OS&#x2F;400 doesn&#x27;t run on s390&#x2F;zenterprise. It runs on pSeries (POWER8), which also run AIX and Linux.<p>OS&#x2F;400&#x2F;IBM i (or whatever its called this week) is actually probably one of the cooler OS&#x27;s still around. It should be mandatory study in any comp sci&#x2F;comp eng OS classes, but sadly its not and because of that, a lot of wheels are being reinvented.