6.1 Assigning Values to Variables

After declaring various variables using the Dim statements, we can assign values to those variables. The syntax of an assignment is

Variable=Expression

The variable can be a declared variable or a control property value. The expression could be a mathematical expression, a number, a string, a Boolean value (true or false) and more.

The following are some examples variable assignment:

firstNumber=100
secondNumber=firstNumber-99 
userName="John Lyan"
userpass.Text = password 
Label1.Visible = True 
Command1.Visible = false 
Label4.Caption = textbox1.Text 
ThirdNumber = Val(usernum1.Text) 
X = (3.14159 / 180) * A
 

6.2 Operators in Visual Basic

To compute inputs from users and generate results, we must use the mathematical operators. In Visual Basic, except for + and -, the symbols for the operators are different from normal mathematical operators, as shown in Table 6.1.

Example 6.1

Private Sub Command1_Click()

Dim firstName As String
Dim secondName As String
Dim yourName As String

 firstName = Text1.Text
 secondName = Text2.Text
 yourName = secondName +"" + firstName
 Label1.Caption = yourName
End Sub

In Example 6.1, three variables were declared as string. Variables firstName and secondName will receive their data from the user’s input in textbox1 and textbox2, and the variable yourName will be assigned the data by combining the first two variables.  Finally, yourName will be displayed on Label1.

Example 6.2

Dim number1, number2,number3 as Integer
Dim total, average as variant
Private sub Form_Click()
 number1=val(Text1.Text) 
 number2=val(Text2.Text) 
 number3= val(Text3.Text)
 Total=number1+number2+number3
 Average=Total/5 
 Label1.Caption=Total
 Label2.Caption=Average
End Sub

In the Example 6.2, three variables were declared as integer and two variables were declared as variant. Variant means the variable can hold any data type. The program computes the total and average of the three numbers that are entered into three text boxes.

Example 6.3 Easy Math

This is a simple math drill program where the user enter two numbers and calculate its sum. The program will tell him whether the answer is right or wrong. To add some gist to the program, the user needs to enter the password before he or she can proceed.

The Code

Dim password As String
Dim yourName As String
Dim firstnum As Integer
Dim secondnum As Integer
Dim total As Integer
Dim doDate As Date

Private Sub Command1_Click()
If userpass.Text = password Then
 Label2.Visible = True
 number1.Visible = True
 number2.Visible = True
 sum.Visible = True
Label3.Visible = True
 Command3.Visible = True
 usernum1.Visible = True
 usernum2.Visible = True
 OK.Visible = True
 Label4.Visible = True
 Label4.Caption = textbox1.Text
 textbox1.Visible = False
 userpass.Visible = False
 username.Visible = False
 Label1.Visible = False
 Command1.Visible = False
Else
 userpass.Text = ""
 userpass.SetFocus
End If
End Sub

Private Sub Form_Load()
 password = "liewxun"
End Sub

Private Sub OK_Click()
 firstnum = usernum1.Text
 secondnum = usernum2.Text
 total = sum.Text
 If total = firstnum + secondnum And Val(sum.Text) <> 0 Then
  correct.Visible = True
 wrong.Visible = False
Else
 correct.Visible = False
 wrong.Visible = True
End If

End Sub

The Output