Option Explicit

Dim Num_of_digit As Integer

Dim key As Integer

Dim displayValue As Variant

Dim a, b, c, d, e, f, g As Variant

Dim memo As Variant

Dim newNumber As Boolean

Private Sub BZero_Click(Index As Integer)

If Num_of_digit > 0 Then

panel.Caption = panel.Caption + "0"

Else

panel.Caption = "0"

Num_of_digit = Num_of_digit + 1

End If

CheckValue

End Sub

Private Sub Form_Load()

Left = (Screen.Width - Width) \ 2

Top = (Screen.Height - Height) \ 2

End Sub

Sub CheckValue()

displayValue = Val(panel.Caption)

End Sub

Private Sub ButtonNum_Click(Index As Integer)

If Num_of_digit > 0 Then

If Num_of_digit < 30 Then

panel.Caption = panel.Caption + Right$(Str$(Index), 1)

Num_of_digit = Num_of_digit + 1

End If

Else

panel.Caption = Right$(Str$(Index), 1)

Num_of_digit = 1

End If

CheckValue

End Sub

Private Sub Clear_Click()

panel.Caption = "0"

displayValue = "0"

Num_of_digit = 0

End Sub

Private Sub ClearAll_Click()

panel.Caption = "0"

displayValue = "0"

memo = 0

End Sub

Private Sub Equal_Click()

CheckValue

If newNumber = True Then

If key = 1 Then

e = displayValue + a

ElseIf key = 2 Then

e = b - displayValue

ElseIf key = 3 Then

e = displayValue * c

ElseIf key = 5 Then

e = (f * displayValue) / 100

ElseIf key = 4 And displayValue <> 0 Then

e = d / displayValue

Else

GoTo error

End If

If Abs(e) < 1 Then

panel.Caption = Format(e, "General Number")

Else

panel.Caption = Str(e)

End If

Else

panel.Caption = displayValue

End If

GoTo finish

error: panel.Caption = "E"

finish:

Num_of_digit = 0

newNumber = False

End Sub

Private Sub MemoCancel_Click()

memo = 0

End Sub

Private Sub Memory_Click()

CheckValue

memo = displayValue

Num_of_digit = 0

End Sub

Private Sub Operator_Click(Index As Integer)

CheckValue

If Index = 11 Then

a = displayValue

key = 1

ElseIf Index = 12 Then

b = displayValue

key = 2

ElseIf Index = 13 Then

c = displayValue

key = 3

ElseIf Index = 14 Then

d = displayValue

key = 4

ElseIf Index = 15 Then

f = displayValue

key = 5

End If

Num_of_digit = 0

newNumber = True

End Sub

Private Sub Percent_Click(Index As Integer)

End Sub

Private Sub Plus_minus_Click()

CheckValue

g = -1 * displayValue

displayValue = g

panel.Caption = Str$(displayValue)

CheckValue

End Sub

End Sub

Private Sub Poin_Click()

Static point_lock As Integer

If point_lock = 0 And Num_of_digit < 20 Then

panel.Caption = panel.Caption + "."

Num_of_digit = Num_of_digit + 1

End If

CheckValue

End Sub

Private Sub Recall_Click()

panel.Caption = Str$(memo)

End Sub

Private Sub SqRoot_Click()

CheckValue

If displayValue >= 0 Then

panel.Caption = Str$(Sqr(displayValue))

Else

panel.Caption = "E"

End If

Num_of_digit = 0

End Sub

Private Sub Summation_Click()

CheckValue

memo = memo + displayValue

Num_of_digit = 0

End Sub