IST 256
Lab Week 8, Part 2 (really) – Wednesday, October 15, 2008
1. Understanding Procedures with ByRef parameters
Assume that there is a Form for an application that has one TextBox where the user types
in a sales total and one label where the amount of tax is shown for that total. There is
also the following definition of a general procedure and a button function that calls the
procedure:
' Procedure to compute tax amount from the total (of a sales)
Private Sub ComputeTax(ByRef tb As TextBox, ByRef taxamount As Single)
' Tax rate is fixed at 8%
Dim taxrate as Single
taxrate = 0.08
taxamount = CSng(tb.Text) * taxrate
End Function
' User gives the total sales bought in a textbox,
' Compute the amount of tax and Display in a label
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
Dim result as Single
Call ComputeTax(TextBox1, result)
' Show the result
Label1.Text = "Resulting Tax = " & Format(result, "currency")
End Sub
Suppose that the user types the number “100” in the textbox. What will be displayed in
Label1.Text? Write your answer here.
Suppose that the user types the number “3” in the textbox. What will be displayed in
Label1.Text? Write your answer here.
