Mastering COBOL Programming: From Basics to Expert Proficiency

Mastering COBOL Programming

From Basics to Expert Proficiency

Copyright © 2024 by HiTeX Press

All rights reserved. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the publisher, except in the case of brief quotations embodied in critical reviews and certain other noncommercial uses permitted by copyright law.

Contents

1 Introduction to COBOL

1.1 History of COBOL

1.2 Importance and Use Cases

1.3 COBOL Language Overview

1.4 Structure of a COBOL Program

1.5 Understanding COBOL Divisions

1.6 The Role of Different Divisions

1.7 Basic COBOL Program Example

1.8 Summary and Future of COBOL

2 COBOL Environment Setup

2.1 Introduction to COBOL Development Environments

2.2 Setting Up a Local COBOL Environment

2.3 Installing and Configuring GnuCOBOL

2.4 COBOL Integrated Development Environments (IDEs)

2.5 Setting Up Online COBOL Environments

2.6 Writing Your First COBOL Program

2.7 Compiling and Running a COBOL Program

2.8 Troubleshooting Common Setup Issues

3 Basic COBOL Syntax

3.1 COBOL Program Structure

3.2 COBOL Keywords and Reserved Words

3.3 Understanding COBOL Statements

3.4 COBOL Identifiers and Naming Conventions

3.5 Comments in COBOL

3.6 Paragraphs and Sections

3.7 Importance of Columns and Formatting

3.8 Using Literals and Constants

3.9 Writing a Simple Hello World Program

4 Data Types and Variables

4.1 Introduction to Data Types in COBOL

4.2 Defining Variables in COBOL

4.3 Numeric Data Types

4.4 Alphanumeric Data Types

4.5 Picture (PIC) Clauses and Their Usage

4.6 Understanding Level Numbers

4.7 Working with Redefines and Renames

4.8 Data Initialization and Value Assignment

4.9 Using Figurative Constants

5 Conditional Statements

5.1 Introduction to Conditional Statements

5.2 IF...ELSE Statements

5.3 Nested IF Statements

5.4 EVALUATE Statements (Case Statements)

5.5 Conditions and Relational Operators

5.6 Logical Operators in COBOL

5.7 Combining Conditions

5.8 Using Sign and Class Conditions

5.9 Conditional Abbreviations

6 Looping and Iteration

6.1 Introduction to Looping in COBOL

6.2 Performing Iterative Processes

6.3 Simple Perform Loop

6.4 Perform Varying Loop

6.5 Perform Until Loop

6.6 Nested Loops in COBOL

6.7 Using the EXIT Statement

6.8 Working with Inline Perform

6.9 Best Practices for Looping

7 Arrays and Tables

7.1 Introduction to Arrays and Tables

7.2 Defining Single-Dimensional Arrays

7.3 Accessing and Modifying Array Elements

7.4 Working with Multi-Dimensional Arrays

7.5 Table Handling and Indexing

7.6 Using the OCCURS Clause

7.7 Dynamic Arrays in COBOL

7.8 SEARCH and SEARCH ALL Statements

7.9 Common Use Cases for Tables

8 File Handling in COBOL

8.1 Introduction to File Handling

8.2 Types of Files in COBOL

8.3 Defining Files in COBOL Programs

8.4 File-Control and File Section

8.5 File Operations: OPEN, CLOSE

8.6 Reading Data from Files

8.7 Writing Data to Files

8.8 Rewriting and Deleting Records

8.9 Handling Sequential Files

8.10 Handling Indexed Files

8.11 Handling Relative Files

8.12 Error Handling in File Operations

9 Subroutines and Functions

9.1 Introduction to Subroutines and Functions

9.2 Creating Subroutines

9.3 CALL Statement and Its Variants

9.4 Passing Parameters to Subroutines

9.5 Using COPY and INCLUDE Statements

9.6 Writing Functions in COBOL

9.7 Intrinsic Functions in COBOL

9.8 Calling Subroutines from Other Programs

9.9 Error Handling in Subroutines

9.10 Best Practices for Modular Programming

10 Debugging and Error Handling

10.1 Introduction to Debugging

10.2 Identifying Common COBOL Errors

10.3 Using Debugging Tools

10.4 Setting Up Breakpoints

10.5 Step-by-Step Execution

10.6 Viewing and Modifying Variable Values

10.7 Understanding COBOL Error Codes

10.8 Handling SYNCHRONIZED and ALIGNMENT

10.9 Using DISPLAY for Debugging

10.10 Writing Fault-Tolerant Code

10.11 Logging and Tracing Techniques

10.12 Best Practices for Error Handling

Introduction

COBOL (Common Business-Oriented Language), conceived in 1959, marks one of the earliest high-level programming languages. Its creation was driven by the need for a language that could be used across various hardware and software platforms, making it a linchpin in the realms of business, finance, and administrative systems.

