Calculator Processing

Start Fresh
Download from
TPITVB.blogspot.com
2
1

Start fresh
Start VS 2005 and Create a new project: Calculator_IT1C_xx
Choose appropriate directory and remember its path
Exit VS 2005
Unzip start_cal.zip: Form1.vb and Form1.Designer.vb
Use File explorer to replace the two newly created project files in Calculator_IT1C_xx

ButtonSqrt_Click
Double click on the button for Sqrt to generate the ButtonSqrt_Click subroutine
Copy the codes from ButtonEqual_Click
Modify the following line to use Math.Sqrt
total = total + x
total = Math.Sqrt(x)

ButtonPercent_Click
Double click on the button for % to generate the ButtonPercent_Click subroutine
Copy the codes from ButtonEqual_Click
Modify the following line to use Math.Sqrt
total = total + x
total = x / 100

Dot
Private Sub ButtonDot_Click
‘ Copy the codes from Button0
‘ Replace “0” with “.”
Dim existingString As String = TextBox1.Text
If existingString <> "" Then
TextBox1.Text = existingString & "0"
End If
End Sub
“.”

Testing
1.5 OK
0.5 NG => How?

Dot
‘ Add else condition
‘ to add “0.”
TextBox1.Text = existingString & “.”
End If
End Sub
Else
TextBox1.Text = existingString & “0.”
End If
End Sub

Testing
1.5 OK
0.5 OK
1.5.5. => should not allow – How?

How to stop “1.5.5.”?
We need to use a global variable to track if “.” has been set
Then add additional codes in ButtonDot to check this variable

Dot
Global variable:
Public Class Form1
Dim isDotted As Boolean = False

Dot
‘ Add Condition to check for isDotted
TextBox1.Text = existingString & “.”
Else
TextBox1.Text = existingString & “0.”
End If
End Sub
If isDotted = False Then
isDotted= True ‘ Set isDotted to True
End If
End Sub

Testing
1.5 OK
0.5 OK
1.5.5. OK
1.5 Clear 1.5 => NG - How?

Dot
Private Sub ButtonClear_Click
:
:
‘ Reset isDotted to False
isDotted = False
End Sub

Testing
1.5 OK
0.5 OK
1.5.5. OK
1.5 Clear 1.5 OK
1.5 + 1.5 => NG – How?

Dot
Private Sub ButtonPlus_Click
:
:
‘ Reset isDotted to False
isDotted = False
End Sub

Testing
1.5 OK
0.5 OK
1.5.5. OK
1.5 Clear 1.5 OK
1.5 + 1.5 OK
Anymore cases?

Minus, Multiply and Divide
Before we proceed to add the processing for Minus, Multiply and Divide,
we need to modify the current processing for Plus and Equal

Modify Plus and Equal
:
:
total = total + x
:
End Sub
total = x ‘ Now, Plus can only be ‘ pressed once.

Global variable:
Public Class Form1
Dim whatFunction As String = “None”

:
:
whatFunction = “Plus”
End Sub

Private Sub ButtonEqual_Click
:
:
total = total + x
:
End Sub
Select Case whatFunction
Case “Plus”
total = total + x
End Select
Case “Minus”

Add Minus, Multiply and Divide
Complete the processing for minus, multiply and divide.
Take care of divide by zero error with if then else statement
Do testingand debugging to take care of other errors