下面程序的功能是把文件file1.txt中重复字符去掉后(即若有多个字符相同,则只保留1个)写入文件 file2.txt。请填空。Private Sub Command1_Click()Dim in char As String,temp As String,out char As StringOut char=""Open"file1.txt"For Input As#1Open"file2.txt"For Output As【 】n=LOF( 【 】) in char=Input$(n,1)For k=1 To ntemp=Mid(in char,k,1)If InStr (out.char,temp)= 【 】ThenOut char=out char&tempEnd IfNext kPrint #2, 【 】Close #1Close #2End sub