小雨:1d(或24h)降雨量小于10mm者。

中雨:1d(或24h)降雨量10~25mm者。

大雨:1d(或24h)降雨量25~50mm者。

暴雨:1d(或24h)降雨量50~100mm者。

大暴雨:1d(或24h)降雨量100~250mm者。

特大暴雨:1d(或24h)降雨量在250mm以上者。

Private Sub Command1_Click()

Dim a As Single

Dim s as      ①            

a =         ②             

If a > 250 Then

    s = "特大暴雨"

ElseIf a > 100 Then

    s = "大暴雨"

ElseIf a > 50 Then

    s = "暴雨"

ElseIf a > 25 Then

    s = "大雨"

ElseIf a > 10 Then

    s= "中雨"

ElseIf    ③        Then

    s = "小雨"

Else

    s = "无雨"

End If

Label3.caption=    ④           

End Sub

实现上述功能的VB程序如下，但加框处代码有错误，请改正。

  Dim a(1 To 15) As Integer

Dim n As Integer 'n为计数器

Dim key As Integer 'key存放筛选条件的数字部分

Dim f As String 'f存放筛选天健的符号部分：大于号或者小于号

Private Sub FormLoad()

Randomize

For i = 1 To 15

a(i) = Int(Rnd * 100)

List1.AddItem Str(a(i))

Next i

 End Sub

Private Sub Command1Click()

Dim c As Integer

Dim st As String

n = 0

c = Len(st)

f = Mid(st, 1, 1)

If f = "<" Then Se2 '调用过程

If f = ">" Then Se1 '调用过程

Label2.Caption = "有" + Str(n) + "个筛选结果"

End Sub

Private Sub Se1() '筛选过程1

For i = 1 To 15

   If a(i) > key Then

      List2.AddItem Str(a(i))

      n = n + 1

   End If

Next i

End Sub

Private Sub Se2() '筛选过程2

For i = 1 To 15

List2.AddItem Str(a(i))

       n = n + 1

    End If

Next i

End Sub

程序代码如下：

Private Sub Command1_Click()

  Dim n As Integer, i As Integer

  List1.Clear

  n = Val(Text1.Text)

  If n Mod 2 = 0 Then

    For i = 2 To Int(n / 2)

      If isodd(i) = (isodd(n - i)) Then

        List1.AddItem Str(n) + " =" + Str(i) + " +" + Str(n - i)

      End If

    Next i

  Else

    Text1.Text = Str(n) + "不是偶数！"

  End If

End Sub

Private Function isodd(n As Integer) as boolean

   Dim f As integer

   f = 0

   For i = 2 To Sqr(n)

     If n Mod i = 0 Then f = 1: Exit For

   Next i

   isodd =  f

End Function

型包括瀑布模型、快速原型模型、螺旋模型、增量模型和送代模型等，其中瀑布模型是从时间角度对软件开发和维护进行分解。该模型规定了一个自上而下，相互衔接的固定次序，如同瀑布流水，逐级下落。（如下图所示）