content: Linux is based on Minix, which is a simplification on Unix and obey the POSIX industry standard : It is indeed way older than 20 years. ( Hell, Linux is only the kernel : GNU existed long before it was available. And that's why the proper name for the OS is GNU/Linux ) Now how likely is it to still have 20 years old code in it? Pretty likely : some specific version for it still exist ( like the one for my sony Clié ), and there must be some code in it that simply can't be improved without sacrificing portability. It doesn't make it a bad thing though. Also windows NT is more than 20 years old too, and every Windows since Windows 2000 is based on it. So there is some code that old in windows 10 too.    By the way, did you know Windows NT was meant to be multiplatform too? Great success there, as you can see. So, Linux has at least one great advantage on Windows : it can run on almost anything.    ( Now if I could remember where to find a comparison between the same supercomputer running windows and linux, I could also argue the efficiency side of it too )