为防止机密通知被盗，某公司制定了网上发通知的加密要求：
⑴通知中包含的空格，标点符号等按原格式输出
⑵通知中涉及到字母的内容，所发文件的英语单词全部都是倒序的。如：This is a dog!通知显示内容为： sihT si a god!
⑶通知中涉及到数字的内容， 把本组数字的最后一位移动到第一位，例如原文为 1234，通知显示内容为：4123
小王编写了一个VB程序，实现加密功能，在文本框 Text1中输入原文，单击“加密”按钮Command1 后，在文本框Text2中显示加密后的密文。程序运行界面如图所示。
实现上述功能的VB程序如下，请回答下列问题：
Private Sub command1_Click()
Dim s As String, ch As String, rv As String, rv1 As String
Dim i As Integer, j As Integer, k As Integer
s = Text1.Text
rv = ""
i = 1
Do While True
ch = Mid(s, i, 1)
Do While 
__________ And i <= Len(s)
rv = rv + ch
i = i + 1
ch = Mid(s, i, 1)
Loop
j = i
ch = ①
Do While sz(ch) And j <= Len(s)
j = j + 1
If j > Len(s) Then Exit Do
ch = Mid(s, j, 1)
Loop
rv1 = ""
rv1 = Mid(s, j - 1, 1) + Mid(s, i, j - i - 1)
rv = rv + rv1
i = ②
If i > Len(s) Then Exit Do
Do While zf(ch) And j <= Len(s)
j = j + 1
If j > Len(s) Then Exit Do
ch = Mid(s, j, 1)
Loop
rv1 = ""
For k = i - 1 To j - 1
rv1 = Mid(s, k, 1) + rv1
Next k
rv = rv + rv1
If j <= Len(s) Then rv = rv + Mid(s, j, 1)
i = j + 1
If i > Len(s) Then Exit Do
Loop
Text2.Text = rv
End Sub
Function zf(s As String) As Boolean
zf = False
If s >= "A" And s <= "Z" Or s >= "a" And s <= "z" Then
zf = True
End If
End Function
Function sz(s As String) As Boolean
sz = False
If ③ Then
sz = True
End If
End Function
