Beej's Guide to C Programming

Beej’s Guide to C Programming is a free, continuously updated guide to C by Brian “Beej Jorgensen” Hall, the author of the well-known Beej’s Guide to Network Programming. It’s written for people who already know another language and want to learn C properly, in the same informal, joke-filled style as his other guides. The latest release (v0.10.x, 2026) runs to more than forty chapters.

What it covers

The guide comes in two volumes:

• Tutorial: starts with “Hello, World!” and the build process, then covers variables, operators and control flow, functions, pointers and pointer arithmetic, arrays, strings, structs, file I/O, typedef, manual memory allocation, scope and storage classes, and the preprocessor.
• Advanced topics: later chapters cover the parts of C most tutorials skip: variadic functions, locales and Unicode/wide characters, setjmp/longjmp, signal handling, variable-length arrays, goto, type qualifiers, compound literals and generic selections, multithreading with <threads.h>, and atomics and the C memory model.
• Library reference: a separate volume documents the C standard library, header by header, with examples.

Why it’s worth reading

C is the language under almost everything else: operating systems, Python’s interpreter, CUDA’s host code, database engines. This guide explains why C behaves the way it does (memory layout, undefined behavior, what a pointer really is) rather than just listing syntax, and it targets modern C (C11/C23) instead of older textbook C. It’s freely available in HTML, PDF and print at beej.us/guide/bgc.