1. Repetition - Counting and Accumulating
Yonglei Tao

2. Flow Chart – Pretest Loop

3. Flow Chart – Posttest Loop

4. Counting and Accumulating
Write a program to process input, the number of input values are unknown
Sample input
<empty string>
<empty string>
<empty string>

5. Loop Design Get a value If it is not the empty string
Process the value
Get next value …
If it is the empty string
Done
Get a value Do While it’s not an empty string Process the value Get next value Loop

6. Program Version One
Private Sub btnCalculate_Click ( … ) Dim sales As String Dim numSales As Integer sales = InputBox (“Enter a sales amount. Click Cancel to end.“, “Sales Entry”) Do While sales <> String.Empty ‘ process the value Loop ‘ display the average End Sub

7. Program Version Two
Private Sub btnCalculate_Click ( … ) Dim sales As String Dim numSales As Integer Dim totalSales, avgSales As Currency sales = InputBox (“Enter a sales amount. Click Cancel to end.“, “Sales Entry”) Do While sales <> String.Empty ‘ process the value numSales = numSales + 1 totalSales = totalSales + Val (sales) Loop ‘ display the average End Sub

8. Private Sub btnCalculate_Click ( … ) Dim sales As String Dim numSales As Integer Dim totalSales, avgSales As Currency sales = InputBox (“Enter a sales amount. Click Cancel to end.“, “Sales Entry”) Do While sales <> String.Empty numSales = numSales + 1 totalSales = totalSales + Val (sales) Loop If ( numSales > 0 ) Then avgSales = totalSales / numSales lblAerage.Text = Format ( avgSales. “Currency”) else lblAerage.Text = “No Sales” end If End Sub