程序功能：在文本框Text1中输入课程号，单击“查询”按钮Command1,在列表框List1中显示选修本课程的学生信息。如果没有找到，在列表框中显示“该课程当前无人报名”。按此要求将程序补充完整。

Private Sub command1_click()

Dim xh(1 to 40),xm(1 to 40) As String   '学号和姓名的数组

Dim i,num as integer

Dim conn As New ADODB.Connection, rs As New ADODB.Recordset

Dim strSQL As String

conn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + App.Path + "\student.accdb"     '打开到数据库的链接

 conn.Open

strSQL ="select xh,xm from data where '课程=&(Text1.Text) & '" '设置查询的SQL语句

 Set rs.ActiveConnection = conn      '设置rs的ActiveConnection属性，指定与其关联的数据库链接

  rs.Open strSQL   '打开记录集，将从表student中读取的结果集保存到记录集rs中

  List1.Clear

num=0

Do while not rs.EOF

             ①       

    xh(num)=rs.Fields("xh")

      xm(num)=rs.Fields("xm")

  rs.MoveNext

loop

rs.Close

  conn.close

set rs=nothing

set conn=nothing

For  i=1 to num

      ②     

Next i

if num=0 then list1.additem("该课程当前无人报名")

End Sub

Private Sub Commandl_Click( )

Dim s, p As String

Dim a, n As Integer

Dim kms As Integer

s=      ①     

n = Len ( s )：a = 0 ：kms = Val(Text2.Text)

If n Mod kms = 0 Then

For i=     ②_______

p = Mid(s，i，1)

If p= "A" or p= "a"  Then a = a+l

Next i

Text3.Text = Str(a)

Else

Text3.Text="学生等级信息不正确"

End  If

End  Sub

请回答下列问题：

图1

Private Sub Command1_Click()

  Dim sjzs As Integer

  Dim rjzs As String

  sjzs = Val(Text1.Text)

  rjzs = ""

  Do While Int(sjzs / 2) > 0

    rjzs = Str(sjzs Mod 2) + rjzs

    sjzs = Int(sjzs / 2)

  Loop

  Label1.Caption = rjzs

End Sub

图a

图b

小王编写的“模拟撤销”VB程序如下，文本框 Text1中的内容是撤销前字符串，文本概Text2中的内容是历史记录，单击“撤销”按钮Command1后，在标签Label1中显示撤销过程，程序运行界面如图b所示。