Zed A. Shaw - Learn C the Hard Way. Practical Exercises on the Computational Subjects You Keep Avoiding (Like C)

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Practical Exercises on the Computational Subjects You Keep Avoiding (Like C)

Zed A. Shaw

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Library of Congress Cataloging-in-Publication Data

Shaw, Zed, author.
Learn C the hard way : practical exercises on the computational subjects you keep avoiding (like C) /
Zed A. Shaw.
pages cm
Includes index.
ISBN 978-0-321-88492-3 (pbk. : alk. paper)ISBN 0-321-88492-2 (pbk. : alk. paper)
1. C (Computer program language)Problems, exercises, etc. I. Title.
QA76.73.C15S473 2016
005.133dc23 2015020858

Copyright 2016 Zed A. Shaw

All rights reserved. Printed in the United States of America. This publication is protected by copyright, and permission must be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise. To obtain permission to use material from this work, please submit a written request to Pearson Education, Inc., Permissions Department, 200 Old Tappan Road, Old Tappan, New Jersey 07657, or you may fax your request to (201) 236-3290.

ISBN-13: 978-0-321-88492-3
ISBN-10: 0-321-88492-2

Text printed in the United States on recycled paper at RR Donnelley in Crawfordsville, Indiana.
First printing, August 2015

I would like to thank three kinds of people who helped make this book what it is today: the haters, the helpers, and the painters.

The haters helped make this book stronger and more solid through their inflexibility of mind, irrational hero worship of old C gods, and complete lack of pedagogical expertise. Without their shining example of what not to be, I would have never worked so hard to make this book a complete introduction to becoming a better programmer.

The helpers are Debra Williams Cauley, Vicki Rowland, Elizabeth Ryan, the whole team at Addison-Wesley, and everyone online who sent in fixes and suggestions. Their work producing, fixing, editing, and improving this book has formed it into a more professional and better piece of writing.

The painters, Brian, Arthur, Vesta, and Sarah, helped me find a new way to express myself and to distract me from deadlines that Deb and Vicki clearly set for me but that I kept missing. Without painting and the gift of art these artists gave me, I would have a less meaningful and rich life.

Thank you to all of you for helping me write this book. It may not be perfect, because no book is perfect, but its at least as good as I can possibly make it.

Please dont feel cheated, but this book is not about teaching you C programming. Youll learn to write programs in C, but the most important lesson youll get from this book is rigorous defensive programming. Today, too many programmers simply assume that what they write works, but one day it will fail catastrophically. This is especially true if youre the kind of person who has learned mostly modern languages that solve many problems for you. By reading this book and following my exercises, youll learn how to create software that defends itself from malicious activity and defects.

Im using C for a very specific reason: C is broken. It is full of design choices that made sense in the 1970s but make zero sense now. Everything from its unrestricted, wild use of pointers to its severely broken NUL terminated strings are to blame for nearly all of the security defects that hit C. Its my belief that C is so broken that, while its in wide use, its the most difficult language to write securely. I would fathom that Assembly is actually easier to write securely than C. To be honest, and youll find out that Im very honest, I dont think that anybody should be writing new C code.

If thats the case, then why am I teaching you C? Because I want you to become a better, stronger programmer, and there are two reasons why C is an excellent language to learn if you want to get better. First, Cs lack of nearly every modern safety feature means you have to be more vigilant and more aware of whats going on. If you can write secure, solid C code, you can write secure, solid code in any programming language. The techniques you learn will translate to every language you use from now on. Second, learning C gives you direct access to a mountain of legacy code, and teaches you the base syntax of a large number of descendant languages. Once you learn C, you can more easily learn C++, Java, Objective-C, and JavaScript, and even other languages become easier to learn.

I dont want to scare you away by telling you this, because I plan to make this book incredibly fun, easy, and devious. Ill make it fun to learn C by giving you projects that you might not have done in other programming languages. Ill make this book easy by using my proven pattern of exercises that has you doing C programming and building your skills slowly. Ill make it devious by teaching you how to break and then secure your code so you understand why these issues matter. Youll learn how to cause stack overflows, illegal memory access, and other common flaws that plague C programs so that you know what youre up against.