Ironically this page typesets Prof. Kernighan's email in a <pre> tag so mobile users could enjoy scrolling left and right 100 times to read it.
Hi, Ramakrishnan --
Thanks for the kind words on the typography. The core formatting is just troff (groff, really) with the -ms macro package. We tried Latex briefly but neither Alan or I care for its output, and I personally find it impossible to control. Troff is the devil I know -- it's ugly and irregular in many ways but it will put characters where you want them.
The input was in XML, with a tag set of about 25 items for headings, paragraphs, index terms, program insertion, simple tables, and the like. A Go program converted this either into HTML for rapid viewing on the screen and potentially for an e-book version, or into troff for printing. Using XML was a mild nuisance when writing but the error checking was very helpful.
We wrote a variety of small Go programs and scripts to fix things up, including one that rewrites troff output to do vertical justification so all pages are the same height. There is also some fiddling with the generated postscript to put on printer's marks.
The fonts are Alan's choice, the result of a lot of work on his part to find them and get the right sizes and appearances. The handful of Asian characters were tough to get right; troff doesn't do wide Unicode characters properly, and there are a few places where we rewrote text to hide that fact.
The drawings are all Alan's work, using Google's drawing program. We toyed briefly with using pic but it wasn't really up to the job, and it would not have worked with HTML without a lot of work. We avoided mathematics beyond superscripts, and the tables are pretty limited; eqn and tbl would have been ok but again would not have dealt with HTML.
We should probably write a more organized description of what we did and make the tools available, though I think most readers are less interested in the process than you (and I) are. The other thing is that although one starts with grand ideas of being clean and orderly, by the end the process is somewhat of a mess, with a complicated makefile to keep it running.
Thanks again for writing.
Brian