The Mark Williams Company was a small software company in Chicago, Illinois (later moved to Northbrook, Illinois) that created Coherent, one of the first Unix-like operating systems for IBM PCs and several C programming language compilers. It was founded by Robert Swartz in 1980 and discontinued operations in 1995. The name comes from the middle name of Robert Swartz's father, William Mark Swartz.
Robert Swartz moved the company (originally producing a soft drink called Dr. Enuf) into software with his father's help and the company became known as the Mark Williams Company.
Mark Williams successfully won a patent lawsuit centered around 'byte ordering'. Separately and at that time, Linux had made serious inroads in the UNIX clone market. Being that Coherent was a commercially available package and Linux was distributed freely on the Internet via their GNU public license, Coherent sales plummeted and Mr. Swartz had no choice but to cease operations in 1995.