rtenv

1. UNIX-origin
   1. BSD Family
      1. BSD
         1. FreeBSD
            1. DragonFly BSD
         2. NetBSD
            1. OpenBSD
         3. SunOS
         4. NextStep (Steve Jobs, not @ Apple)
            1. Darwin (Apple)
               1. macOS (Apple)
         5. GNU
            1. GNU Hurd
            2. Minix
            3. Linux – kernel
               1. Linux Distros, distributions
               2. Debian
                  1. Ubuntu
                  2. Raspbian
               3. Slackware: SUSE, OpenSUSE, ….
               4. RedHat: SCO OpenLinux, Mandrake, CentOS, Oracle Enterprise., Oracle Linux
               5. Enoch: Gentoo > Chrome OS, Chromium OS
               6. many more, smaller markets, specialized, …: uClinux, OpenWRT, webOS
               7. Android (see Google-driven)###
   2. Sys III and Sys V family
      1. AT&T Commercial UNIX, UnixWare
         1. Solaris (SUN/Oracle)
         2. HP-UX
         3. AIX
         4. IRIX
2. Apple-origin
   1. macOS
   2. iOS
   3. iPadOS
   4. tvOS
   5. watchOS
3. Microsoft-origin
   1. …
4. Google-driven
   1. Android – family
      1. Android (mobile)
      2. Android TV
      3. Wear OS (Android Wear)
5. Other special purpose: VRTX, …

https://www.google.com/search?q=operating+systems+VRTX

https://en.wikipedia.org/wiki/Microkernel

https://en.wikipedia.org/wiki/Linux

https://upload.wikimedia.org/wikipedia/commons/1/1b/Linux_Distribution_Timeline.svg

https://en.wikipedia.org/wiki/Linux_distribution

https://en.wikipedia.org/wiki/Android_(operating_system)