If my guess is correct, it seems that you have missed a chance to work on relatively popular AS/400 servers ... :-)

I have no idea, but the engineer I was talking to was describing the unique challenge of working with the OS, as it was the sole system compiled in that language, and how about half of the bugs they fixed were OS bugs and the other half were compiler bugs, and I ran away from there as fast as I could. This would've been somewhere around 2005, so it could've been.

I see. Yeah, it sounds pretty scary. Well, hopefully, the job that you have accepted instead of that one has been much better.

Could you explain why are AS/400 relatively popular? I don't read much about these mainframes, and am a user of Personal Computers (macbook, thinkpad) and EC2 instances (something that runs Linux?) , so I am not sure what AS/400 servers are, but I'd love to learn more!

Well, by "relatively popular" I meant that AS/400 servers (aka AS400 or IBM iSeries or IBM System i: https://en.wikipedia.org/wiki/IBM_System_i) have been quite popular mostly only within certain industries and/or niches (e.g., banking, insurance, manufacturing, supply chain). They are still widely used there for legacy reasons, however demand for AS/400 developers (which implies proficiency in RPG language, since, as I understand, most legacy applications are written in RPG: https://en.wikipedia.org/wiki/IBM_RPG) is tiny; so, it's a good language to know to potentially expect a relatively high salary or consulting rate (hello, Delphi!), but a dead end for IT career growth. I would also venture to guess that some (many? most?) companies currently using AS/400 plan to migrate their legacy applications to the cloud.

I wouldn't want to work on the AS/400 systems, but its Technology-Independent Machine Interface (TIMI) was basically Android Runtime decades before flip phones were even a thing: ship all of your userspace binaries as bytecode, and compile that bytecode to optimized machine code for your CPU at program installation time.

That's quite fascinating. I appreciate your comment.

"Popular" was a touch sarcastic. AS/400s were most recently called the IBM system I, and are now a discontinued product. IBM still sells mainframes, and they have discontinued the AS/400.

They are most certainly not a discontinued product. We just purchased a brand new Power9 server at work. The model we purchased was just released. Everyone at work still calls it an AS400. They are bulletproof and run many large businesses today. They are also not mainframes but are a class of machines called minicomputers.

IBM Power Series is closer to the RS6000, no? Running real AIX and having a full JCL makes them a far sight better than the RPGII stuff on the AS/400. Night and day.

IBM AS/400 is not discontinued, but rather has been rebranded as IBM Power System: https://www.ibm.com/it-infrastructure/power.

As a former IBMer you missed nothing.

IBM is a terrible work place if you are technically inclined, if you are a slime ball of a manager it’s perfect for you.

IBM "Midrange", aka AS/400: https://en.wikipedia.org/wiki/IBM_System_i

They were an interesting - but dead - sideline of computing evolution. I never used one, but they had a interesting object-based (instead of file based) operating system.

A friend used one of these (the shorter models) as a coffee table -- I distinctly remember how hard it was to move the big, dense metal cube in and out of his room!

My only experience on them was interacting with some API hosted in an AS/400 via FTP protocol. Felt like I was going back to the 90s.

I guess it wasn't a real country after all.