Troff and Knuth's TeX programs are roughly contemporary. Troff had some advantages, it was more sophisticated about how equations, pictures and tables interworked. Two problems occured though, first the man who wrote Troff was killed in a car accident, and the complex program was never again fully undstood by anyone. He wrote it in PDP-11 assembly langauge, so when it was translated into C, it literally looked like "int r0, r1, r2, r3, r4;". Secondly, Bell Labs decided to make UNIX more proprietary and stopped releasing new versions of Troff to the public, and the open source versions like groff were never well maintained. I was lucky to be able to use the internal version of Troff, which had some cool new features (like an organic molecule typsetter, and such things), but the outside world never saw that stuff.