"...TeX famously began its life as a distraction. In 1977, Donald Knuth, a computer scientist, wanted a better way to typeset his mammoth book about computer science, The Art of Computer Science, a book which he is still in the process of writing. The results of phototypesetting a book heavy on math weren't particularly attractive; Knuth reasoned that he could write a program that would do a better job of it. He set himself to learning how typesetting worked; in the end, what he constructed was a markup language that authors could write in and a program that would translated the markup language into files representing finished pages that could be sent to any printer. Because Knuth didn't do anything halfway, he created this in his own programming language, WEB..." -- auctex: http://www.gnu.org/software/auctex/