From the Wikipedia article (https://secure.wikimedia.org/wikipedia/en/wiki/Literate_programming https://secure.wikimedia.org/wikipedia/en/wiki/Literate_prog...)

From the Wikipedia article (https://secure.wikimedia.org/wikipedia/en/wiki/Literate_programming https://secure.wikimedia.org/wikipedia/en/wiki/Literate_prog...): The first published literate programming environment was WEB, introduced by Donald Knuth in 1981 for his TeX typesetting system; it uses Pascal as its underlying programming language and TeX for typesetting of the documentation. That is delicious. He programmed in a way that would generate both the documentation for TeX (in TeX) and the source code for TeX (in Pascal). Compiling the source code generates a program that can process that TeX documentation. In other words, the documentation is an integral part of the source code, and the compiled source code is an integral tool in producing the documentation.