Operating-Systems-programming

A collection of C programs exploring core Operating Systems concepts, including process management and FAT32 filesystem parsing on Linux.

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Repository Structure

Operating-Systems-programming/
│
├── Lab 1 – Process Management & GCC Pipeline
│   ├── code_tp.c       # Base version: compile and run a C program via child processes
│   └── pg.c            # Extended version: adds signal-based abnormal termination handling
│
├── Lab 2 – FAT32 Filesystem Analysis
│   ├── Part1.c         # Read GPT partition table and FAT32 boot sector metadata
│   └── Part2.c         # Extended version: also lists root directory contents
│
└── README.md

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Lab 1 — Process Management & GCC Pipeline

Description

This lab demonstrates Unix process creation and management using fork() and exec(). The program simulates a mini build system: it asks the user for a C source file, object file name, and executable name, then orchestrates three child processes to compile and run the program step by step.

Process flow:

Parent
  └── P1 (fork) → gcc -c source.c -o object.o      [compile to object file]
        └── P2 (fork) → gcc object.o -o executable  [link to executable]
              └── P3 (fork) → ./executable           [run the program]

Each child process is waited on before the next is spawned. Exit status is inspected via WIFEXITED, WEXITSTATUS, and in the extended version (pg.c), WIFSIGNALED and WIFSTOPPED to detect signal-based termination.

Files

File	Description
code_tp.c	Base implementation — detects normal vs abnormal termination
pg.c	Extended version — also catches WIFSIGNALED and WTERMSIG/WIFSTOPPED/WSTOPSIG for P3

Key Concepts

• fork() — create child processes
• execlp() — replace a process image with a new program
• wait() / WIFEXITED() / WEXITSTATUS() — synchronize and inspect child exit status
• WIFSIGNALED() / WTERMSIG() / WIFSTOPPED() / WSTOPSIG() — handle abnormal termination

How to Build & Run

gcc code_tp.c -o code_tp
./code_tp

When prompted:

Veuillez entrer le nom du fichier source (***.c) : hello.c
Veuillez entrer le nom du fichier objet (***.o) : hello.o
Veuillez entrer le nom du fichier exécutable : hello

Note: The target source file (e.g. hello.c) must exist in the current directory before running.

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Lab 2 — FAT32 Filesystem Analysis

Description

This lab involves low-level disk and filesystem parsing in C. The programs read raw sectors from a block device, parse a GPT (GUID Partition Table) to locate a FAT32 partition, then decode the FAT32 boot sector to extract filesystem metadata.

Part 2 goes further by traversing the root directory and listing all files with their sizes, cluster numbers, and LBA addresses.

Files

File	Description
Part1.c	Reads GPT entries, locates the FAT32 partition, and prints boot sector info
Part2.c	Extends Part 1 — also prints a formatted table of root directory contents

Key Concepts

• MBR & GPT parsing — reading sector 0 (protective MBR) and sector 1 (GPT header) to locate partition entries
• FAT32 Boot Sector — decoding BPB fields: bytes per sector, sectors per cluster, reserved sectors, FAT count, FAT size, root cluster
• LBA addressing — computing the logical block address of the root directory from boot sector parameters
• Directory entry parsing — reading 32-byte FAT32 directory entries to extract file names, sizes, and first cluster numbers
• /dev enumeration — listing available block devices (sd*, hd*) by scanning /dev

Output Example (Part 2)

LBA début de la partition FAT32: 2048
Taille en secteurs de la partition FAT32: 204800
Numéro du premier cluster du répertoire racine: 2
LBA début du répertoire racine: 8284
Taille d'un cluster en secteurs: 8

    ******************* Contenu du répertoire racine *******************

|-----------|-----------------------|------------------|-----------------|---------------------|
| Nom       |    Taille(secteurs)   |  Taille Ko       | Premier cluster |  LBA premier Cluster|
|-----------|-----------------------|------------------|-----------------|---------------------|
| HELLO      |                     1 |             0.50 |               3 |                8292 |
...

How to Build & Run

⚠️ Root privileges are required to read raw block devices.

gcc Part1.c -o part1
sudo ./part1

gcc Part2.c -o part2
sudo ./part2

By default the programs target /dev/sdb2 (Part2) or /dev/sda (Part1). Edit the disque variable in main() to match your target device before compiling.

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Requirements

• Linux (tested on Ubuntu)
• GCC
• Root access (for Lab 2 disk reading)

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Notes

• Lab 2 assumes a GPT-partitioned disk where the FAT32 partition is the second GPT entry (index 1). Adjust the pointer offset in main() if your layout differs.
• All disk reads use raw fopen/fread at the sector level (512 bytes per sector).
• Lab 1 is entirely self-contained and safe to run on any Linux system without elevated privileges.