COBOL Language Fundamentals Quick Start

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Disclaimer

The contents of this book are based upon the author’s understanding of and experience with the COBOL language programming language.  Every attempt has been made to provide correct information.  However, the author and publisher do not guarantee the accuracy of every detail, nor do they assume responsibility for information included in or omitted from it. All of the information in this book should be used at your own risk.

Copyright

The contents of this book may not be copied in whole, or in part, without the explicit written permission of the author. The contents are intended for personal use only. Secondary distribution for gain is not allowed.  Any alteration of the contents is absolutely forbidden. 

Copyright, 2020 by Robert Wingate

DB2, DB2 UDB, UDB, and MVS are all registered trademarks of the IBM Corporation. 

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Introduction

Welcome

Assumptions:

Approach to Learning

COBOL Language Fundamentals

Introduction

COBOL Language Basics

Programming Format

Four Divisions

IDENTIFICATION DIVISION

ENVIRONMENT DIVISION

DATA DIVISION

PROCEDURE DIVISION

Optional Entries and Sections

Variables, Data Types and Assignment

Data Types

COMP Variables

Data Structures

Sample Program

Sequence, Selection, Iteration

Sequence

Selection

Iteration

File I/O

Program Listing for COBTRN3

Reporting

ANSI Carriage Control

Report Program Sample

Calculations

Calculations with GIVING

Calculations with COMPUTE

Edits and Validation

Tables

Sub Programs

Review Questions

Questions and Answers

Additional Resources

Other Titles by Robert Wingate

About the Author

Introduction

Welcome

Congratulations on your purchase of COBOL Language Fundamentals Quick Start.  This book will teach you the basic information and skills you need to develop applications with COBOL on IBM mainframes running z/OS. The instruction, examples and sample programs in this book are a fast track to becoming productive as quickly as possible using basic COBOL. The content is easy to read and digest, well organized and focused on honing real job skills.  

This is not an everything you need to know about COBOL book.  Rather, this text will teach you what you need to know to become productive quickly with COBOL.  For additional detail, you can download and reference the IBM manuals and Redbooks associated with these products. 

Assumptions:

While I do not assume that you know a great deal about IBM mainframe programming, I do assume that you’ve logged into an IBM mainframe and know your way around.  Also I assume that you have a working knowledge of computer programming in some language (it can be a language other than COBOL). All in all, I assume you have:

1.   A working knowledge of ISPF navigation and basic operations such as creating data sets.

2.   A basic understanding of structured programming concepts.

4.   Access to a mainframe computer running z/OS and DB2 (with a COBOL compiler available).

Approach to Learning

I suggest you follow along and do the examples yourself in your own test environment.  There’s nothing like hands-on experience.  Going through the motions will help you learn faster.

If you do not have access to a mainframe system through your job, I can recommend Mathru Technologies.  You can rent a mainframe account from them at a very affordable rate, and their environment supports COBOL.  The URL to the Mathru web site is: 

http://mathrutech.com/index.html

Besides the instruction and examples, I’ve included questions at the end of each chapter. I recommend that you answer these and then check yourself against the answers in the back of the book.

Knowledge, experience and practice questions.  Will that guarantee that you’ll succeed as a COBOL application developer?  Of course, nothing is guaranteed in life.  But if you put sufficient effort into this well-rounded training plan that includes all three of the above, I believe you have a very good chance of becoming productive as an IBM Application Developer as soon as possible.  This is your chance to get a quick start!  

Best of luck!

Robert Wingate

IBM Certified Application Developer – DB2 11 for z/OS

COBOL Language Fundamentals

Introduction

COBOL is an acronym for Common Business-Oriented Language.  It’s a third generation procedural language that has been around since 1959.  COBOL was developed primarily for business use.  It generally focuses on record or database input/out, as well as calculations and reports. 

You may hear that COBOL is gone or on the way out, but its demise is probably exaggerated.  While lots of mainframe COBOL programming has been rewritten in other languages (or replaced by commercial packages), COBOL is still heavily used in legacy applications that run on IBM mainframe computers.  This is true especially for banking and finance applications. Check out this article if you don’t believe it:

https://thenewstack.io/cobol-everywhere-will-maintain/

If you are used to programming in languages such as C or Java, you’ll find that COBOL is a bit more English-like.  This can be an advantage or disadvantage depending on how you look at it. For example, a data assignment to a variable in most programming languages can be as simple as:

X = 27

In COBOL you would code this same operation as:

MOVE 27 TO X

The latter is somewhat more verbose.  It also has the receiving variable on the right side of the equation which is different. 

Also, in COBOL you can spell out Booleans such as > or < using English phrases, such as:

IF X IS GREATER THAN 100

Whatever your view of the verbosity, COBOL is a very usable language and worth learning. As legacy COBOL programmers retire, there is still much code to be maintained or converted.  This chapter will help make you productive for these tasks quickly.

COBOL Language Basics

Programming Format

Unlike more freeform languages, COBOL is very particular about exactly where you can put executable code. Here is a summary of the formatting rules you must follow in COBOL.