This article follows my introduction to the COBOL language. I advise you to reread the first part that deals with the general principles of COBOL. Here: https://128mots.com/index.php/2020/10/07/ibm-cobol/ and English https://128mots.com/index.php/en/2020/10/07/ibm-cobol-3/ (IBM COBOL FREE TRAINING)
Here we discuss the general concepts of the structure of a COBOL program.
DATA DIVISION
All the data that will be used by the program is located in the Data Division. This is where all the memory allowances required by the program are taken care of. This division is optional.
FILE MANAGEMENT:
FILE SECTION describes data sent or from the system, especially files.
The SYNtax in COBOL is the following
DATA DIVISION.
FILE SECTION.
FD/SD NameOfFile[RECORD CONTAINS intgr CHARACTERS]
[BLOCK CONTAINS intgr RECORDS]
[DATA RECORD IS NameOfRecord].
[RECORDING MODE IS {F/V/U/S}]
FD describes the files and SD the sorting files.
FILE IN INPUT
In FILE-CONTROL the statement will be:
SELECT FMASTER ASSIGN FMASTER
FILE STATUS W-STATUS-FMASTER.
If the input file is indexed:
SELECT FMASTER ASSIGN FMASTER
ORGANIZATION IS INDEXED
RECORD KEY IS FMASTER-KEY
FILE STATUS W-STATUS-FMASTER.
In this case at the file-SECTION level we will have:
FMAITRE as an appetizer
FD FMAITRE.
01 ENR-FMAITRE.
Statements from the registration areas
At the JCL level the statement will be of the form:
ENTREE DD DSN-SAMPLE. INPUTF,DISP-SHR
FILE OUT
The JCL statement will then be:
OUTFILE DD DSN-SAMPLE. OUTPUTF,DISP(,CATLG,DELETE), LRECL-150,RECFM-FB
RECFM specifies the characteristics of records with fixed length (F), variable length (V), variable length ASCII (D) or indefinite length (U). Records that are said to be blocked are described as FB, VB or DB.
OPENING AND CLOSING FILE IN PROCEDURE DIVISION
COBOL uses PROCEDURE DIVISION mechanisms to perform writing, closing and file openings.
Entry file opening:
OPEN INPUT FICENT
Opening the output file:
OPEN OUTPUT FICSOR
File closure:
CLOSE FICENT CLOSE FICSOR
File playback:
READ ACTENR AT END MOVE 'O' TO LAST-RECORD END-READ
File writing
WRITE SOR-ENR
EXTERNAL LINKS TO RESOURCES (IBM COBOL FREE TRAINING)
Below are some links that I found interesting that also deal with file management with COBOL.
Example of IBM file management: https://www.ibm.com/support/knowledgecenter/en/SS6SGM_5.1.0/com.ibm.cobol51.aix.doc/PGandLR/ref/rpfio13e.html
REFM Format: https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.2.0/com.ibm.zos.v2r2.idad400/d4037.htm
Tutorialspoint an article on file management https://www.tutorialspoint.com/cobol/cobol_file_handling.htm
COURSERA COBOL with VSCODE: https://www.coursera.org/lecture/cobol-programming-vscode/file-handling-YVlcf
MEDIUM an interesting article for COBOL beginners: https://medium.com/@yvanscher/7-cobol-examples-with-explanations-ae1784b4d576
Also on his blog: http://yvanscher.com/2018-08-01_7-cobol-examples-with-explanations–ae1784b4d576.html
Many example COBOL free tutorials and sample code: http://www.csis.ul.ie/cobol/examples/default.htm
GITHUB Awesome-cobol https://github.com/mickaelandrieu/awesome-cobol you
IBM COBOL FREE TRAINING