SET # POINTER
1. `SET #Channel_Number : POINTER BEGIN`
moves the file pointer to the beginning.
Note that it is not allowed to overwrite the existing records.
2. `SET #Channel_number : POINTER END`
moves the file pointer to the end.
Use this to append records to the existing records.
Even if the file is empty, no exception shall be raised.
Example.

    10 OPEN #1:NAME "A:ABC.TXT"
    20 SET #1: POINTER END
    30 PRINT #1: DATE$,TIME$
    40 CLOSE #1
    50 END

3. `SET #Channel_Number : POINTER SAME`
moves the file pointer back to the beginning of the line read just before.
4. `SET #Channe_Number : IF MISSING THEN EXIT DO`
executes EXIT DO if the file pointer exceeds the end.
[Note]
Just after a file is opened with ACCESS OUTPUT, the file pointer points the end.