real operating system

n. The sort the speaker is used to. People from the BSDophilic academic
community are likely to issue comments like System V? Why don't you use a
real operating system? , people from the commercial/industrial Unix sector
are known to complain BSD? Why don't you use a real operating system? , and
people from IBM object Unix? Why don't you use a real operating system? Only
MS-DOS is universally considered unreal.