son.

About the Author

    I have been working in IT organization for several years. My foray into programming starts with Pascal, C, and Java. Later when I joined my career in IT I was introduced to mainframe. That was a big leap ahead in my career. All my academic I have coded mainly interactive program whereas mainframe is mainly batch. Initially it was a big challenge to my career whether I can survive. Slowly I gathered my pace around batch programming.

Preface

    During my mainframe career I have faced several difficulties. There are lots of books available in the market but all these books mainly describe the theory. There are lots of training center that only provide theoretical class. IT companies to cut cost they only provide online training without any hands on.

    In this book my main aim is to fill up that gaps. If you are already familiar with the COBOL than you will find this book very useful. Even if you are new to COBOL, there are plenty of theory to boost your knowledge.

    In this book I have designed each chapter the way real application works. In first few chapters there are only theoretical concept to make you familiar with COBOL. Later I have introduced the real practical example to each chapter. These example not only give you practical knowledge at the same time give you feel of the real application.

    All the examples in this book are very simple and easy to follow. Each example has description about how to code, and explanation of input and how to execute it.

About the Book

1.  All the programs are written based on Enterprise COBOL 6.2.

2.  All programs are executed in mainframe.

3.  All programs except CICS programs are batch programs.

4.  Covered vast range of topics so that you do not have to follow multiple books. Once you are become familiar with the topics you can follow more advanced books.

5.  All the programs are from my lengthy programming experience.

6.  Although program looks lengthy they are simple.

7.  Some of the programs look same. Two things to note here, if you can understand one thing, you can easily follow the next topic since both are similar.

8.  Programs mainly focused on read and write. My goal is to give you the data you need then apply your business logic and process the data.

9.  Most programs have add, update and delete operations together. All the operations are similar and these ways to reduce the number of programs.

10.  Program does not have enough error handling.

11.  All the programs have been tested for one set of input.

12.  All the programs have associated with input and output data. In the examples data have been changed to make it more readable. For example binary and packed decimal data have been presented in decimal form. If you see different out, this is just for above reasons.

13.  Some programs might have dead codes, meaning codes that never executed. I might have missed them.

14.  All the statements are described with full options. In practice, hardly all of them are used. Optional parameter is coded in square bracket.

15.  The book covers vast range of topics but not all chapters are complete. I assume you have some knowledge of C and Java programming.

