MANAGING VARIABLES

1. Variable Names
The following are the rules when naming the variables in Visual Basic
* It must be less than 255 characters
* No spacing is allowed
* It must not begin with a number
* Period is not permitted

Sample:


2.Declaring Variables
In Visual Basic 2008, one needs to declare the variables before using them by assigning names and data types. If you fail to do so, the program will show an error. They are normally declared in the general section of the codes' windows using the Dim statement.
The format is as follows:

Dim Variable Name As Data Type

Example 1:

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

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

End Sub

You may also combine them in one line , separating each variable with a comma, as follows:

Dim password As String, yourName As String, firstnum As Integer,.............

For string declaration, there are two possible formats, one for the variable-length string and another for the fixed-length string. For the variable-length string, just use the same format as example 6.1 above. However, for the fixed-length string, you have to use the format as shown below:

Dim VariableName as String * n, where n defines the number of characters the string can hold.

Example 2:

Dim yourName as String * 10

yourName can holds no more than 10 Characters.

3. Assigning Values to Variables
After declaring various variables using the Dim statements, we can assign values to those variables. The general format 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 etc.

examples:

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)
total = firstNumber + secondNumber+ThirdNumber