下列VB程序运行时，单击命令按钮Command1后，在文本框Text1中输入“1024”，语句“a(i)=a(i+1)/2”共被执行了________次。
Private Sub Command1_C1ick ( )
Dim a(9) As Integer
a(9)=Val(Text1.text)
For i="8" to 1 step -2
a(i)=a(i+1)/2
Next i
Text2.text=str(a(i))
End Sub