Harry Fairhead - Fundamental C: Getting Closer to the Machine

Fundamental C:

Getting Closer To The Machine

First Edition

Harry Fairhead

I/O Press

I Programmer Library

Copyright 2019 IO Press

All rights reserved. This book or any portion thereof may not be reproduced or used in any manner whatsoever without the express written permission of the publisher except for the use of brief quotations in a book review.

Harry Fairhead Fundamental C: Getting Closer To The Machine.

1st Edition

ISBN Paperback: 978-1871962604

First Printing, 2019

Revision 1

Published by IO Press

www.iopress.info

In association with I Programmer

www.i-programmer.info

The publisher recognizes and respects all marks used by companies and manufacturers as a means to distinguish their products. All brand names and product names mentioned in this book are trade marks or service marks of their respective companies and our omission of trade marks is not an attempt to infringe on the property of others.

Preface

C is a classic language and it is still an important language. This is because it is closer to the machine than other languages, but it still has enough abstraction for you to create programs that are more or less portable. Perhaps more important, it means you dont have to learn a new assembly language every time you switch hardware. So learn C and gain the advantage of its speed, simplicity and stay close to the metal. This approach is essential if you are going to create programs for the IoT or embedded processors, but it is also relevant to any program that makes direct use of hardware.

Most books on C treat it as if it was just a slightly different take on Java, or some other high-level language. C isnt Java with limited facilities. It is designed to do a very different job from most modern languages. The key to understanding C is not to just understand the language, what the specifications say, but how this relates to the hardware. C is only a logically constructed language when seen in terms of how it relates to the hardware.

For this reason it needs its own approach.

But what is that approach?

Low-level code works with the underlying representations of the data at the level of bits. In languages such as Java, Python and so on you dont often question how the data is stored or represented, but the creation of low-level C

code does just this. You need to know about addresses, pointers and how things are represented using just binary. Dealing with such topics also brings us into contact with the scourge of the C world undefined behavior. This cannot be ignored, as it is in so many other books on C, and here not only is it acknowledged, it is explained together with ways to avoid it.

C is a simple language and lends itself to being introduced in simple ways, but the simple constructs of C can be put together in ways that produce something complex or at least unexpected. I have tried to indicate how the simple parts of C are combined to make it more powerful than you might expect and how to avoid going too far and making it so obscure that it is difficult to understand.

In this book the emphasis is on standard C. If you want to know more about using C on POSIX-compliant and Linux-based systems, this is covered in its companion volume, Applying C For The IoT With Linux ISBN: 978-1871962611.

Harry Fairhead

March 2019

This book is a revised and updated version of the series of articles on the I Programmer website: www.i-programmer.info

To keep informed about forthcoming titles visit the I/O Press website: www.iopress.info . This is also where you will also find any errata and update information. You can also provide feedback to help improve future editions.

Table of Contents

About C

Why C?...............................................................................................11

Standards and C................................................................................13

Platform Dependent or Independent Undefined Behavior...........14

Safe Coding........................................................................................16

Summary...........................................................................................17

Getting Started

NetBeans and GCC............................................................................19

NetBeans C/C++ Under Linux and Windows.................................20

Installing GCC...................................................................................21

A First Program.................................................................................22

Using Tool Collections......................................................................24

Remote C/C++ Build Servers...........................................................25

Creating a Hello World Program.......................................................29

From the Command Line..................................................................30

Summary...........................................................................................31

Control Structures and Data

Variables, assignment and expressions............................................33

Program Structure.............................................................................35

Comments..........................................................................................36

The Flow of Control..........................................................................37

The Conditional................................................................................40

The Compound Statement................................................................41

Loops..................................................................................................42

Flow of Control in Practice...............................................................52

Fractional Loops Break and Continue...........................................55

Nesting...............................................................................................56

The Switch Statement.......................................................................57

Summary...........................................................................................61

Chapter 4

Variables

Memory Basics..................................................................................64

The Numeric Data Types..................................................................65

The char Type...................................................................................66

Working With Boolean values..........................................................67

Floating Point....................................................................................67

Complex Numbers.............................................................................68

Declaring Variables...........................................................................68

Initialization......................................................................................69

Literals...............................................................................................71

Implementing Variables....................................................................72

Exact Size Variables..........................................................................73

Type Modifiers..................................................................................74