Describing the structure of a file in detail

In the FILE SECTION of the DATA DIVISION, start a file description by using the keyword FD and the same file-name you used in the corresponding SELECT clause in the FILE-CONTROL paragraph.

DATA DIVISION.
FILE SECTION.
FD  filename
01  recordname
    nn . . . fieldlength & type
    nn . . . fieldlength & type
    . . .

In the example above, filename is also the file-name you use in the OPEN, READ, and CLOSE statements.

recordname is the name of the record used in WRITE and REWRITE statements. You can specify more than one record for a file.

fieldlength is the logical length of a field, and type specifies the format of a field. If you break the record description entry beyond level 01 in this manner, map each element accurately to the corresponding field in the record.

related references  
Data relationships (COBOL for AIX Language Reference)  
Level-numbers (COBOL for AIX Language Reference)  
PICTURE clause (COBOL for AIX Language Reference)  
USAGE clause (COBOL for AIX Language Reference)