16.  By convention, I have used PDSE as load library.

Contents

Table of Contents

About the Author

Preface

About the Book

Contents

1  Introduction to Mainframe and COBOL

Evolution of mainframe

Features of Mainframe

Reason of Popularity

Security

Reliability

Performance

COBOL

Development of COBOL

Structure of COBOL

2  Data types: Numeric and Characters

Variable or Data name

LEVEL number

Variables or data names

Data Types

Literals

Figurative Constants

Initializing variables

SET statement

POINTER variable

INITIALIZE statement

JUSTIFIED RIGHT clause

USAGE clause

SIGN clause

Sign Character in packed decimal

SYNCHRONIZED clause

BLANK WHEN ZERO clause

Data format conversion

3  Operations: Arithmetic, Conditional, Character

Arithmetic Operations

Numeric Statements

Numeric Operators

Numeric class test

Sign test

NOT keyword

ADD statement

SUBTRACTION statement

MULTIPLY statement

DIVIDE statement

COMPUTE statement

Numeric Intrinsic Functions

Conditional Operations

Operators

IF conditional statement

Null Statement

EVALUATE statement

Defining a switch

Defining a flag

GO TO statement

Character Operations

Class test

STRING statement

UNSTRING statement

EXAMINE statement

INSPECT statement

MOVE statement

DISPLAY statement

FILLER clause

Substring

Intrinsic functions

Special register

LENGTH OF Special Register

4  Tables

Table

Subscript

Index

Difference between subscript and index

OCCURS clause

Format 1

Format 2

OCCURS DEPENDING clause

Initializing a table

Loading a table

Searching a table

SEARCH statement

SEARCH ALL statement

Sorting a table

Processing table

PERFORM statement

Examples

5  Modules: Copy Member and Sub Programs

COPY statement

CALL statement

Types of CALL

Static Call

Dynamic Call

Difference between static call and dynamic call

Parameter Passing

CALL BY REFERENCE

CALL BY CONTENT

CALL BY VALUE

Difference between CALL BY CONTENT and CALL BY VALUE

RETURNING phrase

Program states

INITIAL clause

CANCEL statement

COMMON clause

RECURSIVE clause

Data name scope

GLOBAL clause

EXTERNAL clause

Attributes of subprograms

Subprogram design considerations

6  Preparation: Program Execution and Best Practices

JCL

Syntax

JCL code sheet

Preparing a Program

Compile JCL

RUN JCL

Logical record length and block size

Parameter passing

Severity codes for compiler diagnostic messages

Compiler Options

Compile Options

Conflicting compiler options

Storage and addressability

Design a Program

Best Practices

Practice Examples

Practice Example 1

7  COBOL Playground

Practice Examples

Practice Example 1

Practice Example 2

Practice Example 3

Practice Example 4

Practice Example 5

Practice Example 6

Practice Example 7

Practice Example 8

Practice Example 9

Practice Example 10

Practice Example 11

Practice Example 12

Practice Example 13

Practice Example 14

Practice Example 15

Practice Example 16

Practice Example 17

Practice Example 18

Practice Example 19

Practice Example 20

Practice Example 21

Practice Example 22

Practice Example 23

Practice Example 24

Practice Example 25

Practice Example 26

Practice Example 27

Practice Example 28

Practice Example 29

Practice Example 30

Practice Example 31

Practice Example 32

Practice Example 33

Practice Example 34

Practice Example 35

Practice Example 36

Practice Example 37

Practice Example 38

Practice Example 39

Practice Example 40

Practice Example 41

Practice Example 42

Practice Example 43

8  File Access: Sequential File

Mainframe Files

Record structure

File Processing

File Declaration

File Definition

File structure

Performing file i-o operations

File Status

Variable File

Format 1

Format 2

Practice Examples

Practice Example 1

Practice Example 2

Practice Example 3

Practice Example 4

Practice Example 5

9  File Access: VSAM File

VSAM

Types of VSAM Files

ESDS

KSDS

RRDS

LDS

Summary of access methods and allowed operations

Defining VSAM Files

IDCAMS utility

COBOL syntax for VSAM files

ESDS

KSDS

RRDS

Performing file i-o operations

OPEN statement

CLOSE statement

File Operations

START statement

READ statement

READ NEXT statement

WRITE statement

REWRITE statement

INVALID KEY phrases

Statements to update a VSAM record

File Status

Practice Examples

Practice Example 1

Practice Example 2

Practice Example 3

Practice Example 4

Practice Example 5

Practice Example 6

Practice Example 7

Practice Example 8

Practice Example 9

Practice Example 10

Practice Example 11

Practice Example 12

Practice Example 13

Practice Example 14

10  Sort and Merge

SORT Types

Sorting in COBOL

Defining SORT

Describing SORT

Sorting in COBOL

SORT statement

Format 1

Format 2

RELEASE statement

RETURN statement

MERGE statement

Practice Examples

Practice Example 1

Practice Example 2

Practice Example 3

Practice Example 4

Practice Example 5

Practice Example 6

Practice Example 7

Practice Example 8

Practice Example 9

11  Report Writing

Types of Output Files

Extract file

Text file

Delimited file

Report file

Practice Examples

Practice Example 1

Practice Example 2

Practice Example 3

Practice Example 4

Practice Example 5

12  Database Access

Concept of RDBMS

Data types

DB2 data types

Large Objects (LOBs)

