Private Sub Command1_Click()

Dim a(1 To 1000) As Integer, b(1 To 1000) As Integer

Dim n As Integer, m As Integer

Dim s As String, s1 As String, c As Integer, ch As String

s = Text1.Text: Text2.Text = ""

n = Len(s)

k = 1

For i = 1 To n                  ‘获取字符的二进制数据存放在数组a()中

  n = Asc(Mid(s, i, 1))

  Do While n <> 0

   a(k) = n Mod 2

   n = n \ 2

   Text2.Text = Text2.Text + Str(a(k))

   k = k + 1

  Loop

Next i

              ①                   

List1.Clear

For m = 1 To (k - 1) \ 16    '对字符二进制按规则进行位变换，变换后的数据存放在数组b()中并输出

  For i = 1 To 4

    b(16 * (m - 1) + 4 * (i - 1) + 1) = a((m - 1) * 16 + i)

             ②              

  Next i

  For i = 1 To 3

    b(16 * (m - 1) + 4 * (i - 1) + 3) = a((m - 1) * 16 + 10 + i)

    b(16 * (m - 1) + 4 * (i - 1) + 2) = a((m - 1) * 16 + 17 - i)

  Next i

  For i = 1 To 2

    b(16 * (m - 1) + 13 + i) = a((m - 1) * 16 + 4 + i)

  Next i

 For i = 1 To 4

  s1 = ""

  For j = 1 To 4

  s1 = s1 + Str(b(16 * (m - 1) + (i - 1) * 4 + j))

  Next j

  List1.AddItem s1

  Next i

List1.AddItem ""

Next m

s1 = ""

For i = ((k - 1) \ 16) * 16 + 1 To k - 1

   b(i) = a(i)

    If          ③         Then

    s1 = s1 + Str(a(i))

    List1.AddItem s1

    s1 = ""

    Else

    s1 = s1 + Str(a(i))

    End If

Next i

List1.AddItem s1

Text3.Text = ""

For i = 1 To k - 1

Text3.Text = Text3.Text + Str(b(i))

Next i

End Sub

实现上述功能，请在划线处填入适当的代码：

程序中①处填入的是。

程序中②处填入的是。

程序中③处填入的是。