In 1977, Donald E. Knuth at Stanford University began an extraordinary typography project.
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TeX is a remarkable program. Despite being one of the most stable and well-documented programs in existence, it is understood by very few people.
My interest in these pages is to understand and explain the algorithms of TeX, rather than to solve anybody's immediate typesetting needs or increase TeX adoption or whatever.
Good pages to start would be those on boxes-and-glue and on the TeX program itself (yet to be written!)