C Programming Course: Learn C

C Programming is a step-by-step tutorial to learn C programming from zero, in 45 short lessons.
Start with your first program and go all the way to pointers, memory, files and debugging, with diagrams and practice questions.

This C tutorial teaches modern standard C (C17) in a clear order, one idea at a time, and explains what changed in the newest standard, C23. Each lesson builds on the one before, so beginners can learn C from the very start, while every page also works as a quick reference later.

Every complete program in the lessons was compiled and run, and its real output is shown under the code. 13 original diagrams show what happens inside the computer: how a program is built, how loops run, how arrays and strings sit in memory, how pointers work and how the call stack grows during recursion.

What you will learn (11 sections, 45 lessons)
• Getting Started: what C is, setting up a compiler (Windows, macOS, Linux, online and on Android), your first program, how compilation works, comments
• Basics: keywords and identifiers, variables, constants and literals, data types and sizes, operators, precedence and conversions, output with printf, input with scanf and fgets
• Control Flow: if and else, the switch statement, the for loop, while and do-while loops, break and continue
• Functions: functions, arguments and return values, scope and lifetime, recursion
• Arrays and Strings: arrays, multi-dimensional arrays, strings, string functions and safety
• Pointers and Memory: pointers, pointers and arrays, pointers and functions, dynamic memory with malloc, calloc, realloc and free
• Your Own Types: structures, unions, enumerations, typedef
• Files: opening and writing files, reading files, binary files
• Larger Programs: the preprocessor, macros and their pitfalls, multi-file programs and header files
• Errors and Debugging: common mistakes with real compiler messages, undefined behaviour, debugging tips
• Reference: a quick-reference cheat sheet and what is new in C23

How the lessons teach
• Short explanations in plain language, followed by a complete example program and its output
• 13 diagrams for compilation, data types, conditions, loops, arrays, strings, pointers, dynamic memory, structures and recursion
• 15 programs with a deliberate mistake, shown with the real compiler message and the fix
• 121 practice questions with answers at the end of almost every lesson, to check what you learned
• Tips and warnings about the mistakes beginners make most often

Features
• Search across all lessons
• Works offline, no account needed
• Available in 8 languages: English, Español, Português, Français, Deutsch, العربية, हिन्दी and Bahasa Indonesia (explanations are translated; the C code stays the same)
• Clean, modern design with dark mode
• Code blocks scroll sideways, so programs stay readable on a phone

Who it is for
• Beginners who want to learn C programming as their first language
• Students taking a C programming course at school, college or university
• Self-learners who want to understand how programs work close to the hardware
• Programmers who know another language and want a clear C tutorial

This app is an independent study aid. It is based on the ISO C standard and the documentation of the GCC and Clang compilers, and is not affiliated with any compiler vendor, university or standards body.