Lesson 2: Building Visual Basic Applications.

2.1 Creating Your First Application

In this lesson, we will not delve into the technical aspects of Visual Basic programming yet, we just want you to try out the examples below to see how does a Visual Basic program behave.

First of all, launch Microsoft Visual Basic 6 compiler that you have installed earlier. In the New Project Dailog , choose Standard EXE to enter Visual Basic 6 integrated development environment. In the VB6 IDE, a default form with the name Form1 will be presented to you. Now, double click on Form1 to bring up the source code window for Form1 as shown in Figure 2.1 . The top of the source code window consists of a list of objects and their associated events or procedures. In the source code window, the object displayed is Form1 and the associated procedure is Load.

Figure 2.1 Source Code Window

When you click on the object box, the drop-down list will display a list of objects you have inserted into your form as shown in figure 2.2. Here, you can see a form with the name Form1, a command button with the name Command1, a Label with the name Label1 and a Picture Box with the name Picture1. Similarly, when you click on the procedure box, a list of procedures associated with the object will be displayed as shown in Figure 2.3. Some of the procedures associated with the object Form1 are Activate, Click, DblClick (which means Double-Click) , DragDrop, keyPress and more. Each object has its own set of procedures. You can always select an object and write codes for any of its procedure in order to perform certain tasks.

You do not have to worry about the beginning and the end statements (i.e. Private Sub Form_Load.......End Sub.); Just key in the lines in between the above two statements exactly as are shown here. When you press F5 to run the program, you will be surprised that nothing shown up .In order to display the output of the program, you have to add the Form1.show statement like in Example 2.1.1  or you can just use Form_Activate ( )  event procedure as shown in example 2.1.2. The command Print does not mean printing using a printer but it means displaying the output on the computer screen. Now, press F5 or click on the run button to run the program and you will get the output as shown in Figure 2.4.
You can also perform arithmetic calculations as shown in Example 2.1.2. VB uses * to denote the multiplication operator and / to denote the division operator. The output is shown in Figure 2.5, where the results are arranged vertically.

Figure 2.2: List of Objects

Figure 2.3: List of Procedures

Example 2.1.1

Private Sub Form_Load ( )
Form1.show
Print “Welcome to Visual Basic tutorial”
End Sub

Figure 2.4 : The output of Example 2.1.1

Example 2.1.2

Private Sub Form_Activate ( )
Print 20 + 10
Print 20 - 10
Print 20 * 10
Print 20 / 10
End Sub

Figure 2.5: The output of Example 2.1.2

You can also use the + or the & operator to join two or more texts (string) together like in example 2.1.4 (a) and (b)

Example 2.1.4(a)

Private Sub

A = "Tom"
B = “likes"
C = “to"
D = “eat"
E = “burger"
Print A + B + C + D + E

End Sub

Example 2.1.4(b)

Private Sub

A = "Tom"
B = “likes"
C = “to"
D = “eat"
E = “burger"
Print A & B & C & D & E

End Sub

The Output of Example 2.1.4(a) &(b) is as shown in Figure 2.7.

Figure 2.7

2.2 Steps in Building a Visual Basic Application

Step 1 : Design the interface by adding controls to the form and set their properties
Step 2 : Write code for the event procedures

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