NULL value

DEFAULT value

Naming Standards

Data Processing

Where to run SQL

INSERT statement

SELECT statement

UPDATE statement

DELETE statement

WHERE clause

Joining Columns

Joining Rows

COMMIT statement

ROLLBACK statement

SAVEPOINT statement

CURSOR

DCLGEN

SQL Codes

SQLCODE in COBOL output

DSNTIAR: SQLCODE handling

SQLCA

LOCK

Lock Size

Lock State or Lock Mode

ISOLATION

Cursor Stability

Repeatable Read

Read Stability

Uncommitted Read

Column Functions

Scalar Function

Aggregate Function

String unit specifications

Coding DB2 Program

Steps to write and execute a COBOL DB2 Program

DB2 Program Execution Process

PACKAGE

PLAN

COLLECTION

Compile JCL

Precompiler Options

BIND JCL

Run JCL

Create tables for Practice Example

CREATE Tablespace

Account Table

Customer Table

DROP Indexes

DROP Tables

GRANT Access on Tablespace

DROP Tablespace

Practice Examples

Practice Example 1

Practice Example 2

Practice Example 3

13  CICS

Functions of CICS

Control Tables and Control Programs

Common Terms

Terminal

Keyboard

CICS Concepts

Task

Transaction

Multitasking

Multithreading

Re-entrant Program

Quasi re-entrant

CICS Transactions

Coding Technique

Pseudo Conversational Technique

BMS

BMS Terms

Field

MAP

MAPSET

BMS MACRO

Creating MAP

Physical Map

Symbolic Map

Compiling MAP

Coding CICS Commands in COBOL Program

Programming Consideration

Program Preparation

Compile JCL

CICS Compiler Options

CICS Basic Commands

SEND TEXT

SEND CONTROL

SEND PAGE

LOAD command

RELEASE command

SEND MAP command

RECEIVE MAP

RETURN

CICS Copybooks

DFHAID

DFHEIBLK

DFHCOMMAREA

DFHATTR

Calling Subprogram

COBOL CALL

LINK

XCTL

Program Hierarchy

Passing Data

File Handling Commands

Direct Access

Sequential Access

Execution Steps of a CICS program

Practice Examples

Practice Example 1

Practice Example 2

EMPLOOYEE File

Practice Example 3

Practice Example 4

Practice Example 5

Practice Example 6

14  Application Development Cycle

Category of Source elements

Roles and Responsibilities

Documentations

Projects

Development Steps

Environment

Migration Path

Version Control or Change Control

Retrofit

Batch and Online

Testing

Testing Artifacts

Testing Methods

15  Debugging

Causes of Abend

Using DISPLAY statement

Using Compiler Options

Using Language Environment runtime options

Familiar with the dump

Using Language Environment Callable Service

Using TEST compiler option

Using OPT compiler option

Using Language Environment TERMTHDACT runtime option

Dump DD statements

Practice Examples

Practice Example 1

Practice Example 2

Practice Example 3

16  Language Environment

Usage

Compiler option

Language Environment specific data set

LE Program Management Model

Common Services

Storage Management Service

Condition Handling

Message Handling Service

Date and Time Service

Locale callable service

General callable service

Math Service

Practice Example

Practice Example 1

Practice Example 2

Practice Example 3

Practice Example 4

Practice Example 5

Practice Example 6

Practice Example 7

Practice Example 8

Practice Example 9

Practice Example 10

17 Communication with Java and JZOS

Java

Sample Java

Data types

Array

String

Method

Calling a method

Constructors

class and object

Communicating with Java methods

REPOSITORY paragraph

OBJECT REFERENCE phrase

Invoking a method

Java Native Interface (JNI)

