Question

这段程序看不懂，求高人帮忙解释一下，感激不尽

Dim v As Boolean
Dim s As Integer
Dim x As Double
Dim y As Double
Private Sub Command1_Click(Index As Integer)
If Form1.Tag = "s" Then
If Index = 10 Then
Text1.Text = "0."
Else
Text1.Text = Command1(Index).Caption
End If
Form1.Tag = ""
Else
Text1.Text = Text1.Text & Command1(Index).Caption
End If
End Sub
Private Sub Command2_Click(Index As Integer)

Form1.Tag = "s"

If v Then
x = Val(Text1.Text)
v = Not v

Else
y = Val(Text1.Text)
Select Case s
Case 0
Text1.Text = x + y
Case 1
Text1.Text = x - y
Case 2
Text1.Text = x * y
Case 3
If y <> 0 Then
Text1.Text = x / y
Else
MsgBox ("不能以0为除数")
Text1.Text = x
v = False
End If
Case 4
y = 0
v = False
End Select
x = Val(Text1.Text)
End If
s = Index

End Sub

Answer 1

这是MFC里面定义的消息映射，斜杠部分不做解释了，本来就是注释
BEGIN_MESSAGE_MAP(CPApp, CWinApp)           //消息映射起始
ON_COMMAND(ID_APP_ABOUT, OnAppAbout)        //名字为ID_APP_ABOUT的按钮按下去之后响应OnAppAbout函数
ON_COMMAND(ID_FILE_NEW, CWinApp::OnFileNew) //名字为ID_FILE_NEW的按钮按下去之后响应CWinApp::OnFileNew函数
ON_COMMAND(ID_FILE_OPEN, CWinApp::OnFileOpen)//名字为ID_FILE_OPEN的按钮按下去之后响应CWinApp::OnFileOpen函数
ON_COMMAND(ID_FILE_PRINT_SETUP,CWinApp::OnFilePrintSetup) //名字为ID_FILE_PRINT_SETUP的按钮按下去之后响应CWinApp::OnFilePrintSetup函数
END_MESSAGE_MAP()   //消息映射定义结束