Advent of Computing Episode 30 - Coherent Is Not UNIX!
May 17, 2020
Explore the fascinating evolution of UNIX-like systems and how Linux emerged as a leader. Learn about the early contender, Coherent, which was a closed-source clone that shared many traits with UNIX. Discover the impact of AT&T's licensing constraints on software distribution, and how it helped foster an open-source culture. Delve into Coherent's origins, development on the PDP-11, and its capabilities, including multiuser support. Also, uncover the reasons behind its decline in the face of competition from BSD and Linux.
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Unix For The PC Era
- Coherent was a Unix-like OS built without AT&T code to bring Unix to personal computers in the early 1980s.
- Mark Williams targeted a niche of users who needed Unix features on smaller, cheaper hardware.
Soda Company Turned Software House
- The Mark Williams Company began as a soft-drink and chemical firm and pivoted into software under Robert Swartz.
- Swartz recruited University of Waterloo colleagues and steered the company toward personal computing products.
Portability By Design
- Coherent development started on a PDP-11 before being ported to PCs, leveraging C for portability.
- Writing all-new C code let Mark Williams avoid Unix's legacy dependencies and ease future ports.