COBOL has support to 3 principle file organizations
:
All these three organizations can be used on DISK
files; only the SEQUENTIAL organization can be used with TAPE
files.
All files must be declared in the ENVIRONMENT division
by proper SELECT statements which should contain a phrase describing
to the compiler what type of organization the file should have.
A second important declaration should be placed in the FILE-SECTION
where the programmer desrcibes the record format associated to
the file in FD blocks.
Finally, the PROCEDURE division should have proper
OPEN/CLOSE and READ/WRITE etc. statements used in compliance with the
logic (algorithm) of the program.