IT Applications (OLD)- Revision Notes

 CBSE Class 12 Informatics Practices

Revision Notes
Visual Basic Interface Styles

Interfaces describe the characteristics of properties, methods, and events, but leave the implementation details up to structures or classes.

For example, the following code defines an interface with one function, one property, and one event.

Interface mycbseguide
Event ComittedChange(ByVal Success As Boolean)
Property Division() As String
Function GetID() As Integer
End Interface

1. Interface is the visual part of the application, which the user interact with.
VB support following three types of interface styles:
(i) Single Document Interface (SDI)
(ii) Multiple Document Interface (MDI)
(iii) Explorer Style Interface

SDI : A Single-Document Interface (SDI) is a type of GUI(Graphical User Interface). Any program not capable of displaying more than one document per window is considered to use an SDI interface. Examples of this include Windows Notepad.

MDI : A multiple document interface (MDI) is a GUI in which multiple windows reside under a single parent window.

2. Difference between SDI and MDI
Single Document Interface (SDI) support single document in its window. i.e., the moment we open another document the previously opened document is closed and then the new document is loaded in its window. An example of the SDI interface is the Wordpad application included with Microsoft Windows. In Wordpad, only a single document may be opened; we must close one document in order to open another, simply because it is an SDI application.
Multiple Document Interface (MDI) on the other hand, allows us to display multiple documents at the same time, with each document displayed in its own window. MS-Word, MS-Excel etc are example of MDI applications as they allow opening of several documents simultaneously.

3. It is discouraged to create separate menus for child forms because when a child form is loaded and activated, its menu takes over the menu of parent form and the menu of parent form is lost.

4. We can convert existing forms to MDI child forms, by setting their MDIChild properties to True.

5. The controls that can be placed on an MDI parent form are Timer control and Image box.

6. An MDI child form is not a top-level window, it needs a container i.e., an MDI parent form, to be displayed. That is why if a child form is loaded first, its parent form gets loaded automatically.

7. Me is a special keyword used to refer to the active form object in which it is used.

8. A splash screen is a special form with minimal functionality that is loaded as soon as a user executes an application. This screen has few graphics/ text displayed on it.

9. A VB application can have only one MDI parent window.

10. An MDI application must have an MDI Parent form and at least one MDI Child form (i.e. a form with its MDI Child property set to True).

11 . A child form cannot be displayed modally.

12. An MDI application can contains as many MDI child forms.