VB calculator code
This article is mainly for the beginners. I am trying to explain the use of Control Arrays with the help of Calculator Sample.I feel control arrays are overlooked in classic visual basic. if the way to implement is understood, it is much useful in reducing the code. Control Arrays can be used in the situations like whenever the need of same controls being used several times in an application. We can make them as an array, and the controls can be accessed by their index in all the respective events
VB 6 Control Arrays in form
As shown in the following figure, Design the form. Create a Command Button named as Command1 and copy that and paste it 11 times. This will create a control array.
Then assign the text as shown in the figure. all the controls under red boxes are under one group. So design it accordingly.
like wise create cmdOperator control array for the green box group.
Now you can use the sample code to try
VB Calculator
we actually storing the Last Operator used and The first part of the number used in a class level variable. so that they can be accessed across the events and functions. Since the operators also created as control arrays. we had drastically reduced the amount of code required for a simple calculator.
Source Code - Simple(VB 6.0)
Private LastOperator
As StringPrivate FirstPart
As String Private Sub cmdClear_Click()
FirstPart = ""
LastOperator = ""
End Sub
Private Sub cmdEquals_Click()
Select Case LastOperator
Case Is = "+"
Text1.Text = FirstPart + Text1.Text
Case Is = "-"
Text1.Text = FirstPart - Text1.Text
Case Is = "/"
Text1.Text = FirstPart / Text1.Text
Case Is = "*"
Text1.Text = FirstPart * Text1.Text
End Select
FirstPart = ""
LastOperator = ""
End Sub
Private Sub cmdOperator_Click(Index As Integer)
LastOperator = cmdOperator(Index).Caption
FirstPart = Text1.Text
Text1.Text = ""
End Sub
Private Sub Command1_Click(Index As Integer)
Text1.Text = Text1.Text + Command1(Index).Caption
End Sub
Source Code - Enhanced Calculator(VB 6.0)
Now few places we need to lock the Calculator stop entering invalid entries. If not done then runtime error will be thrown. To prevent entering the alpha characters the textbox can be locked by enabled=false.
For improved usability, we can hook the keyboard to handle most of the keystrokes to minimize the use of mouse. After enabling KeyPreview in the Form, all the key strokes will be routed through the form. So handling event of form’s keypress will be able to handle the keyboard keys. Source Code - Enhanced Calculator(VB 6.0)
Private LastOperator As String
Private FirstPart As String
Private Sub Form_Load()
txtResult.Enabled = False
Me.KeyPreview = True
End Sub
Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)
' numbers in main keyboard
If (KeyCode >= 48 And KeyCode <= 57) Then
AddDigits (Chr(KeyCode))
End If
' numbers in numpad
If (KeyCode >= 96 And KeyCode <= 105) Then
AddDigits (Chr(KeyCode - 48))
End If
'if backspace
If (KeyCode = 8) Then
If (txtResult.Text <> "") Then
txtResult.Text = Left(txtResult.Text, Len(txtResult.Text) - 1)
End If
End If
'for various operators
If (KeyCode = 111) Then RegisterOperator ("/")
If (KeyCode = 106) Then RegisterOperator ("*")
If (KeyCode = 109) Then RegisterOperator ("-")
If (KeyCode = 107) Then RegisterOperator ("+")
End Sub
Private Sub cmdOperator_Click(Index As Integer)
RegisterOperator (cmdOperator(Index).Caption)
End Sub
Private Sub cmdClear_Click()
FirstPart = ""
LastOperator = ""
txtResult.Text = ""
End Sub
Private Sub cmdEquals_Click()
Select Case LastOperator
Case Is = "+"
txtResult.Text = FirstPart + txtResult.Text
Case Is = "-"
txtResult.Text = FirstPart - txtResult.Text
Case Is = "/"
txtResult.Text = FirstPart / txtResult.Text
Case Is = "*"
txtResult.Text = FirstPart * txtResult.Text
End Select
FirstPart = ""
LastOperator = ""
End Sub
Private Sub Command1_Click(Index As Integer)
AddDigits (Command1(Index).Caption)
End Sub
Private Sub AddDigits(Digit As String)
txtResult.Text = txtResult.Text & Digit
End Sub
Private Sub RegisterOperator(OperatorText As String)
LastOperator = OperatorText
FirstPart = txtResult.Text
txtResult.Text = ""
End Sub