Local and global references

Deleting, saving, and freeing local references

JNI services for local and global references

Creating instances of classes

Sharing data with Java

Interoperable data types for COBOL and Java

Miscellaneous argument types for COBOL and Java

Handling Java array and String

Preparing a COBOL client

compiler options

Linking OO Application

Invoking Java from a batch COBOL program

JZOS

JZOS Capabilities

Dataset IO

Accessing the z/OS data set

Referring z/OS data set

Access file using BPXWDYN callable service

Library functions used in examples

Position parameters used in examples

I-O mode

Data type comparison between COBOL and JZOS

Practice Examples

Practice Example 1

Practice Example 2

Practice Example 3

Practice Example 4

Practice Example 5

Practice Example 6

Practice Example 7

JZOS Batch Launcher

Practice Example 8

Practice Example 9

Practice Example 10

Practice Example 11

Practice Example 12

Practice Example 13

Practice Example 14

Practice Example 15

Practice Example 16

Practice Example 17

Practice Example 18

Practice Example 19

Practice Example 20

Practice Example 21

Practice Example 22

Practice Example 23

18  DLL

Advantages of DLL

Compiling DLL

Compile options for your programs

Linking DLL

Binder options for DLL applications

Invoking DLL

CALLINTERFACE directive

Calling DLL from non-DLLs

Pointers in DLL

Practice Examples

Practice Example 1

Practice Example 2

Practice Example 3

Practice Example 4

Practice Example 5

19  Multithreading

Compiling Options

LOCAL-STORAGE Section

Concepts

Process

Run unit

Thread

Program invocation

Program termination

Coding in multi thread environment

Serialization techniques

Limitations in COBOL

20  JSON and z/OS® JSON Parser

JSON

JSON data types

JSON Schema

Processing JSON input

JSON PARSE statement

JSON-CODE special register

Reason codes for JSON exception conditions

JSON-STATUS special register

Reason codes for JSON nonexception conditions

Parsing JSON names that are not valid COBOL data names

Producing JSON output

JSON GENERATE statement

Practice Examples

Practice Example 1

Practice Example 2

Practice Example 3

Practice Example 4

Practice Example 5

Practice Example 6

Practice Example 7

Practice Example 8

Practice Example 9

Practice Example 10

Practice Example 11

Practice Example 12

Practice Example 13

Practice Example 14

z/OS® JSON Parser

Practice Example 15

Practice Example 16

Practice Example 17

Practice Example 18

21  XML and XML Toolkit for z/OS®

XML

XML tree

Entity References

XML Element

XML Attributes

XML Namespaces

XML schema

Processing XML input

XML PARSE statement

Compiler options

Link-edit consideration

XML Special Registers

XML-CODE special register

Decoding XML-CODE

XML-EVENT special register

XML-INFORMATION special register

XML-NAMESPACE special register

XML-NNAMESPACE special register

XML-NAMESPACE-PREFIX special register

XML-NNAMESPACE-PREFIX special register

XML-NTEXT special register

XML-TEXT special register

XML documents

Preparing XML schema

Encoding XML documents

Handling XML split

Terminating XML parsing

Exceptions Handling

Producing XML output

XML GENERATE statement

Encoding the XML output

Exceptions handling

Practice Examples

Practice Example 1

Practice Example 2

Practice Example 3

Practice Example 4

Practice Example 5

Practice Example 6

Practice Example 7

Practice Example 8

Practice Example 9

Practice Example 10

Validating XML with schema

Practice Example 11

Practice Example 12

Practice Example 13

Practice Example 14

Practice Example 15

Practice Example 16

Practice Example 17

Practice Example 18

Practice Example 19

XML Toolkit for z/OS®

Practice Example 20

Practice Example 21

22 Interlanguage Communication with C

C

Sample program

Data types

Scope terminator

Comment line

Functions

Calling function

Comparison of COBOL and C/C++ data types

Passing data without pragma

Supported data types under pass by value (direct)

Supported data types under pass by indirect (indirect)

Passing data with pragma

Supported data types for pass by value

Supported data types for pass by reference

Passing strings

Handling function return from COBOL

Handling function return from C

Referring z/OS data set

Library function used in examples

Position parameter for flocate()

I-O mode

Practice Examples

Practice Example 1

Practice Example 2

Practice Example 3

Practice Example 4

Practice Example 5

Practice Example 6

Practice Example 7

Practice Example 8

Practice Example 9

Practice Example 10

Practice Example 11

Practice Example 12

Practice Example 13

Practice Example 14

Practice Example 15

Practice Example 16

Practice Example 17

Practice Example 18

Practice Example 19

Practice Example 20

Practice Example 21

Practice Example 22

Practice Example 23

RRDS Record Structure

Practice Example 24

Practice Example 25

Practice Example 26

Practice Example 27

Practice Example 28

Practice Example 29

I Auxiliary Codes

Program: TRAVJSON

Program: TRAVOBJ

Program: TRAVARR

Program: DISPVAL

Program: PRETTY

II Character Encoding

A bit, A byte and a word

Characters Formats

ASCII and EBCDIC Characters Set

III UNIX: Some Useful Commands

IV BPXBATCH Utility

BPXBATCH

Set the variables in JCL

1 Introduction to Mainframe and COBOL

    Mainframe computers or simply mainframes are computers that are huge in size and can process a bulk amount of data in no time. It evolved around middle of twentieth century. Early days mainframe was the only computer that was available. It was developed with a goal to process bulk amount of business and scientific data. Over the years mainframe computers have evolved several times. What we know see almost in size of 240 litters refrigerator.

    We do not have a direct access to mainframe. Mainframe is a server. There are mainframe terminals available to access it. Most commonly terminal is named 3270. But there are emulators available in market through which you can connect to mainframe from your desktop without a need of terminal.

    There are several companies that build mainframe computers. Most famous of them are IBM, Amdahl, Hitachi. Each companies have their own operating system and manufacture different mainframe typed computer. But in this book I will talk about only IBM manufactured mainframe. More specifically only IBM manufactured (huge) computers are called mainframe. Each companies manufacture mainframe computers have different name. It is right to say other companies slowly vanished from mainframe market. Perhaps IBM is the only company that manufacture mainframe typed computer or mainframe. IBM’s mainframe is secure, reliable, scalable and score 100 percent in terms of availability.

    There are several components attached to it. Initial days all the components were attached to a frame thus the name mainframe.

Evolution of mainframe

All the big companies and some governments use mainframe. Although you will never realize it. All major banks, ATMs, telephones, healthcare, insurance, electric and power companies, airplane ticket reservation systems, rail ticket reservation systems, supermarket and auto manufacturing companies use it.