With an enduring presence in the software landscape, COBOL remains critical to today’s enterprise ecosystems. The language underpins mission-critical systems in government agencies, financial institutions, and myriad large-scale industries. A testament to its robustness and reliability, COBOL applications handle everything from payroll processing to credit card transactions, tasks which require unfailing accuracy and performance.

COBOL’s syntax is designed to be readable and self-documenting. The language’s verbosity might seem anachronistic in the context of modern programming paradigms, but it provides unparalleled clarity. This explicit nature is a boon for maintenance and troubleshooting, allowing developers to understand and modify code with greater ease.

This book, Mastering COBOL Programming: From Basics to Expert Proficiency, aims to furnish readers with a thorough understanding of COBOL from fundamental principles to advanced techniques. We will embark on a structured educational path that introduces you to COBOL’s core components, guiding you through the setup of your development environment, and acquainting you with essential syntax and programming constructs.

Beginning with the history and significance of COBOL, we will dive into its distinctive divisions—the Identification Division, Environment Division, Data Division, and Procedure Division—each serving a specific purpose within a COBOL program. An exploration of data types and variable handling will illuminate how COBOL manages data, an essential aspect given the language’s primary application in data processing tasks.

Conditional statements and looping constructs form the backbone of any programming language’s control flow. In COBOL, these constructs are straightforward yet powerful. We will examine their syntax and practical applications, providing a solid foundation for writing efficient and logical COBOL programs.

Arrays and tables in COBOL are critical for handling collections of data and facilitating operations on these collections. Our comprehensive coverage will include defining, accessing, and manipulating single- and multi-dimensional arrays, with a focus on efficient data handling techniques.

File handling, another cornerstone of COBOL programming, will receive extensive treatment. From defining files within a COBOL program to performing read, write, rewrite, and delete operations, you will gain the expertise needed to manage various file types—sequential, indexed, and relative files—essential for real-world applications.

Procedural abstraction through subroutines and functions will be discussed in detail, emphasizing best practices for modular programming and code reuse. We will explore intrinsic functions and the CALL statement, equipping you with the tools to write maintainable and scalable COBOL applications.

Debugging and error handling are crucial skills for any programmer. You will learn to utilize debugging tools, set breakpoints, and step through code. Techniques for handling runtime errors, understanding error codes, and logging will also be covered to ensure your programs are robust and reliable.

This book strives to balance theoretical knowledge with practical application. Each chapter is designed to build on the previous ones, creating a coherent and comprehensive guide to mastering COBOL programming. By the end of this journey, you will possess both the foundational and advanced skills necessary to excel in the field of COBOL programming.

As you proceed through the chapters, it is our hope that you will not only gain proficiency in COBOL but also appreciate its enduring importance in the modern world. Whether you are re-skilling, up-skilling, or simply broadening your technical horizons, Mastering COBOL Programming: From Basics to Expert Proficiency will serve as a valuable resource in your learning journey.

Chapter 1

Introduction to COBOL

COBOL, an acronym for Common Business-Oriented Language, was developed in 1959 to address the need for a universal programming language across disparate computer systems. It remains a cornerstone of enterprise-level and governmental data processing. This chapter covers the history, significance, and structure of COBOL programs, providing a foundational understanding of its divisions and their respective roles, complemented by a basic example to illustrate core concepts. The enduring relevance of COBOL in modern computing is also discussed.

1.1

History of COBOL

COBOL, short for Common Business-Oriented Language, was initiated in response to the 1959 Conference on Data Systems Languages (CODASYL). The objective was to create a universal programming language capable of running on multiple machines, thereby facilitating business and administrative computing tasks across different hardware platforms. The development of COBOL is attributed to the collaborative efforts of multiple stakeholders, including computer manufacturers, guided by the principles of achieving both machine independence and readability akin to English.

The genesis of COBOL can be traced back to the recommendations of a committee formed by the United States Department of Defense. The primary challenge was the lack of compatibility between different programming languages used in business applications, which hindered efficient data processing. As a result, the committee aimed to create a language that possessed excellent compatibility, making inter-system portability achievable and simplifying user training.

