问答题

如下程序的功能是将一位整数转换为二进制形式的字符串，如果字符串长度小于4，将在其前面补“0”至4位。完善下列程序。
Private Sub Command1_Click()  
Dim t As Integer, b As String, k As Integer
t = InputBox("输入一位整数")
Do Until t = 0      
       k =____________
b = CStr(k) & b     
t = t \ 2
Loop  
If _________________< 4 Then   
b = "0000" & b   
b = Right(b, 4)
End If
Print b
End Sub