Features of Mainframe

Reason of Popularity

    There are several reasons behind the huge popularity of mainframe. Apart from the fact there is huge chunk of code that are there. Everyday thousands of new development take place in mainframe. There are no existing systems that have the same capacity and capabilities of mainframe currently exist.

Security

    The world’s most trusted servers offer 100% encryption to protect your data from internal and external threats.

Reliability

IBM mainframes deliver record uptime and 99.999% availability.

Performance

    Process billions of transactions on a single server with speeds 2.8x faster than competitors.

COBOL

COBOL is an acronym COmmon Business Oriented Language is an English language like programming language. COBOL was designed in 1959 by CODASYL a consortium for developing a computer programming language. Much of COBOL was developed from the idea of Grace Hopper. Hopper was an US marshal navy before she worked as computer scientist. Hopper’s believed that programs should be written in a language that was close English. Academic scientists were not very impressed at the time of its development because of its verbose nature rather than numbers. But COBOL developed for business soon become only language for industry.

Grace Hopper(Dec 9, 1906 – Jan 1, 1992) was an American scientist. She was the pioneer of the development of machine independent programming language. This led the development  of COBOL. An English like programming language for business. She was also a part of a team that developed UNIVAC.

COBOL is batch only. That means it support file mode input and output functionality. However COBOL with CICS you can write user interactive program. COBOL does not have user defined function or procedure. All the functions are intrinsic. However you can write subprograms that can be called by other program written by any user.

    As popularity emerges lots of companies started offering their own version of COBOL. And ever growing competitions from high level language COBOL also has seen lots of improvements over the years. Lots of variety of COBOL have emerged from non IBM institutions. Now a days you can write and run a COBOL program in Windows.

    Since inception many company apart from CODASYL started developing their own version of COBOL. None of these were compatible to each other. In late 1962 both ISO and American national standards institute (ANSI) formed a group to create a standards. Together they first published the standard version of COBOL in 1968.

Development of COBOL

IBM has released COBOL, COBOL II and Enterprise COBOL. Enterprise COBOL supports JSON and XML data, Object Oriented features. All these compilers run on z/OS. Microfocus has variation of COBOL called MicroFocus COBOL or MFCOBOL, Visual COBOL. All of Microfocus compilers run on Windows and Unix. Fujitsu has its variation of COBOL called Fujitsu COBOL and netCOBOL run only on Fujitsu systems.

Structure of COBOL

A COBOL program has English like structure. It has verbs. Verbs form sentences. Sentences form paragraphs. Paragraphs form sections. Sections form divisions. And divisions form program. Each sentence, paragraph, section and division are terminated by full stop.

COBOL sentence starts at column 8. Column 1-6 are used for sequence number. Now a days sequence numbers are no longer used. You may find lots of them in old code though. Column 7 is used for marking. If column 7 is marked with a * [asterisk] entire line will become a comment line. There is no syntax for block commenting or multi lines commenting in COBOL. If you want to comment multiple lines you have to mark column 7 of each line with an asterisk [*].

    A ‘hello world’ program in COBOL.

COBOL has four divisions and eight sections. Only two divisions IDENTIFICATION and PROCEDURE divisions are mandatory. I will explain each of these divisions and sections in more details in following sections.

A COBOL program has a name by which it is identified and it must have an indicator that indicates the end of program. During execution when control reaches the end of program marker, control is returned to the higher level. A higher level can be another COBOL program or operating system. 

    Once a COBOL program is developed it is compiled and linked to create a load module. Load module is stored in load library. Load module is executed by JCL. This is a standard execution process in mainframe environment. I have used PDSE library to store the load module.

COBOL coding sheet

    Traditionally COBOL programs were written on coding forms and then punched on to punch cards. This form has particular format for computer to understand the syntax. Although nowadays programs were directly entered into computer. But this practice of formatting is still followed across the COBOL world.

Division

COBOL has four divisions.

IDENTIFICATION DIVISION

ENVIRONMENT DIVISION

DATA DIVISION

PROCEDURE DIVISION

    Only IDENTIFICATION and PROCEDURE divisions are mandatory.

Section

COBOL divisions are further divided by SECTION. There are seven sections in COBOL. SECTIONs are optional but if appear they appear in their respective locations.

IDENTIFICATION DIVISION.

PROGRAM-ID.

ENVIRONMENT DIVISION.

CONFIGURATION SECTION.

