Learn C
five minutes at a time.

#include <stdio.h>

int main(void) {
    printf("Hello, Pebble!\n");
    return 0;
}

Hello, Pebble!

The Codiqo C course starts at printf() and builds up to arrays, strings, pointers, structs and memory you manage yourself. Every example was compiled with warnings treated as errors and run with undefined-behaviour checks.

How the C lessons work

The full C curriculum

1. Foundations

   Programs, variables, types, input and operators.

   First Steps: Write, compile and run your first C programs.

   • Hello, C: Write main(), print with printf() and understand compiling
   • Variables and int: Declare, assign and print whole numbers with %d
   • Arithmetic and Integer Division: Calculate with + - * / % and predict integer results
   • Format Specifiers and Comments: Print numbers, characters and text with %d %f %c %s

   Types and Input: Choose the right type and read values from the user.

   • Numeric Types: Use int, double and char and know their limits
   • Reading Input with scanf: Read numbers and words from the keyboard safely
   • Constants: Name fixed values with const and #define
   • Project: Unit Converter: Convert between units with input and formatted output

   Logic and Operators: Make true or false decisions and update values.

   • Comparisons and Booleans: Compare values and use bool from stdbool.h
   • Logical Operators: Combine conditions with && || and !
   • Updating and Casting: Use ++, += and casts between int and double
   • Project: Leap Year Checker: Decide leap years from several rules

2. Control Flow

   Decisions, loops and functions.

   Making Decisions: Run different code depending on conditions.

   • if and else: Run code only when a condition is true
   • else if and Nesting: Choose between several paths
   • switch: Choose between many exact values
   • Project: Grade Calculator: Turn scores into grades

   Loops: Repeat work with while, do-while and for.

   • while and do-while: Repeat while a condition is true
   • for Loops: Count with for and nest loops
   • break and continue: Leave loops early and skip iterations
   • Project: Number Guessing: Loop until the right answer is found

   Functions: Split programs into reusable pieces.

   • Defining Functions: Write and call your own functions
   • Parameters and Return Values: Pass values in and get results out
   • Scope and Prototypes: Understand local variables and declare functions before use
   • Project: Temperature Table: Print a formatted conversion table with functions

3. Memory and Data

   Arrays, strings and pointers.

   Arrays: Store many values of the same type.

   • Declaring and Indexing Arrays: Create arrays and read and change items
   • Looping over Arrays: Total, search and find the largest item
   • Arrays and Functions: Pass arrays and their sizes to functions
   • Project: Score Statistics: Summarise a list of scores

   Strings: Work with text as arrays of characters.

   • Characters and the Null Terminator: Understand char arrays and the terminating zero
   • String Functions: Use strlen, strcpy, strcat and strcmp
   • Building Strings Safely: Use fgets, snprintf and character tests
   • Project: Palindrome Checker: Check words and phrases read from input

   Pointers: Work directly with memory addresses.

   • Addresses and Pointers: Use & and * to read and write through pointers
   • Pointers and Functions: Change a caller's variables through pointers
   • Pointer Arithmetic: Walk through arrays with pointers
   • Project: Reverse in Place: Reverse an array using two pointers

4. Building Programs

   Structs, dynamic memory, files and a complete project.

   Structs: Group related data into your own types.

   • Defining Structs: Create struct types and access members
   • Arrays of Structs: Store and search many records
   • typedef and Struct Pointers: Name types and use -> through pointers
   • Project: Contact Book: Manage a list of contacts

   Dynamic Memory: Allocate memory while the program runs.

   • malloc and free: Request memory and give it back
   • Growing Arrays with realloc: Build arrays that grow as needed
   • Avoiding Memory Bugs: Prevent leaks, dangling pointers and NULL crashes
   • Project: Dynamic List: Build a list that grows as items are added

   Capstone Project: Plan and build a complete C program.

   • Planning and Modelling: Turn an idea into structs and functions
   • Core Logic: Implement the main features
   • Files and Errors: Save data to a file and handle failures
   • Polishing: Improve output, structure and readability

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