9 of the Best Free C Books

1. The C Book

The C Book is designed for programmers who already have some experience of using a modern high-level procedural programming language. The book concentrates on the things that are special to C. In particular, it is the way that C is used which is focused on.

Chapters include:

• An Introduction to C
• Variables and Arithmetic - introduces some of the fundamentals of C, including keywords and identifiers, declaration of variables, real types, integral types, expressions and arithmetic, and constants
• Control of Flow and Logical Expressions - looks at the various ways that the control of flow statements can be used in a C program, including some statements that have not been introduced so far. Control of flow, more logical expressions, and strange operators
• Functions - the type of functions, recursion and argument passing, and linkage
• Arrays and Pointers - arrays, pointers, character handling, sizeof and storage allocation, pointers to functions, expressions involving pointers, arrays, the & operator and function declarations
• Structured Data Types - structures, unions, bitfields, enums, qualifiers and derived types, and initialization
• The Preprocessor - how the preprocessor works, and directives
• Specialized Areas of C - declarations, definitions and accessibility, typedef, const and volatile, and sequence points
• Libraries - diagnostics, character handling, localization, limits, mathematical functions, non-local jumps, signal handling, variable numbers of arguments, input and output, formatted I/O, character I/O, unformatted I/O, random access functions, general utilities, string handling, and date and time
• Complete Programs in C - putting it all together, arguments to main, interpreting program arguments, a pattern matching program, and a more ambitious example

2. Learn C The Hard Way

Learn C The Hard Way fills in the "beginning programmer" gap in the literature on the C Programming language. It teaches good modern C programming practices and avoid habits that lead to buffer overflows, security defects, and other problems that even experienced programmers run into.;

This book is designed for:

• Students who have read Learn Python The Hard Way or Learn Ruby The Hard Way
• Programmers with skill in one other "scripting" language
• Programmers who need to relearn C
• Objective-C programmers who want better C skills
• People who like a challenge

The purpose of this book is to teach you how your computer really works, and included in that is how various data structures and algorithms function.

Chapters cover:

• Make is your Python now - a crash course in make, and you will be learning to use it as you learn C
• Formatted Printing
• Introducing Valgrind - an instrumentation framework for building dynamic analysis tools. There are Valgrind tools that can automatically detect many memory management and threading bugs, and profile your programs in detail
• The Structure of a C Program - break down a simple C program line-by-line so you know how one is structured
• Types of Variables - integers, floating point, character, and string
• More Variables, Some Math - more things you can do with variables by declaring various ints, floats, chars, and doubles. Then use these variables in various math expressions so you get introduced to C's basic math
• Sizes and Arrays - introduces a few more concepts: sizeof and arrays
• Arrays of Strings, Looping - shows you that C stores its strings simply as an array of bytes, terminated with the '\0' (nul) byte
• While-Loop and Boolean Expressions - see how a while-loop works
• If, Else-If, Else - something common in every language is the if-statement, and C has one
• Switch Statement - some code that we will break down to understand this concept of "jump tables"
• Writing and Using Functions - write some functions and use some other functions
• Pointers Dreaded Pointers - demystifies pointers
• Structs and Pointers to them - learn how to make a struct, point a pointer at them, and use them to make sense of internal memory structures
• Heap and Stack Memory Allocation - create an entire small program to manage a database
• Pointers to Functions - functions in C are actually just pointers to a spot in the program where some code exists
• A Simple Object System - this exercise will build a simple game where you kill a Minotaur in a small little castle
• Zed's Awesome Debug Macros - a small set of "debug macros" that implement a basic debugging and error handling system for C
• Advanced Data Types and Flow Control - this exercise will be a complete compendium of the available C data types and flow control structures you can use
• The Stack, Scope, and Globals - learn about scope by learning about how a stack data structure works, and then feeding that concept back in to how modern C does scoping
• Meet Duff's Device - this exercise is a brain teaser introducing a famous hack in C
• Input, Output, Files - use the functions fscanf and fgets to build information about a person in a structure. After this simple introduction to reading input, you will get a full list of the functions that C has for I/O
• Variable Argument Functions - knowing how a variable argument function works helps debug them and provides a greater understanding of the computer
• Write a First Real Program - recreate a piece of software, devpkg - a simple C program that installs other software
• Creative and Defensive Programming - advanced concepts and feature more talking than code
• Intermediate Makefiles - create a skeleton project directory to use in building your C programs later
• Libraries and Linking - learning how C links things helps you understand how your OS works and how it runs your programs
• Automated Testing - used frequently in other languages like Python and Ruby, but rarely used in C
• Debugging Code - Debug Printing vs GDB vs Valgrind
• Double Linked Lists
• Linked List Algorithms - covers two algorithms you can do on a linked list that involve sorting
• Dynamic Array - an array that grows on its own and has most of the same features as a linked list
• Sorting and Searching - covers four sorting algorithms and one search algorithm
• Safer Strings - designed to get you into using bstring from now on, why C's strings are an incredibly bad idea, and then have you change the liblcthw code to use bstring
• Hashmaps - Hash Maps (Hashmaps, Hashes, or sometimes Dictionaries) are used frequently in many dynamic programming for storing key/value data
• Hashmap Algorithms - implement three hash functions: FNV-1a, Adler-32, and DJB Hash
• String Algorithms - gist of this algorithm is that it calculates a "skip characters list" as a first operation, then it uses this list to quickly scan through the string
• Binary Search Trees - the simplest tree based data structure
• Using Cachegrind and Callgrind for Performance Tuning - a quick course in using two tools for Valgrind called callgrind and cachegrind
• Stacks and Queues - very simple data structures that are really variants of the List data structure
• A Simple Statistics Engine - a simple algorithm used for collecting summary statistics "online"
• Ring Buffer - useful when processing asynchronous IO. They allow one side to receive data in random intervals of random sizes, but feed cohesive chunks to another side in set sizes or intervals
• A Simple TCP/IP Client - use the RingBuffer to create a very simplistic little network testing tool called netclient
• Ternary Search Tree
• A Fast URL Router - use the TSTree to do fast URL routing in web servers
• A Tiny Virtual Machine - implements a version of the DCPU16 virtual machine using the algorthms created previously

3. Introduction to C Programming

Introduction to C Programming is, as its name suggests, a book for anyone completely new to programming and wants to learn C.

Chapters include:

• Computers
• Programming Languages - examines what is programming, and a brief examination of programming languages
• C - looks at the advantages and disadvantages of C
• A First C Program - making C run, creating C programs, what comprises a C program, the advantages and disadvantages of C
• Variables - looks at types of variables, declaration (int, float, char variables, missing types), variable declaration, giving values to variables, and getting values into the program
• Writing a Program
• Functions - identified by name and can return a single value. They act on parameters, which are used to pass information into them. In our case we want a function which is given the maximum and minimum values which something can have, and returns a value in that range
• Arrays - explains why arrays are needed, array types and sizes
• Switching - making multiple decisions
• Strings - computer jargon for lumps of text
• Structures - explains what is a structure, how they work, pointers to structures, and defining your own types
• Files - when are files used, fopen and fclose, and file functions
• Memory - fetching memory (malloc and free), and the heap
• C and Large Programs - building large programs in C, and the C pre-processor