Early development of COBOL was spearheaded by several key individuals, with Grace Hopper often heralded as a pioneer due to her significant contributions in designing early compilers. A notable moment in COBOL’s history was the delivery of the first COBOL specifications on January 3, 1960, known as COBOL-60. The language’s syntax and semantics were developed over an extensive period of meetings and refinements, leading to COBOL’s first successful compilation and execution on both an RCA 501 and a Remington-Rand UNIVAC computer.

To facilitate the understanding of COBOL’s historical progression, consider the timeline of significant milestones:

1959: Development initiated by CODASYL, with the foundational goal of creating a universal business-oriented language.

1960: Delivery of the first COBOL specifications (COBOL-60). The language was designed to be easily readable, with a verbose English-like syntax to minimize the learning curve.

1961: COBOL demonstrated the practical feasibility of its design by running successfully on different computer brands, proving its machine-independent capabilities.

1968: The American National Standards Institute (ANSI) adopted COBOL as a standard, designated as ANS COBOL. This standardization provided substantial momentum, propelling widespread adoption.

1974: Introduction of the revised standard, COBOL-74, which included numerous enhancements to improve reliability and performance across various systems.

1985: Further standardization efforts result in COBOL-85, which introduced important features such as structured programming constructs, improved debugging capabilities, and enhanced data processing functions.

2002: ANSI and the International Organization for Standardization (ISO) released COBOL 2002, enhancing object-oriented capabilities, adding support for user-defined functions, and extending the language’s internationalization features.

2014: The most recent standard, COBOL 2014, includes modern features such as dynamic memory allocation, improved interoperability with other languages, and better integration with contemporary software environments.

COBOL’s development has been pragmatic, focusing on meeting the evolving needs of business data processing. Initially, it was predicted that COBOL would fade as newer programming languages emerged. However, its adaptability and enduring efficiency in handling large-scale transaction processing have ensured its continued relevance, particularly in legacy systems of financial, governmental, and administrative domains.

The sustainability of COBOL is partially attributed to its backward compatibility. Programs written in older versions of COBOL can generally run on newer systems without substantial modifications. This characteristic reduces the risk and cost associated with migrating to new systems and technologies.

As the migration from old systems proves costly and risky, many organizations prefer to upgrade their existing COBOL-based systems. Additionally, COBOL’s performance in processing extensive datasets and complex transactions remains unmatched by many modern languages. Hence, extensive investment in training and maintaining a proficient workforce skilled in COBOL persists.

IDENTIFICATION

DIVISION

.

PROGRAM-ID

.

HELLO-WORLD

.

PROCEDURE

DIVISION

.

DISPLAY

’

HELLO

,

WORLD

’.

STOP

RUN

.

HELLO, WORLD

The above COBOL code represents an archetypical starting point, illustrating the language’s straightforward syntax. The IDENTIFICATION DIVISION and PROCEDURE DIVISION exemplify COBOL’s emphasis on readability and structure, reflecting its historical design principles. Over the years, COBOL has maintained its core philosophy while incorporating necessary modernizations to stay relevant.

COBOL’s historical evolution is emblematic of sustained adaptation and specialization, rooted in practical requirements of business data processing. Considering the massive codebases and critical systems dependent on COBOL, its history provides vital insights into foundational computing principles that continue to inform modern practices, ensuring its prominence in enterprise computing environments.

1.2

Importance and Use Cases

COBOL’s significance in the field of information technology is deeply rooted in its capabilities as a robust and versatile programming language designed specifically for business applications. Since its inception, COBOL has played a crucial role in various industries due to its readability, maintainability, and ability to handle large volumes of data. The importance of COBOL can be classified into several key areas:

Business and Financial Applications: COBOL is extensively used in the financial sector including banking, insurance, and governmental agencies. These applications require precise calculations and the capability to handle extensive records, which COBOL’s data processing abilities cater to effectively.

Maintainability and Readability: COBOL’s syntax resembles the English language, which makes it more accessible for business professionals. This readability ensures that even non-programmers can understand and contribute to the development and maintenance of COBOL programs.

Legacy Systems: Many legacy systems, which are still operational, have been written in COBOL. These systems continue to function efficiently in critical applications, making it essential to maintain and occasionally enhance COBOL code.

Interoperability with Modern Systems: Despite its age, COBOL has been adapted to work with modern technologies, including web services and cloud environments. This ensures that COBOL-based systems can be integrated seamlessly with contemporary IT infrastructures.

