Tex By Topic: A Texnician's Reference

TEX BY TOPIC, A TEXNICIAN’S REFERENCE VICTOR EIJKHOUT∗ ELECTRONIC VERSION 1.0, DECEMBER 2001 ∗ This is – apart from minor changes – the full text of the book TEX by Topic, copyright 19912001 Victor Eijkhout. This book was printed in 1991 by Addison-Wesley UK, ISBN 0-201-56882-9, reprinted in 1993. This book may be copied; the pdf file of this book may be printed and given away, and it may be included in archives and on web sites; the book may be distributed in unaltered form both on paper and electronic media. You are not allowed to make any changes to the file or to reverse engineer its source; you are not allowed to charge for its distribution – whether in physical or electronic form – beyond reasonable material costs. If you have comments or want to express your appreciation that you are getting this book that formerly sold for ≈$30 for free, please visit http://www.eijkhout.net/tbt/. If you already made a donation, thank you. You are a credit to your species. Contents 1 1.1 1.2 1.2.1 1.2.2 1.3 1.3.1 1.3.2 1.3.3 1.4 1.5 1.6 1.6.1 1.6.2 2 The Structure of the TEX Processor 1 Four TEX processors 1 The input processor 2 Character input 2 Two-level input processing 2 The expansion processor 3 The process of expansion 3 Special cases: \expandafter, \noexpand, and \the 3 Braces in the expansion processor 4 The execution processor 4 The visual processor 5 Examples 5 Skipped spaces 5 Internal quantities and their representations 6 Category Codes and Internal States 7 2.1 Introduction 7 2.2 Initial processing 7 2.3 Category codes 8 2.4 From characters to tokens 10 2.5 The input processor as a finite state automaton 10 2.5.1 State N: