Commodore 1541-II - Adding to a Sequential File

Of course, this erases all our old phone numbers, so make sure that any information that
may be deleted is of no importance. After writing our phone file, we remove our diskette
and turn off the system. Later, to recall the data in the file, we would reopen it with
something like
OPEN 8,8,8,"0:PHONES,S,R"
It doesn't matter whether the file and channel numbers match the ones we used before, but
the file name does have to match. However, it is possible to use an abbreviation form of
the file name, if there are no other files that would have the same abbreviation:
OPEN 10,8,6,"0:PH*,S,R"
If we have too many phone numbers, they might not fit in one file. In that case, we
might use several similar file names, and let a program choose the correct file.
100 INPUT "WHICH PHONE FILE (1-3)";PH
110 IF PHO1 AND PHO2 AND PH<>3 THEN 100
120 OPEN 4,8,2,"PHONE" + STR$(PH) + ",S,R"
You can omit the drive number on an Open command to read a file. Doing so allows those
with dual drives to search both diskettes for the file.
Note: Basic 2 and Basic 3.5 use the same file handling commands and the same
direct access commands (chapters 7-8). Unless otherwise noted, you may use the
same commands for both throughout the remainder of this book.
ADDING TO A SEQUENTIAL FILE
On Commodore's PET and CBM models, an Append command allows you to reopen
an existing sequential file and add more information to the end of it. The same thing can
be done another way on the 1541. In place of the "type" and "direction" parameters in
your Open statement, substitute ",A" for Append. This will reopen your file, and
position the disk head at the end of the existing data in your file, ready to add to it.
FORMAT FOR THE APPEND OPTION
OPEN file #,device #,channel #,"drive #:file name,A"
where, everything is as on the previous page except for the ending "A" replacing the
"type" and "direction" parameters.
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