Update OS

operating_system.md

@@ -22,15 +22,16 @@ TODO
 Below are some of the most notable OSes.
 
 - [Android](android.md)
-- [BSD](bsd.md) systems such as [OpenBSD](openbsd.md) and [freeBSD](freebsd.md)
+- [BSD](bsd.md) systems such as [OpenBSD](openbsd.md) and [freeBSD](freebsd.md): Unix-like OSes
 - [Collapse OS](collapseos.md)
 - [DOS](dos.md), [FreeDOS](freedos.md)
 - [GNU](gnu.md)/[Linux](linux.md) systems encompassing many [distributions](distro.md)
+- [Inferno](inferno.md): OS in the style of Plan 9
 - [MacOS](macos.md)
-- [Plan 9](plan9.md)
+- [Plan 9](plan9.md): research OS, continuing the ideas of [Unix](unix.md)
 - [ReactOS](reactos.md)
 - [Replicant](replicant.md)
 - [Solaris](solaris.md)
 - [TempleOS](templeos.md)
 - [Unix](unix.md)
-- [Windows](windows.md)
+- [Windows](windows.md): very bad [proprietary](proprietary.md) [capitalist](capitalist_software.md) OS