The North Star Horizon microcomputer was first built in 1978. Now, in 1984, the Horizon has become a multiuser multiprocessor. It uses North Star's version of the TurboDOS operating system. North Star decided to go with TurboDOS because it has a multiprocessing networking architecture, it provides true multiuser operation, it permits simultaneous operation of eight and sixteen bit applications and it comes as close to being a minicomputer operating system as is practical on a microcomputer.