Rules - Write to File What do each Const mean?

Question

I have a sub routine in my rules to write to file.
It contains a line that says: Const ForReading = 1, ForWriting = 2, ForAppending = 8
What do each one of these do?
Write?
Read?
Append?
I usually use append but it seemed to be placing duplicate items in the file each time I ran it.
Then I tried the write and it only gave me one record.
Thanks!
Here is the entire sub routine:
Sub WriteToFile(txtStringToWrite,FName)
     On Error Resume Next
     Const ForReading = 1, ForWriting = 2, ForAppending = 8
     Dim fso, f
     Set fso = CreateObject("Scripting.FileSystemObject")
     Set f = fso.OpenTextFile("C:\Hyperion\Extracts\" & FName, ForAppending, True)
     f.WriteLine txtStringToWrite
     f.Close
     On Error GoTo 0
End Sub 'WriteToFile

Answer 1

Appending Means adding to the same file - the number of times you run the rule it appends to the same file.
Write means clear the file first and wirte.
Does that help??
Nick