有如下VB程序段:
s = Text1.Text
For i = 1 To Len(s)
c = Mid(s, i, 1)
If c >= "A" And c <= "Z" Then c = ①
If c >= "a" And c <= "z" Then
m = ②
c = Chr(Asc("a") + m)
End If
s1 = s1 + c
Next i
Label1.Caption = s1
程序运行时,在文本框Text1中输入“ABC123xyz”,在标签框Label1中输出“bcd123yza”,则划线处的代码为