See, it's not all that hard, it's just like climbing an ice wall with without crampons... you can learn to be very good at it.... if you survive :-)

Win 3.1 grew from DOS which sorta grew out of another OS - MPM (multiuser), which sorta grew from CPM (single user) - but got inspiration from main frame and mini OSes. MS is just one big set of hacks built on top of the previous set of hacks...

UNIX was an attempt to do from the beginning all the big boxes could do (timshare and multi user and multi program) with the minimum resources - which is why the shell and the tiny little utils that are linked with pipes and redirects. Very powerful once you begin to understand. The old tale was that you can write a spell checker in the shell script with about a dozen lines of code... :-)