Tutorial use of multiple type faces

A speaker conveys information not only by pronouncing words; he also uses pitch, inflection, and varying amplitude. The writer conveys information using printed letters concatenated to make words, these, in turn made into sentences. He has available similar mechanisms to supplement his written communication but rarely uses them: he can use different type faces; he can lay out the information upon the page in different fashions; he can vary the size of the printed material. Only the last, the use of different type faces to supplement communication is examined here, with examples from books which teach computer science. The salient feature of multiple type faces is that they increase intelligibility with no diminution in the information transmitted.