Problem Requirements

1
Problem Requirements
Create a cash register form to enter customer
information and multiple items name and cost,
then display the items total, discount, subtotal,
tax and amount due. The customer gets a 10
discount on all items if he/she has been a
customer for more than 6 months, an additional
5 discount is given if they have been a customer
for longer than 18 months. The tax is 6 on the
discounted subtotal.
2
Customer Information
First Purchase Date
3
Customer Information
First Purchase Date
Item Description
Item Cost
Next Item
4
Customer Information
First Purchase Date
Item Description
Item Cost
Next Item
Final Totals
Total of items
Discount
Totals
Subtotal
Tax
Amount Due
5
Customer Information
From customer database
A Customer Since
MemberInitialDateTextBox
Item Description
Item Cost
Next Item
ItemDescriptionTextBox
ItemCostTextBox
NextItemButton
Final Totals
Total cost of items
Discount
TotalsButton
Totals
TotalCostLabel
Subtotal
DiscountAmtountLabel
Tax
SubTotalLabel
Amount Due
TaxLabel
AmountDueLabel
6
Pseudocode

• Button Next Item
• Parse ItemCostTextBox to itemCost
• Add Itemcost to TotalCost
• Clear ItemDescriptionTextBox and
  ItemCostTextBox
• Set focus to ItemDescriptionTextBox and
  Select all

• Button Display Totals
• Compute Discount with a Function call passing
  TotalCost
• Compute SubTotal TotalCost - Discount
• Compute Tax SubTotal TaxRate
• Compute AmountDue SubTotal Tax
• Display results in labels as currency
• Clear All Entry TextBoxes and set focus to First
  name

7
Code

• Button Next Item
• Parse itemCostDecimal Decimal.Parse(itemCostText
  Box.Text)
• Add TotalCostDecimal ItemCostDecimal
• Clear ItemDescriptionTestBox.Clear() and
  ItemCostTextBox.Clear()
• Set focus and select all ItemDescriptionTextBoxF
  ocus()
• 
  ItemDescriptionTextBox.SelectAll()

• Button Display Totals
• Compute DiscoutDecimal Discount(TotalCostDecima
  l)
• Compute SubTotalDecimal TotalCostDecimal
  DiscountDecimal
• Compute TaxDecimal SubTotalDecimal
  TAX_RATE_Decimal
• Compute AmountDueDecimal SubTotalDecimal
  TaxDecimal
• Display results in labels as currency
• Set TotalCost 0 and Clear all entry TextBoxes
  and set focus to First Name

8
Next Item Button

• Module level variable
• Dim TotalCostDecimal as Decimal 0D
• Private Sub NextItemButton_Click( to VB
  generated Arguments )
• Declare local variables
• Dim ItemCostDecimal as Decimal
• Try
• Parse input numerical Values
• ItemCostDecimal Decimal.Parse(ItemCostTextB
  ox.Text)
• Compute values
• TotalsDecimal ItemCostDecimal
• Clear TextBoxes
• ItemDescriptionTextBox.Clear()
• ItemCostTextBox.Clear()
• ItemDescriptionTextBox.Focus()
• Catch AnError As Exception
• MessageBox(AnError.Message,Error)
• ItemCostTextBox.Focus()
• End Try

9
Display Totals Button

• Private TotalCostDecimal as Decimal
  module Variable
• Declare variables and Constants
• Dim DiscountDecimal as Decimal
• Dim SubTotalDecimal as Decimal
• Dim TaxDecimal as Decimal
• Dim AmountDueDecimal as Decimal
• Const TAX_RATE_Decimal as Decimal 0.07D

• Calculate Values
• DiscountDecimal Discount(TotalCostDecimal)
• SubTotalDecimal TotalCostDecimal
  DiscountDecimal
• TaxDecimal SubTotalDecimal TAX_RATE_Decimal
• AmountDueDecimal SubTotalDecimal TaxDecimal

10
Totals Button

• Try
• Compute Values
• DiscountDecimal Discount(TotalCostDecimal)
• SubTotalDecimal TotalCostDecimal
  DiscountDecimal
• TaxDecimal SubTotalDecimal TAX_RATE_Decimal
• AmountDueDecimal SubTotalDecimal TaxDecimal

• Format and display values
• TotalCostLabel.Text TotalCostDecimal.ToString(C
  )
• DiscountAmountLabel.Text DiscountDecimal.ToStrin
  g(C)
• SubTotalLabel.Text SubTotalDecimal.ToString(C)
  
• TaxLabel.Text TaxDecimal.ToString(C)
• AmountDueLabel.Text AmountDueDecimal(C)
• ClearTextBoxes()
• Catch
• Error Message, set focus and select all
• End Try

11
ClearTextBoxes Procedure
Three possibilities

• Private sub ClearAllBoxes()
• FirstNameTextBox.Clear()
• LastNameTextBox.text
• AddressTextBox.Text String.Empty
• etc.
• TotalCostLabel.text String.Empty
• etc
• TotalCostDecimal 0
• firstNameTextBox.Focus()

Two possibilities
12
Totals Button Code

• Call of cuntion
• DiscountDecimal Discount(TotalCostDecimal)
• Function heading
• Private Function Discount(ByVal TotalDecimal as
  Decimal) As Decimal

13
Function DiscountAmount

• Private Function Discount(ByVal TotalDecimal as
  Decimal) as Decimal
• 10 discount on all items if a customer for more
  than 6 months, an additional 5 discount if a
  customer longer than 18 months.
• Const FIRST_DISCOUNT_RATE_Decimal as Decimal
  0.05DConst SECOND_DISCOUNT_RATE_Decimal As
  Decimal0.10D

The method below uses the second discount on the
discounted price. Dim MemberDate as Date
Dim MonthsDouble As Double Parse
numeric/date textboxes MemberDate
Date.Parse( MemberInitialDateTextBox.text)
Calculate Months MonthsDouble
DateDiff(DateInterval.Months, MemberDate, Today)
Discount 0 IF monthsDouble gt 6
Then Discount TotalDecimal
FIRST_DISCOUNT_RATE_Decimal EndIf IF
monthsDouble gt 18 Then Discount (TotalDecimal
-DiscountDecimal)SECOND_DISCOUNT_RATE_Decimal
EndIf End Function