Today, we introduce someone whose mission includes music, mainframes, and mentorship.
Geoffrey Decker
Co-Founder and Instructor, Eli Madison Memorial Apprenticeship (EMMA)
Instructor, Northern Illinois University, Dept. of Computer Science
Chicago, Illinois, USA
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View the entire 2025 Influential Mainframers group here.
Geoffrey Decker’s career balances music and mainframes. With over 35 years in software development and 20+ years teaching at Northern Illinois University (NIU), Decker is a cornerstone of mainframe education. His curriculum, widely regarded as one of the deepest and most comprehensive in the country, prepares students with technical skills and confidence to enter the workforce ready.
Decker’s students at NIU aren’t just learning COBOL or JCL, they’re mastering real-world enterprise programming. His advanced mainframe courses cover everything from QSAM programming in Assembler to COBOL Db2 SQL, external subprogramming, and complex linkage.
“Each year, 40 to 60 students complete this course. It’s hands-on, it’s rigorous, and it’s why so many companies recruit here,” Decker explains.
But Decker’s influence extends beyond the university. In 2024, he co-founded the Eli Madison Memorial Mainframe Apprenticeship (EMMA), a program that reimagines how mainframe talent is cultivated. EMMA offers non-traditional students, many of whom never saw themselves in tech, the chance to gain in-demand skills and break into the mainframe field.
“It’s incredibly gratifying to see how this program changes lives,” Decker reflects. “EMMA students come out with the equivalent of over a year of experience. They’re ready to contribute immediately.”
His influence has earned him numerous accolades, including the IBM Z Champion title from 2022 through 2025 and a spot on the Open Mainframe Project Governing Board. He also serves as a 2025 ambassador for the Open Mainframe Project, continuing to shape industry-wide strategies for education and talent development.
Yet for all his technical expertise, Decker is known just as much for his mentorship. Students describe him as “personable and easy to communicate with,” commenting on his ability to explain complex programming topics with patience and clarity. He offers free advice, including the sage reminder, “NEVER EVER EVER EVER leave lengths off packed decimal operands in Assembler!”
Outside the classroom, Decker plays French horn in the DeKalb Municipal Band and Kishwaukee Symphony Orchestra, writes concert program notes, and reviews classical music. Fluent in German, he brings the same intellectual curiosity to his hobbies as his teaching.
Whether he’s developing coursework, mentoring a student toward a leadership role, or co-founding an apprenticeship that changes lives, Geoffrey Decker remains a tireless advocate for the mainframe platform and the people who keep it running. His work ensures that the next generation is prepared, passionate, and poised to succeed.
Influential Mainframer
Mainframe technology continues to evolve because of the dedicated professionals, educators, mentors, and innovators who drive it forward. We’re shining a spotlight on the individuals who are making waves—whether they’re advancing technology, mentoring new talent, sharing knowledge, championing modernization, or quietly keeping mission-critical systems running every day. These are the people shaping the future of mainframe. They come from all backgrounds and experience levels, but they all have one thing in common: they’re making a difference.
Check back daily as we reveal a new honoree. Read their stories, celebrate their impact, and be inspired.
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