Commodore 1541 - Creating a Relative File

7. RELATIVE FILES
RELaiive Tiles allow you to easily zero in on exactly the piece of data thai you
want from the file, ll [s more convenient for data handling because it allows you to
structure your files inio records, and into fields within those records.
The DOS keeps track of the tracks and blocks used, and even allows records to
overlap from one block to Ihc next. 31 is able 10 do this because it establishes side sec
tors, a series of pointers for the beginning of each record. Each side sector can point to
up to 120 records, and there may be 6 side sectors in a file. There can be up to 720
records in a file, and each record can be up to 254 characters, so the file couid be as
large as (he entire diskette.
CREATING A RELATIVE FILE
When a RELaiive file is first to be used, the OPEN statement will create that file;
after that, that same file will be used. The replace option (with the @ sign) does not
erase and re-creale the file. The file can be expanded, read, and written into.
FORMAT FOR THE OPEN STATEMENT TO CREATE RELATIVE FILE:
OPEN file#t device*, channel*, "name,L," + CHRS(record length)
EXAMPLES OF OPEN STATEMENT CREATING RELATIVE FILES;
OPEN 2, 8, 2, "FILE.L," + CHRS(IOO)
OPENF, 8, F, A$+",L,"
OPEN A, B, C, "TEST,L/' + CHRS{33)
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