MyOS

A minimal 32-bit x86 hobby operating system written from scratch in C and assembly. It boots with GRUB (Multiboot), prints to the VGA text screen, reads the PS/2 keyboard, and drops you into an interactive shell.

========================================
             Welcome to MyOS
========================================
Type 'help' to list commands.
PgUp/PgDn scroll the screen, Up/Down recall commands.

MyOS> sysinfo
System summary
--------------
OS                : MyOS 1.2.0 (32-bit x86)
CPU               : QEMU Virtual CPU version 2.5+
Memory            : 130559 KiB (127 MiB) usable
Bootloader        : GRUB 2.12
PCI devices       : 5
Virtualization    : yes (TCGTCGTCGTCG)

Features

• Multiboot-compliant boot (GRUB loads kernel.elf)
• Freestanding kernel with no libc
• VGA text-mode console (80x25) with colors, a working hardware cursor and 275 lines of scrollback
• PS/2 keyboard driver (scancode set 1): Shift, Caps Lock, arrow keys, Page Up/Down, Home/End
• Interactive shell with command history (Up/Down) and backspace editing across wrapped lines
• Hardware information: memory map from GRUB, CPU details via CPUID, PCI device list, RTC date and time
• Kernel panic handler (kernel_panic) that shows an error screen and halts the CPU

Download

Ready-to-boot ISO images and source archives are on the Releases page. Each release includes SHA-256 checksums.

qemu-system-i386 -cdrom myos-1.2.0.iso -m 128M

Shell commands

Command	Description
help	List available commands
about	About MyOS
version	Show the kernel version
sysinfo	System summary (OS, CPU, memory, bootloader, PCI devices)
meminfo	Memory size, kernel location and the full memory map
cpuinfo	CPU vendor, model, family/model/stepping, features, virtualization
lspci	List PCI devices (network, storage, graphics, ...)
date	Date and time from the RTC clock
history	Commands typed so far
echo <text>	Print text to the screen
clear	Clear the screen and scrollback
reboot	Restart the computer
halt / shutdown	Halt the CPU

Keys: Up/Down recall previous commands, PgUp/PgDn scroll the screen, Home/End jump to the oldest/newest output.

Project layout

myOS/
├── src/
│   ├── boot.S        # Multiboot header, stack setup, entry point (_start)
│   ├── kernel.c      # kernel_main: init console, start shell
│   ├── console.c     # VGA console: colors, cursor, scrollback
│   ├── keyboard.c    # PS/2 keyboard driver
│   ├── keys.h        # Special key codes (arrows, Page Up/Down, ...)
│   ├── shell.c       # Command-line shell
│   ├── multiboot.c   # Boot information from GRUB (memory map, bootloader)
│   ├── cpu.c         # CPU information (CPUID)
│   ├── pci.c         # PCI device scanning
│   ├── rtc.c         # Real-time clock (date and time)
│   └── panic.c       # Kernel panic handler
├── iso/
│   └── boot/grub/grub.cfg   # GRUB menu entry
├── linker.ld         # Linker script (kernel loads at 1 MiB)
├── Makefile
└── LICENSE

Requirements

• GCC with 32-bit support, and GNU Make
• GRUB tools (grub2-mkrescue, or grub-mkrescue on Debian/Ubuntu) and xorriso
• QEMU (qemu-system-i386) to run it; VirtualBox or VMware also work

Fedora

sudo dnf install gcc glibc-devel.i686 make qemu-system-x86 grub2-tools grub2-tools-extra xorriso

Debian / Ubuntu

sudo apt install build-essential gcc-multilib grub-pc-bin xorriso mtools qemu-system-x86

Build

make clean
make                  # builds kernel.elf

Check that GRUB recognizes the kernel as Multiboot (optional):

grub2-file --is-x86-multiboot kernel.elf && echo "Multiboot OK"

If grub2-file is unavailable, use grub-file instead.

Build the bootable ISO:

make iso            # copies kernel.elf into iso/ and runs grub(2)-mkrescue

Or do it by hand:

cp kernel.elf iso/boot/kernel.elf
grub2-mkrescue -o myos.iso iso      # or: grub-mkrescue -o myos.iso iso

Run

make run            # builds the ISO and starts QEMU
# or, by hand:
qemu-system-i386 -cdrom myos.iso -m 128M

A QEMU window opens with the MyOS welcome banner and shell prompt. Try:

sysinfo
meminfo
cpuinfo
lspci

To boot the kernel directly, without an ISO:

qemu-system-i386 -kernel kernel.elf -m 128M

VirtualBox / VMware: create a 32-bit Other/Unknown VM with at least 64 MB of RAM and no hard disk, then attach myos.iso as the optical drive.

Real hardware: write the ISO to a USB drive or CD and boot in BIOS / legacy mode. Take care to select the correct device, as writing an image can erase existing data.

How it works

1. GRUB reads grub.cfg, loads kernel.elf at 1 MiB and jumps to _start using the Multiboot protocol.
2. boot.S sets up a 16 KiB stack and calls kernel_main.
3. kernel_main clears the screen and starts the shell.
4. The shell prints a prompt, reads keys through the keyboard driver (polling ports 0x64 and 0x60), and runs the command entered.

Roadmap

• Interrupts (IDT, PIC) and an IRQ-driven keyboard
• Physical page allocator (the memory map is already parsed)
• Kernel heap (malloc)
• Calling kernel_panic from kernel error paths
• Left/Right arrow editing inside the command line
• A simple filesystem

Planned architecture

The roadmap below will move the kernel from a flat src/ folder to a modular layout. The files under arch/, drivers/, mm/, fs/ and proc/ do not exist yet. This is the target structure, not the current one.

myOS/
├── boot/
├── src/
│   ├── kernel.c
│   ├── console.c
│   ├── keyboard.c
│   ├── shell.c
│   ├── arch/i386/
│   │   ├── gdt.c          # Global Descriptor Table
│   │   ├── idt.c          # Interrupt Descriptor Table
│   │   └── interrupts.S   # Interrupt/IRQ entry stubs
│   ├── drivers/
│   │   ├── timer.c        # PIT timer
│   │   └── disk.c         # Disk driver
│   ├── mm/
│   │   ├── physical.c     # Physical page allocator
│   │   └── heap.c         # Kernel heap
│   ├── fs/                # Filesystem
│   └── proc/              # Processes and scheduling
├── linker.ld
├── Makefile
└── iso/boot/grub/grub.cfg

Create the directories with:

mkdir -p src/arch/i386 src/drivers src/mm src/fs src/proc src/lib iso/boot/grub

Contributing

Issues and pull requests are welcome. For larger changes, please open an issue first to discuss what you would like to change.

License

Released under the MIT License.