Coherent (operating system)
The Coherent operating system was introduced in 1983 by the now-defunct Mark Williams Company as one of the first Unix-like computer operating systems for IBM PC-compatible computers. Coherent was capable of running on most Intel-based PCs with 286, 386, and 486 processors and, like a true Unix, was capable of multitasking and of having multiple users. Coherent also had support for X11.
Coherent is sometimes mistaken referred to as "Coherent Unix", which is incorrect as Coherent was a Unix clone not based on either System V or BSD. Coherent is thought to be more like System V. The Mark Williams Company went bankrupt in 1995.