VB6 Tutorial 55: Using Data Types
Visual Basic 6 is rich in data types. So you should know the usage of all the data types to make a powerful application.
Integer values
Among the data types for storing integer values, Integer is the most used data type for its efficiency. But sometimes you may use the Long data type instead of Integer especially when you want to reduce the overflow error as it can hold a very large value, from -2,147,483,648 to 2,147,483,647 where an Integer can only store a value from -32,768 to 32767.
For small integer values, use the Byte data type, the value range is from 0 to 255 only in this case.
The Boolean Data Type
The Boolean variables stores only 0 and 1 that stand for False and True respectively. To use a Boolean variable in your code, firstly declare the variable as Boolean and then assign a True/False value.
Example
Private Sub cmdCheck_Click()
Dim TextOff As Boolean 'Declaring the variable
'Assigning value
If Text1.Visible = False Then
TextOff = True
End If
'Using the Boolean variable
If TextOff = True Then
MsgBox "TextBox is hidden"
Else
MsgBox "TextBox is shown"
End If
End Sub
Can you guess what the output of this script is?
Floating point values
Single and Double are the mostly used data types. For small decimal values, use the Single data type and Double for large values. Decimal is a floating point data type. The Decimal data type is higher in precision and lower in range compared to Double. In case of Decimal data type, you can't explicitly declare it (As Decimal). To use it, convert a value to Decimal data type with the CDec function and assign it to a variant.
Example
The Decimal Data Type Dim num As Variant expr = 22.45 * 5.987 num = CDec(expr)The String Data Type
String data types can be variable length or fixed-length. When you know the length of your string value, you may use the fixed-length data type. But remember that variable length strings are faster than the fixed-length strings.
Example
Dim s As String 'variable length string Dim s1 As String * 10 'fixed-length string
The fixed-length string in the above example takes 10*2=20 bytes memory space.
The Currency Data Type
The value range of a Currency data type from -922,337,203,685,477.5808 to 922,337,203,685,477.5807. Currency values always include 4 decimal digits. This data type is used for storing monetary values.
The Date Data Type
The Date data types are useful in the sense that they can be used to perform math operations on date values. You can truncate, add or subtract the date values. You first need to assign the date value to a variable for that.
Example
Private Sub cmdShow_Click()
Var = Now
Var = Var + 14 '14 days from today
Print Var
End Sub
The Object Data Type
Visual Basic is fully an object-based programming language. So Object data type plays a very important role in the language. The Object data type is used to store a reference object. There are several objects in visual basic like forms, textbox, database and so on.
You first need to declare the object variable and then assign an object reference to the object variable using the Set keyword.
After assigning, you can use the object variable to access the properties and methods of the original object.
Example
'Declaration Dim frm As Form Dim txt As TextBox 'Assign object reference Set frm = Form1 Set txt = Text1 'Using object variable to access the original object frm.BackColor = vbGreen txt.Text = "hello world"
Clearing a group of TextBox controls
Create a control array of text boxes with the name "Text1" and then write the following code.
Example
Private Sub cmdClear_Click()
Dim field As TextBox 'Declaring as Object
For Each field In Text1 'Text1 is a control array
field.Text = ""
Next
End Sub
This is just a brief discussion on Object data type. You'll learn more later in the tutorial.
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