Programmer at IdSoftware, responsible for Wolfenstein, Doom and Quakes 1, 2 and QuakeThreeArena. Considered one of the best Graphics programmers alive (vying with MichaelAbrash for the title). Also one of the brains behind ArmadilloAerospace? (http://www.armadilloaerospace.com).
Interesting footnotes in the JohnCarmack history is that he started Quake (and reportedly finished Doom) on NeXt operating systems. I'd imagine that he was working on PaRisc rather than the original NeXt hardware, since a few years ago they advertised they were giving away PaRisc machines running NextStep.
A quote from his .plan (6/27/99):
More like ExtremeProgrammingForOne, I'd say. He always works alone, as I understand it.
extremely genius!
Lots of information and history about Carmack can be found in "Masters of Doom" by David Kushner ISBN 0375505245