Acknowledgments

A book of this scope is never the product of its authors alone. It is shaped by the contributions, generosity, and accumulated knowledge of an entire community. We owe deep thanks to the many individuals and organizations whose work, support, and encouragement made this book possible.

The COBOL Community

Our foremost thanks go to the global COBOL community -- the programmers, systems analysts, architects, and operations professionals who have kept the world's most critical business systems running for over six decades. Many of you have answered questions in public, written articles and documentation, and shared war stories from the trenches of enterprise computing. Your willingness to pass on what you know, despite the demands of your own work, reflects the best traditions of professional craftsmanship, and it is the public record this book draws on.

We are particularly grateful to the members of the COBOL user groups, online forums, and mailing lists who keep that knowledge open and searchable for the next generation of programmers.

The GnuCOBOL Project

The dual-platform approach that defines this book would not have been possible without GnuCOBOL, the free and open-source COBOL compiler that allows anyone with a personal computer to learn, write, and run COBOL programs without mainframe access or commercial licenses.

We owe special thanks to Simon Sobisch, the lead developer and maintainer of GnuCOBOL, whose tireless work on the compiler, documentation, and community support has made COBOL accessible to a new generation of learners. We also thank the broader GnuCOBOL development team and contributor community, including those who work on the compiler runtime, the test suite, and the extensive compatibility layers that make GnuCOBOL a credible learning platform for enterprise COBOL concepts. The GnuCOBOL project demonstrates that open-source principles and mainframe-era languages are not only compatible but complementary.

IBM and the Z Ecosystem

We gratefully acknowledge IBM's contributions to COBOL education and the mainframe ecosystem. The IBM Z Xplore program (formerly Master the Mainframe) has introduced thousands of students and early-career professionals to mainframe computing, and its learning resources informed several aspects of our approach to the enterprise-focused chapters of this book. We also thank the IBM Enterprise COBOL development team, whose compiler documentation and redbooks provided essential reference material throughout the writing process.

The availability of IBM's z/OS development and testing environments for educational purposes reflects a corporate commitment to workforce development that we hope will continue and expand in the years ahead.

Grace Hopper and the CODASYL Committee

This book stands on a foundation laid in 1959. We honor the memory and legacy of Rear Admiral Grace Murray Hopper, whose insistence that programming languages should be written in English-like syntax for the benefit of human readers led to the creation of COBOL. Hopper's vision was radical in its time and vindicated by history. Every chapter of this book is an extension of the idea she championed: that computing should be accessible, readable, and oriented toward the problems of the real world.

We also acknowledge the Conference on Data Systems Languages (CODASYL) committee, the remarkable cross-industry collaboration of government agencies, computer manufacturers, and private-sector organizations that designed and standardized COBOL. The committee's commitment to a vendor-neutral, portable language established principles that the software industry would take decades to rediscover. The CODASYL model of cooperative standardization remains one of the most consequential acts of technical governance in the history of computing.

The Mainframe Professionals

A particular debt of gratitude is owed to the mainframe professionals who maintain the critical infrastructure that COBOL powers -- the systems programmers, database administrators, operations staff, network engineers, and capacity planners who ensure that the world's financial systems, government agencies, and essential services run without interruption. Your work is largely invisible to the public, and that invisibility is the highest compliment: it means the systems are working. This book was written in part to ensure that a new generation understands and appreciates what you have built and what you continue to sustain.

Corrections Welcome

This book was drafted with AI assistance and published free by DataField.Dev. Its code examples and its descriptions of compiler behavior should be checked against your own GnuCOBOL or IBM Enterprise COBOL installation and documentation. If you are an instructor, a working COBOL professional, or a student and you find an error, an outdated practice, or an example that does not compile, corrections and suggestions are welcome (see https://datafield.dev/about.html#contact). The errors that remain are the book's own.

To everyone who has ever written, maintained, debugged, or extended a COBOL program in production: thank you. The world depends on your work more than it knows.