TeX was the first serious examination of what good typographical layout was and how to codify it. Previously there were many rules of thumb, and lots of exampl

TeX was the first serious examination of what good typographical layout was and how to codify it. Previously there were many rules of thumb, and lots of examples, and a handful of programs for typesetting (like RUNOFF, which was and is pretty damned ugly, although it beats the pants off a typewriter) but in TeX Knuth created an algorithm for things like mathematical layout, for paragraph layout. I am unaware of anything that has surpassed TeX in this field—programs like Lout use the same algorithm TeX does, just with a less idiosyncratic surface syntax and with a rewritten core.