Mark Williams Company

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Mark Williams Company
IndustrySoftware industry
Founded1977 in Chicago, Illinois, U.S.
FoundersRobert Swartz
FatePermanently discontinued

The Mark Williams Company was a small software company in Chicago, Illinois (later moved to Northbrook) 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 (father of Aaron Swartz) in 1977[1] 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[2][3]) into software with his father's help and the company became known as the Mark Williams Company.

Mark Williams won a patent lawsuit (U.S. patent 4,956,809) centered on 'byte ordering'.[citation needed] Separately, and at that time,[when?] Linux had made serious inroads in the UNIX clone market. Since Coherent was a commercially available package and Linux was distributed freely on the Internet via their GNU General Public License, Coherent sales plummeted and Swartz had no choice but to permanently cease operations in 1995.[citation needed]


  • Produced Coherent, a clone of Unix.
  • csd, C source debugger.[4]
  • Let's C, low-cost professional C compiler for the IBM PC.[5]
  • Mark Williams C for CP/M-86.
  • Mark Williams C for the Atari ST, first major C programming environment for the ST computers.
  • XYBasic, a process control BASIC running on CP/M that could be burned on to memory (EPROM) and run on an 8080 standalone processor.


  1. ^ Ness, Stephen. "XYBASIC". Ness Software. Retrieved 20 May 2017.
  2. ^ Lee, Joseph. "Dr. Enuf: The story of Johnson City Tennessee's most famous product". Retrieved 2013-03-03. In 1949 William Mark Swartz, President of Mark Williams Chemical Co. of Chicago, Ill., decided to create a soft drink that would relieve fatigue, headaches, indigestion etc….  He applied for a trademark for the drink on May 19, 1951.
  3. ^ Sauceman, Fred (2009). The Place Setting: Timeless Tastes of the Mountain South. Vol. 3. Mercer Univ. Press. pp. 89–97. ISBN 9780881461404. According to corporate lore, Bill Schwartz [sic], a Chicago chemist, developed the formula after hearing his co-workers complain of lethargy.
  4. ^ "Does your C compiler understand you're only human? (advertisement)". PC Magazine. May 14, 1985. p. 284.
  5. ^ Brown, T. D. (1990). C for Fortran Programmers. Silicon Press. p. x. ISBN 0-929306-01-5.

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