Topic: Introduction-to-IDE-and-creating-a-Sample-Application

What is Visual Basic-6?

      Visual Basic-6 has its origin in Basic which was developed round about the year 1960, when high level languages were just being introduced to the computer community.   Microsoft has made it extremely powerful by gearing all its good features to the Windows environment.   Starting with the version 3 and then with 4, and then with 6, Visual Basic is now at version 6.   Basic is a Procedure Oriented Language intended to implement single tasks in  text based environment whereas Visual Basic is an Event Driven Language intended to implement Projects or Applications containing multiple tasks in Windows Environment. 
          

What can Visual Basic do for you?

     Visual Basic can serve as an ideal front end tool for the clients to interact.   It has got connectivity mechanisms for all types of databases situated far and wide in a network and so it can cater to the needs of a large body of clients.   Using the latest ActiveX technologies, it can integrate the functionalities provided by other applications like Word Excel and other Windows.   Its internet capabilities provide easy access to documents and applications across the internet.   Above all it embodies the Object Oriented Technology, which is the cutting edge technology for all the present day developments in the Software World.   The final application is a true EXE file and so can be freely distributed.

Structure of  VB-6 Projects:

     We said earlier that VB-6 implements projects or applications.   A project is developed using one or more Forms.   A Form is simply a window containing  one or more Controls.  Controls in VB consist of labels, text boxes, list boxes, combo boxes, scroll bars etc. which are the constituents of windows environment.  It is only the controls that give VB, its immense power and so there is a lot of interest in creating more and more powerful controls. ActiveX controls mark a significant development in controls technology. In fact all controls in VB-6 are ActiveX controls, which have the extension .ocx.  These controls have properties whose values can be initialized at design time and also varied during run time.   The properties are something like variables.  The controls are activated by codes written in a high level language.  By associating our problem variables with the properties of the controls,  our problem variables can be manipulated to give the problem solution.   In summary  we can say that a VB project is made of forms, controls and their properties and codes.

Integrated Development Environment:

     The working environment in VB is often referred to as the Integrated Development Environment or IDE, because it integrates many different functions such as design, editing, compiling and  debugging  within a  common environment.   Since all our projects are developed only in the IDE,  let us now  have a brief look at its features.    You will be able to understand their uses at the time of building projects.  The VB IDE looks  as shown in the figure 1.

Elements of Visual Basic IDE:

     The VB IDE consists of the following elements.

• 1. Menu Bar
• 2. Context Menus
• 3. Toolbars
• 4. Toolbox
• 5. Project Explorer Window
• 6. Properties Window
• 7. Object Browser
• 8. Form Designer
• 9. Code Editor Window
• 10. Form Layout Window
• 11. Immediate, Locals and Watch Windows.

Menu Bar:

     Menu Bar displays the commands you use to work with Visual Basic and is located at the top. Besides the standard File, Edit, View, Windows and Help menus, menus are provided to access functions specific to programming such as Project, Format  or Debug.

Context Menus:

     Context Menus provide certain short cuts to frequently performed actions.   To open a context menu, click the right mouse button on the object you are using.   The specific list of shortcuts available from  context menus depends on the part of the environment where you click the right mouse button.   For example, the context menu displayed when you right click on the Toolbox lets you display the components dialog box, hide the Toolbox, dock or undock the Toolbox, or add a custom tab to the Toolbox  etc.

Toolbars:

     Toolbars provide quick access to commonly used commands in the programming environment and is located below the menu bar.   You click a button on the toolbar once to carry out the action represented by that button.   By default, the Standard toolbar is displayed when you start VB.   Additional toolbars, for editing, form design, and debugging can be toggled on or off from the Toolbars command on the View Menu.    Toolbars can be docked beneath the menu bar or can “float” if you select the vertical bar on the left edge and drag it away from the menu bar.

Toolbox:

     Toolbox provides a set of controls that you use at design time to place them on the form and is located on the left side.   In addition to the default controls layout,  you can create your own custom layouts by selecting Add Tab from the context menu and adding controls to the resulting tab.

