> it sounds a bit oxymoronic, at least on practice. I'm yet to see a normally functioning system written using "safe system programming language".
Just some examples of operating systems that worked for several years in certain circles.
Xerox Star systems coded in Mesa.
Lilith coded in Modula-2.
Spin coded in Modula-3.
Oberon coded in Oberon.
AOS coded in Active Oberon.
Ethos coded in Oberon.
Original version of OS/400 coded in Modula-2.
Mac Lisa and initial versions of Mac OS coded in Object Pascal.
VME in Algol 68
The real time systems driving lots of trains, planes, helicopters and medical devices running Ada code deployed directly to firmware.
> i hope you don't mean Unix here because Unix has nothing to do with either "text based" or "GUI based" - it is completely orthogonal to that.
I sure do.
UNIX System V does not offer any GUI interface.
POSIX does not offer GUI support.