I know at least one of the two top major EHR systems uses MUMPS (Epic Software) at its core. If your a member of Kaiser Permanente, or hundreds and hundreds of other hospitals/medical systems, you rely on it for your medical records..
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It was about 3 years too long. Yes, that math is correct.
As far as I recall, MUMPS is essentially the dedicated coding language for a b-tree based database, and the only reason to ever use it for anything is for processing huge numbers of transactions through your NoSQL database every second, forever. I guess you also might want it if none of your employees knew how to correctly normalize a relational database.
Other than the nightmarish accumulation of technical debt continually rolled over since 1979, and the ungodly high turnover of people jumping ship after realizing MUMPS was a golden ball-and-chain, it was a pretty nice place to work. But management had a culture that it needed to force down everyone's throats, and the tech stack was a real resume killer. I still get contacted by recruiters desperate for MUMPS developers, and they make me feel like someone trapped inside a house besieged by zombies. I get really quiet, and hope they don't break any windows.
It only works because they throw a huge amount of money at it, and no one has any incentive to cheap out on medical management software.
Since I was more in their systems department I had limited opportunity to observe their archaic superstitions about code structure, but the short introduction course to M they provided confirmed that most current and new employees were willing to accept that certain control flow tools or function structures were dangerous because they were necessarily slower than something that made sense in hand assembly programming, since there had obviously been no developments in compiler optimization since M was designed (in the good old days, before C existed).
You weren't even allowed to touch the infrastructural M code. Mostly, you worked on superficial or peripheral M code, or on the GUI in VB6. I heard rumors of a GUI modernization team, but never saw any direct evidence of it.
It was a result of the iron grip of the top management. They didn't want to yield control of the company to the people actually running it. You were expected to use your expertise to do what you were told to do, in the best way you could, while still remaining completely within your lane.
After the 6 months of training, I gave it a year to read the character of the company, and then another 6 months to soak some potentially major family health care costs with that sweet insurance plan, then spent 4 months job hunting. It was the best employer-offered health insurance plan I ever had.
But make no mistake. Companies like Epic are why health care costs in the US are huge and growing. Epic never refactors anything that still works well enough to hold together with some expensive human labor. It is a technology company that runs on well-trained people instead of well-designed code and processes.
Some functional areas use Hadoop and SQL now. New server development can be done in VisualStudio using Typescript (which gets converted to M).
There are automated tools to set and verify OS parameters.
Most new installs are Linux now. No one uses VMS today. HP-UX and Solaris will be out of use in a couple years. InterSystems licensing is why people continue to use AIX (you have to buy new licenses to switch from AIX to Linux).
See the intersystems cache talk page on wikipedia: https://en.wikipedia.org/wiki/Talk:InterSystems_Cach%C3%A9