Project Explorer Window:

     The  Project Window lists the forms, and modules in your current project.   To recapitulate, a project is simply a collection of files you use to build your application.

Properties Window:

      Properties Window displays the different properties of the different objects, such as size, caption, color etc., which can be set at the design time and located at the right side.

Object Browser:

     The Object browser lists the available objects  in your project, and gives you a way to navigate through your code.   You can use the Object browser to explore objects in VB ,  see what methods and properties are available for those objects, and paste code procedures into your application.

Form Designer:

    The Form serves as the designer window or the container for placing the different controls, graphics and pictures needed for your applications and is located at the center. There can be more than one form or a designer window for a single application.  

Code Editor Window:

     Every form has its own code editor window, where you write the codes for manipulating the objects in the designer window.

Form Layout Window:

     The Form Layout Window allows you to position the forms in your application using a small graphical representation of the screen.

Immediate Window:

     The Immediate Window is provided for debugging purposes and is located below the form window.   You can use it in the calculator mode to immediately compute big expressions.

     Visual Basic provides a great deal of flexibility, allowing you to configure the working environment to best suit your individual style. You can choose between a single or multiple document interface, and you can adjust the size and positioning of the various Integrated Development Environment (IDE) elements. Your layout will persist between sessions of Visual Basic.

SDI or MDI Interface

     Two different styles are available for the Visual Basic IDE: single document interface (SDI) or multiple document interface (MDI). With the SDI option, all of the IDE windows are free to be moved anywhere on screen; as long as Visual Basic is the current application, they will remain on top of any other applications. With the MDI option, all of the IDE windows are contained within a single resizable parent window.
    To switch between SDI and MDI modes
1. Select Options from the Tools menu.
The Options dialog box is displayed.
2. Select the Advanced tab.
3. Check or uncheck the SDI Development Environment check box.
The IDE will start in the selected mode the next time you start Visual Basic.
–    or         –
Run Visual Basic from the command line with a /sdi or /mdi parameter.

Docking Windows

     Many of the windows in the IDE can be docked, or connected, to each other or to the edge of the screen. These include the Toolbox, Form Layout Window, Project Explorer, Properties window, Color Palette, and Immediate, Locals, and Watch windows.
     With the MDI option, windows can be docked to any side of the parent window; with SDI they can only be docked beneath the menu bar. Docking capabilities can be toggled on or off for a given window by selecting the appropriate check box on the Docking tab of the Options dialog box, available from the Options command on the Tools menu.
    To dock or undock a window
1. Select the window you wish to dock or undock.
2. Drag the window to the desired location by holding down the left mouse button.
          The outline of the window will be displayed as you drag.
3. Release the mouse button.

Creating an Application or a Project:

     Let us now wet our hands by actually creating an application using the IDE.   Creating any VB application consists of only three steps.  

• 1. Create the interface by placing the required controls in the form window.
• 2.  Set Properties to the controls using the Properties window of each control.
• 3. Write codes to manipulate the properties of the controls in the Code Window.

You start VB by clicking the start button on the task bar.   The screen displays the programs list
as shown in the figure 2.

Now click on the items Visual Studio and then Visual Basic 6.    You will get the opening
Screen as shown in the figure 1.
 
Controls used in this Project:

     We use five command buttons and one text box in this project.   For drawing a control in the form window, double click on the appropriate control.   The control with default characteristics is brought into the form.   It can be dragged and resized according to your requirements.  Drag the above mentioned 6 controls from the Toolbox and position them as shown in the figure 3.  Of course you can size and position them according to your liking.

Setting the Properties of  the Controls:

     Each control has a separate Properties window.  The Properties window will be normally visible on the right side.   If it is not visible it can be opened by clicking ‘Properties Window’ from the View menu after selecting the required control.   We can initialize the properties like size, caption, color etc. by selecting the desired values using the drop-down menu for the controls as well as the properties.   The Text property of the text box is given blank.   We simply retain the names of the other controls as they are.  The form window with the five controls will be as shown in the figure 3.

