Solved by KFrank in post #2 
              
              
                Hello Namo! 

It means that the operating system (“os”) is a microsoft 
operating system of the NT lineage, such as windows 
10 or windows 7 (or windows NT), as distinct from the 
older dos and semi-dos windows systems such as 
windows 3.1 or windows 95 (and also distinct from other 
operating syste…