这是个计算器
Dim num(1) As String
Dim flag As Byte
Dim operator
Private Sub Command1_Click(Index As Integer)
Label2.Caption = ""
Label1.Caption = Label1.Caption & Index
num(flag) = num(flag) & Index
End Sub


Private Sub Command2_Click(Index As Integer)
If num(0) = "" Then Exit Sub
num(0) = Label1.Caption
    Select Case Index
    Case 0: Label1.Caption = Label1.Caption & "+"
    Case 1: Label1.Caption = Label1.Caption & "-"
    Case 2: Label1.Caption = Label1.Caption & "*"
    Case 3: Label1.Caption = Label1.Caption & "/"
    End Select
operator = Index
flag = 1

For i = 0 To 3
   Command2(i).Enabled = False
   
Next

End Sub

Private Sub Command3_Click()
On Error GoTo out‘这个语法怎么理解
Select Case operator
    Case 0: Label2.Caption = CLng(num(0)) + CLng(num(1))'clng是什么意思
    Case 1: Label2.Caption = CLng(num(0)) - CLng(num(1))
    Case 2: Label2.Caption = CLng(num(0)) * CLng(num(1))
    Case 3: Label2.Caption = CLng(num(0)) / CLng(num(1))
End Select
   Label2.Caption = "=" & Label2.Caption
For i = 0 To 1
    num(i) = ""
Next
    flag = o

out:
End Sub

Private Sub Command4_Click()
Label1.Caption = ""
Label2.Caption = ""
For i = 0 To 3
   Command2(i).Enabled = True
Next

End Sub

Private Sub Form_Load()

num(0) = ""
num(1) = ""
flag = 0  '这个起到什么作用,
End Sub

On Error Go To out: 程序运行出现错误的时候, 跳到out那一行;
clng: convert to long;
flag = 0: 确保下一次运行程序时flag的初始值=0.

[ 本帖最后由 alwaysfocus 于 2010-12-16 14:03 编辑 ]

谢谢