In this program, two text boxes are inserted into the form together with a few labels. The two text boxes are used to accept inputs from the user and one of the labels will be used to display the sum of two numbers that are entered into the two text boxes. Besides, a command button is also programmed to calculate the sum of the two numbers using the plus operator. The program use creates a variable sum to accept the summation of values from text box 1 and text box 2.The procedure to calculate and to display the output on the label is shown below. The output is shown in Figure 3.1.
Private Sub Command1_Click()
‘To add the values in text box 1 and text box 2
Sum = Val(Text1.Text) + Val(Text2.Text)
‘To display the answer on label 1
Label1.Caption = Sum
End Sub
Figure 3.1 
3.2.2 The Label 
The label is a very useful control for Visual Basic, as it is not only used to provide instructions and guides to the users, it can also be used to display outputs. One of its most important properties is
Caption. Using the syntax
label.Caption, it can display text and numeric data . You can change its caption in the properties window and also at runtime. Please refer to Example 3.1 and Figure 3.1 for the usage of label.
3.2.3 The Command Button 
The command button is a very important control as it is used to execute commands. It displays an illusion that the button is pressed when the user click on it. The most common event associated with the command button is the Click event, and the syntax for the procedure is
Private Sub Command1_Click ()
Statements
End Sub
3.2.4 The Picture Box 
The Picture Box is one of the controls that used to handle graphics. You can load a picture at design phase by clicking on the picture item in the properties window and select the picture from the selected folder. You can also load the picture at runtime using the
LoadPicture method. For example, the statement will load the picture grape.gif into the picture box.
Picture1.Picture=LoadPicture ("C:\VB program\Images\grape.gif")
You will learn more about the picture box in future lessons. The image in the picture box is not resizable.
3.2.5 The Image Box 
The Image Box is another control that handles images and pictures. It functions almost identically to the picture box. However, there is one major difference, the image in an Image Box is stretchable, which means it can be resized. This feature is not available in the Picture Box. Similar to the Picture Box, it can also use the LoadPicture method to load the picture. For example, the statement loads the picture grape.gif into the image box.
Image1.Picture=LoadPicture ("C:\VB program\Images\grape.gif")
3.2.6 The List Box 
The function of the List Box is to present a list of items where the user can click and select the items from the list. In order to add items to the list, we can use the
AddItem method. For example, if you wish to add a number of items to list box 1, you can key in the following statements
Example 3.2 Private Sub Form_Load ( )
List1.AddItem “Lesson1”
List1.AddItem “Lesson2”
List1.AddItem “Lesson3”
List1.AddItem “Lesson4”
End Sub
The items in the list box can be identified by the
ListIndex property, the value of the ListIndex for the first item is 0, the second item has a ListIndex 1, and the second item has a ListIndex 2 and so on
3.2.7 The Combo Box 
The function of the Combo Box is also to present a list of items where the user can click and select the items from the list. However, the user needs to click on the small arrowhead on the right of the combo box to see the items which are presented in a drop-down list. In order to add items to the list, you can also use the
AddItem method. For example, if you wish to add a number of items to Combo box 1, you can key in the following statements
Example 3.3 Private Sub Form_Load ( )
Combo1.AddItem “Item1”
Combo1.AddItem “Item2”
Combo1.AddItem “Item3”
Combo1.AddItem “Item4”
End Sub
3.2.8 The Check Box 
The Check Box control lets the user to select or unselect an option. When the Check Box is checked, its value is set to 1 and when it is unchecked, the value is set to 0. You can include the statements Check1.Value=1 to mark the Check Box and Check1.Value=0 unmark the Check Box, and use them to initiate certain actions. For example, the program will change the background color of the form to red when the check box is unchecked and it will change to blue when the check box is checked. You will learn about the conditional statement If….Then….Elesif in later lesson. VbRed and vbBlue are color constants and BackColor is the background color property of the form.
Example 3.4 Private Sub Check1_Click ()
If Check1.Value = 0 Then
Form1.BackColor = vbRed
ElseIf Check1.Value = 1 Then
Form1.BackColor = vbBlue
End If
End Sub
3.2.9 The Option Box 
The Option Box control also lets the user selects one of the choices. However, two or more Option Boxes must work together because as one of the Option Boxes is selected, the other Option Boxes will be unselected. In fact, only one Option Box can be selected at one time. When an option box is selected, its value is set to “True” and when it is unselected; its value is set to “False”. In the following example, the shape control is placed in the form together with six Option Boxes. When the user clicks on different option boxes, different shapes will appear. The values of the shape control are 0, 1, and 2,3,4,5 which will make it appear as a rectangle, a square, an oval shape, a rounded rectangle and a rounded square respectively.
Example 3.5 Private Sub Option1_Click ( )
Shape1.Shape = 0
End Sub
Private Sub Option2_Click()
Shape1.Shape = 1
End Sub
Private Sub Option3_Click()
Shape1.Shape = 2
End Sub
Private Sub Option4_Click()
Shape1.Shape = 3
End Sub
Private Sub Option5_Click()
Shape1.Shape = 4
End Sub
Private Sub Option6_Click()
Shape1.Shape = 5
End Sub
3.2.9 The Drive List Box 
The Drive ListBox is used to display a list of drives available in your computer. When you place this control into the form and run the program, you will be able to select different drives from your computer as shown in Figure 3.2
Figure 3.2 The Drive List Box 
3.2.10 The Directory List Box
The Directory List Box is used to display the list of directories or folders in a selected drive. When you place this control into the form and run the program, you will be able to select different directories from a selected drive in your computer as shown in Figure 3.3
Figure 3.3 The Directory List Box 
3.2.11 The File List Box 
The File List Box is used to display the list of files in a selected directory or folder. When you place this control into the form and run the program, you will be able to a list of files in a selected directory as shown in Figure 3.4
Figure 3.4 
You can coordinate the Drive List Box, the Directory List Box and the File List Box to search for the files you want. The procedure will be discussed in later lessons.
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