Calculator Project In VB

The basic layout of the screen is shown in the figure 5. There are two control arrays of buttons one for the digits 0 to 9 and another for operators +, -, /, * and =. The form is given the name ‘calculator’ and its icon property is set to calculator icon. The display label is given the name ‘Readout’ and the caption ‘0.’. The number buttons 0 to 9 are given the same name ‘Number’, their captions and indexes are set as 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 respectively. The operator buttons /, +, X, - and = are given the same name, “Operator” , and their indexes are set as 0, 1, 2, 3 and 4 respy. The ‘%’ button is given the name ‘Percent’, the ‘.’ button is given the name ‘Decimal’, the ‘C’ button is given the name ‘Cancel’ and the ‘CE’ button is given the name ‘CancelEntry’. The codes are entered in the code window as shown in the figure 5a. Save and run the project and check that the calculator functions properly.

Option Explicit
Dim Op1, Op2 ' Previously input operand.
Dim DecimalFlag As Integer ' Decimal point present yet?
Dim NumOps As Integer ' Number of operands.
Dim LastInput ' Indicate type of last keypress event.
Dim OpFlag ' Indicate pending operation.
Dim TempReadout
' Click event procedure for C (cancel) key.
' Reset the display and initializes variables.
Private Sub Cancel_Click()
Readout = Format(0, "0.")
Op1 = 0
Op2 = 0
Form_Load
End Sub
' Click event procedure for CE (cancel entry) key.
Private Sub CancelEntry_Click()
Readout = Format(0, "0.")
DecimalFlag = False
LastInput = "CE"
End Sub
' Click event procedure for decimal point (.) key.
' If last keypress was an operator, initialize
' readout to "0." Otherwise, append a decimal
' point to the display.
Private Sub Decimal_Click()
If LastInput = "NEG" Then
Readout = Format(0, "-0.")
ElseIf LastInput <> "NUMS" Then
Readout = Format(0, "0.")
End If
DecimalFlag = True
LastInput = "NUMS"
End Sub

' Initialization routine for the form.
' Set all variables to initial values.
Private Sub Form_Load()
DecimalFlag = False
NumOps = 0
LastInput = "NONE"
OpFlag = " "
Readout = Format(0, "0.")
'Decimal.Caption = Format(0, ".")
End Sub
' Click event procedure for number keys (0-9).
' Append new number to the number in the display.
Private Sub Number_Click(Index As Integer)
If LastInput <> "NUMS" Then
Readout = Format(0, ".")
DecimalFlag = False
End If
If DecimalFlag Then
Readout = Readout + Number(Index).Caption
Else
Readout = Left(Readout, InStr(Readout, Format(0, ".")) - 1) + Number(Index).Caption + Format(0, ".")
End If
If LastInput = "NEG" Then Readout = "-" & Readout
LastInput = "NUMS"
End Sub
' Click event procedure for operator keys (+, -, x, /, =).
' If the immediately preceeding keypress was part of a
' number, increments NumOps. If one operand is present,
' set Op1. If two are present, set Op1 equal to the
' result of the operation on Op1 and the current
' input string, and display the result.
Private Sub Operator_Click(Index As Integer)
TempReadout = Readout
If LastInput = "NUMS" Then
NumOps = NumOps + 1
End If
Select Case NumOps
Case 0
If Operator(Index).Caption = "-" And LastInput <> "NEG" Then
Readout = "-" & Readout
LastInput = "NEG"
End If
Case 1
Op1 = Readout
If Operator(Index).Caption = "-" And LastInput <> "NUMS" And OpFlag <> "=" Then
Readout = "-"
LastInput = "NEG"
End If
Case 2
Op2 = TempReadout
Select Case OpFlag
Case "+"
Op1 = CDbl(Op1) + CDbl(Op2)
Case "-"
Op1 = CDbl(Op1) - CDbl(Op2)
Case "X"
Op1 = CDbl(Op1) * CDbl(Op2)
Case "/"
If Op2 = 0 Then
MsgBox "Can't divide by zero", 48, "Calculator"
Else
Op1 = CDbl(Op1) / CDbl(Op2)
End If
Case "="
Op1 = CDbl(Op2)
Case "%"
Op1 = CDbl(Op1) * CDbl(Op2)
End Select
Readout = Op1
NumOps = 1
End Select
If LastInput <> "NEG" Then
LastInput = "OPS"
OpFlag = Operator(Index).Caption
End If
End Sub
' Click event procedure for percent key (%).
' Compute and display a percentage of the first operand.
Private Sub Percent_Click()
Readout = Readout / 100
LastInput = "Ops"
OpFlag = "%"
NumOps = NumOps + 1
DecimalFlag = True
End Sub

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