cOS, an OS made in C

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• The Operating System
  • 💽 Bootloader
    • Legacy booting
    • 💾 FAT32
    • 📀 Reading sectors from the 'disk'
    • 📃 GDT - Global Desriptor Table
    • 🔒 Protected Mode
  • 🖥️ Kernel
    • 🔌 Ports
    • ⏱️ Interrupts
      • 📜 IDT - Interrupt Descriptor Table
    • ⌨️ Keyboard
    • ⌛ Timer / PIC - Programmable Interrupt Controller
    • 🖥️ Screen
      • Cursor
      • Color
      • Printing
      • Scrolling
    • 💿 Disk I/O
      • Read / Write
• 🚀 Dependencies
  • make
  • nasm
  • mtools
  • Install on Manjaro / Arch
  • Install on Ubuntu
  • Install on Fedora / CentOS
  • Building the cross compiler
• Repository structure

• Links

Table of contents generated with markdown-toc

The Operating System

💽 Bootloader

Legacy booting

The bios loads the first sector of the bottable device and look for the magic number (0xAA55, chosen number to represent a bootable signature). If the number is found, the bios jumps to the first instructions in the sector.

💾 FAT32

📀 Reading sectors from the 'disk'

📃 GDT - Global Desriptor Table

🔒 Protected Mode

🖥️ Kernel

🔌 Ports

⏱️ Interrupts

📜 IDT - Interrupt Descriptor Table

⌨️ Keyboard

⌛ Timer / PIC - Programmable Interrupt Controller

🖥️ Screen

Cursor

Color

Printing

Scrolling

💿 Disk I/O

Read / Write

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🚀 Dependencies

make

Make is used to automate the build process. It is used to compile the kernel, and to build the bootloader.

nasm

Compiles assembly code into machine code.

mtools

A collection of utilities for manipulating MS-DOS filesystems.

Install on Manjaro / Arch

sudo pacman -S make nasm qemu mtools

⚠️ On manjaro, there is a bug in mcopy (part of mtools). It is recommended to build an older version yourself (mtools-4.0.31.tar.gz). from https://ftp.gnu.org/gnu/mtools/

Install on Ubuntu

sudo apt-get install make nasm qemu mtools 

Install on Fedora / CentOS

sudo dnf install make nasm qemu mtools

Building the cross compiler

To build the cross compiler, you can use a script inside the scripts folder. The credit for the script goes to mell-o-tron. If no script are available for your distro, you can refer to this table from the osdev wiki and install the dependencies yourself.

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Repository structure

.
├── Docs
│   ├── assets
│   │   └── drive.png
│   ├── build.md
│   ├── Links.md
│   ├── schematics.drawio
│   └── TODO.md
├── LICENSE
├── Makefile
├── README.md
├── scripts
│   ├── setup-gcc-arch.sh
│   └── setup-gcc-ubuntu.sh
└── src
    ├── bootloader
    │   ├── bootsector.asm
    │   └── Makefile
    └── kernel
        ├── drivers
        │   ├── disk
        │   │   ├── ata
        │   │   │   ├── ata.c
        │   │   │   └── ata.h
        │   │   └── fat32
        │   │       ├── fat32.c
        │   │       └── fat32.h
        │   ├── keyboard
        │   │   ├── ch-fr_keymap.h
        │   │   ├── keyboard.c
        │   │   └── keyboard.h
        │   ├── ports
        │   │   ├── ports.c
        │   │   └── ports.h
        │   └── screen
        │       ├── color
        │       │   ├── color.c
        │       │   └── color.h
        │       ├── cursor
        │       │   ├── cursor.c
        │       │   └── cursor.h
        │       └── print
        │           ├── print.c
        │           └── print.h
        ├── interrupts
        │   ├── interrupts.c
        │   └── interrupts.h
        ├── kernel.c
        ├── kernel_entry.asm
        ├── Makefile
        └── stdlibs
            ├── stdlib.c
            ├── stdlib.h
            ├── string.c
            └── string.h

Links

https://ecotrust-canada.github.io/markdown-toc/