Skynet is a OS that only fail once.
AmigaOS - The OS used by the Amiga computers.
DOS - OS for retro people.
Linux - OS used by people who have a fetish for the terminal interface.
OS X - OS used by Apple's computers.
Windows - OS used by everyone.
Android - Mobile OS based on Linux.
iOS - Mobile OS used for Apple products.
Reference
OSDev org
Alt OS Development FAQ
Operating System resource center
Operating System Development Series
os-tutorial - 2018
https://github.com/cfenollosa/os-tutorial