Holberton School — Low-Level Programming in C

Projects completed during the low-level programming track of Holberton School. Starting from "Hello, World", the curriculum works down to how C programs are compiled, how memory is laid out and managed, and how classic data structures and algorithms are built from scratch — without relying on the standard library where possible.

Table of contents

• Projects
• Requirements
• Getting started
• Repository structure
• Author

Projects

Project	Topic	Key concepts
0x00	Hello, World	Compilation stages, gcc, puts/printf, type sizes
0x01	Variables, if, else, while	Control flow, loops, ASCII, putchar
0x02	Functions, nested loops	Prototypes, header files, nested loops
0x03	Debugging	Test cases, edge cases, fixing logic errors
0x04	More functions, more nested loops	Drawing shapes, printing numbers digit by digit
0x05	Pointers, arrays and strings	Pointers, arrays, null-terminated strings, atoi
0x06	More pointers, arrays and strings	strcat/strcmp, ROT13, arbitrary-precision add, hex dump
0x07	Even more pointers, arrays and strings	memset/memcpy, string search, 2D arrays, double pointers
0x08	Recursion	Base/recursive cases, palindromes, wildcard matching
0x09	Static libraries	ar, ranlib, linking with -L/-l
0x0A	argc, argv	Command-line arguments, input validation
0x0B	malloc, free	Heap allocation, 2D grids, valgrind
0x0C	More malloc, free	exit, calloc, dynamic ranges
0x0D	Preprocessor	Macros, include guards, predefined macros
0x0E	Structures, typedef	struct, typedef, deep copies
0x0F	Function pointers	Callbacks, dispatch tables, calculator
0x10	Variadic functions	stdarg.h, va_list, format-driven printing
0x12	Singly linked lists	Nodes, traversal, insertion, freeing
0x13	More singly linked lists	Indexed insert/delete, pop, sum
0x14	Bit manipulation	Binary conversion, get/set/clear bits, endianness
0x15	File I/O	open/read/write/close, permissions, cp clone
0x17	Doubly linked lists	prev/next links, indexed insert/delete
0x18	Dynamic libraries	-fPIC, -shared, LD_LIBRARY_PATH, Python ctypes
0x1A	Hash tables	djb2, chaining, sorted hash table
0x1C	Makefiles	Rules, targets, variables
0x1E	Search algorithms	Linear, binary, jump, interpolation, exponential, Big O

Each project directory has its own README.md with learning objectives, the list of tasks and their prototypes, and a compilation example.

Requirements

• OS: Ubuntu 20.04 LTS
• Compiler: gcc with the flags -Wall -Werror -Wextra -pedantic -std=gnu89
• Style: Betty (Linux-kernel-like style, documented functions, max. 40 lines per function and 5 functions per file)
• No global variables
• Prototypes of every function are declared in the project's header file (main.h, lists.h, hash_tables.h, ...), protected by include guards
• Where printf is not allowed, output goes through _putchar, a one-line wrapper around write(2)

Getting started

git clone https://github.com/pipeleon/holbertonschool-low_level_programming.git
cd holbertonschool-low_level_programming/0x08-recursion

# Compile a task together with its test driver
gcc -Wall -Werror -Wextra -pedantic -std=gnu89 _putchar.c 0-main.c 0-puts_recursion.c -o 0-puts_recursion
./0-puts_recursion

Projects that work with dynamic memory are best checked with valgrind:

valgrind --leak-check=full ./program

Repository structure

0xNN-project_name/
├── README.md        # project description, tasks and usage
├── main.h           # prototypes (or lists.h, dog.h, hash_tables.h, ...)
├── N-task_name.c    # solution to task N (100+ are advanced tasks)
├── N-main.c         # test driver for task N (provided by Holberton)
└── _putchar.c       # write(2)-based character output, when needed

• Files are named after their task number: 0-… to N-… are mandatory tasks, 100-… and above are advanced tasks.
• Each source file starts with a /* Task N 0xNN. ... */ line and every function has a Betty-style documentation block describing its parameters and return value.

Author

pipeleon — github.com/pipeleon