pointer in nth position
in DAG.
41. To validate a range of values for a property whenever the
property values changes,which type of property procedure you use?
42. What are 3 main differences between flexgrid control and
dbgrid control?
43. What is the difference between change event in normal
combobox and dbcombobox?
44. To populate a single column value which dbcontrols you to
use?
45. What is ODBC?
46. Parts of ODBC?
47. What is DSN?
48. What is DAO?
49. Types of cursors in DAO?
50. Types of LockEdits in DAO? 51 .Types of Recordsets.
51. Difference between Tabletype and Snapshot?
52. Draw Sequence Modal of DAO? Explain.
53. Difference between Dynaset and Snapshot?
54. Difference between Recordset and Querydef?
55. What is the use of Tabledef?
56. Default cursor Type and LockEdit type in DAO?
57. What is the default workspace?
58. 1s it posible to Create Tables Through Querydef?
59. It is possible to access Text (x.txt) files? Explain.
60. What is ODBC Direct and Microsoft Jet Database Engine ?
61. Is it possible to Manipulate data through flexgrid? Explain.
62. Types of DBCombo boxes
63. What do you mean by Databound Controls? Explain.
64. What is RDO?
65. Types of cursors in RDO.
66. Types of LockEdits in RDO.
67. Types of LockEdits in RDO.
68. Types of Resultsets.
69. Difference between Recordset and Resultsets.
70. Explain Default cursor Type and LockEdits type in RDO
71. Draw Sequence Modal of RDO? Explain.
72. What is meant by Establish Connection in RDO?
73. Is it possible to Access BackEnd procedures? Explain.
74. What is OLE? Explain.
75. What is DDE?
76. Difference between Linked Object and Embedded Object?
77. Explain OLE Drag and Drop.
78. Difference between DDE and OLE.
79. What is the difference between Object and Class?
80. Give brief description about class?
81. Does VB support object-oriented concepts? Explain..
82. Difference between Class Module and Standard Module?
83. Explain Get, Let, Set Properties.
84. Difference Types of Procedures in VB?
85. What is the use of NEW Keyword? Explain.
86. What is constructors and distructors.
87. Types of Modal windows in VB.
88. What is ActiveX? Explain.
89. Types of ActiveX Components in VB?
90. Difference between ActiveX Control and Standard Control.
91. Difference between ActiveX Exe and Dll.
92. What is instantiating?
93. Advantage of ActiveX Dll over Active Exe.
94. Difference Types of Instancing Property in ActiveX Dll and
Exe.
95. What is ActiveX Dll and ActiveX Exe?
96. Write the steps in Creating ActiveX Dll and Active Exe?
97. Explain the differences between ActiveX Dll and ActiveX Exe?
98. How would you use ActiveX Dll and ActiveX Exe in your
application?
99. How would you access objects created in ActiveX Exe and
ActiveX D1T
100. What is the use of ActiveX Documents?
101. What is ActiveX Document?
102. What is the use of Visual Basic Document file?
103. What is hyperlink?
104. How would you create Visual basic Document file?
105. What is Internet Explorer and its uses?
106. How would you navigate between one document to another
document in Internet Explorer ?
107. How would you run your ActiveX Document Dll?
108. How would you view html code in Active Server Pages?
109. How would you cre.ate your application in DHTML?
110. What is ActiveX Control?
111. Write the Steps in Creating an ActiveX Control?
112. How would you attach an ActiveX control in Your Application?
113. How would you create properties in ActiveX Control?
114. What is the-use of property page Wizard in ActiveX Control?
115. How would you add elements in TreevieW Control.
116. What are the types of line styles available in Treeview
Control?
117. What is the use of Imagelist Controls
118. How would you attach pictures in Treeview Control?
119. What are the uses of List View Control?
120. Explain the types of Views in Listview Control.
121. How would you attach pictures in column headers of List View
Control?
122. How would you add column headers in listview control?
123. How would you add elements and pictures to listitems in
listview control?
124. How would you activate animation control?
125. What is the use of progress Bar Control?
126. How would you find out the value property in Slider Bar
Control?
127. What is the use of Data Form Wizard?
128. How would you map properties to controls by using ActiveX
Control Interface Wizard?
129. How would you convert a form into document?
130. How would you Create a Query Builder and Explain its uses
131. How would you create properties by using class Builder
Wizard?
132. HTML stands for What? Use of HTML ?
133. Whether HTML supports multimedia: and document links?
134. DHTML Is used for what?
135. What do you mean by HTTP?
136. What is the use of Hyperlink control for DHTML applications?
137. How can you Navigate from the DHTML application to another
DHTML application? .
138. What are the Internet tools available in VB
139. 0?
140. Explain the usage of Web Browser Control?
141. What do you mean by ADO?
142. What is the difference Between ADO and other data access
objects0
143. What is OLEDB?
144. What are the important components of OLEDB?
145. Through which protocol OLEDB components are interfaced?
146. It possible to call OLEDB's Features directly in VB without
using any control?
147. What type of databases you can access through AD I Data
Access Object?
148. How many objects resides in ADO ?
.
149. What is the use of Connection object?
150. What is the use of command Object?
151. Record set object consists of what?
152. What is the use of parameters collection?
153. Which type of object requires this object?
154. Is it possible to call backend procedures with ADO control?
155. Is there any Edit method in ADO Data Access method?
156. How can you check whether a record is valid record or Invalid
record using ADO control or Object?
157. What do you mean by provider?
158. What type of record sets are available in ADO?
159. Is it possible to call oracle database through ADO control or
Object?
160. How many File System Controls are there ? Explain.
161. How can you filter out specific type of file using file
system controls?
162. How can you get selected file from file system Control?
163. How many ways we can access file using VB?
164. Which method is preferred to save data like database to the
disk?
165. How to get free file location in memory?
166. How to find size of the file. Which method or function is
used to occomplish this?
167. Using which type we can access file line by line?
168. Which method is used to write context Into file?
169. How can you read content from file?
170. Binary Access-method is used to access file in which manner?
171. How can you check Beginning and End of the file?
172. What is the use of Scalewidth and ScaleHeight Proeperty?
173. What is the use of Active Control Property?
174. How can you save and Get data from Clipboard/
175. What are the types of Error?
176. In which areas the Error occurs?
177. What are the tools available for Debug in VB?
178. What is the use of Immediate, Local Window?
179. What is the use of debug Window?
180. How can you Implement windows functionality in VB?
181. How many types of API functions are available in VB?
182. How can you Add API functions to your Application?
183. How to get Cursor position using API?
184. Is it possible to change menu runtime using API? If yes?
Specify the function names.
185. What are the types of API Types.
186. Scope of API's can be of types, what are they? Why API
functions are Required?