Use Cases:

1. Banking and Financial Services: COBOL is deeply embedded in the banking industry. A significant portion of core banking systems, such as transaction processing systems, customer information management, and credit card processing systems, is written in COBOL. The language’s ability to process heavy transaction loads with precision makes it indispensable in these environments.

Consider a simple COBOL program designed to process a batch of financial transactions:

IDENTIFICATION

DIVISION

.

PROGRAM-ID

.

TRANSACTION-PROCESSOR

.

DATA

DIVISION

.

FILE

SECTION

.

FD

TRANSACTION-FILE

.

01

TRANSACTION-RECORD

.

05

ACCOUNT-NUMBER

PIC

9(10)

.

05

TRANSACTION-AMOUNT

PIC

S9

(9)

V99

.

05

TRANSACTION-TYPE

PIC

X

(3)

.

WORKING-STORAGE

SECTION

.

01

WS-TOTAL-DEPOSIT

PIC

S9

(11)

V99

VALUE

ZEROS

.

01

WS-TOTAL-WITHDRAWAL

PIC

S9

(11)

V99

VALUE

ZEROS

.

PROCEDURE

DIVISION

.

OPEN

INPUT

TRANSACTION-FILE

.

PERFORM

UNTIL

EOF

=

TRUE

READ

TRANSACTION-FILE

INTO

TRANSACTION-RECORD

AT

END

MOVE

’

YES

’

TO

EOF

NOT

AT

END

EVALUATE

TRANSACTION-TYPE

WHEN

’

DEP

’

ADD

TRANSACTION-AMOUNT

TO

WS-TOTAL-DEPOSIT

WHEN

’

WDR

’

ADD

TRANSACTION-AMOUNT

TO

WS-TOTAL-WITHDRAWAL

END-EVALUATE

END-PERFORM

CLOSE

TRANSACTION-FILE

.

DISPLAY

’

TOTAL

DEPOSIT

:

’

WS-TOTAL-DEPOSIT

.

DISPLAY

’

TOTAL

WITHDRAWAL

:

’

WS-TOTAL-WITHDRAWAL

.

STOP

RUN

.

The combination of simplicity and precision in COBOL’s syntax allows for efficient batch processing of financial transactions. This particular program reads a file of transactions and calculates the total amounts for deposits and withdrawals.

2. Government and Public Sector: Governments utilize COBOL for managing public records, payroll systems, and welfare programs. This is attributed to the reliability and scalability of COBOL programs, which can effectively handle and process large datasets inherent in public sector applications.

A typical COBOL application in this domain might involve the computation of social security benefits based on various parameters such as income, age, and contribution history.

IDENTIFICATION

DIVISION

.

PROGRAM-ID

.

BENEFIT-CALCULATOR

.

DATA

DIVISION

.

WORKING-STORAGE

SECTION

.

01

WS-INCOME

PIC

9(7)

V99

.

01

WS-AGE

PIC

99.

01

WS-CONTRIBUTIONS

PIC

9(7)

V99

.

01

WS-BENEFIT-AMOUNT

PIC

9(7)

V99

.

01

WS-MULTIPLIER

PIC

V99

VALUE

1.05.

PROCEDURE

DIVISION

.

DISPLAY

’

ENTER

INCOME

:

’.

ACCEPT

WS-INCOME

.

DISPLAY

’

ENTER

AGE

:

’.

ACCEPT

WS-AGE

.

DISPLAY

’

ENTER

CONTRIBUTIONS

:

’.

ACCEPT

WS-CONTRIBUTIONS

.

COMPUTE

WS-BENEFIT-AMOUNT

=

(

WS-INCOME

+

WS-CONTRIBUTIONS

)

*

WS-MULTIPLIER

.

DISPLAY

’

BENEFIT

AMOUNT

:

’

WS-BENEFIT-AMOUNT

.

STOP

RUN

.

In this example, the program calculates benefits by accepting user inputs for income, age, and contributions, and then applying a multiplier to determine the benefit amount.

3. Insurance: The insurance industry also relies heavily on COBOL for policy management systems, claims processing, and actuarial computations. The language’s ability to perform accurate and reliable data processing is critical in managing the vast amounts of data associated with policies and claims.

A COBOL-based insurance claim processing system might process claims as follows:

IDENTIFICATION

DIVISION

.

PROGRAM-ID

.

CLAIM-PROCESSOR

.

DATA

DIVISION

.

FILE

SECTION

.

FD

CLAIM-FILE

.

01

CLAIM-RECORD

.

05

POLICY-NUMBER

PIC

9(10)

.