INOUT-OUTPUT SECTION.

DATA DIVISION.

FILE SECTION.

WORKING STORAGE SECTION.

REPORT SECTION.

LOCAL-STORAGE SECTION.

LINKAGE SECTION.

PROCEDURE DIVISION.

    You can write your own SECTION in procedure division. SECTION is not always a preferable way of coding. SECTION in PROCEDURE division makes program structural.

Paragraph

SECTION is further divided into paragraph. There are many paragraph in each section and division. Paragraphs are optional but if appear they appear in their respective locations.

IDENTIFICATION DIVISION.

ENVIRONMENT DIVISION.

CONFIGURATION SECTION.

INOUT-OUTPUT SECTION.

DATA DIVISION.

FILE SECTION.

WORKING STORAGE SECTION.

REPORT SECTION.

LOCAL-STORAGE SECTION.

LINKAGE SECTION.

PROCEDURE DIVISION.

PROGRAM-ID and FILE-CONTROL are paragraph name.

    You can write your own paragraph in PROCEDURE division. Paragraph are preferable way to make your code structural.

    Sections and paragraphs are further subdivided into sentences, statements, and entries.

    Sentences are subdivided into statements, and statements are subdivided into phrases. Entries are subdivided into clauses.

IDENTIFICATION Division

    This division is mandatory. This division has PROGRAM-ID that uniquely identify a program.

PROGRAM-ID is where you specify program name. Other programs use this name to call your program. Length can be up to 30 characters and includes alphabetic characters, digits 0 to 9 and hyphen. But limit your program name to 8 characters only in accordance of PDS member name. At least one characters must be alphabetic.

AUTHOR specifies the developer of the program.

INSTALLATION specifies the name and location of developing center.

DATE-WRITTEN species specific date program was written.

DATE-COMPILED specifies specific date program was first compiled. This date appear in source listing.

SECURITY specifies confidentiality level.

Example

ENVIRONMENT Division

    This division is optional. It describes the computer environment on which program is compiled and executed. It has two sections CONFIGURATION SECTION and INPUT-OUTPUT SECTION.

You specify the computing environment in CONFIGURATION SECTION.

You specify file name and its characteristic and access mode in INPUT-OUTPUT SECTION.

CONFIGURATION Section

SOURCE-COMPUTER

computer-name is system name.

WITH DEBUGGING MODE activates the debugging statement written in the program. You can write statement that is specific for debugging. Code character D in column 7 for debugging statement.

OBJECT-COMPUTER-NAME specify object computer name.

SPECIAL-NAMES

Relates IBM-specified environment-names to user-defined mnemonic-names.

Relates alphabet-names to character sets or collating sequences.

Specifies symbolic characters.

Specifies one or more currency sign values and defines a picture symbol to represent each currency sign value in PICTURE clauses.

Specifies that the functions of the comma and decimal point are to be interchanged in PICTURE clauses and numeric literals.

Example

INPUT-OUTPUT Section

INPUT-OUTPUT section is further discussed in chapter 8 and 9.

Example

DATA Division

    This division is also optional. It has four sections: FILE SECTION, WORKING STORAGE SECTION, LOCAL-STORAGE SECTION and LINKAGE SECTION.

FILE SECTION describes the layout of file structure.

FILE section is discussed further in following chapters.

Example

WORKING-STORAGE SECTION describes temporary or intermediate variables. WORKING-STORAGE SECTION is allocated at the start of program execution and deallocated at the termination of program. All the variables are initialized to their respective value if VALUE clause is specified and persist still the program terminates.

    If program is defined with INITIAL clause, each time it is called, WORKING-STORAGE SECTION is initialized.

    If program has no INITIAL clause, first time it is in initial state, subsequent call it retains its value till the duration of its execution.

Example

LOCAL-STORAGE SECTION defines temporary or intermediate variables.  LOCAL-STORAGE SECTION is allocated each time CALL statement is executed and free the memory on return from subprogram. LOCAL-STORAGE section is mandatory for recursive programming.

Example

LINKAGE SECTION is used by subprogram to receive value passed from calling program.

Example

PROCEDURE Division

    This division is mandatory. It has one optional REPORT-WRITING SECTION.  REPORT-WRITING SECTION is not covered. It requires precompiler. Enterprise COBOL does not have this section.

PROCEDURE DIVISION is where you specify your program logic.

Example

End of Program

    There are several ways to indicate end of a program.

END PROGRAMprogram-name

EXIT PROGRAM

STOP RUN

GOBACK