Functionalities required for the different Controls:

     Let us  assume that on clicking the first button, a message box  should be displayed.   On clicking the second button a rectangle filled with yellow color should appear.   On clicking the third button a welcome message should appear in the text box.   On clicking the fourth button the welcome message should be erased.  

Writing Codes for the Controls:

     The code window is opened by double clicking the concerned control.   The header line and the ending line of the relevant function will automatically appear on the code window.   You have to enter only the body for the function.   For referring to a property, the usual dot notation used in OOP is used.   For example the Text property of a text box named Text1 is referred to as Text1.Text.   In a similar fashion methods can also be referenced.  The codes for all the controls will  be on the same window  and the final  code window will  look as shown in the figure 3a.

Private Sub Command1_Click()
'display message box
MsgBox ("this is a sample message")
End Sub

Private Sub Command2_Click()
ScaleMode = 3
Line (100, 10)-(300, 150), RGB(255, 255, 0), BF
End Sub

Private Sub Command3_Click()
Text1.Text = "welcome to VB6"
End Sub

Private Sub Command4_Click()
Text1.Text = ""
End Sub

Private Sub Command5_Click()
End
End Sub

Saving the Project:

     When a project is saved for the first time it is done in two steps.  When you select ‘Save Project as’ from the File menu, you will get the first dialog box which asks you to save the form file with .frm extension.   On saving the form file another dialog box appears asking you to save the Project file itself.   We can give appropriate names to the form and the project, but in this case we retain the default names form1 and project1.   The project is now saved as project1.vbp and the form file is stored as form1.frm.   When you want to save the project after any subsequent editing, it is enough if you click ‘Save Project’.  Both the form and the project are saved by this single Save command.

Running the Project:

     For running the project click Run->Start.   The output window appears with all the controls.   This  window represents the Run mode.   Click the buttons one by one and check the outputs obtained.  A typical output is shown in the figure 4.

Closing  and Reopening the Project:

    For Closing the project click on the  closing button of the output window or click  End from the Run menu or the exit button in the output window.   If you want to reopen the project, click ‘open project’ from the File menu.   Opening a project will open all the files in the project.

Viewing the Project Explorer Window:

     As we said earlier, when you develop an application, you work with a project to manage all the different files that make up the application.   In order to view the constituents of the project, open the project explorer window by selecting the item ‘Project Explorer’ from the View Menu.   The Project Explorer window for the above application is also shown in the figure 3.   This project uses only two files, one project file(project1.vbp ) and one form file(form1.frm).   But in                         general a Project may consist of the following files.

• 1.  One Project File that keeps track of all the components(.vbp).
• 2.  One file for each form(.frm).
• 3.  One binary data file for each form containing data for properties of controls

           on the form(.frx).   These files are not editable and are automatically generated
           for any .frm file that contains binary properties, such as Picture or Icon.

• 4.  Optionally, one file for each class module(.cls).
• 5.  Optionally, one file for each standard module(.bas).
• 6.  Optionally, one or more files containing ActiveX controls(.ocx).
• 7.  Optionally a single resource file(.res).

     Thus a project file is simply a list of all the files and objects associated with the project, as well as information on the environment options you set.   This information is updated every time you save the project.  All of the files and objects can be shared by other projects as well.

Creating an EXE File:

     After completing all the files for a project, you can convert the project into an executable file(.exe) by selecting ‘the make project.exe’ command from the file menu.    An EXE file can be executed outside VB environment and so can be freely distributed.

Summary:

     In this lesson we have seen some features of the Visual Basic Integrated Development Environment, and how to create an application, using the three elements, form, controls and codes.  It may be noted that any complex application will consist of only these three elements, possibly using more forms, more controls with complex functionalities(pre-defined as well as user defined) and some complex logic involving the properties of the controls.