www.mfcad
Option Explicit
Private StoredValue As Double
Private Const opNone = 0
Private Const opAdd = 1
Private Const opSubtract = 2
Private Const opMultiply = 3
Private Const opDivide = 4
Private Operator As Integer
Private NewEntry As Boolean
'删除最后的字符
Private Sub DeleteCharacter()
Dim txt As String
Dim min_len As Integer
txt = txtDisplay.Text
If Left$(txt, 1) = "-" Then
min_len = 2
Else
min_len = 1
End If
If Len(txt) > min_len Then
txtDisplay.Text = Left$(txt, Len(txt) - 1)
Else
txtDisplay.Text = "0"
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End If
End Sub
'清除显示内容，保存运算符
Private Sub cmdClear_Click()
cmdClearEntry_Click
StoredValue = 0
Operator = opNone
End Sub
'清除显示内容
Private Sub cmdClearEntry_Click()
txtDisplay.Text = ""
End Sub
' 显示小数点
Private Sub cmdDecimal_Click()
If InStr(txtDisplay.Text, ".") Then
Beep
Else
If NewEntry Then
txtDisplay.Text = "."
NewEntry = False
Else
txtDisplay.Text = txtDisplay.Text & "."
End If
End If
End Sub
'计算上一操作符的运算结果
Private Sub cmdEquals_Click()
Dim new_value As Double
If txtDisplay.Text = "" Then
new_value = 0
Else
new_value = CDbl(txtDisplay.Text)
End If
Select Case Operator
Case opNone
StoredValue = new_value
Case opAdd
StoredValue = StoredValue + new_value
Case opSubtract
StoredValue = StoredValue - new_value
Case opMultiply
StoredValue = StoredValue * new_value
Case opDivide
StoredValue = StoredValue / new_value
End Select
Operator = opNone
NewEntry = True
txtDisplay.Text = Format$(StoredValue)
End Sub
' 显示数字
Private Sub cmdNumber_Click(Index As Integer)
If NewEntry Then
txtDisplay.Text = Format$(Index)
NewEntry = False
Else
txtDisplay.Text = txtDisplay.Text & Format$(Index)
End If

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