05

CLAIM-AMOUNT

PIC

S9

(9)

V99

.

05

CLAIM-DATE

PIC

X

(10)

.

WORKING-STORAGE

SECTION

.

01

WS-TOTAL-CLAIMS

PIC

S9

(11)

V99

VALUE

ZEROS

.

01

WS-CLAIM-COUNT

PIC

9(5)

VALUE

ZEROS

.

01

WS-AVG-CLAIM

PIC

S9

(9)

V99

VALUE

ZEROS

.

PROCEDURE

DIVISION

.

OPEN

INPUT

CLAIM-FILE

.

PERFORM

UNTIL

EOF

=

TRUE

READ

CLAIM-FILE

INTO

CLAIM-RECORD

AT

END

MOVE

’

YES

’

TO

EOF

NOT

AT

END

ADD

CLAIM-AMOUNT

TO

WS-TOTAL-CLAIMS

ADD

1

TO

WS-CLAIM-COUNT

END-PERFORM

CLOSE

CLAIM-FILE

.

IF

WS-CLAIM-COUNT

>

0

COMPUTE

WS-AVG-CLAIM

=

WS-TOTAL-CLAIMS

/

WS-CLAIM-COUNT

END-IF

DISPLAY

’

TOTAL

CLAIMS

:

’

WS-TOTAL-CLAIMS

.

DISPLAY

’

NUMBER

OF

CLAIMS

:

’

WS-CLAIM-COUNT

.

DISPLAY

’

AVERAGE

CLAIM

AMOUNT

:

’

WS-AVG-CLAIM

.

STOP

RUN

.

This program reads a file containing claim records, calculates the total claims, the claim count, and the average claim amount. The simplicity and readability of COBOL ensure that these calculations are performed accurately and efficiently.

The importance and use cases of COBOL extend beyond these examples, reinforcing the language’s continued relevance in modern computing environments. Its ability to evolve and adapt to new technological paradigms ensures its enduring presence in the IT landscape.

1.3

COBOL Language Overview

COBOL, or Common Business-Oriented Language, is a high-level programming language primarily designed for business, finance, and administrative systems. Its syntax and structure are purposefully crafted to be accessible for those with a business background, emphasizing readability and straightforward data manipulation. COBOL excels in processing bulk data, and its verbosity ensures that programs are self-documenting to a considerable extent.

A COBOL program is typically composed of four main divisions: Identification Division, Environment Division, Data Division, and Procedure Division. Each of these divisions serves a distinct role and contributes to the overall structure and functionality of the program.

The Identification Division is mandatory and provides metadata about the program, including the program’s name and any relevant author information. It establishes a unique identifier for the program and is crucial for documentation and maintenance.

The Environment Division specifies the computer environment in which the program will run. It includes details about the configuration, such as file system organization and device allocations. This division ensures that the program can interact correctly with its surrounding hardware and operating system.

The Data Division is where all data items the program manipulates are defined. The division is subdivided into several sections:

File Section: Describes the files utilized by the program, their structure, and record layouts.

Working-Storage Section: Declares variables that retain their values throughout the program’s execution.

Local-Storage Section: Similar to Working-Storage, but variables in this section are freshly allocated and de-allocated with each program invocation.

Linkage Section: Specifies data items passed to the program from other programs or systems.

The Procedure Division contains the actual code that manipulates the data declared in the Data Division. This division is composed of a series of paragraphs, each containing COBOL statements that define the program’s logic and operations. The statements in the Procedure Division are notably English-like, which enhances the readability and maintainability of the program.

Here’s an illustrative COBOL program structure:

IDENTIFICATION

DIVISION

.

PROGRAM-ID

.

HELLO-WORLD

.

ENVIRONMENT

DIVISION

.

DATA

DIVISION

.

WORKING-STORAGE

SECTION

.

01

WS-MESSAGE

PIC

X

(12)

VALUE

’

HELLO

WORLD

!’.

PROCEDURE

DIVISION

.

DISPLAY-MESSAGE

.

DISPLAY

WS-MESSAGE

.

STOP

RUN

.

In the example above, the Identification Division includes the PROGRAM-ID attribute, uniquely identifying the program as HELLO-WORLD. The Environment Division is present but empty, as no environmental specifications are required. The Data Division includes a Working-Storage Section defining a data item WS-MESSAGE as a 12-character string containing the value ’HELLO WORLD!’. The Procedure Division contains a single paragraph, DISPLAY-MESSAGE, which executes a display command to output