Evolution of Operating Systems Designs/Historiography

CP derivatives

1. CP
2. CP-VM
3. CP/M
   1. CP/M-86
      1. DOS
      2. DRDOS
         1. FreeDOS
4. Microsoft Windows
   1. Windows 3.x
   2. Windows 95/98/Me
   3. See NT-based versions below

MULTICS derivatives

1. UNIX
   1. Unix V5 (SCO Unix)
   2. Modern Unix (Solaris / BSD)
      1. FreeBSD
      2. OpenBSD
   3. Xenix
   4. Linux
   5. Plan 9
      1. Inferno
   6. QNX
   7. VSTa
   8. Mac OSX
   9. MIPS RISC/os
   10. RISC iX

VMS derivatives

1. VMS
   1. OpenVMS
2. OS/2
   1. eComStation
3. Microsoft Windows NT-based
   1. Windows NT
   2. Windows 2000
   3. Windows XP
   4. Windows Vista
   5. Windows 7
   6. Windows 8 (and 8.1)
   7. Windows 10
   8. ReactOS (clone of Windows NT-based, not from Microsoft)

MacOS derivatives

1. Mac OS
   1. Mac OS 9

Cambridge CAP Computer derivatives

1. KeyKOS
   1. EROS
      1. Coyotos
      2. CapROS

IBSYS derivatives

1. OS/360
2. OS/400

AmigaOS derivatives

1. AmigaOS
2. AROS
   1. AmigaOS 4.x
   2. MorphOS

Misc. operating systems

1. Grasshopper
2. ITS
3. BeOS
4. RISC OS